US20100019609A1 - End turn configuration of an electric machine - Google Patents

Abstract

A stator for an electric machine includes multiple conductive coils. Each coil defines a loop that extends axially through the elongate core, exits the core through an end face, and reenters the core through the end face. A first subset of the coils collectively form a first radial layer axially exterior the core and a third radial layer axially exterior the core. Each coil in the first subset resides in both the first layer and the third layer. A second subset of the coils collectively forms a second radial layer axially exterior the core and a fourth radial layer axially exterior the core. Each coil in the second subset residing in both the second layer and the fourth layer.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application claims the benefit of U.S. Provisional Application No. 61/084,238, filed Jul. 28, 2008 and U.S. Provisional Application No. 61/096,290, filed Sep. 11, 2008, the entire disclosures of which are incorporated by reference herein.
BACKGROUND
• Some electric machines operate to convert mechanical movement (e.g., kinetic energy) into electrical power, convert electrical power into mechanical movement, or both. For example, an electric machine system that operates to convert mechanical movement into electrical power (i.e., generate electrical power) can include an electric machine coupled to a companion device that is a prime mover. The prime mover supplies mechanical movement to the electric machine, which converts the mechanical movement into electrical power. An electric machine system configured to convert electrical power into mechanical movement (i.e., motor) can include an electric machine coupled to a companion device that is driven by the mechanical movement output from the electric machine. In certain instances, electric machine systems configured to both generate electrical power and mechanical movement can include an electric machine coupled to a companion device (e.g., a prime mover) that may be driven by the electric machine and that may drive the electric machine.
SUMMARY
• A stator of an electric machine includes a core that carries conductive coils. The conductive coils form four layers of end turns axially external the core.
• In one general aspect, a stator for an electric machine includes an elongate core having an end face and an opposing end face, the elongate core adapted to internally receive a rotor of an electric machine. The stator includes multiple conductive coils. Each coil defines a loop that extends axially through the elongate core, exits the core through the end face, and reenters the core through the end face. A first subset of the coils collectively form a first radial layer axially exterior the core and a third radial layer axially exterior the core. Each coil in the first subset resides in both the first layer and the third layer. A second subset of the coils collectively forms a second radial layer axially exterior the core and a fourth radial layer axially exterior the core. Each coil in the second subset residing in both the second layer and the fourth layer. The second layer resides radially between the first and third layers. The third layer resides radially between the second and fourth layers.
• In another general aspect, a stator for an electric machine includes an elongate core adapted to internally receive a rotor of an electric machine. The stator includes a first set of coils and a second set of coils. The first set of coils are arranged in a first lap winding configuration. The first set of coils form a first set of end turns that each extend through a first radial layer of end turns and a third radial layer of end turns. A second set of coils are arranged in a second lap winding configuration. The second set of coils form a second plurality of end turns that each extend through a second radial layer of end turns and a fourth radial layer of end turns. The second layer resides radially between the first and third radial layers. The third layer resides radially between the second and fourth radial layers.
• In another general aspect, a first set of coils are installed in a core of a stator. The first plurality of coils collectively form a first radial layer of end turns and a third radial layer of end turns axially external the core. Each coil in the first set defines a loop that extends axially through the core, exits the core through the end face, extends through the first radial layer, extends through the third radial layer, and reenters the core through the end face. A second set of coils are installed in the core of the stator. The second set of coils collectively form a second radial layer of end turns and a fourth radial layer of end turns axially external the core. Each coil in the second subset defines a loop that extends axially through the core, exits the core through the end face, extends through the second radial layer, extends through the fourth radial layer, and reenters the core through the end face. The second radial layer resides radially between the first and third radial layers, and the third layer resides radially between the second and fourth radial layers.
• Implementations may include one or more of the following features. The loop defined by each coil in the first subset exits the core through the end face at an exit location in the first radial layer and reenters the core through the end face at a reentry location in the third radial layer. The loop defined by each coil in the second subset exits the core through the end face at an exit location in the second radial layer, and reenters the core through the end face at a reentry location in the fourth radial layer. The first and second sets of coils form two radial layers in the elongate core, and each of the coils resides in both radial layers in the elongate core. The two radial layers in the elongate core define two radii including a second radius that coincides with the second radial layer of end turns and a third radius that coincides with the third radial layers of end turns. The loop defined by each coil in the first subset exits the core through the end face at an exit location on the second radius, turns toward the first radial layer, extends through the first radial layer, turns toward the third radial layer, extends through the third radial layer, and reenters the end face at its reentry location on the third radius. The loop defined by each coil in the second subset exits the core through the end face at an exit location on the second radius, extends through the second radial layer, turns toward the fourth radial layer, extends through the fourth radial layer, turns toward the third radius, and reenters the end face at its reentry location on the third radius. The core defines slots to carry the coils. A first subset of the slots each carry two of the first subset of coils. A second subset of the slots each carry two of the second subset of coils. A radial distance between two coils in each slot and an azimuthal distance between two sides of the slot define a gap in the slot. The fourth radial layer is an inner-most radial layer, and the first radial layer is an outer-most radial layer. The first subset of slots have a first radial depth, and the second subset of slots have a second radial depth. The second radial depth is less than the first radial depth. The first subset of slots and the second subset of slots all have substantially equal radial depths. The first plurality of coils are coupled to the second plurality of coils to form a three-phase conductive winding. The electric machine is operated as a two-pole electric machine or a four-pole electric machine. Installing the first plurality of coils and/or the second plurality of coils includes forming a winding structure outside of the core and installing the formed winding structure in the core. Installing the first plurality of coils and/or the second plurality of coils includes installing each of the plurality of coils by successively forming individual turns of the coil in the core of the stator. Installing the first plurality of coils and installing the second plurality of coils can include simultaneously or substantially simultaneously installing the first plurality of coils and the second plurality of coils.
• The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.
DESCRIPTION OF DRAWINGS
• FIG. 1A is a schematic of an example electric machine system.
• FIG. 1B is a cross-sectional view of an example electric machine system including a subsea pump.
• FIG. 1C is a cross-sectional view of an example electric machine system including a subsea compressor.
• FIG. 2A is a cross-sectional view of an example rotor.
• FIG. 2B is a detail cross-sectional view of an end of the example rotor ofFIG. 2A.
• FIG. 2C shows an example rotor with a composite sleeve formed by a metallic tape wrapped around an outer jacket of the rotor.
• FIG. 2D is a detail cross-sectional view of an end of an example rotor having a rotor sleeve formed from a metal alloy tape.
• FIG. 2E is a detail cut-away view of an example rotor sleeve.
• FIG. 2F is a detail cross-sectional view of another example rotor.
• FIG. 2G is a detail, perspective view of the example rotor ofFIG. 2E.
• FIGS. 2H-2P are schematic cross-sectional views of different example rotors having segmented magnets, wherein the arrows associated with each magnet segment represent the respective magnet segment's north pole orientation.
• FIG. 2Q is a side view of an example rotor showing a plurality of flow path channels formed by segments of the rotor magnets.
• FIG. 2R is a side view of another example rotor having grooves formed in the rotor to facilitate introduction of a filler material thereinto.
• FIG. 2S is a side view of another example rotor having anannular channel264 formed therein along with an inlet formed in a end ring thereof.
• FIG. 2T is a cross-sectional view of a magnet segment or magnet segment row having uniform radial magnetization.
• FIG. 2U is a cross-sectional view of a magnet segment or magnet segment row having true radial magnetization.
• FIG. 3A shows a cross-sectional view of an example electric machine.
• FIG. 3B shows a perspective view of an example stator core for use in an electric machine.
• FIG. 3C shows two adjacent yoke portions formed, each yoke portion formed from a plurality of individual portions.
• FIG. 3D shows an example portion used to form part of the yoke portions ofFIG. 3C.
• FIG. 3E shows an example stator bar of the example stator ofFIG. 3B used to provide alignment and rigidity to the stator.
• FIG. 3F is an example end plate of the example stator ofFIG. 3B.
• FIG. 3G is a partial detail view of an end of the example stator ofFIG. 3B.
• FIG. 3H shows an example stator tooth lamination for use in the example stator ofFIG. 3B.
• FIG. 3I shows a side view of two adjacent stator tooth laminations having respective protrusions and receptacles for aligning and/or attaching the stator tooth laminations.
• FIG. 3J shows an alternate configuration for aligning and/or attaching adjacent stator tooth laminations.
• FIG. 3K is a schematic view of tooth segments disposed in a channel formed in adjacent yokes.
• FIG. 3L is a cross-sectional view of an example electric machine having a protective barrier around the stator.
• FIGS. 3M-3Q are partial cross-sectional views illustrating example constructions of the protective barrier.
• FIG. 4A is a partial schematic end view of an example core of a stator for an electric machine.
• FIG. 4B is a partial schematic end view of an example core of a stator for an electric machine.
• FIG. 4C is a partial schematic end view of an example core of a stator for an electric machine.
• FIG. 4D is a partial schematic end view of an example core of a stator for an electric machine.
• FIG. 4E is a partial schematic end view of an example core of a stator for an electric machine.
• FIG. 4F is a schematic end view of example end turns of a stator for an electric machine.
• FIG. 4G is a schematic end view of example end turns of a stator for an electric machine.
• FIG. 4H is a schematic side view of example end turns of a stator for an electric machine.
• FIG. 4I is a schematic side view of example end turns of a stator for an electric machine.
• FIG. 4J is a schematic cross-sectional view of an example stator for an electric machine.
• FIG. 4K is a schematic cross-sectional view of example end turns of a stator for an electric machine.
• FIG. 4L is a schematic of two example end turns.
• FIG. 4M is a schematic of example end turns.
• FIG. 4N is a schematic of example end turns.
• FIG. 4O is a schematic of example end turns.
• FIG. 4P is a schematic side view of example end turns of a stator for an electric machine.
• FIG. 4Q is a schematic perspective view of example end turns of a stator for an electric machine.
• FIG. 4R is a partial schematic cross-sectional view of an example core of a stator for an electric machine.
• FIG. 4S is a partial schematic cross-sectional view of an example core of a stator for an electric machine.
• FIG. 4T is a partial schematic cross-sectional view of an example core of a stator for an electric machine.
• FIG. 4U is a partial schematic cross-sectional view of an example core of a stator for an electric machine.
• FIG. 4V is a perspective view of an example wedge for insertion into one or more stator core slots.
• FIG. 4W is a wiring diagram showing connections for one phase of a three phase electric machine.
• FIG. 4X is a wiring diagram showing connections for one phase of a three phase electric machine.
• FIG. 4Y is a wiring diagram showing connections for one phase of a three phase electric machine.
• FIG. 4Z is a partial schematic end view of an example core of a stator for an electric machine.
• FIG.4AA is a partial schematic end view of an example core of a stator for an electric machine.
• FIG.4BB is a partial schematic end view of an example core of a stator for an electric machine.
• FIG.4CC is a partial schematic end view of an example core of a stator for an electric machine.
• FIG.4DD is a partial schematic end view of an example core of a stator for an electric machine.
• FIG.4EE is a schematic end view of example end turns of a stator for an electric machine.
• FIG.4FF is a schematic end view of example end turns of a stator for an electric machine.
• FIG.4GG is a schematic end view of example end turns of a stator for an electric machine.
• FIG.4HH is a schematic side view of example end turns of a stator for an electric machine.
• FIG.4II is a schematic cross-sectional view of an example stator for an electric machine.
• FIG.4JJ is a schematic cross-sectional view of an example stator core for an electric machine.
• FIG.4KK is a schematic cross-sectional view of an example stator core for an electric machine.
• FIG.4LL is a perspective view of an example wedge for insertion into one or more stator core slots.
• FIG.4MM is a perspective view of an example wedge for insertion into one or more stator core slots.
• FIG.4NN is a schematic end view of an example stator core for an electric machine.
• FIG.4OO is a perspective view of an example wedge for insertion into one or more stator core slots.
• FIG.4PP is a schematic end view of an example stator core for an electric machine.
• FIG.4QQ is an example slot liner for a stator slot of an electric machine.
• FIG.4RR is an end view of an example stator core for an electric machine showing the slot liner of FIG.4QQ residing in the slot and retained by a liner clamp.
• FIG.4SS is an end view of an example stator core for an electric machine showing the slot liner of FIG.4QQ residing in the slot and retained by an alternate liner clamp.
• FIG.4TT is a partial perspective view of an example stator for an electric machine.
• FIG.4UU is an end view of an example stator for an electric machine.
• FIG.4VV is a partial perspective view of an example stator for an electric machine.
• FIG.4WW is a partial side view of an example stator for an electric machine.
• FIG.4XX is a partial perspective view of an example stator for an electric machine.
DETAILED DESCRIPTION
• Referring toFIG. 1A, anelectric machine system100 includes anelectric machine102 coupled to acompanion device104. Theelectric machine102 can operate as a generator, producing electrical power from mechanical movement, operate as a motor producing mechanical movement from electricity, or alternate between generating electrical power and motoring. In generating electrical power, a prime mover supplies mechanical movement to theelectric machine102, and theelectric machine102 converts the mechanical movement into electrical power. In certain instances, thecompanion device104 may be the prime mover. In motoring, the mechanical movement output from theelectric machine102 can drive another device. In certain instances, theelectric machine102 can drive thecompanion device104. In certain instances, theelectric machine102 can operate to motor and drive the prime mover during specified conditions, and switch to generating electrical power and be driven by the prime mover during specified conditions. Theelectric machine102 can be configured for primarily generating electrical power, primarily motoring, or to be reasonably efficient at both generating electrical power and motoring.
• In general terms, theelectric machine102 includes a stationary member and a movable member that, by interaction of magnetic fields, generates electrical power as the movable member moves relative to the stationary member and/or moves the movable member as electrical power is applied to the stationary member. For convenience of reference herein, theelectric machine102 is described as a rotating electric machine, where the movable member is arotor106 supported to rotate in the stationary member, astator108.Rotor106 is coupled to thecompanion device104 to drive thecompanion device104 and/or be driven by thecompanion device104. WhileFIG. 1A illustrates a horizontally-oriented electric machine coupled to a horizontally-orientedcompanion device104, other implementations may provide for a vertically-oriented electric machine coupled to and capable of driving vertically-oriented companion devices, among other orientations. Additionally, in other instances, theelectric machine102 can be another type of electric machine. For example, theelectric machine102 can be a linear electric machine, where the movable member is a linearly reciprocating shaft. The linearly reciprocating shaft may be coupled to thecompanion device104 to drive and/or be driven by thecompanion device104. As described in more detail below, theelectric machine102 is an alternating current (AC), synchronous, permanent magnet (PM) electric machine having arotor106 that includes permanent magnets andstator108 that includes a plurality of formed or cable windings about a core. In other instances, the electric machine can be an other type of electric machine, such as an AC, asynchronous, induction machine where both the rotor and the stator include windings or another type of electric machine. In certain instances, theelectric machine102 is carried by and contained within ahousing110. Thehousing110 can be wholly separate from thecompanion device104, separate from and coupled to thecompanion device104, or partially or wholly shared with the companion device104 (i.e., theelectric machine102 andcompanion device104 carried by and contained within a common housing).
• In certain instances, theelectric machine system100 may be a subsea electric machine configured for subsea operation, submerged in the open sea (i.e., outside of a well or a pipeline). To this end, thehousing110 is a pressure vessel sealed against passage of fluid between the interior of thehousing110 and the surrounding environment (e.g., the surrounding seawater). Thehousing110 is constructed to withstand the ambient pressures about theelectric machine system100 and thermal loads exerted by the surrounding environment, as well as pressures and thermal loads incurred in operating theelectric machine102 andcompanion device104. Thehousing110 may be constructed of a material that resists corrosion, for example, stainless steel, nickel alloys such as Inconel a registered trademark of Special Metals Corporation, and/or other materials. Thehousing110 may additionally or alternatively be plated or coated with a material that resists corrosion, for example, Inconel, epoxy, polyetheretherketone, ethylene chlorotrifluoroethylene and/or other materials. In certain instances, thehousing110 may carry anodes (not shown) to assist in resisting corrosion. In certain instances, thehousing110 may be coupled to a skid or other structure that aligns with and engages (e.g., by way of guide tubes that receive guide cones) other subsea structures.
• In instances where thecompanion device104 is a prime mover, the companion device can include a number of different possible devices. For example, the prime mover may include one or more of a fluid motor operable to convert fluid (gas/liquid) flow into mechanical energy, a gas turbine system operable to combust an air/fuel mixture and convert the energy from combustion into mechanical energy, an internal combustion engine, and/or other type of prime mover. In instances where thecompanion device104 is driven by theelectric machine102, the companion device can include a number of different possible devices. For example, thecompanion device104 can include one or more of a rotating and/or reciprocating pump, rotating and/or reciprocating compressor, mixing device, or other device. Some examples of pumps include centrifugal pump, axial pump, rotary vane pump, gear pump, screw pump, lobe pump, progressive cavity pump, reciprocating positive displacement or plunger pump, diaphragm pump, and/or other types of pumps. Some examples of compressors include centrifugal compressor, axial compressor, rotary vane compressor, screw compressor, reciprocating positive displacement compressor and/or other types of compressors. Theelectric machine102 can be coupled to two ormore companion devices104 at the same time.
• Although shown with asingle companion device104, theelectric machine102 can also be coupled to two or more companion devices104 (to drive and/or be driven by the devices104). In certain instances, one ormore companion devices104 can be provided at each end of theelectric machine102. For example, in a configuration with twocompanion devices104, one may be provided at one end of theelectric machine102 and another provided at an opposing end of the electric machine. In another example, a configuration with twocompanion devices104 can have one provided at one end of theelectric machine102, and another coupled to the first companion device. Also, ifmultiple companion devices104 are provided, they need not all be of the same type of companion device.
• FIG. 1B depicts an exampleelectric machine system100awhere thecompanion device104ais a pump driven by theelectric machine102a.Onepump companion device104ais shown. In other instances, morepump companion devices104acan be provided. For example, twopump companion devices104acould be provided on opposing ends of theelectric machine102a(e.g., in a configuration similar to thecompressor companion devices104bshown below). In certain instances, two or morepump companion devices104acould be provided on the same side of theelectric machine102a.The exampleelectric machine system100ais configured for subsea operation, submerged in the open sea (i.e., outside of a well). In other words, the exampleelectric machine system100ais a subsea pump system.
• Thehousing110ais a pressure vessel sealed against passage of fluid between the interior of thehousing110aand the surrounding environment (e.g., the surrounding seawater). In certain instances, the housing is flooded with a heat transfer fluid that is communicated to both therotor106 and thestator108. In certain instances, the heat transfer fluid includes a liquid, is primarily a liquid and/or is entirely liquid. The heat transfer fluid can include water, mono-ethylene glycol (MEG), mono-propylene glycol (MPG), an oil, a fluid similar to or the same as that being pumped by thepump companion device104a,and/or other fluid. Although referred to herein as a heat transfer fluid, the fluid may perform functions other than to provide heat transfer with theelectric machine102a.In certain instances, the fluid lubricates bearing surfaces and/or performs other functions. In certain instances, the heat transfer fluid is maintained at pressure above the maximum operating pressure attained by thepump companion device104a.Because the heat transfer fluid is at a pressure above the maximum operating pressure attained by thepump companion device104a,leakage between theelectric machine102aand thepump companion device104 tends to be leakage of the heat transfer fluid towards thepump companion device104a.In certain instances, the pressure of the heat transfer fluid is above the ambient pressure about the exterior of theelectric machine system100aby an amount substantially greater than the incidental pressure incurred in circulating the heat transfer fluids through theelectric machine system100a.Thehousing110ahas aflange112 proximate the drive end of theelectric machine102a.Flange112 is configured to be sealingly joined, by bolts and/or otherwise, to thecompanion device104a,for example, at acorresponding flange124 of thecompanion device104a.In certain instances, a seal (e.g., ring gasket, o-ring and/or other) may be provided betweenflange112 andflange124.FIG. 1B depicts a close-coupled subsea pump system, in that thehousing110aof theelectric machine102aattaches directly to thehousing148 of thepump companion device104a.In other instances, the subsea pump system can be of an integrated configuration where the electric machine and companion device have a common housing and/or common shaft. For example, in some common housing configurations, the housing body that surrounds both the electric machine and the companion device can be a unitary piece (i.e., not readily separable, such as by removal of fasteners). In some common shaft configurations, the rotor of the electric machine can be unitary with the drive shaft of the companion device (i.e., not readily separable, such as by removal of fasteners or by release of the drive coupling). In other instances, subsea pump system can be of a non-integrated configuration having the housing ofelectric machine102awholly separate (not coupled and/or substantially coupled) from the housing of thepump companion device104a.
• Thehousing110aas shown is configured in four main elements including ahousing body114, adrive end plate116aproximate the drive end of theelectric machine102a,anon-drive end plate118aopposite the drive end of theelectric machine102a,and anend cap119 at the end of thehousing body114 adjacent thenon-drive end plate118a.In certain instances, thehousing110amay be configured in fewer or more elements. One or more seals120 (e.g. gaskets, o-rings and/or other) may be provided between theend cap119 and thehousing body114 to seal against passage of fluid into and/or out of thehousing110a.In certain instances, seals may additionally or alternatively be provided between thedrive end plate116aand thehousing body114 and/or between thenon-drive end plate118aand thehousing body114. Adrive stub117aof therotor106 extends through thedrive end plate116ato communicate mechanical movement with thecompanion device104a.
• Theend plates116a,118acarry bearings122 that receive and support therotor106 to rotate about a rotational axis in thestator108. Thebearings122 can be a number of different possible types of bearings, and the number and types of bearings carried by thedrive end plate116acan be different from the number and types of bearing carried by thenon-drive end plate118a.Thebearings122 can include one or more of journal bearings (e.g., a tilt-pad journal bearing and/or other type), magnetic bearings (e.g., such as that described in U.S. Pat. No. 6,700,258, U.S. Pat. No. 6,727,617, U.S. Patent Publication No. 2002/0175578 and/or other type), hybrid magnetic bearings, ball bearings and/or other types of bearing. One or more of thebearings122 is a thrust bearing (e.g., a tilt-pad thrust pad and/or other type). In certain instances,non-drive end plate118aincludes at least one axial or thrust bearing to axially retain therotor106 relative to thehousing110aand at least one radial bearing to provide radial support to therotor106 relative to thehousing110a,and thedrive end plate116aincludes at least one radial bearing to provide radial support to therotor106 relative tohousing110a.
• Thestator108 is generally cylindrical and the outer diameter thereof is closely received in the inner diameter of thehousing110ato support thestator108 relative to thehousing110a.The outer diameter of thestator108 may be keyed (using a protruding male key received in a female receptacle), bolted and/or otherwise secured to the inner diameter of thehousing110ato rotationally affix thestator108 relative to thehousing110a.In certain instances, thestator108 is axially retained with end rings126 that are bolted and/or otherwise affixed to thehousing110a.One or more penetrators128 (one shown for simplicity of illustration) are provided through and sealed or substantially sealed with thehousing110ato communicate fluid and/or electrical power into the interior thereof. In certain instances, for example in connection with a three phaseelectric machine102a,at least three penetrators128 are provided to conduct electrical conductors from a power electronics system (i.e., control system for the electric machine) to the windings of thestator108. Anotherpenetrator128 may be provided that includes a conduit coupled to a supply heat transfer fluid to replenish any heat transfer fluid leaked from thehousing110a.
• The non-drive end of therotor106 carries afluid circulation pump130 that circulates the heat transfer fluid in thehousing110aand through anexternal heat exchanger132. Thepump130 is coupled to the non-drive end of therotor106 to rotate with therotor106. Thepump130 can be a number of different types of pumps, including a shrouded or unshrouded centrifugal impeller pump, radial impeller pump, rotary vane pump, gear pump, screw pump, lobe pump and/or other type of pump. In certain instances, theexternal heat exchanger132 includes a continuous conduit helically coiled around the exterior of thehousing110a.The external heat exchanger has an outlet proximate the drive end of theelectric machine102aand an inlet proximate thepump130. Thepump130 pumps heat transfer fluid throughports134 in thenon-drive end plate118ainto theexternal heat exchanger132. The fluid flows toward the drive end of theelectric machine102aover thestator108 and through the gap between thestator108 and therotor106 and through gaps between thestator108 and thehousing110a.In instances where the heat transfer fluid is cooler than thestator108 and/orrotor106, the fluid extracts heat from (i.e., cools) thestator108 and/orrotor106. In some instances, when the shaft-driven circulation pump is mounted on the drive end, the fluid at the drive end of theelectric machine102aflows into theheat exchanger132, is cooled as it is circulated through the helical coil and is returned to the non-drive end of theelectric machine102aover thestator108 and through the gap between thestator108 and therotor106 and through axial gaps between thestator108 and thehousing110a,and back to thepump130 to repeat circulation. In other instances, the fluid circulation gaps between thestator108 and thehousing110acan be omitted. In instances where theelectric machine system100ais subsea, seawater helps cool the heat transfer fluid circulated through the helical coil of theheat exchanger132. Although shown as cooling the heat transfer fluid from within thehousing110a,theexternal heat exchanger132 could additionally or alternatively receive and cool process fluids being acted upon by the companion device. Additionally, as described below the heat transfer fluid in thehousing110aand the process fluids can be one in the same. In certain instances, theheat exchanger132 could be used for cooling fluids from within thehousing110aand an additional external heat exchanger (not shown) can be provided about thehousing110ato receive and cool process fluids being acted upon by the companion device.
• Although thepump companion device104acan be a number of different types of pumps,FIG. 1B depicts a multistage centrifugal pump. Eightcentrifugal impellers140aare depicted arranged oncentral drive shaft142aof thepump companion device104a.In other instances fewer or more impellers can be provided. Thedrive shaft142ais shown coupled to thedrive stub117aofrotor106 by adrive coupling144. Althoughdrive coupling144 is shown as having two female ends that internally receive male ends of thedrive stub117aanddrive shaft142a,in other instances thedrive coupling144 can be a male coupling received into female receptacles provided in thedrive stub117aand thedrive shaft142a.In certain instances, the manner of coupling thedrive stub117aand thedrive shaft142acan include a combination of both male and female drive coupling configurations and/or other configurations. In certain instances, thedrive shaft142acould be integral with the rotor106 (i.e., constructed as unitary part with therotor106, having no coupling, gear box, screw thread or other mechanical connection). Thedrive shaft142ais supported onbearings122 carried in apump body146asecured to thecompanion machine housing148. As above, thebearings122 can be a number of different possible types of bearings, and the number and types of bearings can be different at different locations along thedrive shaft142a.Thebearings122 can include one or more of journal bearings (e.g., a tilt-pad journal bearing and/or other type), magnetic bearings, hybrid magnetic bearings, ball bearings and/or other types of bearing. One or more of thebearings122 is a thrust bearing (e.g., a tilt-pad thrust pad and/or other type). In certain instances, drive end of thedrive shaft142a(nearest drive coupling144) includes at least one axial or thrust bearing to axially retain thedrive shaft142arelative to thepump body146aand at least one radial bearing to provide radial support to thedrive shaft142arelative to thecompanion machine housing148, and the non-drive end of thedrive shaft142aincludes at least one radial bearing to provide radial support to thedrive shaft142arelative to thecompanion machine housing148. Aseal120 may be provided about thedrive shaft142ato seal or substantially seal against flow of fluids from thecentrifugal impellers140atowards theelectric machine102a.
• Thecompanion machine housing148 includes aninlet150 through which the process fluid being pumped is communicated to thecentrifugal impellers140a.Rotating thecentrifugal impellers140apumps the fluid towards anoutlet152 of thecompanion machine housing148. In other implementations, the fluid flow may be reversed such that thecentrifugal impellers140aare adapted to produce a fluid flow from theoutlet152 through themachine housing148 and out through theinlet150.
• In operation of theelectric machine system100a,three phase AC electric current is provided to thestator108 of theelectric machine102avia thepenetrators128. The electrical current energizes windings of thestator108, and causes therotor106 to rotate. Rotating therotor106 drives thedrive shaft142aof thepump companion device104aand pumps process fluid from theinlet150 to theoutlet152. Rotating therotor106 also drives thefluid circulation pump130 to pump fluid from non-drive end of theelectric machine102ainto theheat exchanger132, towards the drive end, over thestator108 and through the gap between thestator108 and therotor106, towards the non-drive end of theelectric machine102a.Fluid proximate the non-drive end of theelectric machine102aflows into theheat exchanger132 and is cooled as it passes through the helical coil of theheat exchanger132 to drive end of theelectric machine102a.Depending on the configuration of the shaft-driven fluid circulation pump, fluid can alternatively flow in the reverse direction (i.e., through theheat exchanger132 toward the non-drive end).
• FIG. 1C depicts an exampleelectric machine system100bwhere the companion device is acompressor104b.InFIG. 1C, the exampleelectric machine system100bincludes twocompressor companion devices104barranged on opposing ends of theelectric machine102b.In other instances, fewer or morecompressor companion devices104bcan be provided. In certain instances, two or morepump companion devices104acould be provided on the same side of theelectric machine102a.The exampleelectric machine system100bis configured for subsea operation, submerged in the open sea (i.e., outside of a well). In other words, the exampleelectric machine system100bis a subsea compressor system.
• In general, the configuration of theelectric machine system100bis similar to that of theelectric machine system100adiscussed above.FIG. 1C shows thesystem100bconfigured for a cartridge type installation/removal of theelectric machine102. To this end, all or a majority of theelectric machine102, including thestator108 and therotor106, is carried in anintermediate housing115 that is received by thehousing110b.Theintermediate housing115 carryingelectric machine102 components can be installed into or removed from themain housing110bas a unit or cartridge. The cartridge type installation/removal simplifies service or replacement of theelectric machine102, because theelectric machine102 need not be assembled/disassembled piece by piece into themain housing110b.Moreover, theelectric machine102 can be assembled into theintermediate housing115 and tested prior to installation into themain housing110b.
• Also notable, the interior of thehousing110bis in communication with the process fluids on which thecompressor companion devices104bare operating. Thus, the components of the electric machine are exposed to the process fluids during operation of theelectric machine system100b.The process fluids are under pressure, because they have been compressed by thecompressor companion devices104b.In certain instances, the process fluids are above the ambient pressure about the exterior of theelectric machine system100bby an amount substantially greater than the incidental pressure incurred in circulating the process fluids through theelectric machine system100b.In certain instances, communication is established by omitting a seal or providing an imperfect seal about thedrive shaft142bof thecompressor companion device104band/or providing other fluid communication paths from thecompressor companion device104b.Theend plates116b,118bmay be additionally provided withports154 to facilitate communication of process fluids into the gap between therotor106 andstator108. Theelectric machine102bmay also be provided without an integratedfluid circulation pump130.
• In certain instances, the fluids used in operation of the electric machine, including heat exchange fluids and other process fluids, can contain constituents that may be corrosive, reactive and/or otherwise harmful to one or more of the components of theelectric machine102b.As described in more detail below, therotor106 andstator108 may be fortified against exposure to the process fluids. In certain instances, as described in more detail below, therotor106 and/orstator108 may be sealed against exposure to the process fluids and/or coated with protective coatings.
• Although thecompressor companion device104bcan be a number of different types of compressors,FIG. 1C depicts multistage centrifugal compressors. Eightcentrifugal impellers140bare depicted arranged oncentral drive shaft142bof thecompressor companion device104b.In other instances fewer or more impellers can be provided. As above, thedrive shaft142bis shown coupled to the drive end ofrotor106 by adrive coupling144. In other instances, thedrive shaft142bcould be integral with the rotor106 (i.e., constructed as unitary part with therotor106, having no coupling, gear box, screw thread or other mechanical connection).
• FIG. 1C depicts anelectric machine system100bincorporatingmagnetic bearings122. In certain instances, one end of therotor106 may be supported by an axial and radialmagnetic bearing122 carried in theend plate118band the other end of therotor106 supported by a radialmagnetic bearing122 carried inend plate116b.Additional conventional bearings, for example cartridge ball bearings and/or another type, may be provided to provide secondary and/or contingency support therotor106. Thecompanion devices104bcan also be provided withmagnetic bearings122 carried in thecompressor body146b.
• In operation of theelectric machine system100b,three phase AC electric current is provided to thestator108 of theelectric machine102bvia the penetrators. The electric current energizes windings of thestator108, and causes therotor106 to rotate. Rotating therotor106 drives thedrive shaft142bof thecompressor companion devices104band compresses process fluid from theinlet150 to theoutlet152. A portion of the process fluids is communicated with the interior ofhousing110b,causing process fluid to circulate over thestator108 and through the gap between thestator108 and therotor106. An additional flow of fluid may be provided through theheat exchanger132 to be cooled as it passes through the helical coil of theheat exchanger132.
• FIG. 2A depicts a cross-sectional view of anexample rotor200 for use in an electric machine system, such as a motor and/or a generator.Rotor200 could be used asrotor106 described above. Additionally, implementations of therotor200 can be adapted for subsea operation and/or operation in corrosive environments. In certain instances, portions of therotor200 and rotor components can be coated or treated for corrosive resistance with Inconel, epoxy, polyetheretherketones (PEEK), ethylene chlorotrifluoroethylene copolymer and/or other treatments. Therotor200 can include rotor core having arotor hub202 androtor shaft206. Therotor hub202 is adapted to supportpermanent magnets204 positioned so as to magnetically interact with a stator provided in the electric machine system. Themagnets204 can be bonded or otherwise connected to therotor hub202. High energypermanent magnets204 can be used, for example neodymium-iron-boron based, or samarium-cobalt based magnets. In certain instances, thepermanent magnets204 are bonded to therotor hub202. Arotor shaft206 can be provided, forming a rotational axis of therotor200. Therotor shaft206 extends axially from both ends of therotor hub202. Therotor shaft206 may be constructed as a single piece or modularly from a plurality of shaft segments. In certain instances, therotor shaft206 can be hollow, including the rotor hub, to promote rotor cooling or to facilitate flow of fluid through the electric machine. Therotor200 can further include one ormore cooling passages217 through the interior thereof to communicate fluid through the interior of the rotor. InFIG. 2A, acentral passage217 through center of rotor, entering on circumferential surface of therotor hub202, is shown.
• Arotor sleeve212 can serve to enclose the outer surface of theentire rotor200 or portions of therotor200, such as therotor hub202 andmagnets204. Therotor sleeve212 can be manufactured from material that allows the sleeve to protect rotor components as well as provide structural support to rotor components, such as therotor hub202. In certain instances, therotor sleeve212 can be constructed from a fiber reinforced composite, such as a carbon fiber composite, aramid fiber composite (e.g., Kevlar a registered trademark of I.E. Dupont De Nemours), or fiber glass composite, a metal (e.g., Inconel, stainless steel, MP35N a registered trademark of SPS Technologies, Inc. and/or other metal), and/or other material. For instance, a sleeve covering212 can serve to provide radial support for therotor hub202 andmagnets204 positioned thereon, preventing loosening or detachment ofmagnets204 from therotor hub202 during operation of therotor200 at high rotational speeds.
• In certain instances, thesleeve212 can also serve to insulate therotor200 and rotor components from outside elements. For example, in rotors adapted for subsea and/or exposure to corrosive environments operation, thesleeve212 can be adapted to be air- or water-tight, in order to seal the rotor components. For example, the electric machine system in which therotor200 is disposed may contain heat transfer fluid, process fluids, and/or other fluids harmful to therotor200. Thesleeve212 may cover and isolate those portions of therotor200 sensitive to corrosion or otherwise adverse to contact with the fluid.
• In certain instances, therotor200 may incorporate rotor elements and techniques for mounting therotor sleeve212 to therotor200 so as to seal at least therotor hub202. As shown in the example ofFIG. 2B,rotor200 can include end rings214 positioned at one or both ends of therotor hub202 and mounted coaxially on therotor shaft206. In this example, theend ring214 is bonded or otherwise attached to therotor200 so that the inner surface of theend ring214 abuts the end of therotor hub202, extending radially so as to provide axial support tomagnets204 positioned on therotor hub202. The end rings214 are positioned at each end of therotor hub202. Theend ring214 can be of metallic material (e.g., Inconel, MP35N and/or other material). In certain instances, the material can be selected for its ferromagnetic properties as well, so as to enhance or avoid interference with the electromagnetic function of themagnetic rotor hub202. Additionally, certain instances of theend ring214 may be constructed so as to make the end ring corrosion-resistant, for example, through galvanization or anodization of the end ring material. In other instances, the end rings214 can be built into or integrated into therotor hub202 itself. For example, arotor hub202 may be provided with an inset for mounting the magnets, resulting in the end sections of the hub having a larger diameter than the inset.
• Aledge217 can be provided circumferentially on the outside diameter of theend ring214. Theledge217 serves as a landing platform for the positioning of anend treatment strip220 around the outside diameter of theend ring214, theend treatment strip220 forming a cylinder or a hoop. In certain instances, the outer diameter of the thinend treatment strip220 is equal or approximately equal to the diameter of therotor hub202, including themagnets204 mounted thereon. Theend treatment strip220 can be a composite material capable of bonding to thesleeve212. In certain instances, theend treatment strip220 andsleeve212 are constructed from similar materials, such as pre-impregnated carbon fiber or other material. Acircumferential groove221 can also be provided on theledge217 of theend ring214, in order to provide for a seal222 (e.g., an o-ring, gasket and/or other seal) to be positioned on theledge surface217. Theseal222 seals or substantially seals between theend ring214 and theend treatment strip220 wrapped around the end ring'sledge217. Of note, in certain instances, thecircumferential groove221 can be machined onto the end rings214 before and/or after the end rings214 are installed to the rotor200 (as discussed below).
• In one example, thesleeve212 can be sealed to therotor200 by sliding and/or threading the end rings214 onto theshaft206 so as to abut the ends of therotor hub202. In certain instances, a seal (e.g., o-ring, gasket and/or other seal) and/or sealant (e.g. thread sealant, sealant applied to the juncture between theshaft206 and end rings214, and/or other sealant) can be provided between theshaft206 and the end rings214. Theseal222 can be positioned in theend ring214 before or after positioning and connecting theend ring214 to theshaft206. In an instance where the end rings214 are threaded onto theshaft206, the respective threads of the end rings214 can be oriented so that the end rings214 are tightened to theshaft206 when therotor200 is rotated in normal operation. In some instances, the end rings214 can additionally be affixed to therotor hub202 with an adhesive.
• After rigidly connecting theend ring214 to the shaft206 (e.g., by threading, welding and/or otherwise), theend treatment strip220 is positioned on the outside diameter of theend ring214 on theledge217. Theend treatment strip220 may then be wound onto theledge217, to position thestrip220 on theend ring214, or may simply be slipped over theend ring214 into position on theledge217. With the end rings214, seals222, and end treatment strips220 in place, the construction of thesleeve212 can be completed. Winding or otherwise securely wrapping thesleeve212 onto therotor hub202 and on top of theend treatment strip220 can press theend treatment strip220 radially down onto theledge surface217, causing thestrip220 to shrink tightly onto theend ring214. This pressure, in turn, compresses theseal222 into thegroove221 to form a seal between thestrip220 and theend ring214. As thesleeve212 is wound onto therotor200 thesleeve212 is bonded to thestrip220. This bonding extends the seal between thestrip220 andend ring214 to thesleeve212, thereby sealing therotor hub202 covered bysleeve212. In certain instances, clamps may be employed to secure thestrip220 to theend ring214 while the sleeve is wrapped to therotor200 and bonded to thestrip220. Additionally, the bonding of thestrip220 to thesleeve212 can occur at an elevated temperature, to allow for a bond that will be less temperature sensitive.
• Alternative techniques can be employed to seal the sleeve to the rotor assembly. For example, in some implementations, the end treatment strips220, theseal222, and sealgrove221 may be omitted. In some instances, the sleeve may be securely wound onto therotor hub202 and the circumferential surfaces of the end rings214. Thesleeve212 may be fabricated from carbon fiber impregnated with thermoplastic material such as polyetheretherketone (PEEK). Thermoplastic material, such as PEEK, may also be applied to or pre-coated on the outer diameter of the end rings214 prior to having thesleeve212 wound on the hub assembly. Where grinding of the rotor assembly may be required, pre-coated end rings214 may be provided with sufficient material so that a coating formed from PEEK (or other material), for example, remains on the end rings214 following grinding and before thesleeve212 is wound over both the end rings214 and rotor hub assembly. With the sleeve in contact with the PEEK-coated end rings, heat or pressure may be applied to bond the sleeve to the end ring, forming a seal with the PEEK at each end of thesleeve212, thereby isolating the rotor hub, magnet segments, and other components covered by the sleeve from contact with potentially hazardous external fluids and/or other materials.
• After thesleeve212 is wrapped on therotor220 secondary end rings215 may be slid and/or threaded onto theshaft206 so as to abut the end rings214. The secondary end rings215 have a diameter substantially equal to thesleeve212 diameter, and serve to protect the outer surface of thesleeve212 and/or to provide a location for rotor balancing (either by material removal or addition). In certain instances, a seal (e.g., o-ring, gasket and/or other seal) and/or sealant (e.g. thread sealant, sealant applied to the juncture between theshaft206 and secondary end rings215, and/or other sealant) can be provided between theshaft206 and the secondary end rings215. Additionally, the juncture between the secondary end rings215 and the end rings214 can be filed with resin and/or adhesive (thus, adhering the secondary end rings215 to the end rings214 and filling). In an instance where the secondary end rings215 are threaded onto theshaft206, the respective threads of the secondary end rings215 can be oriented so that the secondary end rings215 are tightened to theshaft206 when therotor200 is rotated in normal operation. In certain instances, the outward facing edges of the secondary end rings215 can be rounded or the rings' outer surface may be conical (with the smaller diameter facing outward) to facilitate fluid flow over the secondary end rings215.
• Some implementations may employ additional measures to protect the ends of thesleeve212 in addition to or in lieu of the secondary end rings215. For example, tubular bands, constructed of material more resistant to wear and other damage than the composite sleeve212 (e.g., non-magnetic metal, ceramic, polymer and/or other material), may be positioned at each end of the rotor hub, concentrically atop thesleeve212. Consequently, the tubular bands may cover the ends of the sleeve, thereby protecting the ends of the sleeve from erosion, abrasion, or other damage that may occur during operation of therotor200. In another implementation, illustrated inFIGS. 2C and 2D, a tubular band may be replaced with a thin, non-magnetic, metal alloy tape223 (e.g., nickel alloy (e.g., Inconel), non-magnetic stainless steel, titanium and/or other metal) wrapped around the outer surface of therotor sleeve212 and bonded to end rings (not shown) positioned on therotor shaft206 to form asleeve229. In some instances the metal can be corrosion resistant. In some implementations, a insulating coating and/or surface treatment may be applied to thetape223 to inhibit currents from circulating between adjacent laps of thetape223. Some examples of coating and/or surface treatment include oxidation, anodization, phosphate/chromate/silicate coating (e.g., American Society for Testing and Materials (ASTM) A976 C-4 and/or C-5) and/or other coatings. In some implementations, thesleeve229 may extend axially beyond the edges of therotor sleeve212.
• In one implementation, a first end of a piece oftape223 may be bonded to an end ring adjacent to afirst sleeve end225. Thetape223 may be bonded to the end ring using a laser weld, resistance weld, TIG weld, chemical bond, or any bonding method. Thetape223 may be wound on top of the rotor sleeve with adequate tension so as to cover the sleeve ends and maintain positive pressure between thetape223 and therotor sleeve212 in all operating conditions of therotor200. The resulting tape winding223 may be laid in butt laps across the outer surface of the rotor sleeve, resulting in a smooth surface that minimizes the thickness of the tape wrapping223. Thinalloy tape wrappings223 may, among other advantages, minimize parasitic mass as well as parasitic currents appearing in the metallic tape as a result of the magnetic field of therotor200 or corresponding electric machine. Other implementations may employ other winding techniques as well as various tape material for reinforcing and protecting the rotor sleeve. Upon winding the tape across therotor hub202 to cover the second end of thesleeve227, the second end of the piece oftape223 may be bonded to the opposite end ring. In some instances, for example in a butt lap winding, excess tape may result at the edges of end rings. The excess tape may be trimmed flush with the end ring faces to complete the tape winding223.
• FIG. 2E is a detailed cut-away cross-sectional view of anexample sleeve212. Thesleeve212 can be manufactured or constructed of any material possessing the structural, resistive, and/or chemical properties desired for the particular rotor implementation, for example a fiber-reinforced composite. Thesleeve212 can serve a number of functions. For example, in subsea and/or corrosive environment rotor implementations, thesleeve212 can be constructed of composite material capable of providing structural support and corrosion protection for the rotor hub, as well as sealing the rotor hub from exposure to foreign elements. Heating of therotor200 can result in thermal expansion of one or more of the rotor elements or sleeve. Where heating is uneven across the rotor, some sections of the rotor and rotor sleeve can expand differentially relative to other sections. Differential thermal expansion can result in differential, and potentially damaging, stresses on thesleeve212. Stress can arise due to differential expansion of the sleeve itself or from differential expansion of the underlying rotor structure. Accordingly, the below described sleeve configurations can, among other benefits, more uniformly control and/or accommodate thermal expansion, both of the sleeve and the rotor itself.
• In some instances ofrotor sleeve212, a fiber-reinforced composite sleeve material, such as carbon fiber, can be employed. In certain instances, as illustrated in the example ofFIG. 2E, the sleeve may be multi-layered.FIG. 2E shows a multi-layer fiber-reinforced composite sleeve wrapping212. The top layer224 (or, in certain instances, layers) are cosmetic layers. These layers may possess functional characteristics as well. For example, to achieve strength and rigidity as well as control differential thermal expansion in one or multiple directions, the layers can have fibers oriented predominantly or all in the same direction (e.g. maximum strength in one direction) or different orientations (strength in multiple directions).
• In certain instances,intermediate layer226 can be a first, primarily axially-oriented carbon fiber composite layer layered beneath the cosmetic layer224 (i.e., nearer to the outer circumferential surface of rotor200). Thelayer226 can be made of pre-impregnated carbon fiber composite sheet capable of providing very strong axial support as well as provide corrosion and leakage protection.Layer228, positioned beneathlayer226, can be one or more carbon fiber composite layers with primarily circumferentially-oriented pre-impregnated carbon fiber tape. Layers with circumferentially-oriented carbon fiber, such aslayer228, do not provide substantial axial strength, instead providing circumferential strength. Additionally, circumferentially-oriented carbon fiber layers, while useful in controlling radial thermal expansion, are less effective at useful for limiting axial expansion.Layer230 is a bottom, primarily axially-oriented carbon fiber layer and in certain instances is made from pre-impregnated carbon fiber composite sheet. Axially-oriented layers, such aslayer230, can remedy the structural deficiencies of circumferentially-oriented carbon fiber layers, both in terms of structural and thermal expansion support. Accordingly, in some instances, intermediate226 andbottom layers230 can have substantially axial reinforced composite fibers, thelayer228 having substantially circumferential reinforced composite fibers.
• Layer230 can be wrapped so as to directly contact therotor200,rotor hub202,rotor hub magnets204, and/or end rings214, covering all or a portion of therotor200. In certain instances, additional layers can be provided betweenlayer230 and therotor200. Additional layers may also be provided betweenlayers224,226,228, and230. Indeed, certain instances may make use of repeated layering oflayers224,226,228,230 in similar or different orientations and orders. Although discussed above with respect to axially-oriented and circumferentially-oriented layers, the orientations of one or more of thelayers224,226,228,230 could be oriented in non-axial and/or non-circumferential directions. For example, one or more of thelayers224,226,228,230 could be oriented at 45 degrees, 30 degrees and/or another angle relative to the axial direction. Indeed, in some instances, fibers in a fiber-reinforced composite, need not be oriented in the same direction. Accordingly, in some instances, fiber-reinforced composites can be selected for the axial and circumferential support that have fibers primarily in one of the axial or circumferential direction. The layer, in such an instance, can have a greater density of fibers oriented on one orientation or dimension, than in another dimension.
• The material forming the layers of amulti-layered sleeve212 need not be uniform. In certain instances, the one or more layer materials may be selected so as to minimize stress on therotor hub202,magnets204, as well as the surroundingsleeve212 due to thermal expansion during operation. One technique for minimizing these stresses is to build thesleeve212 so that thesleeve212 expands axially with the interior rotor components at the rotor's200 operating temperature.
• Therotor200, rotor components, and sleeve layers expand according to the coefficient of thermal expansion (CTE) of materials used in the rotor and sleeve. Accordingly,rotor sleeve212 materials can be selected and/or engineered to have CTEs similar to the CTEs of the portion of therotor200 or rotor elements to be covered by therotor sleeve212. For example, in a fiber-reinforced composite rotor sleeve, the fiber and/or resin employed to form the rotor sleeve, can be selected so as to result in a composite sleeve material with a CTE equal or substantially equal to, complimenting, or otherwise matched to the CTE of therotor shaft206,rotor hub202, and/ormagnet204 material. Matching CTE can, among other benefits, allow thesleeve212 to expand with the expansion of the rotor components wrapped in thesleeve212.
• In some instances, in order to achieve a desired CTE in a sleeve layer or rotor component, material used in the sleeve or rotor component can be doped with other material having a higher or lower CTE so as to affect the net CTE of the resulting sleeve or rotor component. For instance, the resin of a carbon fiber sleeve layer could be doped so that the CTE of the carbon fiber sleeve layer matches the CTE of rotor components covered by the sleeve, for example neodymium-iron-boron based, or samarium-cobalt based magnets mounted on therotor hub202. Additionally, the density of fibers used in a fiber-reinforced sleeve can also be adjusted so as to engineer the net CTE of the sleeve or sleeve layer. In certain instances, one or more layers, including axially oriented, circumferentially oriented and/or other oriented layers, may be selected with varying CTEs so as to engineer a sleeve having a net CTE matched to the relevant portions of therotor200 to be covered by thesleeve212. In certain instances, non-CTE-matched sleeve layers can be provided in addition to CTE-matched sleeve layers in thesleeve212. For example, sleeve layers closest to therotor hub202 surface may be selected with CTE matched to the CTE of the rotor hub or rotor hub components, while outer sleeve layer material is selected based on other considerations, such as structural support, puncture resistance, or corrosion resistance.
• In some implementations, the CTE of therotor200 to be covered by thesleeve212, can vary across therotor200, depending, for example, on the rotor elements employed in and on therotor200. Rotors having differential CTE may result in differential thermal expansion in the rotor as well as the sleeve covering the rotor. Accordingly, in some implementations, rotor sleeves can be engineered to have differential CTE, for example by differential doping across the length of the sleeve, to correspond with varying CTEs in the rotor portions to be covered.
• FIGS. 2F and 2G illustrate another implementation of anexample rotor sleeve212.FIG. 2F shows a detailed cross-sectional view of amulti-layered rotor sleeve212.FIG. 2G is a detailed perspective view of the sleeve shown inFIG. 2F. A set ofouter layers232,234 can be provided in thesleeve212 together with a set ofsegmented layers236,238,239,240. Theouter layers232,234 can include one or more composite layers, including axially, circumferentially and/or otherwise oriented layers. Thesegmented layers236,238,239,240 are distinct, hoop-like layers. A segmented layer can expand and contract independent from other segmented layers. Where differential temperatures make differential expansion or contraction likely,segmented layers236,238,239,240 can expand and contract in these regions of differential temperature and propagate less of the associated forces from expansion or contraction to other segmented layers,outer layers232,234, or thesleeve212 generally.
• In certain instances, thesegmented layers236,238,239,240 can assume widths and positions in thesleeve212 coordinating with circumferential segmentation ofmagnets204a,204b,204c,204don therotor200. For example, as shown inFIG. 2F, in rotors having circumferentially segmentedmagnets204, thesegmented layers236,238,239,240 are positioned to align with the circumferential segmentation of one or more of themagnets204a,204b,204c,204dso that each segmented layer is aligned with one or more circumferential rows of magnets. This can allow for the expansion and contraction of eachsegmented layer236,238,239,240 to be influenced by the thermal expansion and contraction ofmagnet row204a,204b,204c,204dpositioned beneath it. While the example ofFIGS. 2F and 2G show segmented layers with axial widths corresponding to a single magnet row, segmented layers can correspond with and cover more than one row of magnet segments. Additionally,segmented layers236,238,239,240 can be fiber-reinforced composite hoops having primarily circumferentially-oriented fiber, so as to provide structural support to the magnet segments positioned beneath the hoop layer. In some instances, magnet segments may be subject to greater thermal expansion and structural vulnerabilities (e.g., during rotation of the rotor at high speed), requiring additional radial support to limit these liabilities.
• In an illustrative example, the temperature atmagnet204amay be higher than the temperature atmagnet204c.The temperature differential betweenmagnet rows204aand204ccan result inmagnet204aexperiencing thermal expansion larger than that experienced atmagnet row204c.Accordingly,segmented layer236 positioned in alignment withmagnet row204amay expand more thansegmented layer239 positioned in alignment withmagnet row204c.Gaps may exist between thesegmented layers236,238,239,240 so that the expansion of one segmented row does not interfere with another segmented layer. Additionally, expansion forces inlayers232,234, positioned above the segmented layer, resulting from differential thermal expansion corresponding with one or more hoop segments, may be focused at or near the corresponding hoop segment, including the gap between the affected hoop segments. For instance, in the above example, thermal expansion forces transmitted tolayers232,234 may be focused at the gap betweenadjacent hoop segments236 and238;238 and239; and239 and240.
• A segmented layer can also be accomplished using a unitary sleeve layer. For example, a sleeve layer can possess strength characteristics that vary across the length of the sleeve layer. Variation in sleeve layer strength can be aligned with elements, such as magnet segment rows, so that areas of highest strength are aligned with areas of the rotor requiring greatest reinforcement or more subject to differential thermal expansion. For example, multiple layers of varying physical characteristics could be grouped to form a sleeve with band-like strength sections, with gaps between the sections exhibiting strength or thermal expansion characteristics different than the sections themselves. One way this may be accomplished is by fabricating sleeves with varied coefficients of thermal expansion (CTE). Additionally, in certain instances, thesegmented layers236,238,239,240, or segmented hoops, aligned withmagnet segment rows204a,204b,204c,204d,may be constructed of material with CTEs matched to the CTE of themagnet204a,204b,204c,204dpositioned beneath it.
• WhileFIGS. 2A,2F, and2G show examples of arotor hub202 withmagnets204 axially segmented (with segment boundaries formed in the circumferential plane along the axial body of the rotor hub202), themagnets204 can also be implemented as single member magnets, extending axially across the length of thehub body202. Additionally, magnets can be segmented circumferentially (with segment boundaries formed in a radial-axial plane) as shown in2E. Segmenting the magnets, however, can be advantageous as certain magnets may be more affordable and easier to implement as segmented pieces. Additionally,segmented magnets204 can alter the electric and electromagnetic characteristics of the rotor and thereby be functionally desirable in some rotor applications.
• FIGS. 2H-2P are cross-sectional views ofexample rotor hubs202.Magnets204, of uniform or non-uniform strength, can be mounted directly to the outer surface of therotor hub202 and/or to therotor hub202 via intermediate materials, for example, to electrically insulate themagnets204 from therotor hub202, bond or improve bonding to therotor hub202, and/or other reasons. In certain instances, the intermediate material can include an adhesive (e.g., an acrylic adhesive and/or other adhesives), electrically insulating tape, a solder material, a reactive nanofilm, and/or another material. In certain instances an interstitial filler material is applied to therotor200 to fill spaces between themagnets204 and/or therotor hub202. An example material, includes stainless steel putty (e.g., stainless steel putty made by ITW Devcon) and/or other materials. In certain instances, therotor200, prior to installation of thesleeve212, can be dipped in or flooded with an epoxy resin to ensure all the gaps between themagnets204, therotor hub202, and/or the end rings214 are filled and further protect against fluid ingression.
• In certain instances interstitial filler material may be injected into the rotor hub assembly while providing a vacuum within the hub assembly. For example, oncemagnet segments204 have been mounted to therotor hub202, themagnets204 androtor hub202 may be enclosed in a disposable sleeve (e.g., a polymer bag and/or other sleeve), and the sleeve may be sealed at both ends of the rotor hub assembly. The vacuum is operable to remove the air and/or other gases (“gases”) within the sleeve, including gases residing in voids between themagnets204 and/or therotor hub202. A pre-catalyzed low-viscosity thermosetting resin may be introduced into the disposable sleeve to penetrate the empty spaces in the rotor hub assembly. Upon curing of the resin, the disposable sleeve may be removed. Thereafter, manufacture of the rotor may be resumed, including wrapping aprotective rotor sleeve212 around the rotor hub assembly.
• In some implementations, therotor sleeve212 itself may be used in lieu of the disposable sleeve of the previous example. Pluggable inlets may be provided on each of the end rings214, allowing a vacuum pump to be connected to one end of the hub assembly and a high pressure pump to be connected to the other end. The vacuum pump vacates air from the hub assembly, sealed by thesleeve212. With air removed from the inside of the hub assembly, the high pressure pump may inject the resin into voids in the hub assembly. The end ring inlets may be plugged and the resin cured to seal the hub assembly interior. Subsequent manufacturing operations may then be performed.
• To facilitate filling the voids within the rotor hub assembly using the described or other techniques, the hub and/or the magnet segments may be provided with flow path channels to guide filler material into voids between thehub202 and themagnet segments204.FIGS. 2Q-2R illustrate examples of such features. For instance,FIG. 2Q shows arotor hub assembly201 including arotor hub202 with a plurality ofmagnet segments204 mounted on thehub202. Themagnet segments204 are each formed to take a geometry that results inflow path channels258 being formed when themagnet segments204 are mounted to thehub202. Thesechannels258 may be aligned with those areas of thehub202 andmagnet segments204 where voids are likely to appear, such as areas betweenadjacent magnet segments204. In some instances, as shown inFIG. 2R,additional grooves260 may be provided on thehub202, in lieu of or in addition to the geometry of themagnet segments204, to provide theflow paths258.
• The end rings of the assembly may also be used to guide the flow of filler material. As shown inFIG. 2S, an interior face of anend ring214, to be set adjacent to the rotor hub, can be provided with anannular channel262 operable to direct filler material around the rotor hub assembly and into voids or other flow path channels positioned around the rotor hub. In some implementations, aninlet264 in communication with thechannel262 may be provided on theend ring214. Theinlet264 may be used to couple one or more vacuum pumps or injection pumps to theend ring214 to deliver and direct filler material into voids within the hub assembly.
• The magnets' dimensions and orientation on therotor hub202 may serve to form substantially a cylinder of magnet segments around thehub202. In some implementations, outer surfaces of the magnet segments may require grinding once the magnetic segments are mounted to thehub202. Grinding the outer surfaces of the magnetic segments may be used to form therotor hub202 into a substantially uniform cylindrical outer surface. Additionally, while the magnets, once coupled to the rotor, may form a uniform cylinder,individual magnet segments204a-tcan vary in magnetic field orientation and magnitude as well as weight in order to achieve the desired electromagnetic, rotational andinertial rotor hub202 profile.
• FIG. 2H illustrates a cross-sectional view of one example rotor hub magnet configuration. In this example, sixteen circumferentially segmentedmagnets204a-tare positioned around the circumference of therotor hub202. The geometry of theindividual magnet segments204a-tand the outer surface of therotor hub202 allow for themagnet segments204a-tto be mounted directly to arotor hub202. As shown inFIG. 2H, the outer surface of therotor hub202 in certain instances may not be perfectly round, for example, the portion of therotor hub202 wheremagnet segments204a-tare mounted may be a regular polygon with a number of equilateral sides equal to the number ofmagnet segments204a-tto be mounted on thehub202.FIG. 2H shows the outer surface of therotor hub202 having sixteen flat surfaces, running the axial length of therotor hub202, against which corresponding flat surfaces of the sixteenmagnet segments204a-tabut. The flat surfaces on therotor hub202 and themagnet segments204a-tare normal to a radial line emanating from the center of thehub202.
• Themagnet segments204a-tcan be arranged into a two pole configuration. For example, sevenmagnet segments204a-gwith magnetic fields directed substantially radially away from the center of therotor hub202 may serve as a base of a north pole of the rotor's magnetic configuration. Sevenother magnet segments204j-scan be positioned on the other side of therotor hub202, eachmagnet segment204j-shaving magnetic fields directed substantially radially toward the center of therotor hub202 serving as a base for a south pole of the rotor's magnetic configuration. Amagnet segment204 may be magnetized so that the magnetic field vector of the magnet segment is uniform. In other words, the magnetic field vector at any one point along a uniform magnetized magnet segment is parallel to the magnetic field vector at any other point along the magnet segment, as illustrated inFIG. 2T. In certain instances, the magnetic field vector at the center of the magnet segment is radial. As discussed in more detail below, in other instances, the magnetic field vectors can be normal to radial or arcuate having the same center as the rotor. Alternatively, as illustrated inFIG. 2U, amagnet segment204 with a true radially-directed magnetic field possesses a magnetic field with magnetic field direction vectors that are each radial. In instances where the outer surface the magnet segment is an arc in the round outer surface of a circular rotor, the magnetic field direction vectors can be normal to theouter surface268 of the magnet segment. In uniform magnetic segments, the magnetic field direction vectors can be configured to all be perpendicular to the mating flat surfaces of the magnet segment and rotor hub. In radial magnetic segments, the magnetic field direction vector at the center line of the magnetic segment can be configured to be perpendicular to the mating flat surfaces of the magnet segment and rotor hub.
• Returning toFIG. 2H, disposed between the two poles areinterpole magnet segments204h,204t.Interpole magnet segments204h,204tcan be provided to adjust the magnetic flux distribution of therotor200, transitioning the magnetic field between the two poles. In the implementation pictured inFIG. 2H theinterpole magnet segments204h,204tpossess geometries similar to theradial magnet segments204a-g,204j-s,the interpole magnet segments having magnetic fields directed normal to these radial fields, or tangent to circumference of therotor200.
• The arrangement of permanent magnet segments on therotor hub202 can result in a net magneticpole center vector270 for therotor200. In the example ofFIG. 2H, the magnetic pole center has a direction vector component centered onmagnet segment204d,the geometric center of the rotor's north pole. The rotor illustrated inFIG. 2H has a regular pole center. Thepole center270 of therotor200 illustrated inFIG. 2P is also regular. As illustrated inFIG. 2P, thepole center vector270 is aligned betweenmagnet segments204band204c,this interface representing the geometric center of the top pole inrotor200. Where themagnetic pole center270 is aligned with the geometric midpoint of the array of magnet segments establishing a north (or south) magnetic pole, the pole center is regular.FIG. 2K, on the other hand, illustrates an example of a rotor with anirregular pole center270. The geometric center ofrotor200 inFIG. 2K, is the arcuate midpoint ofmagnet segment204d.As illustrated,pole center270 inFIG. 2K is not aligned with the geometric center of the rotor. Depending on the design of the stator, and the objectives for the electric machine, it can be desirable to implement rotors with either a regular or irregular pole center vector.
• FIG. 2I illustrates a cross-sectional view of another rotor magnet configuration. The structural dimensions of the rotor magnet configuration ofFIG. 2I can be substantially similar to the structural dimensions of the rotor magnet configuration ofFIG. 2H. The configurations ofFIGS. 2H and 2I can have the same number of magnet segments, the magnet segments having substantially identical physical dimensions. However, whileFIG. 2H illustrates an example two-pole rotor design,FIG. 2I illustrates an example four-pole design. The first pole ofFIG. 2I includesmagnet segments204a,204b,204c,the second pole includesmagnet segments204e,204f,204g,the third pole withmagnet segments204j,204k,204m,and the fourth pole with204p,204q,204s.At least oneinterpole magnet segment204d,204h,204n,204tcan be provided for each pole in the configuration, theinterpole magnet segments204d,204h,204n,204tpositioned between two adjacent poles.Interpole magnet segments204d,204h,204n,204tcan have magnetic fields directed approximately normal to the radial fields of the remaining magnet segments. In certain instances, half of theinterpole magnet segments204h,204tcan have magnetic fields directed in the clockwise direction, the otherinterpole magnet segments204d,204ncan have fields directed in the counter-clockwise directions.
• WhileFIGS. 2H and 2I are each implemented with sixteen magnet segments per row (or sixteen hub facets and equivalently shaped magnet segments), other rotor designs employing permanent magnet segments may also be provided. For example, more or fewer than sixteen facets can be employed, including facets with varying geometries. For example, geometries can be employed, such as those described above in connection withFIGS. 2Q and 2R, providing flow path channels between adjacent magnet segments. In some instances the outer surface of the magnet segment can be flat, as opposed to round as inFIGS. 2H and 2I. The magnet segment's interface with the rotor hub can also affect its geometry (as in the case of a facet, as shown, for example, inFIGS. 2G-2R). Indeed, alternative configurations, numbers of facets, and geometries can be employed as substitutes for other rotor designs with comparable magnetic profiles. For example, a substitute for the two-pole rotor illustrated inFIG. 2H can be achieved using only four circumferential magnet segments mounted to therotor hub202, as illustrated inFIG. 2J. Twopole magnet segments204w,204ycan be employed for the north and south poles of the rotor, with two, additional interpole magnet segments204x,204zdisposed between themagnet segments204w,204y.Given that thepole segments204w,204yare the primary magnetic segments for therotor200, some implementations, including the example illustrated inFIG. 2J, may provide forpolar segments204w,204ywith longer arcuate spans than the transitional interpole magnet segments204x,204z.Additionally, the outer surfaces of the magnet segments, when mounted on therotor hub202, can form a cylindrical outer surface of therotor200, as also illustrated in the sixteen facet example ofFIG. 2H. While the four magnet segment rotor ofFIG. 2J has two poles, as inFIG. 2H, theFIG. 2J rotor may have a magnetic profile and performance characteristics distinct from those of the sixteen facet rotor ofFIG. 2H. Additionally, other configurations, employing the principles illustrated in the examples of theFIGS. 2H and 2J, are within the scope of the disclosure, allowing several facet-based design options tailored to the economics and performance considerations of the designer.
• FIG. 2K is a cross-sectional view of yet another example two-pole magnet configuration. The two-pole magnet configuration example ofFIG. 2K can employinterpole magnet segments204h,204tutilizing split-interpole construction. Eachinterpole magnet segment204h,204tcan be constructed of two separate magnet pieces254,256, bonded together to form a single magnet segment. Radial magnet segment piece254 can be a magnet with a radially-oriented magnetic field.Magnet segment piece254hbelonging tointerpole magnet segment204hcan have a radial magnetic field directed away from the center of therotor hub202.Magnet segment piece254tbelonging tointerpole magnet segment204tcan then have a radial magnetic field directed toward the center of therotor hub202. Normalmagnet segment pieces256h,256tcan be bonded to radialmagnet segment pieces254h,254tto form respectiveinterpole magnet segments204h,204t.Normal magnet piece256h,bonded toradial magnet piece254h,can have a magnetic field directed normal to the radial magnetic field ofpiece254h,and oriented in a counter-clockwise direction.Normal magnet piece256t,bonded toradial piece254t,can have a magnetic field normal to the radial direction, the field ofnormal piece256toriented in the clockwise direction. Magnet pieces254,256 can be constructed of the same or dissimilar magnetic materials. Magnet pieces254,256 can be equal sizes, or alternatively, one magnet piece can be larger than the other. Selecting the materials of the magnet pieces254,256 as well as the size of one piece relative the other can be done to engineer the magnetic characteristics of theinterpole magnet segment204h,204t,allowing rotor designers to refine the magnetic characteristics of theinterpole magnet segments204h,204tand thereby modify some magnetic flux characteristics of the rotor.
• As shown inFIG. 2L, split-interpole magnet segment designs similar to that described above with the example ofFIG. 2K can also be employed in magnet configurations with more than two poles. For example, split-interpole magnet segments204d,204h,204n,204tcan be employed in four-pole magnet configurations similar to, for example, the four-pole magnet configuration described inFIG. 2I.
• Rotor hub202 magnet configurations can employ more than one interpole magnet segment per pole. Therotor hub202 examples illustrated inFIGS. 2H-2I can form the base for building numerous, varied magnet configurations by mounting varied combinations ofmodular magnet segments204a-ton thehub202 with varying magnetic field orientations, magnetic material characteristics, and material densities. For example, the four-pole configuration example ofFIG. 2I can be modified by replacing radially-orientedmagnet segments204a,204c,204e,204g,204j,204m,204p,204swith non-radial magnet segments, as shown inFIG. 2M, so thatadjacent magnet segments204a-c,204e-g,204j-m,204p-spossess parallel-oriented magnetic fields. As shown inFIG. 2N, other implementations may alter the four-pole configuration ofFIG. 2I, exchanging the normal-oriented interpole magnet segments ofFIG. 2I withinterpole magnet segments204d,204h,204n,204tpossessing magnetic fields oriented with directional vectors approximating the vector sum of the two magnet segment pieces of the split-interpole magnet segments ofFIG. 2L.
• Yet another example illustrating the broad compatibility of therotor hub202 andmodular magnet segments204a-t,is shown inFIG. 2O. A two-pole magnetic configuration with uniform magnetization can be constructed withmagnet segments204a-tconstructed so that the magnetic field of each magnet segment is oriented parallel to and in the same direction as every other magnet segment's magnetic field when allmagnet segments204a-tare mounted on therotor hub202. Depending on the configuration of the cooperating stator in the electric machine, substantially uniform rotor magnetizations, such as the two pole design ofFIG. 2O, can provide more efficient electromagnetic power conversion
• In addition to the two pole, uniform magnetization design ofFIG. 2O, four pole uniform rotor designs are attainable using the facet-based approach described. For example, inFIG. 2P, a sixteen facet rotor is provided. In the example ofFIG. 2P, the first pole includesmagnet segments204a,204b,204c,and204d.The magnetic field direction vectors of each of the magnet segments in this first pole, when mounted to therotor hub202 are parallel to the magnetic field direction vectors of the others magnet segments in the pole. Such is also the case in the other three poles of the rotor example ofFIG. 2P. A second pole can includemagnet segments204j,204k,204l,and204m.The second pole magnet segments in this example, have magnetic field direction vectors parallel to the magnetic field direction vectors of the first pole, but oriented in the opposite direction to the first pole magnet segments' magnetic fields. Third and fourth poles are provided, each with magnetic field direction vectors orthogonal to the magnetic fields of poles one and two. The third pole can includemagnet segments204e,204f,204g,204h.A fourth pole can includemagnet segments204n,204p,204q,20r.The magnetic field direction vectors of the third and fourth poles are also parallel and opposite to one another.
• The examples illustrated inFIGS. 2H-2R and discussed above are not intended to limit the possible magnetic configurations contemplated for therotor hub202. Indeed, several additional implementations and magnet configurations can also be implemented to meet a wide array of magnetic and structural characteristics for particular rotor applications. The facet-based rotor concepts described above can be used to develop a versatile variety of potential rotor configurations. Indeed, where a common rotor hub geometry is employed by a rotor manufacturer, common magnet segment geometries can be employed across rotor designs, allowing the designer to build nearly limitless rotor variations by interchanging magnet segments having the appropriate magnetic field vectors. Additionally, whererotor hubs202 are employed allowing for magnet segments with equal arcuate span, fabrication of the magnet segments and the required magnet segment combinations can be simplified, in that only magnet segments of a single geometry need to be fabricated. Additionally, in designs employing magnet segments with the fewest different magnetic profiles, the number of different magnet segments that need to be manufactured and stocked can be further minimized, allowing rotor designers to provide a range of rotor products while minimizing supply chain and manufacturing costs, among other advantages.
• Referring now toFIG. 3A, an exampleelectric machine319 is shown. Theelectric machine319 is similar to and may be used as theelectric machine102ashown inFIG. 1B. Theelectric machine319 includes ahousing314 defining an interior308. Arotor306 is rotatable relative to thestator300 and disposed in theinterior308 thereof. There is agap310 between thestator300 androtor306. Theexample stator300 includes an electromagnetic winding302 mounted on acylindrical stator core304. Thestator300 is suitable for use asstator108 above. Some implementations of the winding302 can be configured for the electric machine to function as a synchronous, AC electric machine. Some implementations of the winding302 can include two-pole windings, forming a three phase electromagnet. Other implementations are possible as well, depending on the electric machine application, including four-pole windings, single-phase windings, and other winding configurations.
• The winding302 can be constructed by winding cable or formed conductors through stator core slots to form the winding loops or coils. Thestator core304 can be constructed of metallic, laminated plates, bonded together to form the core structure. The materials used instator core304 plates can be selected so as to adjust the electromagnetic flux characteristics of the winding302 wound around the core slots. The core material can be selected also by considering the material used in the cable of the winding, so as to achieve a desired electromagnetic stator profile. For example, copper-based, insulated cables can be used for the winding302. The cable can be wound around acore304 built of steel plates laminated together with a silicon-based, low-loss laminate. It is contemplated that the slots of thestator core304, as described in more detail below, can be implemented using a variety of slot shapes and sizes. The selection of the slot geometry can be based on the cable type (or types) used in the windings. Additionally, the winding302 can be constructed as form-wound or random-wound coils. In certain instances, thewindings302 result in winding end turns312 positioned on the axial ends of thestator core304. As set forth in more detail below, various end turn winding techniques can be used to provide for end turns312 with the particular structural and electromagnetic characteristics desired for a certain particular stator design.
• Some implementations of thestator300 can be adapted for subsea and/or corrosive environment operation. For example, certain instances of thestator300 can be sealed or otherwise protected from exposure to heat transfer fluids, process fluids, other corrosive or harmful matter and/or other foreign matter by providing aprotective barrier316 around thestator300 or otherwise sealing thestator300. For example, certain instances of the electric machine system may provide for a “flooded” system. Aprotective barrier316 can be provided to guard against corrosion of elements of thestator300 while allowing the fluid provided in the electric machine system to cool thestator300. Other implementations may provide a coating, or other seal on the stator, so as to seal thestator300 from exposure or corrosion. For example, some or all of the stator can be coated or treated for corrosive resistance with epoxy, polyetheretherketones, ethylene chlorotrifluoroethylene copolymer and/or other treatments. Some implementations ofstator300 can be provided with protective coverings that provide rigid structural support as well as protection.
• The stator, such as the stator shown inFIG. 3A, may be formed from a stator core andwindings302 extending through the stator core. Anexample stator core335 is shown inFIG. 3B. Thestator core335 is formed from a plurality of adjacent yokes303 (i.e., a stator stack) extending in alongitudinal direction305 bounded at opposing ends byend plates307. Further, a plurality of stator bars309 extend in thelongitudinal direction305 and are operable to axially, radially and circumferentially align theyokes303. A plurality ofteeth301 are retained within slots or channels formed by theyokes303, which is discussed in more detail below. See, e.g.,FIG. 3G
• FIG. 3C illustrates astator stack325 formed from a pair ofadjacent yokes303. Thestator stack325, shown without stator teeth and electromagnetic windings, is discussed in more detail below. According to some implementations, astator300 may include a stack of eightyokes303. Other implementations, though, may include additional orfewer yokes303. One or more of theyokes303 may be segmented. That is, one or more of theyokes303 may be formed from a plurality of arc-shapedsegments315. In some implementations, all of theyokes303 are segmented.
• As shown, theyoke303 is formed from foursegments315 and, thus, theyoke303 is divided into quadrants. However, in other instances, theyoke303 may be formed from more orfewer segments315. Anexample segment315 is shown inFIG. 3D in which thesegment315 is formed from a plurality oflaminations311. The illustratedexample segment315 is formed from tenlaminations311, although other implementations may be formed from additional orfewer laminations311. In some implementations, thelaminations311 may be formed from steel, such as low-loss silicon steel. In other implementations, thelaminations311 may be formed from different types of steel or other types of metals, alloys, composites, or other types of suitable materials.Laminations311 may be bonded together chemically or mechanically. For example, thelaminations311 may be bonded together with an adhesive. Alternately, thelaminations311 may be mechanically coupled by interlocking thelaminations311 with each other. In some instances, a portion of onelamination311 may protrude into anadjacent lamination311. Further, in some implementations, somelaminations311 may interlock withadjacent laminations311 whileother laminations311 do not interlock withother laminations311.
• Eachsegment315 includes a plurality of radially inward extendingprotrusions317. Theprotrusions317 define a plurality offirst notches320 formed along aninterior periphery318 of thesegment315. As shown in the illustrated example, eachsegment315 includes sixprotrusions317, although, in other instances, eachsegment315 may include more orfewer protrusions317 defining more or fewerfirst notches320. As shown inFIG. 3C, thefirst notches320 align to form at least a portion oftooth channels321 that accept a tooth301 (described in more detail below). Eachsegment315 also includes a plurality ofsecond notches322 formed on anouter perimeter324 of thesegment315. As illustrated inFIG. 3C, thesecond notches322 align to form at least a portion of achannel326 into which astator bar309 is retained, as illustrated inFIG. 3B. Thestator bar309 retained in thechannel326 provides alignment and structural support to the assembledstator300.
• Anexample stator bar309 is illustrated inFIG. 3E. The illustratedstator bar309 is a slender member having a constant rectangular cross-section. As also illustrated inFIG. 3C, thechannels326 also have a constant rectangular cross-section to accept and retain the stator bars309. However, thestator bar309 shown inFIG. 3E and thechannel326 shown inFIG. 3C are merely examples, and the stator bars309 andchannels326 may have other cross-sectional shapes.
• Referring again toFIG. 3C, theyoke303 is assembled such thatjoints313 formed at adjacent ends of thesegments315 are offset from each other so thatjoints313 inadjacent yokes303 do not align. In other implementations, though,adjacent joints313 may align. As shown, the angular offset (θ) ofjoints313 inadjacent yokes303 is 45°, although other angular offsets may be used. In certain instances, theyokes303 may be welded together, bonded together with an adhesive, assembled with fasteners, interlockingly coupled, and/or assembled in another manner. Still further, the assembledstator300 and/or thestator core335 may be coated with polyetheretherketone (“PEEK”), ethylene chlorotrifluoroethylene copolymer (“ECTFE”), oxide coating and/or another material.
• FIG. 3F shows anexample end plate307 of thestator300. Theend plates307 are disposed at opposing ends of the of the assembledstator core335. In certain instances, theend plate307 may be single, continuous plate. Theend plate307 also includes a plurality protrusions331 formed in aninterior periphery332 of theend plate307. Theprotrusions331 formfirst notches330 therebetween. Theend plate307 also includes a plurality ofsecond notches334 formed in anouter periphery336 of theend plate307. When combined with the stator stack andteeth301,protrusions331 overlay theteeth301 that are retained in thetooth channels321. Thefirst notches330 align with channels formed between theteeth301, i.e., windingchannels350, described below. Thesecond notches334 align with thesecond notches322 to form thechannels326. In certain instances, as shown inFIG. 3G, thetooth channels321 may have the shape of a dovetail-type joint such that theteeth301 and associatedtooth channels321 interlock so that theteeth301 are locking retained therein. However, thechannels321 may form any shape that retains theteeth301. Further, thetooth channels321 may have a high aspect ratio in certain instances, while, in other instances, thetooth channels321 may have lower aspect ratios, i.e., thetooth channels321 may be shallower and wider.
• Eachtooth301 may be formed from a plurality oftooth segments338, an example of which is shown inFIG. 3H. According to the illustrated example, thetooth segment338 has a tapered cross-section. Afirst end340 of thetooth segment338 has a dimension D1 that is larger than a dimension D2 of asecond end342 of thetooth segment338. An end of the assembledtooth301 corresponding to the first ends340 of thetooth segments338 are retained in thetooth channels321.
• In some implementations, thetooth segments338 may be formed from a plurality oflaminations339. As shown, theexample tooth segment338 is formed from ten laminations. In other instances, thetooth segments338 may be formed from additional or fewer laminations. Theteeth301 may be formed fromtooth segments338 having the same or approximately the same length. In other implementations, theteeth301 may be formed fromtooth segments338 having different lengths. In some instances, thetooth segments338 may have different lengths by having more orfewer laminations339 thanother tooth segments338.Laminations339 may be chemically or mechanically bonded. For example, some of thelaminations339 may be bonded together with an adhesive. In other instances, some of thelaminations339 may be interlockingly coupled. For example, a protrusion formed in onelamination339 may be received into a receptacle formed in anadjacent lamination339.
• In some implementations, one or more of theteeth301 may be formed fromtooth segments338 having different lengths. For example,FIG. 3K shows a schematic view of atooth301 extending through thechannel321. Thetooth301 is formed fromtooth segments338aand338bhaving different lengths. In the implementation shown, thetooth segment338ahas a length half of the length oftooth segment338b.Further, the length of theyokes303 may be the same as the length oftooth segment338b.As shown, thetooth301 leads with atooth segment338aabutting theend plate307. Thetooth segment338aoccupies half the length of the portion of thechannel321 extending through thefirst yoke303. Atooth segment338bis placed adjacent thetooth segment338a,causing thetooth segment338bto overlap theadjacent yoke303. That is, a first half of thetooth segment338blies in oneyoke303 while the second half of thetooth segment338bextends into the neighboringyoke303. Overlapping of thetooth segments338bin theadjacent yokes303 provides rigidity and enhances mechanical strength of thestator300. Although thetooth segments338bare described as overlapping by theadjacent yokes303 by half, thetooth segments338bcould overlap theadjacent yokes303 by different amounts. For example, in some implementations, thetooth segments338 may overlapadjacent yokes303 in the following percentages: 60%-40%, 65%-35%, 70%-30%, or 80%-20%. However, it is within the disclosure to use any desired amount of overlap. Still further, thetooth segments338bmay be of a length to extend partly into afirst yoke303, extend completely through one or moreadjacent yokes303, and partially extend into anadditional yoke303.
• Referring toFIG. 3I, eachtooth segment338 may include aprotrusion344 onfirst face346 and areceptacle348 on asecond face347. Theprotrusion344 on onetooth segment338 is accepted into thereceptacle348 on anadjacent tooth segment338 to provide for at least one of alignment or attachment of adjacent tooth laminations.FIG. 3J shows another configuration of theprotrusions344 andreceptacles348 formed ontooth segments338.
• According to some implementations, theteeth301 may be formed from a material different from one or more of theyokes303. Particularly, theteeth301 may include a material that has a higher magnetic flux capacity than the material forming theyokes303. In certain instances, thetooth segments338 are formed, at least in part, from a cobalt-iron alloy. For example, one or more of thelaminations339 forming thetooth segment338 may be formed from cobalt-iron alloy, whileother laminations339 may be formed from a different material. Example cobalt-iron alloys include Hiperco, a product of Carpenter Technology Corporation, Silectron, a product of Arnold Magnetic Technologies Corporation, and/or other alloys. Still further, thetooth segments338 need not all be formed from the same material. That is, in some implementations, some of thetooth segments338 may be formed from one material andother tooth segments338 formed of different materials. In certain instances, since high magnetic flux material is typically more expensive than other materials, some portion of the tooth segments338 (e.g., one ormore segments338 or one ormore laminations339 of one or more segments338) may be formed of a high magnetic saturation flux capacity material and the remainder formed of a less expensive material. In certain instances, the less expensive material may be used to form one or more of thelaminations311. The different materials oftooth segments338 orlaminations339 therein may be alternated in a regular or irregular pattern over the length of thestator300. For example, every second, third, fourth or other specifiedtooth segments338 may be formed from the higher magnetic saturation flux density material while theinterstitial tooth segments338 may be formed from less expensive, lower saturation flux density material. The resultingtooth301 has a higher composite magnetic saturation flux capacity than the less expensive material alone, but cost less than atooth301 made entirely of the higher magnetic flux capacity material. In some implementations, the high magnetic saturation flux material may be distributed through thestator300 so that the ends of thestator300 have a relatively low magnetic saturation flux density. In other instances, the ends of thestator300 may have the lowest magnetic saturation flux density.
• In another example, the types of materials of the tooth segments338 (including the materials of thelaminations339 of the tooth segments338) at different locations along thetooth301 can be selected to achieve a desired temperature distribution across the length of thestator300 and/or to compensate for variations in heat extraction and/or generation along the length of thestator300. In certain instances, the materials of thetooth segments338 can be configured to achieve a uniform temperature distribution or a more uniform temperature distribution across the length of thestator300 than achieved withtooth segments338 of uniform material type. For example, a higher density (number per unit length) of higher magnetic fluxmaterial tooth segments338 can be provided in areas of thestator300 with less cooling heat transfer. By increasing the magnetic flux capacity in these areas, less heat is generated and the lesser cooling can be at least partially offset. Similarly, in areas with greater cooling heat transfer, a lower density of higher magnetic fluxmaterial tooth segments338 can be provided. In certain instances, for example, where the heat transfer fluid is introduced through the ends of the rotor andstator300, thetooth segments338 or portions thereof near the axial center of atooth301 can have a higher density of higher magnetic flux density material thantooth segments338 near the ends of thetooth301 to offset the lower heat transfer at the axial center of thestator300.
• Referring again toFIG. 3G, thelaminated teeth301 are inserted intorespective tooth channels321, as explained above. The assembledstator300 includeschannels350 that are formed betweenadjacent teeth301. Cable and/or formed conductors may be fed through or placed into these windingchannels350 to form windings of thestator300.
• As described, the assembled stator300 (shown inFIG. 3B) provides a stator core that can achieve a higher flux density than if the teeth and yoke portions were made from the same material. Further, such a construction results in a cost savings by using more expensive materials in only certain places, such as in the tooth region, where enhanced magnetic flux density is needed and not in less critical areas, such as the yoke. Further, construction of theyoke303 from the plurality ofsegments315 provides for less waste in manufacturing. Particularly, when producing thelaminations311,339 to form thesegments315 ortooth segments338, respectively, from sheet material, thelaminations311 and339 may be arranged more densely on the sheet, leaving less waste. Additionally, thetooth segments338 andyoke segments315 can be mass produced to further reduce manufacturing costs.
• A stator of an electric machine, such as thestator300 described above, may be assembled in an number of different manners. In certain instances, thestator core335 may be assembled by joining the fouryoke segments315 to form ayoke303 and joining the appropriate number ofteeth segments338 to the yoke303) and then joining the resulting assemblies to one another, along with theend plates307, to form thestator core335. In certain instances, thestator core335 may be assembled by forming complete teeth301 (i.e., by joining theteeth segments338 together to form complete teeth301) and a complete stator stack (i.e., by joining together the plurality of yokes303) and then assembling the completedteeth301 to the completed stator stack and adding theend plates307 to form thestator core335. In certain instances, thestator core335 may be assembled in another fashion. Thewindings302 may be wound to thestator core335 in a number of different manners. In certain instances, thewindings302 may be wound to the completed teeth301 (e.g., theteeth301 held in position relative to one another with a fixture) prior to assembly into the stator stack. In certain instances, thewindings302 may be wound to the completedstator core335, i.e., after the stator stack andteeth301 are assembled together. The assembly of thewindings302 andteeth301 and/or the entire assembledstator300 may be vacuum-pressure impregnated with a coating material and baked, for example, to achieve desired mechanical and electrical properties. In certain instances, locking plates may be attached to the ends of the stator stack to secure theteeth301 to the stator stack.
• As mentioned above, construction of thestator300 permits the use of different materials between the teeth and the yoke. Such a construction allows optimization of flux density and reduction in losses and related construction costs. This assembly process has the further benefits of using winding techniques not otherwise achievable. Further, windings formed in this way may have attached thereto cooling devices. Such a combination would not otherwise be possible with traditional winding techniques.
• FIGS. 3L-3Q illustrate implementations of theprotective barrier316 formed around a stator, such as thestator300 or108 of an electric machine, such as theelectric machine102. Theprotective barrier316 forms astator cavity353 in which thestator300 resides. Thestator cavity353 may or may not be filled with a fluid.FIG. 3L shows a cross-sectional view of an example electric machine, which may be similar to theelectric machine102. The electric machine includes ahousing314, thestator300, therotor306, and theprotective barrier316. Theprotective barrier316 may also prevent intrusion of fluid passing through theelectric machine102 into thestator cavity353. Theprotective barrier316 has a cylindrical shape, aclosed end354 at an inner radius, and anopen end356 at an outer radius. Theclosed end354 is formed by acylinder358, and theopen end356 is defined byside flanges360. Theside flanges360 abut and/or are attached to thehousing314. As explained above, theprotective barrier316 provides protection for thestator300, for example, in flooded applications in which theelectric machine102 has fluid (represented by arrows362) passing therethrough between therotor306 and thestator300. Accordingly, theprotective barrier316 provides protection against exposure of the electric machine and its components to the fluid (e.g., sea water, cooling fluids, process fluids) or other foreign matter passing through the electric machine.
• Additionally, theprotective barrier316 protects the electric machine by preventing contact between thestator300 and therotor306. Further, theprotective barrier316 may be formed of a material resistant to corrosion and/or abrasion, such as abrasion and/or corrosion that may be caused by the fluid (including any particulates and/or contaminants contained therein) passing through theelectric machine102 between thestator300 and therotor306. Theprotective barrier316 may also be constructed to withstand pressure changes between the fluid passing through the electric machine and any fluid contained in thestator cavity353. Theprotective barrier316 may also be constructed to accommodate thermal expansion and contraction of thehousing314 and thestator300.
• FIG. 3M shows a partial cross-sectional view of an example electric machine. As shown, thecylinder358 of theprotective barrier316 includes afirst portion364 and an abutting second portion orring366. In certain instances, thecylinder358 can be a common commercially available pre-formed tubing. According to some implementations, afirst edge368 of thefirst portion364 of thecylinder358 may include an outwardly flaredportion370 and atapered portion372. The taperedportion372 extends from the outwardly flaredportion370. The taperedportion372 is accepted into atapered channel374 formed in one of theside flanges360. The taperedportion372 and the taperedchannel374 may be fit together to provide a seal. For example, the taperedportion372 and the taperedchannel374 may be fit together with an interference fit. In certain instances, the seal prevents the passage of fluid. Further, the taperedchannel374 includes at least oneopening376 extending from an inner portion of the tapered channel to the atmosphere or to thestator cavity353, for example. The at least oneopening376 allows air to escape from the channel during assembly of the taperedportion372 into the taperedchannel374, thereby providing a secured attachment.
• Afirst edge378 of thering366 may also be tapered and, similarly, may be accepted into another taperedchannel374 formed in a second of theside flanges360. Thefirst edge378 of thering366 and the taperedchannel374 may also be fitted together with an interference fit to provide a seal against intrusion of fluid. Also, as described above, the taperedchannel374 may include one ormore openings376, described above, to provide escape of air from the tapered channel374 (i.e., pressure equalization) during assembly of thefirst edge378 and the taperedchannel374.
• Second edges382 and384 of thefirst portion364 andring366, respectively, overlap to form a tapered joint386. Particularly, in some implementations, adjacent surfaces of thesecond edges382,384 of thefirst portion364 and thering366, respectively, overlap and abut against each other to form the tapered joint386. The tapered joint forms a seal to prevent passage of fluid. In certain instances, thesecond edge382 of thefirst portion364 may flare outwardly. The tapered joint386 allows dimensional variations of theprotective barrier354 while still maintaining a seal to prevent intrusion of fluid into thestator cavity353. For example, during operation of theelectric machine102, components of theelectric machine102 may experience expansion and/or contraction, such as due to rotational speeds and/or temperature changes and the tapered joint386 may remain engaged. In certain instances, the tapered joint386 may form a water-tight seal. Further, a contact pressure between thefirst portion364 and thering366 at the tapered joint386 may increase with expansion of thehousing314. Alternately, the tapered joint386 may be configured such that the pressure of the tapered joint386 may increase with contraction of thehousing314.
• According to some implementations, either or both of thefirst portions364 orring366 of the cylinder358 (i.e., the portion proximate the permanent magnets of the rotor), may be formed from a fiber and polymer composite material. In certain instances, thecylinder358 may be formed from a carbon or glass fiber composite material provided in a thermoplastic or thermosetting matrix. Such materials provide high strength, corrosion resistance, and abrasion resistance and are not magnetically permeable. In certain instances, theside flanges360 may be formed from a metal.
• FIG. 3N shows another implementation of theprotective barrier354 without a tapered joint. In such an implementation, thecylinder358 includes opposing taperededges388 are accepted into flaredchannels374. The taperededges388 and the taperedchannels374 may also form an interference fit to create a seal. In certain instances, the seal may be a water-tight seal to prevent intrusion of fluid. Also, as explained above, the taperedchannels374 may include one ormore openings376 to provide pressure equalization during assembly. Further, thecylinder358 may be formed from a composite material, as described above, and the fibers of the composite may be oriented and/or the matrix material selected such that the coefficient of thermal expansion of thecylinder358 matches the coefficient of thermal expansion of thehousing314, thereby eliminating the need for a tapered joint. In certain instances, thecylinder358 can be a common commercially available pre-formed tubing.
• The implementation shown inFIG. 3O shows aprotective barrier354 formed from a composite material having a coefficient of thermal expansion that matches that of thehousing314. In this implementation, thecylinder358 has an integratedside flange392 and atapered edge388. As explained above, thetapered edge388 may be fitted into the taperedchannel374 to provide an interference fit. Pressure may be equalized in the taperedchannel374 and the atmosphere via one ormore openings376 formed in theside flange360 from the taperedchannel374 and thestator cavity353. Theintegrated side flange392 may be secured directly to thehousing314 by aring394 that may also function to protect anouter edge396 of theintegrated side flange392. In certain instances, thering394 may be formed from metal.
• FIGS. 3P and 3Q show additional alternate implementations of theprotective barrier354. Theprotective barriers354 illustrated in these implementations may also be formed from a composite material designed to have a coefficient of thermal expansion that matches that of thehousing314. As shown inFIG. 3P, thecylinder358 of theprotective barrier354 may include alip398 that includes anouter surface391 that abuts aninner surface393 of theside flange360. Aring395 may be used to clamp thecylinder358 in place such that thelip398 is sandwiched between thering395 and theside flange360. In some implementations, thering395 and theside flange360 may be formed from metal, and, in still other implementations, thering395 andside flange360 may be formed from the same type of metal. One or more fasteners may be used to secure thering395,cylinder358, andside flange360 together. Alternately or in combination, an adhesive may be used.
• FIG. 3Q shows another implementation in which aninner surface381 of thecylinder358 atouter edges397 abut anouter surface383 of theside flanges360. Aring385 may be used to secure thecylinder358 to theside flanges360 at theouter edge397. In some implementations, fasteners and/or an adhesive may be used to secure thering385,cylinder358, andside flanges360 together. In addition to these methods or alternatively, the ring may have a slightly larger outer diameter than an inner diameter of thecylinder358. Thus, thering395 andcylinder358 may be held in place relative to theside flange360 by friction caused by an interference fit. Also, thering385 and theside flanges360 may be formed from a metal, and, in still other instances, thering385 and theside flanges360 may be formed from the same type of metal.
• FIG. 4A is a partial schematic end view of anexample core400 of a stator for an electric machine. Theexample core400 is suitable for use in thestator108 ofelectric machine102. Thecore400 defines a substantially cylindrical inner volume to receive a rotor of an electric machine. Thecore400 includes teeth402 extending radially from ayoke422 of the core to an outer circumference of the inner volume of the core. The teeth defineslots404 to receive conductive windings. For example, neighboringteeth402aand402bdefineslot404a,and neighboringteeth402band402cdefineslot404b.Eachtooth404 has a tip420. As shown, for example inFIGS. 4A,4B, and4C, a stator can have slots between each pair of teeth, where each slot has a slot region with parallel slot sides and each tooth has a tooth section with parallel tooth sides.
• Each tooth402 has a radial length extending from theyoke422 to the tip420 of the tooth. For example,tooth402ahas a radial length extending from theyoke422 to tip420a,andtooth402bhas a radial length extending from theyoke422 to tip420b.In the illustrated example, all of the teeth402 have the same radial length. In some implementations, some of the teeth402 have unequal radial lengths. Eachslot404 has a radial depth extending from theyoke422 to the inner volume. The radial depth of aslot404 can be defined by theyoke422 and the sides of the teeth402 that define theslot404. For example, the radial depth of theslot404ais defined by theyoke422 and the sides of theteeth402aand402b,and the radial depth of theslot404bis defined by theyoke422 and the sides of theteeth402band402c.
• Each tooth402 has a width along the radial length of the tooth402. For example, the width of a tooth at a given point is related to the azimuthal angle spanned by the tooth at the given point. A tooth402 may have a first radial section where the tooth width is constant or substantially constant along the radial length of the tooth402. As such, a tooth can have parallel tooth sides in at least a section of the tooth. A tooth402 may have a second radial section where the tooth width varies along the radial length of the tooth402. As such, a tooth can also have non-parallel sides in at least a section of the tooth. The tooth width may vary linearly and/or non-linearly along the radial length of the tooth in the second radial section. The radial length and the width of a tooth can determine an area of the tooth. For example, the area of a tooth may be calculated as an integral of the tooth width over the radial length of the tooth.
• Eachslot404 has a width along the radial depth of theslot404. For example, the width of a slot at a given point is related to the azimuthal angle at the given point between the two teeth402 that define theslot404. Aslot404 may have a first radial section where the slot width is uniform or substantially uniform along the radial depth of theslot404. As such, a slot can have parallel slot sides in at least a region of the slot. Aslot404 may have a second radial section where the slot width varies along the radial depth of theslot404. As such, a slot can also have non-parallel sides in at least a region of the slot. The slot width may vary linearly and/or non-linearly along the radial depth of the slot in the second radial section. The radial depth and the width of a slot can determine an area of the slot. For example, the area of a slot may be calculated as an integral of the slot width over the radial depth of the slot.
• The geometry (e.g., length, depth, width, area) of the teeth402 and theslots404 can influence performance and efficiency aspects of the stator (and hence, of the electric machine). The geometry of aslot404 can influence the position, distribution, and/or cross-sectional area of the conductive coils that can be installed in the slot. A ratio of slot area to tooth area of thecore400 may influence a maximum power, a power factor, and/or an efficiency achievable with thecore400. Teeth with a first radial section where the tooth width varies along the radial length of the tooth and a second radial section where the tooth width is uniform along the radial length of the tooth may define slots with a first radial section where the slot width varies or is uniform along the radial depth and a second radial section where the slot width varies. Slots with a first radial section where the slot width varies along the radial depth and a second radial section where the slot width is uniform along the radial depth can improve the performance and/or efficiency of the electric machine. A core having this type of slot may balance a utilization of a stator core material (e.g., iron or another material) and a conductive winding material (e.g., copper, or another material). For example, slots with a first radial section where the slot width varies along the radial depth and a second radial section where the slot width is uniform along the radial depth can allow a larger cross-sectional area of conductive material in a portion of the slot, and can prevent excess iron in various portions of the tooth (e.g., the “root” of the tooth near the yoke422). Slots having this configuration may accommodate both cable windings (e.g., in the first section) and formed windings (e.g., in the second section). In some cases, excess core material at a tooth root includes magnetically under-utilized material. In some cases, increasing flux density at the tooth tip420 limits the flux loading of the electric machine and allows excessive flux leakage path across theslot404, which may degrade machine performance.
• In theexample core400 ofFIG. 4A, all of the teeth402 andslots404 are identical. Theradial section406bof thetooth402bhas a width that varies along the radial length of thetooth402b,and theradial section410bof thetooth402bhas a uniform width along the radial length of thetooth402b.Theradial section408bof theslot404bhas a uniform width along the radial depth of theslot404b,and theradial section412bof theslot404bhas a width that varies along the radial length of theslot404b.The cross-section of eachslot404 has two rounded corners at theyoke422. The rounded corners can accommodate coils having a round cross-section, such as the cable winding coils shown inFIG. 4B. Each tooth402 inFIG. 4A has a broad tip420 that may enhance the flux and/or other properties of thecore400.
• FIG. 4B is a partial schematic end view of theexample core400 ofFIG. 4A.FIG. 4B illustrates example conducting coils installed in theslot404b.The illustrated coils are the coils of cable windings.Coils414a,414b,414c,and414dreside in thesection408bof theslot404b.Coils414e,414f,414g,414h,414i,414j,414k,and414lreside in thesection412bof theslot404b.
• FIG. 4C is a partial schematic end view of an example core of a stator for an electric machine. Theexample core400 can be the core of thestator108 ofelectric machine102. In theexample core400 ofFIG. 4C, all of the teeth402 andslots404 are identical. Theradial section406bof thetooth402bhas a width that varies along the radial length of thetooth402b,and theradial section410bof thetooth402bhas a uniform width along the radial length of thetooth402b.Theradial section408bof theslot404bhas a uniform width along the radial depth of theslot404b,and theradial section412bof theslot404bhas a width that varies along the radial length of theslot404b.The cross-section of eachslot404 has two substantially square corners at theyoke422. The substantially square corners can accommodate coils having a cross section with square corners, such as the formed winding coils416 shown inFIG. 4C.
• FIG. 4C illustrates example conducting coils installed in theslot404b.Some of the illustrated coils are the coils of formed windings, and some of the illustrated coils are the coils of cable windings. Formed windingcoils416aand416breside in thesection408bof theslot404b.Cable winding coils414 reside in thesection412bof theslot404b.Each tooth402 inFIG. 4C has a narrowed tip420 that may enhance the flux and/or other properties of thecore400.
• FIG. 4D is a partial schematic end view of anexample core400.FIG. 4D illustrates example angular parameters where each tooth includes two sections having non-parallel sides. A first section of each tooth has non-parallel sides at a first angle, and second section of each tooth has non-parallel sides at a second angle. The first angle and the second angle are different. In the example shown, the first angle is 1.9 degrees, and the second angle is 0.7 degrees larger than the first angel (i.e., 2.6 degrees). Other angles and/or angle differences may be used.
• FIG. 4E is a partial schematic end view of an example core of a stator for an electric machine. Theexample core400 can be the core of thestator108 ofelectric machine102. In theexample core400 ofFIG. 4E, all of the teeth402 andslots404 are identical. Theradial section406bof thetooth402bhas a uniform width along the radial length of thetooth402b,and theradial section410bof thetooth402bhas a width that varies along the radial length of thetooth402b.Theradial section408bof theslot404bhas a width that varies along the radial depth of theslot404b,and theradial section412bof theslot404bhas a uniform width along the radial length of theslot404b.The cross-section of eachslot404 has two substantially rounded corners at theyoke422. The substantially rounded corners can accommodate coils having a round cross section, such as the rounded coils of cable windings.
• InFIG. 4E, some of the illustrated coils are the coils of formed windings, and some of the illustrated coils are the coils of cable windings.Cable winding coils414 reside in thesection408bof theslot404b.Formed windingcoils416cand416dreside in thesection412bof theslot404b.Each tooth402 inFIG. 4E has a narrowed tip420 that may enhance the flux and/or other properties of thecore400.
• FIG. 4F is a schematic end view of example end turns of astator450 for an electric machine. Theexample stator450 can be used for thestator108 ofelectric machine102. Only the end turns452 of thestator450 and a portion of thecore454 of thestator450 are illustrated inFIG. 4F. Thestator450 includes other parts that are not illustrated inFIG. 4F.
• Thestator450 includes formed windings. The coils of the formed windings include axial sections (not illustrated inFIG. 4F) that extend the axial length of the stator core. The coils of the formed windings include multiple end turns452 that form an end turn bundle beyond the axial end of the stator core. The end turn bundle includes two groups of end turns452 that form four interleaved radial layers464 of end turns452. Each group forms two of the four layers464. One layer in each group is radially between the two layers of the other group.
• Thestator450 includes a core454 that defines aninner bore451, which is a substantially cylindrical inner volume to receive a rotor of an electric machine. As shown inFIG. 4G, thecore454 hasmultiple teeth456 extending radially inward, toward thebore451; theteeth456 defineslots458 to receive conductive windings (e.g., formed windings, cable windings, or another type). The coils of the windings include axial sections (not shown inFIG. 4G) that span an axial length of the core. Each axial section may extend between the two axial ends of the core. The coils of the windings include end turns452 extending beyond the axial end of the core. Each end turn452 connects two axial sections of a coil. The axial sections of one or more coils may reside in each slot. Each end turn452 has a first end connecting to a first axial section and a second end connecting to a second axial section. As shown inFIG. 4G, the first end of each end turn connects at a first circumferential location, and the second end of each end turn connects at a second circumferential location. In the implementation shown inFIG. 4G, the first end connects at a first radial distance from the radial center of the core, and the second end connects at a second radial distance from the radial center of the core. In some implementations, both ends of an end turn connect to axial sections of a coil at the same radial distance from the center of the core.
• An end turn bundle, as illustrated inFIG. 4F, can include multiple groups of end turns452. Each group of end turns452 can form layers464 at different radii around the radial center of thecore454. A single end turn452 primarily resides in two layers formed by one of the groups. For example, anend turn452ahas a first portion in alayer464a,and theend turn452ahas a second portion in adifferent layer464c.As another example, anend turn452bhas a first portion in alayer464b,and theend turn452bhas a second portion in adifferent layer464d.Thelayers464aand464care formed by a first group of end turns452 radially positioned as theend turn452a.Each end turn452 in the first group is offset circumferentially from the other members of the first group. Thelayers464band464dare formed by a second group of end turns452 radially positioned asend turn452b.Each end turn452 in the second group is offset circumferentially from the other members of the second group. Layer464ais radially inside oflayer464b;layer464bis radially inside oflayer464c;layer464cis radially inside oflayer464d.Thus, the first group of end turns (radially configured as end turn452a) and the second group of end turns (radially configured asend turn452b) are interleaved to form four layers of end turns.
• Each end turn452 passes through a planar cross-section parallel to the end of thecore454. Each end turn452 of the first group of end turns forms two layers of end turns, passing through the planar cross-section at a first radius and a third radius. The first radius is less than the third radius. Each end turn452 of the second group of end turns forms two different layers, passing through the planar cross-section at a second radius and a fourth radius. The second radius is less than the fourth radius. The first group of end turns and the second group of end turns are interleaved, such that the second layer is between the first layer and the third layer (i.e., the first radius is less than the second radius, and the second radius is less than the third radius) and the third layer is between the second layer and the fourth layer (i.e., the second radius is less than the third radius, and the third radius is less than the fourth radius).
• Each end turn452 extends between the two ends of the end turn to form a partial loop extending from thecore454. In some implementations, when two groups of end turns are interleaved, each end turn in one group passes through the partial loop formed by one or more of the end turns in the other group. For example, theend turn452apasses through the partial loop formed by theend turn452b.
• In some cases, an end turn bundle including two groups of end turns that form four interleaved radial layers of end turns can form an end turn bundle that is longitudinally shorter than other configurations. For example, if the two groups of end turns were not interleaved, and instead the two groups formed fewer than four layers of end turns, the end turn bundle may be almost twice as long as the four-layer bundle. A longer end turn bundle consumes more axial space in the electric machine, and may cause the rotor bearing journals to be positioned farther apart. A shorter end turn bundle consumes less axial space in the electric machine, and may allow the rotor bearing journals to be positioned closer together. When the rotor bearing journals are axially closer together, the bearing journals may suffer less stress and damage and/or provide better stability for the rotor. Thus, an end turn bundle that includes two interleaved groups of end turns may consume less axial space in the electric machine, may allow less axial distance between rotor bearing journals, and/or may reduce wear and/or damage to parts of the electric machine. In some cases, an end turn bundle that includes two interleaved groups of end turns may consume approximately half of the axial space that the end turn bundle would consume in other configurations.
• FIG. 4H is a partial schematic side view of theexample stator450.FIG. 4I is a partial schematic side view of a portion of thecore454 and example end turns452a,452bof astator450.FIG. 4J is a schematic cross-sectional view from near the axial center of theexample stator450 toward the axial end of theexample stator450.FIG. 4K is a partial schematic view of end turns452aand452bof astator450.
• FIG. 4L is a schematic of anexample end turn460 and anexample end turn4200. Theexample end turn460 can be included in thestator108 ofelectric machine102. Theexample end turn460 can be included in a lap winding configuration that includes two interleaved sets of end turns that form an end turn bundle having four radial layers. Theexample end turn4200 is designed for a traditional lap winding configuration that does not include interleaved sets of end turns. In their respective configurations in stators of substantially equal radial dimension, the example end turns460 and4200 can span the same azimuthal angle.FIG. 4L includes example dimensions of the end turns460 and4200. In some cases, an end turn has different dimensions.
• FIG. 4M is a schematic perspective view of example end turns460 and a portion of astator core462. The radial dimension of the stator is mapped to a linear dimension inFIG. 4M for purposes of illustration. The end turns460 represent the end turns452 in a rectilinear coordinate system. Thecore462 represents the core454 in a rectilinear coordinate system. The end turns460 include two groups of end turns that form four interleaved radial layers of end turns represented in a rectilinear coordinate system. A first group of end turns, that includesend turn460a,includes multiple end turns at the same radial position as end turn460aand circumferentially offset fromend turn460a.A second group of end turns, that includesend turn460b,includes multiple end turns at the same radial position asend turn460band circumferentially offset fromend turn460b.
• FIG. 4N is a schematic perspective view of the portion of theexample stator core462 and the example end turns460aand460brepresented in a rectilinear coordinate system. As illustrated inFIG. 4N, the ends of the end turns460 and thecore462 define gaps466 in the slots of the stator core. Each slot includes two gaps. One gap is between the ends of two different end turns. A gap466ais formed in a first slot at a first radius between the stator core and the end of an end turn residing in the first slot; a gap466bis formed in a second slot at a second radius between the ends of two end turns residing in the second slot; a gap466cis formed in the first slot at a third radius between the ends of two end turns residing in the first slot; and agap466dis formed in the second slot at a fourth radius beyond the end of an end turn residing in the second slot. In some cases, coolant fluid (e.g., air, nitrogen, or another gas) can flow through the gaps466 in the slots to cool the conductive windings. For example, the gaps466 can extend axially between the axial ends of the stator and provide a coolant flow path along all or part of the axial length of the stator. Coolant fluid can flow between the axial sections of the conductive windings in the stator core (e.g., in gaps466band466c). Coolant fluid can flow between an axial section of the conductive windings and the stator core (e.g., in gap466a). Coolant fluid can flow between an axial section of the conductive windings and the rotor (e.g., ingap466d). The coolant can flow from a mid-stack inlet to a volume surrounding the end turns to cool the end turns and the axial sections of the windings. The coolant can flow to a mid-stack outlet from a volume surrounding the end turns to cool the end turns and the axial sections of the windings. Coolant can additionally or alternatively flow in an gap between the rotor and the stator.
• In some cases, the slots have alternating depths. For example, some of the slots in thecore462 may have a shallow slot depth, eliminating or reducing the volume of the gap466a.This may enhance magnetic flux properties of the stator.
• FIG. 4O is a schematic perspective view of example end turns represented in a rectilinear coordinate system. Only two end turns460aand460bare shown inFIG. 4O for clarity of illustration.
• An end turn bundle that includes two groups of end turns interleaved to form four layers of end turns can include formed windings, cable windings, or a combination thereof.FIGS. 4F,4G,4H,4I,4J,4K,4L,4M,4N, and4O illustrate aspects of an example of a formed end turn bundle that includes two groups of formed end turns interleaved to form four layers of formed end turns. Each of the illustrated end turns ofFIGS. 4F,4G,4H,4I,4J,4K,4L,4M,4N, and4O can be built using standard end turn-forming equipment. However, some un-illustrated implementations may require non-standard end-turn-forming processes.FIGS. 4P, and4Q illustrate an example of a cable end turn bundle that includes two groups of cable end turns interleaved to form four layers of cable end turns.
• FIG. 4P is a schematic side view of an exampleend turn bundle470 of a stator of an electric machine. The exampleend turn bundle470 can be included in thestator108 ofelectric machine102.FIG. 4Q is a schematic perspective view of the exampleend turn bundle470. FIG.4EE is a schematic end view of the exampleend turn bundle470. FIG.4FF is a schematic end view of two end turns of the exampleend turn bundle470. FIG.4GG is a schematic end view of four end turns of the exampleend turn bundle470. FIG.4HH is a schematic side view of two end turns of the exampleend turn bundle470. FIG.4II is a schematic cross-sectional view of theend turn bundle470, viewed from near the axial center of an example stator toward the axial end of the example stator.
• The illustrated exampleend turn bundle470 includes cable windings. The coils of the cable windings include axial sections (not illustrated inFIGS. 4P,4Q,4EE,4FF,4GG,4HH, and4II) that extend the axial length of a stator core. The coils of the cable windings include a plurality of end turns that form theend turn bundle470 beyond the axial end the stator core. Theend turn bundle470 includes two groups of end turns that form four interleaved radial layers of end turns. The first group of end turns includes end turns4001a,4001c,and4001e.The second group of end turns includes end turns4001band4001d.Each group forms two of the four layers. The first group forms a first (outermost) layer of end turns and a third layer of end turns. The second group forms a fourth (innermost) layer of end turns and a second layer of end turns. One layer in each group is radially between the two layers of the other group. In particular, the second layer is radially between the first and third layers, and the third layer is radially between the second and fourth layers.
• As shown in FIGS.4FF,4GG, and4II, the two groups of end turns in the exampleend turn bundle470 form only two radial layers at an axial section of the end turn bundle closest to the stator. In particular, all of the end turns in theend turn bundle470 exit the end face of the core at a first radius on the end face and reenter the core at a second radius on the end face. The first group of end turns (including4001a,4001c,and4001e) exit the core through the end face of the core at an exit location on the first radius, turn toward the first radial layer, extend through the first radial layer, turn toward the third radial layer, extend through the third radial layer, and reenter the core through the end face at a reentry location on the second radius. In the example shown, before reentering the core, the first group end turns each curve radially inward from the third layer toward the second radius.
• The second group of end turns (including4001band4001d) exit the core through the end face at an exit location on the first radius, turn toward the second radial layer, extend through the second radial layer, turn toward the fourth radial layer, extend through the fourth radial layer, and reenter the core through the end face at a reentry location on the second radius. In the example shown, each end turn in the second group accommodates a neighboring coil in the first group. For example, as shown in FIG.4GG, theend turn4001dexits the end face on the first radius, turns radially outward, extends through the second layer of end turns, turn radially inward, extends through the fourth layer of end turns, turn radially inward to accommodate theend turn4001e,and then turns radially outward to reenter the end face on the second radius.
• FIGS. 4R and 4S show partial schematic end views ofexample cores400 of a stator for an electric machine. Theexample cores400 can be the core of thestator108 ofelectric machine102. Theexample cores400 includeslots404 having different shapes according to some implementations of the electric machine. Although theslots404 are shown as including an even number ofcoils414, an odd number ofcoils414 may be used. In some implementations, the shape of theslots404 may carry a winding that includes coils in a lap winding configuration and coil in a concentric winding configuration, although the slots shapes may be used in other types of windings.
• As shown inFIG. 4R, eachslot404 includes afirst slot region421 holdingcoils414 and asecond slot region419 holding coils414. Thefirst slot region421 is defined by two non-parallel opposingslot side portions415cand415d.Thesecond slot region419 is defined by two parallel opposingslot side portions415aand415b.Theslot side portions415aand415cform part of one side of the slot. Theslot side portions415band415dform part of another side of the slot. Theslot side portions415aand415cdefine a first angle at417a,and theslot side portions415band415ddefine a second angle at417b.The first angle and the second angle are different angles, as shown inFIG. 4R. For example, the first angle at417ais an obtuse angle less than 180 degrees, and the second angle at417bis 180 degrees. Other angles may also be used.
• FIG. 4T shows a partial schematic end view of anexample core400 of a stator for an electric machine in which theslots404 include an odd number ofcoils414. In the example shown, thecoils414 includecoils414A,414B, and414C. Although thecoils414A and414B are shown as including an even number of coils, thecoils414A and414B may include an odd number of coils. Further, thecoils414A may be a left-hand coil side of lap coils, and thecoils414B may be a right-hand coil side of lap windings. Thecoils414C are the coils of concentric windings. Thus, by including thecoils414C in eachslot404, the number oftotal coils414 contained in eachslot404 is made an odd number. By having an odd number of coils in each slot, the voltage of the associated electric machine may be changed at smaller incremental levels, providing better control of the electric machine output.
• FIG. 4U shows anothercore400 in which thecoils414 may be different sizes to provide better nesting or packing of thecoils414 within theslots404. Thecoils414A and thecoils414B may be of one size wire or cable, while thecoils414C may be at a different size, such as a smaller size. The different size coils provide for a more closelypacked slot404. Additionally, any of thecoils414A,414B, or414C may be produced by a single turn winding process but multiple cables may be wound in parallel. Further, a generally triangular ortrapezoidal cross-section wedge1000 may be included in one or more of theslots404 to maintain thecoils414A and/or414B in a packed state. Over time and operation of the electric machine, the coils may relax in the slots, which may have an adverse effect on machine performance. For example, if the coils become loose inside the slot, the coils may sag and/or shift in the slot. As a result, the coils may be subject to damage due to vibration and/or chafing. Accordingly, thewedges1000 are included in the slot to maintain thecoils414A and/or414B in a packed condition. According to some implementations, thewedges1000 may apply a biasing force on the coils to maintain the coils in a packed state. For example, thewedge1000 may have a longitudinal curvature, as shown inFIG. 4V In some implementations, thewedge1000 becomes stressed when thewedge1000 is inserted in a slot, and the stress results in the biasing force exerted on the coils in the slot. The biasing force applied by thewedge1000 may hold the coils in a substantially fixed position, which may eliminate or reduce slack and/or sagging in the coils. For example, thewedge1000 in the slot may hold the coils in place and prevent damage that could be caused by loose, sagging, and/or shifted coils.
• InFIG. 4V, theexample wedge1000 is illustrated as having a C-cross-section. Thewedge1000 may be positioned in theslots404 as shown inFIGS. 4U and 4Z with the open portion of the C-cross-section facing the radial center of thecore400. Alternately, thewedge1000 may be inserted into theslots404 so that the open portion of C-cross section faces away from the radial center of thecore400. The wedges may have other shapes.Planar strips1002 may also be used.
• In some implementations, for example when thewedge1000 is positioned as shown inFIGS. 4U and 4Z with the open end of thewedge1000 facing the center of thecore400, the cooling properties of the machine may be enhanced. Friction between the rotor and fluid surrounding the rotor (e.g., fluid in the machine gap between the rotor and the stator) can generate heat. To prevent overheating, cooling fluid (e.g. air or another type of fluid) may be directed through the machine gap between the rotor and the stator. Thewedge1000 can be configured to effectively increase the volume of the machine gap, as illustrated inFIGS. 4U and 4Z. For example, thewedge1000 open to the center of thecore400 and theplanar strip1002 effectively lead to an increase in the volume of the machine gap. The increased volume in the machine gap may reduce demands on the machine's cooling system. For example, the increased volume may reduce the pressure drop along the machine gap, which may thus reduce the demands placed on the blower or pump that generates the flow of cooling fluid through the machine gap.
• FIGS.4AA-4DD show other example configurations ofcoils414 andwedges1000 in astator400 of an electric machine. FIG.4AA shows astator400 that includes a first plurality ofcoils414A in a lap winding configuration and a second plurality ofcoils414B in concentric winding configuration. (Thecoils414A in a lap winding configuration are unshaded in FIGS.4AA-4DD, and thecoils414B in a concentric winding configuration are shaded in FIGS.4AA-4DD.) Theslots404 of FIG.4AA each have the same shape and carry the same number of conductors. In FIG.4AA, each slot carries aconcentric coil414B having one turn, and each slot carries awedge1000. Theconcentric coils414B shown in FIG.4AA can be wired in a “1-1-1” concentric coil configuration of a two pole, three phase electric machine. The “1-1-1” concentric coil configuration is discussed further with respect toFIG. 4W.
• FIG.4BB shows astator400 that includes a first plurality ofcoils414A in a lap winding configuration and a second plurality ofcoils414B in a concentric winding configuration. Thestator400 of FIG.4BB includes slots having different shapes. For example, theslots404C and404D have the same shape and each carry ten conductors, but theslot404E has a different shape than theslots404C and404D and carries nine conductors. In FIG.4BB,slots404C and404D each carry aconcentric coil414B having two turns, whileslot404E carries aconcentric coil414B having one turn. Also in FIG.4BB, each of the slots includes awedge1000. Theconcentric coils414B shown in FIG.4AA can be wired in a “2-2-1” concentric coil configuration of a two pole, three phase electric machine.
• FIG.4CC shows astator400 that includes a first plurality ofcoils414A in a lap winding configuration and a second plurality ofcoils414B in a concentric winding configuration. Thestator400 of FIG.4CC includes slots having different shapes. For example, theslots404C and404E have the same shape and each carry nine conductors, but theslot404D has a different shape than theslots404C and404E and carries ten conductors. In FIG.4CC,slots404C and404E each carry aconcentric coil414B having one turn, whileslot404D carries aconcentric coil414B having two turns. Also in FIG.4CC, each of the slots includes awedge1000. Theconcentric coils414B shown in FIG.4CC can be wired in a “2-1-2/1-2-1” concentric coil configuration of a two pole, three phase electric machine.
• FIG.4DD shows astator400 that includes a first plurality ofcoils414A in a lap winding configuration and a second plurality ofcoils414B in a concentric winding configuration. Thestator400 of FIG.4DD includes slots that all have the same shape, but do not all carry the same number of conductors. For example, theslots404C and404D each carry ten conductors, but theslot404E carries nine conductors. In FIG.4DD,slots404C and404D each carry aconcentric coil414B having two turns, whileslot404E carries aconcentric coil414B having one turn. Also in FIG.4DD, each of the slots includes either afirst wedge1000A or asecond wedge1000B. Thefirst wedge1000A in theslots414C and414D is smaller to leave more space for the conductors in theslots414C and414D. Thesecond wedge1000B in the slot414E is larger and leaves less space for the conductors in the slot414E. Theconcentric coils414B shown in FIG.4DD can be wired in a “2-2-1” concentric coil configuration of a two pole, three phase electric machine.
• FIG.4JJ is a schematic cross-sectional view of anexample core400 for an electric machine. Thecore400 defines multiple slots, and each slot carriesconductive coils414 and a wedge. Two different types of wedges are shown in FIG.4JJ. A first type ofwedge1004 has a C-shaped cross-sectional profile. FIG.4MM shows a perspective view of theexample wedge1004. A second type ofwedge1006 has an E-shaped cross-sectional profile. FIG.4LL shows a perspective view of theexample wedge1006. Both of thewedges1004 and1006 defineholes1008 that allow fluid to flow radially from a first region of the slot to a second region of the slot. For example, in the slots that carry a C-shapedwedge1004, thewedge1004 defines afirst region1005 in the slot, and thecoils414 reside in a second region in the slot. Thefirst region1005 allows an axial flow of cooling fluid through the slot. Theholes1008 defined in thewedge1004 allow fluid to flow from thefirst region1005 to the second region in order to cool thecoils414. Theholes1008 also allow fluid to flow from the second region into thefirst region1005, for example, after the fluid has contacted thecoils414. As another example, in the slots that carry anE-shaped wedge1006, thewedge1006 defines afirst region1009 in the slot, and thecoils414 reside in a second region in the slot. Thefirst region1009 allows axial flow of cooling fluid through the slot. Theholes1007 defined in thewedge1006 allow fluid to flow from thefirst region1009 to the second region in order to cool thecoils414. Theholes1007 also allow fluid to flow from the second region into thefirst region1005, for example, after the fluid has contacted thecoils414.
• Each wedge may define multiple holes along the axial length of the wedge, as shown in FIGS.4LL and4MM. The holes may be spaced at regular intervals, random intervals, or in another manner. Asingle wedge1006 or1004 may define holes of different sizes, shapes, or dimensions in order to control fluid flow to thecoils414. For example, larger holes may be defined in some locations on awedge1006 in order to promote a greater flow rate through the larger holes, and smaller holes may be defined in other locations on thewedge1006 in order to limit a flow rate through the smaller holes. The size, shape, spacing, and other parameters of the holes in a wedge may be configured to improve cooling in a stator of an electrical machine and thereby improve efficiency of the electrical machine. Thus, in some cases, a wedge can be used as a flow control device within the stator. In FIGS.4LL and4MM, a single hole is defined at each of multiple locations along the axial length of the wedge. In some implementations, there may be multiple holes defined at each location along the axial length.
• Thewedges1004 and1006 may have a longitudinal curvature, as thewedge1000 shown inFIG. 4V As a result of the longitudinal curvature, thewedges1004 and1006 may exert a biasing force on thecoils414 that helps stabilize thecoils414 within a slot. For example, the biasing force exerted by a wedge may prevent sagging of thecoils414.
• As seen in FIG.4PP the wedges can be formed in two or more parts, such as afirst part1028 and asecond part1032, longitudinally separated by a shim or stack ofshims1030. When installed in the slot, thefirst part1028 would reside adjacent the open end of the slot and thesecond part1032 would reside adjacent the coils. Different thicknesses of the shim orshim stack1030 can be selected to control the force exerted by thesecond part1032 on the coils. For example, the first andsecond parts1028,1032 can be installed into a given slot, and one ormore shims1032, of the same and/or different thickness, added to increase the force exerted by thesecond part1032 on the coils. In certain instances, different slots of the same electric machine may require different shims to achieve the same force exerted on the coils. The shim orshim stack1030 can be installed after one or more of thefirst part1028 orsecond part1032 is installed in the slot to facilitate achieving the desired force without damaging the insulation or coating of the coils. Alternately, the shim orshim stack1030 can be installed substantially simultaneously with installing the first andsecond parts1028,1032. Theshims1032 thus allow for an adjustable tight fit between the wedge, the coils and the slot without damaging the cables during wedge insertion. Although shown as solid, the first and/orsecond parts1028,1032 can each have a C-shaped cross-section or other cross-section providing an axial channel for fluid flow and holes for radial flow, as described above.
• FIG.4KK is a schematic cross-sectional view of anexample core400 for an electric machine. Thecore400 in FIG.4KK defines multiple slots, and each slot carriescoils414 and awedge1010. The C-shapedwedges1010 each define holes1012 that allow fluid to flow radially between regions of the slot.
• FIG.4NN is an is a schematic end view of anexample core400 havingwedges1014 similar to any of the configurations described above, and/or of another configuration, retained using retaining rings1016. The wedge retaining rings1016 encircle the central opening in thestator core400 and are fixed (e.g., by bolt, screw and/or otherwise) to the end face of thecore400. Retaining rings1016 can be provided at both ends of thestator core400 to capture thewedges1014 and prevent thewedges1014 from moving axially along thestator core400. The retaining rings1016 have slots that receive and interlock withprotrusions1020 at the ends of eachwedge1014, preventing thewedges1014 from moving radially. The retainingring1016 also press thewedges1014 against the top of the stator slot. In instances, such as FIG.4PP, where the wedges are formed in multiple parts and/or include one or more shims, the retainingring1016 can also retain the multiple wedge parts and shims. FIG.4OO is a perspective view of an example C-shapedwedge1014 better illustrating theprotrusion1020 and also havingholes1026. The C-shaped defines anaxial passage1024 through thewedge1014. As seen in FIG.4NN, the retaining rings1016 can haveapertures1022 that align with theaxial passage1024 to allow flow of fluids through the retaining rings1016.
• FIG.4QQ shows anslot liner1034 for lining the interior of a stator slot in astator core400 of an electric machine. Theslot liner1034 is made of a flexible, tear and temperature resistant film, such as polyester, polyamide and/or other material. FIG.4QQ shows theliner1034 laid flat. When installed in a slot, as in FIG.4RR, theliner1034 extends from the slot at both ends ofstator core400, and can be folded onto the end faces of thestator core400. The protruding ends ofliner1034 are clamped to the end faces of thestator core400 with a retaining ring (as in FIG. NN) and/or with other clamps to retain theliner1034 in position. FIG.4RR shows single bar clamps1036a,retained to the end face with fasteners1038 (e.g., bold, screw and/or other fastener), that clamp a portion of two adjacent liners to the end of thestator core400. FIG.4SS showsU-shaped clamps1036b,likewise retained to the end face withfasteners1038. The clamps can be retained to thestator core400 in other manners. Theslot liners1038 are installed prior to winding the coils into the slots to protect cables and the insulation on the cables during winding. In certain instances, theliners1034 can be removed from the slots. In certain instances, theliners1034 can remain in the slots while the remainder of the electric machine is assembled, and remain in the slots during operation of the electric machine. Because theslot liners1034 are retained against the end faces of thestator core400 the liners resist shifting during winding and subsequent operation of the machine, and prevent the cables from rubbing against the stator core. In instances where theliners1034 will be removed, a multipart wedge and shim(s) (as in FIG.4PP) can be used such that with the shim not installed, the coils are loose in the slot and theliner1034 can more easily withdrawn from the slot. Thereafter, the shim would be installed to secure the coils in the slots.
• FIG. 4W shows a windings schematic according to some implementations. The windings scheme shown inFIG. 4W utilizes both concentric coils and lap coils in a single stator. The schematic illustrates windings of a two pole, three phase electric machine. The letter group A, A′, a, and a′ represent the first phase winding. The letter group B, B′, b, and b′ represent the second phase winding. The letter group C, C′, c, and c′ represent the third phase winding. The three coils represented by A and A′ are the lapped portion of the first phase winding. The three coils a and a′ represent the concentric portion of the first phase winding. The solid and dashed lines represent the end turn connections for the first phase winding. Each line may represent a single or multiple turns. The end turn connections for the second and third phase are not shown, but the same connection configuration for the first phase may also be used for the second and third phases.
• FIG. 4W shows an example of a “1-1-1” concentric coil configuration. In the “1-1-1” concentric coil configuration shown, each of the three coils of the concentric portion of the first phase winding includes a single turn. As such, each slot of the stator in the “1-1-1” concentric coil configuration carries the same number of turns, namely one turn each. Theconcentric coils414B shown in FIG.4AA are in a “1-1-1” concentric coil configuration. More generally, an “n-n-n” concentric coil configuration carries “n” concentric coil turns in each slot. Example values of “n” can include 1, 2, 3, . . . 10, and higher values. Other types of concentric coil configurations are also possible. Other example concentric coil configurations include a “2n-n-2n/n-2n-n” concentric coil configuration (e.g., the “2-1-2/1-2-1” concentric coil configuration shown in FIG.4CC, or another), a “2n-2n-n” concentric coil configuration (e.g., the “2-2-1” concentric coil configuration shown in FIG.4DD, or another), and/or others. Example values of “n” can include 1, 2, 3, . . . 10, and higher values.
• Two other example concentric coil configurations are shown inFIGS. 4X and 4Y.FIG. 4X shows an example of a “2-1-1” concentric coil configuration. In the “2-1-1” concentric coil configuration shown, the outermost coil of the concentric portion of the first phase winding includes a two turns, and each of the two inner coils of the concentric portion of the first phase winding include a single turn. As such, different slots of the stator in the “2-1-1” concentric coil configuration carry different numbers of turns. In particular, a first slot carries two turns of the concentric portion of the first phase winding, and a second and a third slot each carry only one turn of the concentric portion of the first phase winding. Other types of “2n-n-n” concentric coil configurations may also be used. Example values of “n” can include 1, 2, 3, 10, and higher values.
• FIG. 4Y shows an example of a “2-1-0” concentric coil configuration. In the “2-1-0” concentric coil configuration shown, the concentric coil configuration includes two concentric coils for each phase winding and three lap coils for each phase winding. The outer concentric coil includes a two turns, and the inner concentric coil includes one turn. As such, different slots of the stator in the “2-1-0” concentric coil configuration carry different numbers of turns. In particular, a first slot carries two turns of the concentric portion of the first phase winding, a second slot carries one turn of the concentric portion of the first phase winding, and a third slot carries no concentric coil turns. Other types of “2n-n-0” concentric coil configurations may also be used. Example values of “n” can include 1, 2, 3, . . . 10, and higher values.
• FIGS.4TT,4UU,4VV,4WW, and4XX show a solid model of anexample stator4100 of an electric machine that includes the windings represented in the diagram ofFIG. 4W. Theexample stator4100 can be used for thestator108 ofelectric machine102. FIGS.4TT and4VV are perspective views of a first end of theexample stator4100. FIG.4UU is an end view of theexample stator4100, viewed from the first end of the stator. FIG.4WW is a side view of a second end of theexample stator4100. FIG.4XX is a perspective view of the second end of theexample stator4100. As shown in FIGS.4TT,4UU,4VV,4WW, and4XX, the example stator includes anelongate stator core4102 and three conductive windings carried by thecore4102. A first winding includes concentric-wound coils4104aand lap-wound coils4106a.A second winding includes concentric-wound coils4104band lap-wound coils4106b.A third winding includes concentric-wound coils4104cand lap-wound coils4106c.The letter labels A, A′, B, B′, C, and C′ for the lap-wound coils and the letter labels a, a′, b, b′, c, and c′ for the concentric-wound coils are included to show correspondence withFIG. 4W. While the end turns of the coils are primarily visible in FIGS.4TT,4UU,4VV,4WW, and4XX, the coils also include axial portions that extend between the end turns within thestator core4102. As shown in FIG.4UU, theelongate core4102 is adapted to internally receive a rotor of an electric machine.
• The coils in each winding are connected in series. Each coil may include multiple turns connected in series or in parallel. Each slot can carry an odd number of turns or an even number of turns. In some implementations, the slots in thestator4102 do not all carry the same number of turns. In some implementations, the concentric-wound coils in a winding all have a first number of turns, and the lap-wound coils in the same winding all have a second number of turns, unequal to the first number of turns. Installing one or more of the coils may include forming a winding structure outside of thecore4102 and installing the formed winding structure in thecore4102. Installing one or more of the coils may include successively forming each of the individual coils in thecore4102.
• The core1402 includes afirst end face4108ashown in FIGS.4TT and4VV The core1402 includes a second, opposingend face4108bshown in FIGS.4WW and4XX. Thecoils4104a,4104b,4104c,4106a,4106b,and4108ceach define a loop that extends axially through theelongate core4102, exits thecore4102 through theend face4108aat an exit location, and reenters the core through theend face4108aat a reentry location. Each of the coils spans a distance on the end face between its exit location and its reentry location.
• The lap-wound coils4106ain the first winding each span a distance that is substantially equal to the distance spanned by each of the other lap-wound coils4106ain the first winding, while the concentric-wound coils4104ain the first winding each span a distance that is unequal to a distance spanned by any of the other concentric-wound coils4104ain the first winding. Similarly, the lap-wound coils4106bin the second winding each span a distance that is substantially equal to the distance spanned by each of the other lap-wound coils4104bin the second winding, the concentric-wound coils4104bin the second winding each span a distance that is unequal to the distance spanned by any of the other concentric-wound coils4104bin the second winding, the lap-wound coils4106cin the third winding each span a distance that is substantially equal to the distance spanned by each of the other lap-wound coils4106cin the third winding, and the concentric-wound coils4104cin the third winding each span a distance that is unequal to the distance spanned by any of the other concentric-wound coils4104cin the third winding.
• The distance on the end face spanned each coil can be an angular distance on the end face between the exit location of the coil and the reentry location of the coil. For example, when the end face of the core defines a circumference, the distance on the end face spanned by a coil can be an angle between the exit location of the coil and the reentry location of the coil with respect to the center point of the circumference. In the example, each coil defines a mid-point on the circumference between its exit location and its reentry location. For the concentric-wound coils4104a,4104b,and4104c,the mid-point of each coil is substantially at the same angle on the circumference as the mid-point of each other concentric-wound coil in the same winding. For the lap-wound coils4106a,4106b,and4106c,the mid-point of each coil is at a different angle on the circumference than the mid-point of any other lap-wound coil in the same winding.
• Thecore4102 includes teeth that extend radially toward an axial center of thecore4102. The teeth define radial slots between the teeth, and the coils are carried in the slots. Thus, the core defines an array of slots to carry the windings. Each coil resides in a pair of non-adjacent slots, and thus, each coil spans a number of slots between the non-adjacent slots in which the coil resides. Each of the lap-wound coils4106ain the first winding spans a number of slots that is equal to the number of slots spanned by each of the other lap-wound coils4106ain the first winding, while each of the concentric-wound coils4104ain the first winding spans a number of slots that is unequal to the number of slots spanned by any of the other concentric-wound coils4104ain the first winding. For example, each of the lap-wound coils4106aspans eight slots, while the three concentric-wound coils4104aspan 6, 8, and 10 slots, respectively. Similarly, each of the lap-wound coils4106bin the second winding spans a number of slots that is equal to the number of slots spanned by each of the other lap-wound coils4106bin the second winding, each of the concentric-wound coils4104bin the second winding spans a number of slots that is unequal to the number of slots spanned by any of the other concentric-wound coils4104bin the second winding, each of the lap-wound coils4106cin the third winding spans a number of slots that is equal to the number of slots spanned by each of the other lap-wound coils4106cin the third winding, and each of the concentric-wound coils4104cin the third winding spans a number of slots that is unequal to the number of slots spanned by any of the other concentric-wound coils4104cin the third winding.
• A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made. Accordingly, other implementations are within the scope of the following claims.

Claims (21)

1. A stator for an electric machine, the stator comprising:

an elongate core having an end face and an opposing end face, the elongate core adapted to internally receive a rotor of an electric machine;

a plurality of conductive coils, each coil defining a loop that extends axially through the elongate core, exits the core through the end face, and reenters the core through the end face, a first subset of the coils collectively forming a first radial layer axially exterior the core and a third radial layer axially exterior the core, each coil in the first subset residing in both the first layer and the third layer, a second subset of the coils collectively forming a second radial layer axially exterior the core and a fourth radial layer axially exterior the core, each coil in the second subset residing in both the second layer and the fourth layer, the second layer residing radially between the first and third layers, the third layer residing radially between the second and fourth layers.

2. The stator ofclaim 1, wherein the loop defined by each coil in the first subset exits the core through the end face at an exit location in the first radial layer and reenters the core through the end face at a reentry location in the third radial layer, and wherein the loop defined by each coil in the second subset exits the core through the end face at an exit location in the second radial layer, and reenters the core through the end face at a reentry location in the fourth radial layer.

3. The stator ofclaim 1, wherein the plurality of coils forms two radial layers in the elongate core, and each of the coils resides in both radial layers in the elongate core.

4. The stator ofclaim 3, wherein the two radial layers in the elongate core define two radii on the end face including a first radius and a second radius, the loop defined by each coil in the first subset exits the core through the end face at an exit location on the first radius, turns toward the first radial layer, extends through the first radial layer, turns toward the third radial layer, extends through the third radial layer, and reenters the core through the end face at a reentry location on the second radius.

5. The stator ofclaim 4, wherein the loop defined by each coil in the second subset exits the core through the end face at an exit location on the first radius, turns toward the second radial layer, extends through the second radial layer, turns toward the fourth radial layer, extends through the fourth radial layer, and reenters the core through the end face at a reentry location on the second radius.

6. The stator ofclaim 1, wherein the core comprises a plurality of slots to carry the coils, a first subset of the slots each carry two of the first subset of coils, and a second subset of the slots each carry two of the second subset of coils.

7. The stator ofclaim 6, wherein a radial distance between two coils in each slot and an azimuthal distance between two sides of the slot define a gap in the slot.

8. The stator ofclaim 6, wherein first subset of slots and the second subset of slots all have substantially equal radial depths.

9. The stator ofclaim 6, wherein an inner-most radial layer comprises the fourth radial layer, an outer-most radial layer comprises the first radial layer, the first subset of slots have a first radial depth, the second subset of slots have a second radial depth, and the second radial depth is less than the first radial depth.

10. A stator for an electric machine, the stator comprising:

an elongate core adapted to internally receive a rotor of an electric machine;

a first plurality of coils arranged in a first lap winding configuration and forming a first plurality of end turns that each extend through a first radial layer of end turns and a third radial layer of end turns; and

a second plurality of coils arranged in a second lap winding configuration and forming a second plurality of end turns that each extend through a second radial layer of end turns and a fourth radial layer of end turns, the second layer residing radially between the first and third layers, the third layer residing radially between the second and fourth radial layers.

11. The stator ofclaim 10, wherein the first plurality of coils and the second plurality of coils collectively form two radial layers in the core, wherein each of the first plurality of coils and each of the second plurality of coils resides in both of the two radial layers in the core.

12. The stator ofclaim 10, wherein the first plurality of coils collectively form four radial layers in the core, the first plurality of coils reside in a first pair of the four radial layers in the core, the second plurality of coils reside in a second pair of the four radial layers in the core.

13. The stator ofclaim 12, wherein the stator defines an array of slots, the first plurality of coils resides in a first subset of the slots, the second plurality of coils resides in a second subset of the slots.

14. The stator ofclaim 13, wherein two of the coils reside in each slot, and a radial spacing between the coils in each slot define a radial gap in the slot.

15. The stator ofclaim 13, wherein the first subset of slots have a first radial depth and the second subset of slots have a second radial depth that is less than the first radial depth.

16. A method of making a stator of an electric machine, the method comprising:

installing a first plurality of coils in a core of a stator, the first plurality of coils collectively forming a first radial layer of end turns and a third radial layer of end turns axially external the core, each of the first plurality of coils defining a loop that extends axially through the core, exits the core through the end face, extends through the first radial layer, extends through the third radial layer, and reenters the core through the end face; and

installing a second plurality of coils in the core of the stator, the second plurality of coils collectively forming a second radial layer of end turns and a fourth radial layer of end turns axially external the core, each of the second plurality of coils defining a loop that extends axially through the core, exits the core through the end face, extends through the second radial layer, extends through the fourth radial layer, and reenters the core through the end face;

wherein the second radial layer resides radially between the first and third radial layers, and the third layer resides radially between the second and fourth radial layers.

17. The method ofclaim 16, further comprising coupling the first plurality of coils to the second plurality of coils to form a three-phase conductive winding.

18. The method ofclaim 16, further comprising operating the electric machine as a multi-pole electric machine.

19. The method ofclaim 16, wherein installing at least one of the first plurality of coils or the second plurality of coils comprises forming a winding structure outside of the core and installing the formed winding structure in the core.

20. The method ofclaim 16, wherein installing at least one of the first plurality of coils or the second plurality of coils comprises installing each of the plurality of coils by successively forming individual turns of the coil in the core of the stator.

21. The method ofclaim 16, wherein installing the first plurality of coils and installing the second plurality of coils comprises simultaneously installing the first plurality of coils and the second plurality of coils.

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