US20110083450A1 - Refrigerant System With Stator Heater - Google Patents

Abstract

A refrigerant system adapted to reduce refrigerant migration therein includes a compressor and a controller. The compressor has a motor with motor windings. The motor windings are responsive to control signals to selectively generate heat in a manner that does not turn the motor. The controller selectively energizes the motor windings to generate heat based on at least one of a monitored temperature or pressure to warm the compressor.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a non-provisional patent application which claims the benefit of U.S. provisional patent application Ser. No. 61/251,424 filed Oct. 14, 2009, the entire contents of which are incorporated herein by reference.
BACKGROUND
• The present invention relates to refrigerant heating and/or cooling systems, and more particularly, to a heating and/or cooling system with a stator heater integral to a compressor to prevent the migration of liquid refrigerant to the compressor.
• Heating, ventilating and air conditioning (HVAC) systems and refrigeration systems (collectively commonly called refrigerant systems) can be used in a variety of applications to heat and/or cool desired units or areas. More particularly, HVAC systems and refrigeration systems operate in a number of different refrigeration cycles. For example, if the HVAC system employs a heat pump, the system can operate in a vapor-compression refrigeration cycle to provide cooling to an indoor unit. In the vapor-compression refrigeration cycle, an outdoor unit with a first heat exchanger (condenser) is coupled to a compressor which circulates liquid refrigerant to a second heat exchanger (evaporator) located in the indoor unit.
• Most refrigeration cycles experience a tendency for liquid refrigerant to try to migrate through the liquid line between the indoor heat exchanger and the outdoor heat exchanger when the compressor is not in operation. This phenomena is due to natural convection, which causes the refrigerant to flow within the refrigerant system and migrate to the coldest point in the system. The relatively large thermal mass of the compressor causes it to be the coldest point in the refrigerant system. When refrigerant migration occurs, some of the liquid refrigerant moves into the compressor, settling in the oil sump located at the bottom of the compressor. When the compressor is next operated, the liquid refrigerant boils into a gaseous state and exits the compressor. Unfortunately, when this occurs the refrigerant carries a portion of the compressor oil with it. This process reduces the amount of lubricant in the compressor. The loss of this oil may cause increased wear and can detrimentally affect the reliability and life of the compressor especially in larger refrigerant systems that employ larger volumes of refrigerant and operate for longer periods of time.
SUMMARY
• A refrigerant system adapted to reduce refrigerant migration therein includes a compressor and a controller. The compressor has a motor with motor windings. The motor windings are responsive to control signals to selectively generate heat in a manner that does not turn the motor. The controller selectively energizes the motor windings to generate heat based on at least one of a monitored temperature or pressure to warm the compressor.
• A method of that reduces refrigerant migration to a compressor includes the compressor which has a motor with motor windings responsive to control signals to selectively generate heat in a manner that does not turn the motor. A controller monitors at least one of a temperature or pressure and controls the motor windings to selectively generate heat based on at least one of the monitored temperature or pressure to reduce or eliminate refrigerant migration to the compressor.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1A is a schematic illustration of a refrigerant system arranged as a heat pump operating in a cooling mode.
• FIG. 1B is a schematic illustration of the heat pump ofFIG. 1A operating in a heating mode.
• FIG. 2A is a schematic illustration of another heat pump utilizing an air cooled inverter drive and operating in a cooling mode.
• FIG. 2B is a schematic illustration schematic illustration of the heat pump ofFIG. 2A operating in a heating mode.
• FIG. 3 is a side view of one embodiment of a compressor with a refrigerant cooled inverter drive fromFIGS. 1A and 1B.
• FIG. 4 is a cross-sectional view of the compressor illustrating interior components including a motor.
• FIG. 5A is a perspective view of one embodiment of a stator portion of the motor.
• FIG. 5B is a perspective view of a single stator portion.
• FIG. 5C is a perspective view of one embodiment of a rotor portion of the motor.
• FIG. 5D is an exploded view of the rotor portion ofFIG. 5B.
• FIG. 6 is a flow chart illustrating a method of controlling a stator to produce heat within the compressor and avoid overheating the inverter drive.
DETAILED DESCRIPTION
• The present application relates to a refrigerant system and methods of controlling the refrigerant system when the refrigerant system is in an off mode to keep refrigerant from migrating to the refrigerant system's compressor. In particular, the refrigerant system includes a compressor having motor windings responsive to control signals to selectively generate heat that keeps refrigerant from migrating to the compressor as a result of natural convection. The motor windings generate heat in a manner that does not turn the motor (i.e., heat is generated by the motor in a manner that does not drive the compressor to compress refrigerant). The refrigerant system also includes a controller that selectively energizes the motor windings to generate the heat based on at least one of a monitored temperature or pressure.
• The methods disclosed control the amount, frequency and duration of heat produced by the motor windings of the compressor. The methods also protect the electrical components of an inverter device from an overheat condition that can result from heating the compressor when the compressor is in the off mode.
• FIG. 1A is a schematic illustration of arefrigerant system10A arranged as aheat pump12A operating in a cooling mode.FIG. 1B is a schematic illustration of theheat pump12A operating in a heating mode.Heat pumps12A are one of a variety ofrefrigerant systems10A used to provide heating or cooling to anindoor unit14. A portion of theheat pump12A extends into anoutdoor unit16 for heat exchange purposes. Theindoor unit14 andoutdoor unit16 are connected by a first conduit orflow path18 and a second conduit orflow path20. In addition to thefirst conduit18 and thesecond conduit20, theheat pump12A includes afirst heat exchanger22 having afirst port24 and asecond port26, afirst expansion device27, a firstair circulation device28, asecond heat exchanger30 having afirst port32 and asecond port34, a secondair circulation device36, areversing valve38 with amain body portion40, anaccumulator42, a compressor anddrive subassembly44A with a refrigerant cooledinverter drive46A and acompressor48. Thecompressor48 includes asuction port50, adischarge port52, and amotor stator54. Theheat pump12A also includes asensor array56. Thisarray56 includes a motorstator temperature sensor58, an invertermodule temperature sensor60, an internalcompressor temperature sensor62, an outdoorair temperature sensor64, an outdoorcoil temperature sensor66, an outdoorsuction temperature sensor68, an indoor air temperature sensor70, and an outdoorsuction pressure sensor72.Transmission media74 or wireless media transmit signals (digital or analog) to asubassembly controller76 orsystem controller78 from thesensors58,60,64,66,68,70,72 and the other components of therefrigerant system10A.
• Thefirst heat exchanger22 is positioned within theindoor unit14. Thefirst heat exchanger22 fluidly communicates with thefirst conduit18 and thesecond conduit20 through thefirst port24 and thesecond port26, respectively. Thefirst expansion device27 is disposed in fluid communication with thesecond conduit20 between thefirst heat exchanger22 and thesecond heat exchanger30 and can be disposed in either theindoor unit14 or theoutdoor unit16. The firstair circulation device28, such as a fan is disposed within theindoor unit14. Theair circulation device28 is arranged to move air over and/or around thefirst heat exchanger22 and circulate air within theindoor unit14. This allows for improved transfer of thermal energy either to or from thefirst heat exchanger22 to theindoor unit14.
• Thefirst conduit18 and thesecond conduit20 extend from theindoor unit14 to theoutdoor unit16. More particularly, thefirst conduit18 fluidly communicates with the reversingvalve38 and thesecond conduit20 fluidly communicates with thesecond heat exchanger30 through thefirst port32. Thus, thefirst heat exchanger22 fluidly communicates with thesecond heat exchanger30. Thesecond heat exchanger30 is disposed within theoutdoor unit16 and fluidly communicates with the reversingvalve38 through thesecond port34. The secondair circulation device36 is disposed adjacent thesecond heat exchanger30 to move ambient air over or past thesecond heat exchanger30 to either add or remove heat from thesystem10A.
• The reversing valve38 (also known as a four-way valve) is fluidly coupled between the first andsecond heat exchangers22 and30 and the compressor and drivesubassembly44A. Themain body portion40 of the reversingvalve38 rotates between a first position for cooling mode (FIG. 1A) to a second position for heating mode (FIG. 1B). In the first position as illustrated inFIG. 1A, themain body portion40 fluidly couples thesecond port34 of thesecond heat exchanger30 to thecompressor48 and couples thefirst conduit18 to theaccumulator42. When rotated to the second position as illustrated inFIG. 1B, themain body portion40 fluidly couples thesecond port34 to theaccumulator42 and couples thefirst conduit18 to thecompressor48. Thus, by rotating themain body portion40, the reversingvalve38 can either direct the refrigerant discharged from thecompressor48 to either thesecond heat exchanger30 in the cooling mode (FIG. 1A), or to thefirst conduit18 in the heating mode (FIG. 1B).
• InFIGS. 1A and 1B, the compressor and drivesubassembly44A is disposed in fluid communication with theaccumulator42 along thesuction line43. More specifically, theinverter drive46A is arranged in fluid communication on thesuction line43 with theaccumulator42 and with thecompressor48 viasuction port50. Refrigerant passes through thecompressor48 and is compressed to a higher pressure before being discharged through thedischarge port52 intodischarge line53.Compressor48 commonly utilizes an internal motor (not shown) to convert electrical energy to mechanical energy and thereby achieve compression of the refrigerant. As will be discussed in greater detail subsequently, the motor has astator54 configured to selectively act as a heater to reduce or eliminate fluid migration to thecompressor48 that would otherwise occur during periods of nonuse of thecompressor48 due to natural convection.
• Thesensor array56 is distributed in various locations throughout theheat pump12A. In the embodiment shown inFIGS. 1A and 1B, thesensor array56 gathers data relating to at least one of the system temperatures and/or pressures and outputs this data as signals to thesubassembly controller76 orsystem controller78 viatransmission media74. Thesubassembly controller76 and/orsystem controller78 monitors the signals supplied by thesenor array56 and controls components of therefrigerant system10A, including themotor stator54 to achieve selective heating. In the embodiment shown inFIGS. 1A and 1B, thesensor array56 includes the motorstator temperature sensor58, the invertermodule temperature sensor60, the internalcompressor temperature sensor62, the outdoorair temperature sensor64, the outdoorcoil temperature sensor66, the outdoorsuction temperature sensor68, the indoor air temperature sensor70, and the outdoorsuction pressure sensor72.
• 100261 In the embodiment shown, the motorstator temperature sensor58 is disposed within oradjacent motor stator54 within thecompressor48. The motorstator temperature sensor58 signals thesubassembly controller76 viatransmission medium74. The invertermodule temperature sensor60 is disposed within theinverter device46A. The internalcompressor temperature sensor62 is disposed within thecompressor48 adjacent a compression area therein. In the embodiment shown, thecompressor48 is a scroll type compressor, and therefore internalcompressor temperature sensor62 would be disclosed next to the scroll of thecompressor48. Similar to the motorstator temperature sensor58, in one embodiment bothsensors60 and62 signal thesubassembly controller76 viatransmission media74. In the embodiment shown inFIG. 1A andFIG. 1B,subassembly controller76 has the ability to monitor signals fromsensors58,60 and62 and control various components of therefrigerant system10A. In particular,subassembly controller76 can control theinverter device46A, and thus, thecompressor48 operation and speed. Additionally, thesubassembly controller76 is capable of selectively energizing the windings of themotor stator54 to generate heat based on at least one of the motor stator temperature, the inverter module temperature and the internal compressor temperature signals. Alternatively, thesubassembly controller76 can output signals (analog or digital) corresponding to the motor stator temperature, the inverter module temperature and the internal compressor temperature to thesystem controller78. In this instance, thesystem controller78 monitors these signals and signals from theother sensors64,66,68,70 and72 and controls various components of therefrigerant system10A including the motor windings to selectively generate heat within thecompressor48 as discussed previously. Thus, thesystem controller78 selectively energizes the motor windings to generate heat based on at least one of the monitored signals received by thecontroller78 from thesensors58,60,62,64,66,68,70 and72. In other embodiments, thesubassembly controller76 can be eliminated entirely in favor of theassembly control78.
• The outdoorair temperature sensor64 can comprise a thermostat, thermistor or thermocouple and can be disposed anywhere within theoutdoor unit16. However, in one embodiment outdoorair temperature sensor64 is disposed within the unit which houses thesystem controller78. The outdoorcoil temperature sensor66 can comprise a thermistor clipped or otherwise mounted to a coil tube of thesecond heat exchanger30. The outdoorsuction temperature sensor68 can comprise a thermistor attached to thesuction line43 adjacent theaccumulator42. The indoor air temperature sensor70 is disposed within theindoor unit14. Additionally, a sensor (not shown) for measuring the indoor unit return air temperature can be utilized in therefrigerant system10A. The outdoorsuction pressure sensor72 can comprise a transducer disposed in thesuction line43 adjacent to thesuction temperature sensor68. Thesensors58,60,62,64,66,68,70 and72 output data signals via thetransmission medium74 which can comprise, for example, wiring, coaxial or fiber optic cable, wireless, radio and infrared signals, or any conductor capable of carrying an electrical signal.
• In controlling the various components of therefrigerant system10A,system controller78 accepts data from thesensors58,60,62,64,66,68,70 and72, theinverter device46A, thecompressor48, and various other components, and executes programs for the purpose of comparing the data to predetermined operational parameters. Several programs compare the operational parameters to predetermined variances (e.g., low temperature, high temperature, low pressure) and if the predetermined variance is exceeded, thesystem controller78 generates a signal that may be used to indicate an alarm or may initiate other control methods that change the operation of theheat pump12A such as reducing or turning on or off energy to the motor windings within thecompressor48.
• Thesubassembly controller76 and thesystem controller78 comprise any suitable electronic device capable of accepting data and executing the instructions to process the data. Thecontrollers76 and78 may have a display for presenting the results and/or receiving instructions. Alternatively, thecontrollers76 and78 can accept instructions through, for example, electronic data card, voice activation means, manually-operable selection and control means and electronic or electrical transfer. Thesubassembly controller76 and thesystem controller78 can be, for example, a microprocessor, a microcomputer, a minicomputer, an optical computer, a board computer, a complex instruction set computer, an ASIC (application specific integrated circuit), a reduced instruction set computer, an analog computer, a digital computer, a solid-state computer, a single-board computer, a buffered computer, a computer network, a desktop computer, a laptop computer, or a hybrid of any of the foregoing.
• During the cooling mode of operation shown inFIG. 1A, themain body portion40 of the reversingvalve38 fluidly couples thesecond port34 of thesecond heat exchanger30 to thecompressor48 and couples thefirst conduit18 to theaccumulator42. In this manner, the refrigerant pressurized in thecompressor48 flows through thedischarge line53 and reversingvalve38 to thesecond heat exchanger30 which operates as a condenser to condense the high pressure vapor into liquid thereby extracting heat from the refrigerant to theoutdoor unit16. From thesecond heat exchanger30 the refrigerant flows to theexpansion device27 which throttles the flow of refrigerant lowering its pressure. Theexpansion device27 can comprise, for example, an expansion valve or a capillary tube. The refrigerant then flows to thefirst heat exchanger22 which operates as an evaporator to evaporate the refrigerant to gas thereby transferring heat from theindoor unit14 to the refrigerant. The refrigerant continues flowing from thefirst heat exchanger22 through thefirst conduit18 and the reversingvalve38 to theaccumulator42. Theaccumulator42 uses an inverted trap to attempt to protect thecompressor48 from liquid refrigerant in thesuction line43. From theaccumulator42, the gas refrigerant is drawn by thecompressor48 along thesuction line43 through theinverter46A to suctionport50.
• When operating the heating mode shown inFIG. 1B, the direction of refrigerant flow within thefirst conduit18 and thesecond conduit20 is reversed. This is accomplished by themain body portion40 of reversingvalve38 which rotates to fluidly couple thesecond port34 of thesecond heat exchanger30 to theaccumulator42. The rotation of themain body portion40 also fluidly couples thefirst conduit18 to thedischarge line53 to thecompressor48. In the heating mode, thefirst heat exchanger22 operates as a condenser to warm theinner unit14. Conversely, thesecond heat exchanger30 operates as an evaporator.
• Heat pump10B illustrated inFIGS. 2A and 2B has components similar to and operates in a manner similar to theheat pump10A illustrated inFIGS. 1A and 1B. Theheat pump10B differs in that it employs an air cooledinverter drive46B, and thus, theinverter drive46B is not connected to thesuction line43. In the embodiment illustrated inFIGS. 2A and 2B, theinverter drive46B does not have a housing so its components are cooled by the secondair circulation device36. Alternatively, theinverter drive46B components can be cooled by a dedicated fan within theoutdoor unit16. In one embodiment, the presence of an overheat condition within the air cooledinverter drive46B can be measured by taking the temperature within theoutdoor unit16 either/both prior to and after thesecond heat exchanger30 with outdoorair temperature sensors64A and64B. As will be discussed in further detail subsequently, thesubassembly controller76 or thesystem controller78 can be configured to control operation of the secondair circulation device36 or dedicated fan (turn the secondair circulation device36 on and off) to selectively move cooling air across the electronic components of theinverter drive46B. In this manner, the electronic components within theinverter drive46B can be cooled. In an alternative embodiment, theinverter drive46B can include the invertermodule temperature sensor60 disposed within or adjacent theinverter device46B to sense the overheat condition.
• FIG. 3 is a side view of the compressor and drivesubassembly44A with a housing removed. InFIG. 3, thesuction line43 and thedischarge line53 fluidly connect the compressor and drivesubassembly44A to the remainder of therefrigerant system10A (FIGS. 1A and 1B). More particularly, thesuction line43 fluidly connects the accumulator42 (FIGS. 1A and 1B) to theinverter drive46A. Thesuction line43 extends through the inverter drive46A to fluidly connect theinverter drive46A with thecompressor48 via thesuction port50. Thecompressor48 pressurizes the refrigerant received therein and discharges the refrigerant to thedischarge line53 through thedischarge port52.
• As will be discussed in further detail subsequently, thecompressor48 can be selectively operated by the subassembly controller76 (FIGS. 1A and 1B) or the system controller78 (FIGS. 1A and 1B) to allow refrigerant to flow through theinverter drive46A. In this manner, the refrigerant can be used to cool the electronic components within theinverter drive46A and alleviate the overheat condition. Additionally,inverter drive46A may include a device such as a cold plate (not shown). The refrigerant cools the cold plate prior to enteringcompressor48 and thereby cools the electrical components of theinverter drive46A. The cold plate functions as a heat exchanger between the refrigerant and theinverter drive46A so that heat frominverter drive46A is transferred to refrigerant prior to the refrigerant entering thecompressor48.
• Thecompressor48 is driven by theinverter drive46A, also commonly referred to as a variable frequency drive (VFD). As illustrated inFIG. 3, theinverter drive46A can be housed within anenclosure80. Theinverter drive46A is disposed adjacent thecompressor48 and receives electrical power from a power supply via apower cable82A and delivers electrical power tocompressor48 via asecond power cable82B connected to a terminal box (not shown) that is also connected to thecompressor48. As previously discussed,inverter drive46A can include the subassembly controller76 (not shown) which can be housed within or outside theinverter drive46A. If utilized, thesubassembly controller76 would include a processor and software operable to modulate and control the frequency of electrical power delivered to the electric motor ofcompressor48. Thesubassembly controller76 also would include a computer readable medium for storing data including the software executed by the processor to modulate and control the frequency of electrical power delivered to the electric motor of thecompressor48 and the software necessary forsubassembly controller76 to execute and perform the protection and control algorithms of the present teachings. In particular,subassembly controller76 would be capable of performing the functions discussed previously such as monitoring data signals from various sensors and selectively energizing or de-energizing the windings within thecompressor48 to generate heat or stop the generation of heat based on the monitored signals. By modulating the frequency of electrical power delivered to the electric motor ofcompressor48, the subassembly controller76 (or system controller78) can thereby modulate and control the speed, and consequently the capacity, of thecompressor48.
• Theinverter drive46A includes solid state electronics to modulate the frequency of electrical power. Generally, theinverter drive46A converts the inputted electrical power from AC to DC, and then converts the electrical power from DC back to AC at a desired frequency. For example,inverter drive46A can directly rectify electrical power with a full-wave rectifier bridge. Theinverter driver46A can then chop the electrical power using insulated gate bipolar transistors (IGBT's) or thyristors to achieve the desired frequency. Other suitable electronic components can be used to modulate the frequency of electrical power from power supply. The speed of the electric motor driving thecompressor48 is controlled by the frequency of electrical power received from theinverter driver46A.
• FIG. 4 is a cross-sectional view of thecompressor48 illustrating various interior components. Thesuction port50 is not visible to the viewer from the cross-section of thecompressor48. In addition to themotor stator54, the motorstator temperature sensor58, the internalcompressor temperature sensor62, and thedischarge port52, thecompressor48 includes amotor86 with arotor88, adrive shaft90 and ascroll92.
• In the embodiment shown inFIG. 4, thecompressor48 comprises a conventional scroll type compressor; however, the invention disclosed herein is equally applicable to reciprocating type, rotary screw and rotary vane type compressors. Themotor86, comprising themotor stator54 androtor88, is disposed within thecompressor48 to convert electrical power into mechanical work. In particular, themotor86 is configured to receive electrical power from theinverter drive46A or46B (FIGS. 1A,1B,2A and2B) and rotate therotor88 and thedrive shaft90 to which therotor88 is coupled. Themotor stator54 remains stationary adjacent therotor88. The rotation of thedrive shaft90 draws refrigerant into thecompressor48 and distributes lubricating oil from a reservoir in a lower portion of thecompressor48. Thedrive shaft90 is connected to thescroll92 which uses two interleaved spiral scrolls to compress the refrigerant drawn in to thecompressor48. After compression in thescroll92, the refrigerant is discharged through thedischarge port52 to the discharge line53 (FIGS. 1A,1B,2A and2B). The motorstator temperature sensor58 is disposed adjacent to or within themotor stator54 and outputs signals corresponding to sensed temperature to thesubassembly controller76 or system controller78 (FIGS. 1A and 1B). The internalcompressor temperature sensor62 is disposed adjacent thescroll92 and outputs signals corresponding to sensed temperature to thesubassembly controller76 or thesystem controller78.
• When therefrigerant system10A or10B (FIGS. 1A,1B,2A and2B) is not in operation, themotor86 does not rotate thedrive shaft90 and thecompressor48 does not compress the refrigerant. To avoid or reduce refrigerant migration to thecompressor48 in this off state due to natural convection (i.e., the tendency of a fluid such as a refrigerant to move from one location to another due to density differences in the fluid occurring because of temperature gradients between the locations), thesubassembly controller76 or thesystem controller78 is configured to control theinverter46A or46B to selectively energize the windings within themotor stator54 to generate heat within thecompressor48. More particularly, in one embodiment themotor86 is a brushless permanent magnet motor, also commonly known as a permanent magnet synchronous motor. During the time period whenrefrigerant system10A or10B andcompressor48 are not in operation, and during a predetermined warm up period aftersystem10A or10B startup, theinverter drive46A or46B is selectively controlled to provide varying levels of power to the motor windings in such a manner so as not to cause rotation (i.e., turn) of therotor88. In particular, if a three-phase power supply is employed, a single-phase current may be applied to the windings within themotor stator54. The resistance of the windings causes the windings to generate heat. The heat generated keeps thecompressor48 from being the heat sink for thesystem10A or10B, thus migration of the refrigerant tocompressor48 is avoided.
• FIGS. 5A-5D illustrate themotor stator54 and therotor88. Additionally, themotor stator54 includeslaminated segments94 withcoil windings96. Therotor88 includes amain body98,magnets100,end caps102 andfasteners104.
• In the embodiment shown, themotor stator54 comprises a conventional segmented stator for a brushless permanent magnet motor. The construction and operation of a similar motor stator and rotor for a permanent magnet motor is further detailed in U.S. Pat. No. 7,122,933 to Horst et al., which are herein incorporated by reference.
• In particular, thelaminated segments94 can be individually assembled and subsequently combined to define themotor stator54. Thelaminated segments94 are connected to define a circuit in a manner known in the art. As illustrated, eachlaminated segment94 has thecoil windings96 disposed therein. In one embodiment, thecoil windings96 are wound as single-layer or double-layer concentrated windings to define three phases. The illustrated embodiment has ninelaminated segments94 and ninecoil windings96. The leads (not shown) of each coil winding96 are electrically connected such that the three phases induce alternating eddy currents when an electrical current is applied. If current in a proper phase (e.g., in this example three phase) is applied, the eddy currents induce rotation of therotor88. Although illustrated with ninecoil windings96 it is anticipated in other embodiments that a different number of coil windings could be used.
• When assembled, themain body98 of therotor88 is disposed adjacent the interior of thelaminated segments94. Themain body98 is adapted to receive thedrive shaft90 therein. Themain body98 is also adapted to receive themagnets100. The end caps102 andfasteners104 secure themagnets100 within themovable rotor88. In the embodiment shown, six magnets having six poles can be disposed within themain body98. In other embodiments a different number of magnets can be used.
• FIG. 6 is a flow chart illustrating onemethod200 of controlling themotor stator54 to produce heat within thecompressor48 to keep refrigerant from migrating therein. Themethod200 protects the electrical components of theinverter module46A or46B from an overheat condition that can result from the stator heating of thecompressor48.
• Themethod200 starts atblock202 and proceeds to queryblock204.Query block204 determines whether the compressor48 (FIGS. 1A-4) is in an off mode where thecompressor48 is not in operation. The off mode includes a warm up or start up mode for thecompressor48. If the compressor is in the off mode, themethod200 proceeds to block206. Inblock206, a check of the temperature sensed within thecompressor48 and/or theinverter device46A or46B is performed periodically using one or more of thesensors58,60, and/or62 (FIGS. 1A,1B,2A and2B). Alternatively or in addition thereto, the outdoor air temperature can be monitored using the outdoorair temperature sensor64. The frequency at which the temperatures are monitored can be varied based on whether the temperatures fall within a predetermined range of temperatures. For example, in one embodiment if the sensed outdoor air temperature is greater than about 55° F. (13° C.) the outdoorair temperature sensor64 is checked every 50 minutes, if the sensed outdoor air temperature is greater than about 20° F. (−7° C.) and less than about 55° F. (13° C.) the outdoorair temperature sensor64 is checked every 30 minutes, and if the outdoor air temperature is less than about 20° F. (−7° C.) the outdoorair temperature sensor64 is checked every 30 seconds.
• In one embodiment,query block208 determines whether the temperature within theinverter device46A or46B (as sensed by the inverter module temperature sensor60) is greater than a minimum inverter temperature. In one embodiment, the minimum inverter temperature is about 0° F. (−18° C.) or below. In another embodiment shown inFIGS. 2A and 2B, one or both outdoorair temperature sensors64A and64B can be utilized to calculate the temperature within theinverter device46B. If the temperature of theinverter device46A or46B is above the minimum inverter temperature, themethod200 proceeds to queryblock210.Query block210 determines whether the temperature within the compressor48 (as sensed by the motorstator temperature sensor58 or the internal compressor temperature sensor62) exceeds a minimum internal compressor temperature. In one embodiment, the minimum internal compressor temperature is in a range of between about −20° F. (−29° C.) and 20° F. (31 7° C.). If the temperature within theinverter device46A or46B is below the minimum inverter temperature or the temperature within thecompressor48 is less than the minimum internal compressor temperature themethod200 proceeds to block212.
• Inblock212, thecompressor48 is locked out for a period of time such that thecompressor48 is restricted from operating until both the temperature within theinverter device46A or46B and temperature within thecompressor48 exceed the minimums. During the lockout period ofblock212 and for the period indicated inblock214 the windings of themotor stator54 are energized to produce heat within thecompressor48. Power can be supplied to the windings of themotor stator54 at various levels to produce various modes of heating within thecompressor48. Inblock214, power is supplied to the windings of themotor stator54 at a higher level than a lower power level which will be discussed subsequently. In one embodiment, themotor stator54 is supplied with 50 Watts of power, however, the amount of power necessary to produce adequate heating of the system will vary depending on system criteria.
• If the temperature within theinverter device46A or46B is above the minimum inverter temperature and the temperature within thecompressor48 is above the minimum internal compressor temperature themethod200 advances to queryblock216.Query block216 determines whether the temperature withincompressor48 is the coldest part of therefrigerant system10A or10B. In one embodiment, this inquiry is conducted by comparing the temperature sensed by the motorstator temperature sensor58 or the internalcompressor temperature sensor62 to either a minimum outdoor air temperature and/or a minimum indoor air temperature. If the temperature within thecompressor48 is colder than either the minimum indoor air temperature or the minimum outdoor air temperature, than thecompressor48 is the coldest part of therefrigerant system10A or10B (and therefore there is a danger of refrigerant migration thereto) and stator heating to warm thecompressor48 is required. Thus, if thecompressor48 is the coldest part of therefrigerant system10A or10B, themethod200 proceeds to block214 where thecompressor48 is warmed. In one embodiment, the minimum outdoor air temperature is below 0° F. (−18° C.) and the minimum indoor air temperature is below 65° F. (18° C.).
• After the period of heating inblock214, themethod200 advances to query block218 which determines whether theinverter drive46A or46B is overheating. In one embodiment, the temperature within theinverter drive46A or46B can be ascertained in the manner used inblock208. A temperature limit used inquery block218 will vary depending on the components used by theinverter drive46A or46B and a safety factor temperature offset used. If the sensed and/or calculated temperature within theinverter drive46A or46B exceeds the temperature limit minus the temperature offset, themethod200 proceeds to queryblock220.
• Query block220 determines whether the inverter drive is a refrigerant cooledinverter46A or an air cooledinverter46B. If the inverter drive is the refrigerant cooledinverter46A, themethod200 advances to query block222 which determines if the inverter temperature exceeds the temperature limit minus the temperature offset by a predetermined temperature value. Although the range of temperatures for the predetermined value may vary, in one embodiment if the predetermined value (temperature interval) is in excess of about 10° F. (>5.6° C.), themethod200 goes to block224 where the amount of power to the windings of themotor stator54 is reduced to a lower level. If the predetermined value (temperature interval) is between about 0° F. and 10° F. (0° C. and 5.6° C.), themethod200 goes to block226 where the windings of themotor stator54 are de-energized completely so that they do not produce heat within thecompressor48. In the embodiment shown inFIG. 6, themethod200 advances fromblock226 to a “bump start” mode of operation inblock228. The “bump start” mode cycles thecompressor48 operationally on and off to circulate refrigerant through the refrigerant cooledinverter drive46A, and thereby cool theinverter drive46A. In one embodiment, when thecompressor48 is in the on cycle of the bump start mode, it operates at over 3000 revolutions per minute for 5 seconds and when thecompressor48 is in the off cycle it operates at 0 revolutions per minute for 15 seconds.
• Ifquery block220 determines the inverter drive is the air cooledinverter46B, themethod200 proceeds to query block230 which determines if the inverter temperature exceeds the temperature limit minus the temperature offset by a predetermined temperature value. Similar to query block220, inquery block230 if the predetermined value (temperature interval) is in excess of about 10° F. (>5.6° C.) themethod200 goes to block232 where the amount of power to the windings of themotor stator54 is reduced to the lower power level. If the predetermined value (temperature interval) is between about 0° F. and 10°0 F. (0° C. and 5.6° C.), themethod200 goes to block234 where the windings of themotor stator54 are de-energized completely so that they do not produce heat within thecompressor48. In the embodiment shown inFIG. 6, themethod200 proceeds fromblock234 to block236, where the secondair circulation device36 is run to cool theinverter drive46B and alleviate the overheat condition of theinverter drive46B.
• Method200 proceeds fromblocks216,224,228,232 or236 to query block238 where it is determined whether thecompressor48 is the coldest part of therefrigerant system10A or10B under altered criteria fromquery block216. Inquery block238, this inquiry is conducted by comparing the temperature sensed by the motorstator temperature sensor58 or the internalcompressor temperature sensor62 to either the minimum outdoor air temperature used inblock216 plus a temperature offset and the minimum indoor air temperature used inblock216 plus a temperature offset. If the temperature within thecompressor48 is colder than either the minimum indoor air temperature plus the temperature offset or the minimum outdoor air temperature plus the temperature offset, than thecompressor48 is the coldest part of therefrigerant system10A or10B (for the purposes of block238) and further stator heating to warm thecompressor48 is required. In one embodiment, the temperature offset for the outdoor air temperature is a temperature interval of about 40° F. (200/9° C.) and the temperature offset for the minimum indoor air temperature is a temperature interval of about 15° F. (75/9° C.). If thecompressor48 is not the coldest part of therefrigerant system10A or10B as determined byblock238, themethod200 proceeds to block239 where it is indicated that thecompressor48 is not the coldest part of therefrigerant system10A or10B under the criteria ofquery block238.
• If thecompressor48 is the coldest part of therefrigerant system10A or10B as determined byblock238, ormethod200 has passed throughblock239, themethod200 proceeds to query block240 where it is determined whether theinverter drive46A or46B is overheating. In particular, inquery block240 if the sensed inventor temperature is greater than the minimum inverter temperature used inblock208 and the sensed compressor temperature is greater than the minimum compressor temperature used inblock210 and block239 indicates that thecompressor48 is not the coldest part of therefrigerant system10A or10B then themethod200 proceeds to block242 where the windings of themotor stator54 are de-energized completely so that they do not produce heat within thecompressor48. Themethod200 moves from block242 (orquery block240 if one of the criteria of that block is not met) to block244 before returning back to block202.
• Method200 represents one embodiment used to controlrefrigerant system10A or10B during the off mode that includes the warm up mode as discussed previously. In other embodiments, the control method maybe altered, for example, by elimination or addition of block steps, by changing the power levels used to heat the windings of the compressor, or by altering the temperature criteria utilized in one or more blocks. Additionally or alternatively, other sensors such as those of the sensor array56 (FIGS. 1A,1B,2A, and2B) can be used with the control method.
• While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (20)

1. A refrigerant system adapted to reduce refrigerant migration therein, the system comprising:

a compressor having a motor with motor windings, the motor windings responsive to control signals to selectively generate heat in a manner that does not turn the motor; and

a controller that selectively energizes the motor windings to generate heat based on at least one of a monitored temperature or pressure to warm the compressor.

2. The system ofclaim 1, wherein the controller is the system controller.

3. The refrigerant system ofclaim 1, wherein the controller determines a length of time during which the compressor has been inoperable and then calculates an operational time period to energize the motor windings to generate heat and/or the amount of heat desired to be generated by the motor windings based on the length of time the compressor has been inoperable.

4. The refrigerant system ofclaim 1, wherein the controller calculates an operational time period during which the motor windings generate heat and/or an amount of heat desired to be generated by the motor windings based on at least one of the monitored refrigerant system temperature or pressure.

5. The refrigerant system ofclaim 4, wherein the controller determines a length of time during which the compressor has been inoperable and then calculates the operational time period to energize the motor windings to generate heat and/or the amount of heat desired to be generated by the motor windings based on the length of time the compressor has been inoperable.

6. The refrigerant system ofclaim 1, wherein the monitored refrigerant system temperature or pressure comprises at least one of a sensed outdoor air temperature, an outdoor coil temperature, an outdoor suction temperature, an indoor air temperature, an indoor unit return air temperature, an outdoor suction pressure, a motor stator temperature, an inverter drive temperature or an internal compressor temperature.

7. The refrigerant system ofclaim 6, wherein the controller monitors the inverter drive temperature and the internal compressor temperature and selectively energizes the motor windings to generate heat based on whether at least one of the inverter drive temperature and the internal compressor temperature is less than at least one of a minimum indoor air temperature, a minimum outdoor air temperature, a minimum inverter drive temperature and a minimum internal compressor temperature.

8. The refrigerant system ofclaim 7, wherein the controller monitors the inverter drive temperature and the internal compressor temperature and restricts the compressor from operating and energizes the motor windings to generate heat until the inverter drive temperature and the internal compressor temperature exceed predetermined temperatures.

9. The refrigerant system ofclaim 7, wherein the controller monitors the inverter drive temperature and the internal compressor temperature at predetermined time increments based on the monitored outdoor air temperature.

10. The refrigerant system ofclaim 6, further comprising a controller subassembly that monitors at least one of the motor stator temperature, the inverter drive temperature or the internal compressor temperature and selectively energizes the motor windings based on the at least one of the motor stator temperature, inverter drive temperature, or internal compressor temperature.

11. The refrigerant system ofclaim 6, wherein the controller monitors the inverter drive temperature and cycles off or reduces current to the motor windings to maintain the inverter drive temperature below a predetermined temperature when the compressor is inoperable.

12. The refrigerant system ofclaim 1, further comprising an inverter drive and wherein the inverter drive is refrigerant cooled and the controller operates the compressor at a minimum speed to allow for refrigerant to flow through and cool the inverter drive.

13. The refrigerant system ofclaim 1, wherein the refrigerant system is configured as a heat pump, the heat pump comprising:

a first heat exchanger in fluid communication with the compressor;

a first air circulation device positioned adjacent the first heat exchanger;

a second heat exchanger in fluid communication with the compressor and the first heat exchanger;

a second air circulation device positioned adjacent the second heat exchanger;

a reversing valve fluidly coupled between the first heat exchanger and the second heat exchanger;

an electronic expansion device fluidly coupled between the first heat exchanger and the second heat exchanger; and

an inverter drive;

wherein the controller selectively energizes the motor windings to generate heat in a manner that does not turn the motor.

14. The refrigerant system ofclaim 13, wherein the controller controls at least one of the first air circulation device and the second air circulation device to render at least one temporarily operable to selectively cool the inverter drive from an overheat condition that can result from the motor windings generating heat within the compressor.

15. The refrigerant system ofclaim 13, further comprising:

an outdoor suction pressure sensor and an outdoor suction temperature sensor disposed adjacent the reversing valve or an accumulator and configured to output the outdoor suction pressure and the outdoor suction temperature to the controller;

a motor stator temperature sensor positioned within the compressor adjacent the motor windings and configured to output the motor stator temperature to the controller;

an inverter drive temperature sensor positioned within the inverter drive and configured to output the inverter drive temperature to the controller; and

an internal compressor temperature positioned within the compressor adjacent a compression area therein and configured to output the internal compressor temperature to the controller;

wherein the controller selectively energizes the motor windings to generate heat to warm the compressor based on at least one of the outdoor suction temperature, inverter drive temperature, the internal compressor temperature, or the motor stator temperature.

16. A method of reducing refrigerant migration to a compressor comprising:

providing compressor having a motor with motor windings responsive to control signals to selectively generate heat in a manner that does not turn the motor;

monitoring at least one of a refrigerant system temperature or pressure; and

controlling the motor windings to selectively generate heat based on at least one of the monitored temperature or pressure to reduce refrigerant migration to the compressor.

17. The refrigerant system ofclaim 16, wherein the controller is the system controller.

18. The method ofclaim 16, wherein the monitored refrigerant system temperature or pressure comprises at least one of a sensed outdoor air temperature, an outdoor coil temperature, an outdoor suction temperature, an indoor air temperature, an indoor unit return air temperature, an outdoor suction pressure, a motor stator temperature, an inverter drive temperature or an internal compressor temperature.

19. The method ofclaim 18, wherein the controller monitors the inverter drive temperature and the internal compressor temperature and selectively energizes the motor windings to generate heat based on whether at least one of the inverter drive temperature and the internal compressor temperature is less than at least one of a minimum indoor air temperature, a minimum outdoor air temperature, a minimum inverter drive temperature and a minimum internal compressor temperature.

20. The method ofclaim 18, further comprising an inverter drive electrically connected to the compressor and configured to vary the speed of the compressor, and wherein the controller monitors the inverter drive temperature and either cycles off or reduces current to the motor windings to maintain the inverter drive temperature below a predetermined temperature or operates the compressor at a minimum revolution per minute or operates a fan adjacent to the inverter to allow for cooling of the inverter drive while the motor windings generate heat.

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