US20110204845A1 - System and method for inductively transferring ac power and self alignment between a vehicle and a recharging station - Google Patents

Abstract

A method and apparatus for hands free inductive charging of batteries for an electric vehicle is characterized by the use of a transformer having a primary coil connected with a charging station and a secondary coil connected with a vehicle. More particularly, the when the vehicle is parked adjacent to the charging station, the primary coil is displaced via a self alignment mechanism to position the primary coil adjacent to the secondary coil to maximize the inductive transfer of charging current to the secondary coil. The self alignment mechanism preferably utilizes feedback signals from the secondary coil to automatically displace the primary coil in three directions to position the primary coil for maximum efficiency of the transformer.

Description

• This application claims the benefit of U.S. provisional patent application No. 61/308,099 filed Feb. 25, 2010.
BACKGROUND OF THE INVENTION
• It is now well established that our nation, and many other nations, face serious environmental and fuel supply problems with internal combustion engines. Most internal combustion engines run on either gasoline or diesel fuels, both of which are petroleum products. As is well known, the world's oil supply is generally found far beneath the planet's surface, and in only a few specific locations. Enormous amounts of infrastructure and significant costs are involved in finding, extracting, and processing the oil into gasoline and diesel fuels, and further significant costs are incurred in the storage, transportation, and sale of the finished gasoline and diesel fuel products.
• It is well established that there is only a finite supply of petroleum in our world, and further that the byproducts of combustion, among them carbon monoxide (CO), can and have caused environmental damage to our planet, and have created health risks to humans as well. Thus our nation, as well as many others, faces the problems of a strong reliance on petroleum products for transportation, heating and manufacturing, and that those petroleum products are in short supply and damaging our world and ourselves.
• As a result, there is increased attention on lessening both the reliance on petroleum products and on the negative effects of burning petroleum products. A partial solution is the use of electric vehicles. Electric vehicles, whether purely electric or in the form of gasoline-electric hybrid vehicles, will reduce pollution and the use of petroleum products, especially in the form of gasoline since most electricity-producing power plants run on either natural gas, oil, nuclear power, or coal. While each of these alternative fuel sources produces its own set of issues in regard to the environmental and supply debate, it is generally believed that if a nation, in particular the United States of America, could replace significant amounts of its internal combustion automobile engines with electric vehicles, local, national and perhaps global pollution levels would decrease.
• There have been, therefore, significant expenditures of time, effort, and financial resources to launch the use of at least gasoline-electric hybrid (herein after “hybrid”) vehicles, as well as vehicles that run exclusively on electricity (herein after, both types of automobiles shall be referred to simply as “electric vehicles”), by private automobile manufacturers, and government leaders. Of the many obstacles that have presented themselves to those in the industry of manufacturing electric vehicles, one significant problem is that of recharging the batteries, cells, or other electrical energy storage devices.
• Vehicle energy storage systems are normally recharged using direct contact conductors between an alternating current (AC) source such as is found in most homes in the form or electrical outlets; nominally 120 or 240 VAC. A well known example of a direct contact conductor is a two or three pronged plug normally found with any electrical device. Manually plugging a two or three pronged plug from a charging device to the electric automobile requires that conductors carrying potentially lethal voltages be handled. In addition, the conductors may be exposed, tampered with, or damaged, or otherwise present hazards to the operator or other naïve subjects in the vicinity of the charging vehicle. Although most household current is about 120 VAC single phase, in order to recharge electric vehicle batteries in a reasonable amount of time (two-four hours), it is anticipated that a connection to a 240 VAC source would be required because of the size and capacity of such batteries. Household current from a 240 VAC source is used in most electric clothes dryers and clothes washing machines. The owner/user of the electric vehicle would then be required to manually interact with the higher voltage three pronged plug and connect it at the beginning of the charging cycle, and disconnect it at the end of the charging cycle. The connection and disconnection of three pronged plugs carrying 240 VAC presents an inconvenient and potentially hazardous method of vehicle interface, particularly in inclement weather.
• In order to alleviate the problem of using two or three pronged conductors, exemplary embodiments of the present invention utilize an inductive charging system to transfer power to the electric vehicle. Inductive charging, as is known to those of skill in the art, utilizes a transformer to charge the battery of the target device. One example of known inductive charging systems is that used to charge electric toothbrushes.
• Some electric toothbrushes use non-rechargeable batteries, some use rechargeable batteries that are physically connected to two or more external connectors that interface with matching connectors on a base station. But in an inductive recharging system for an electric toothbrush, there are no such external connects. Instead, a first transformer in the base receives the primary voltage from either a wall source, or a stepped down voltage from some internal circuitry, and creates a time-varying magnetic field through the effect of a ferro-magnetic iron core used in the base transformer. The time-varying magnetic field permeates into the secondary transformer core in the electric toothbrush, and a time-varying voltage is produced on the windings that surround the secondary transformer core. This voltage is fed to internal circuitry where it is rectified and filtered and then input to the battery to recharge it. The same general principles apply to electric vehicle inductive charging systems.
• One item briefly discussed above is the time varying aspect of the AC voltage, and hence the time-varying aspect of the magnetic fields in both the primary and secondary transformer cores. Typically, house current in the U.S. operates at about 60 hertz (Hz), or cycles per second. The problem with using a voltage that oscillates at 60 Hz, is that the size of the components in an inductive charging system is inversely proportional to the frequency, and thus the lower the frequency of the voltage, the greater the size of the inductive charging system. As those of ordinary skill in the automotive industry can attest, size is extremely critical to vehicle manufacturers because it is very important to automotive owners. The size and weight of an object directly affects the fuel mileage of the vehicle. Thus in other inductive charging systems, high frequency voltages, normally above 10 kHz, have been used to transfer power by radiation and tuned coils. There is, however, a cost associated with the use of higher frequency voltages and that is the subsequent loss of efficiency. The higher the frequency at which the charging system operates, the less efficient is the charging system. A less efficient charging system means that much more power must be input into the primary side of the recharging system resulting in greater cost.
FIELD OF THE INVENTION
• The present invention relates to inductive proximity charging. More particularly, the invention relates to a system and method for increasing the efficiency and reducing the noise of a gapped transformer used in inductive charging of a vehicle and to a self-aligning proximity recharging station for a parked vehicle.
BRIEF DESCRIPTION OF THE PRIOR ART
• Gapped transformers are transformers that are formed with two component pieces known as cores. Gapped transformers generally are less efficient for similarly sized and configured transformers than non-gapped transformers which are manufactured as one continuous iron core. As used herein, efficiency is measured as the ratio of power output by the secondary windings of the gapped transformer to the power input by the primary windings of the gapped transformer, which is usually connected to some primary source of power, normally 120 or 240 volts alternating current (VAC).
• Thus, a general need exists for gapped transformers for inductive charging that can increase efficiency and minimize induced noise.
SUMMARY OF THE INVENTION
• It is therefore a general aspect of the invention to provide a system and method for reducing induced noise, increasing the efficiency of a gapped transformer used in inductive charging, and a self-aligning proximity recharging station that will obviate or minimize problems of the type previously described.
• According to a primary object of the invention, the apparatus for charging a battery in a vehicle includes a fixture having an interface plate which is movable in a number of directions. The gapped transformer includes a primary coil mounted on the interface plate and secondary coil mounted on the vehicle. A displacement mechanism is connected with the interface plate to position the primary coil proximate to the secondary coil to maximize the inductive transfer of power from the primary coil to the secondary coil which is used to charge the battery.
• In one embodiment, the displacement mechanism includes a guide plate mounted on the interface plate. When a vehicle is parked adjacent to the fixture, a member on the vehicle engages the guide plate to displace the interface plate laterally and longitudinally relative to the vehicle to align the primary coil with the secondary coil. In addition, a spring connected with the interface plate displaces the interface plate vertically to position it closer to the secondary coil.
• In a preferred embodiment, the interface plate is positioned relative to the vehicle by wireless communication system. The transformer includes control modules connected with the primary and second coils, with each module including a wireless communication device. When the vehicle is parked adjacent to the fixture, a low level of AC current is supplied to the primary coil to induce an AC current in the secondary coil. The level of the induced current in the secondary coil is transmitted to the control module connected with the primary coil. The control module activates the displacement mechanism to move the interface plate laterally, longitudinally, and vertically to position the primary coil proximate to the secondary coil in a position to maximize the inductive transfer of power. Once properly positioned, the level of AC current delivered to the primary coil is maximized to inductively transfer the current to the secondary coil where it is delivered to a charger to charge the vehicle batter.
• The transformer further includes first and second cores for the primary and secondary windings, respectively, each of the cores including first, second, and third pole areas which are separated by first, second and third air gaps, respectively, when the primary core is positioned adjacent to the secondary core.
• The transformer cores are formed in a flared C configuration and a semi-permeable magnetic membrane coats the poles on each core. The membrane is formed of an epoxy binder with a ferromagnetic material embedded therein.
BRIEF DESCRIPTION OF THE FIGURES
• Other objects and advantages of the present invention will become apparent from a study of the following specification when read in conjunction with the accompanying drawing, in which:
• FIG. 1 is a block diagram of a self-aligning inductive alternating current (AC) power transfer system according to a first embodiment of the present invention;
• FIG. 2 is a schematic view of a charging station and the vehicle incorporating the self-aligning inductive AC power transfer system ofFIG. 1;
• FIG. 3 is a more detailed block diagram of the components of the self-aligning inductive AC power transfer system illustrated inFIG. 1;
• FIGS. 4 and 5 top and side views, respectively, of the self-aligning inductive AC power transfer system as shown inFIG. 1 for charging a vehicle;
• FIG. 6 is front view of a floor mounting system for the charging portion of the system shown inFIGS. 4 and 5;
• FIG. 7 is a block diagram of a self-aligning inductive AC power transfer system according to a further embodiment of the present invention;
• FIG. 8 is a side view of a gapped transformer for use in the power transfer system according to the present invention;
• FIG. 9 is a view taken along line9-9 ofFIG. 8 showing a first pole cross sectional surface area of the secondary core of the gapped transformer ofFIG. 8;
• FIG. 10 is a cross sectional view taken along line10-10 ofFIG. 8 showing a first core cross sectional surface area of the secondary core of the gapped transformer shown inFIG. 8;
• FIG. 11 is a side view of secondary core of a gapped transformer according to an embodiment of the present invention;
• FIG. 12 is a bottom view of the secondary core ofFIG. 11 illustrating first and second pole cross sectional surface areas;
• FIG. 13 is a cross sectional view along line13-13 ofFIG. 11 showing a first core cross sectional surface area of the secondary core;
• FIG. 14 is side view of a gapped transformer showing an air space between a primary core and secondary core according to an embodiment of the present invention;
• FIG. 15 is a front perspective view of the secondary core ofFIG. 11.
• FIG. 16 is a side cut-away view of the gapped transformer ofFIG. 14 including a hermetic epoxy sealing case and a semi-permeable magnetic membrane according to an embodiment of the present invention;
• FIG. 17 is a side view of primary and secondary cores of a gapped transformer according to an alternate embodiment of the present invention;
• FIG. 18 is a perspective view of the cores ofFIG. 17;
• FIG. 19 is a top view of a pole of one of the primary or secondary cores ofFIG. 17;
• FIG. 20 is a side view of the pole ofFIG. 19;
• FIG. 21 is a front view of a vehicle induction coil according to an embodiment of the present invention;
• FIGS. 22A and 22B illustrate a first decrease in magnetic flux field fringing when a semi-permeable magnetic membrane is used with a first power transfer system according to an embodiment of the present invention;
• FIGS. 23A and 23B illustrate a second decrease in magnetic flux field fringing when a semi-permeable magnetic membrane is used with a second power transfer system according to an embodiment of the present invention;
• FIG. 24 is a front perspective view of a floor mounting system that can be used with a self-aligning inductive alternating current (AC) power transfer system according to the present invention;
• FIG. 25 is a top view of the floor mounting system ofFIG. 24;
• FIG. 26 is a front cut-away perspective view of the floor mounting system ofFIG. 24;
• FIG. 27 is a cut-away side view of the floor mounting system ofFIG. 24;
• FIG. 28 is a partial cut-away side view of the floor mounting system ofFIG. 24;
• FIG. 29 is a partial top view of a vehicle approaching the floor mounting system ofFIG. 24;
• FIGS. 30A and 30B illustrate different angles of approach between a vehicle and the floor mounting system;
• FIG. 31 is a partial top view of an alternate embodiment of a floor mounting system that can be used with a self-aligning inductive alternating current (AC) power transfer system;
• FIG. 32 is a side view of the floor mounting system ofFIG. 31;
• FIG. 33 is a flow diagram illustrating operation of a self-aligning inductive alternating current (AC) power transfer system; and
• FIG. 34 is a block diagram of a multiple-user floor mounted station system according to the present invention.
DETAILED DESCRIPTION
• The self-aligning AC power transfer system (PTS)100 according to the invention will initially be described with reference toFIG. 1 Thesystem100 includes a floor mounting station (FMS)102 and avehicle unit108.Floor mounting station102 includes a station electronic power transfer control unit (station control unit)104, a station computer control andcommunications module132,station unit indicators140, and astation induction coil303 which is part of an inductive, low noise, high efficiency ACpower transfer system300.Vehicle unit108, which is mounted to and within avehicle124, includes a vehicle induction coil301 (also part of the inductive low noise, high efficiency AC power transfer system300), a vehicle electronic power transfer control unit (vehicle control unit)112, and a vehicle computer control andcommunications module134. Further shown inFIG. 1 as part ofvehicle124 are acharger114, abattery116, and anelectrical engine144. The floor mounting station is shown in more detail inFIGS. 4-6 andFIG. 7 illustrates the system architecture for the self-aligningpower transfer system100 according to the invention.
• Self aligningpower transfer system100 operates to transfer electrical power in an efficient and low-noise manner tovehicle124 havingbatteries116 that require recharging. Generally, such vehicles will be motor vehicles, but such vehicles can also include airplanes, including unmanned aerial vehicles, civilian and military aircraft, including helicopters, gyroplanes, and all types of fixed and rotary winged aircraft. Furthermore, self aligningpower transfer system100 can be used to rechargebatteries116 that are used in boats, submarines, and any and all types of water borne vessels (e.g., hydrofoils, hovercraft, ground-effect vehicles, among others). Other, non-limiting examples of vehicles that can use self aligningpower transfer system100 for rechargingbatteries116 include motorcycles, scooters, trucks, and recreational vehicles.
• FIG. 2 illustrates the self-aligning inductivepower transfer system100 as shown inFIG. 1 according to an exemplary embodiment. InFIG. 2,vehicle124 includes avehicle unit108 having avehicle induction coil301 which is visible on the front-bottom ofvehicle124 as it approachesfloor mounting station102.Floor mounting station102 is electrically connected to a power grid. The power from the mounting station is rectified and filtered and its frequency is changed prior to being input tostation induction coil303 that is visible on the top offloor mounting station102. The operator of thevehicle124 will useindicator lights140 to guide thevehicle124 to substantially close to the proper position, andfloor mounting station102 can self-align itself such that the two induction coils are neatly aligned as will be developed in greater detail below.
• The self aligningpower transfer system100 transfers power tovehicle124 using inductive coupling. In inductive coupling, an alternating current magnetic field is generated in the primary induction coil, and is transferred to, or coupled to, a secondary induction coil that is a component of the vehicle. There, the alternating current voltage is output from the secondary induction coil to a charger, which converts the AC voltage to a direct current (DC) voltage that is used to charge the rechargeable battery. In order to more efficiently transfer the power inductively, the self aligningpower transfer system100 uses specially shaped transformer cores that efficiently transfer the magnetic field from the primary induction coil through an air gap to the secondary induction coil with a minimum of loss. Furthermore, the specially shaped transformer cores minimize induced noise that is a direct result of the choice of the AC frequency. According to exemplary embodiments, the AC voltage can alternate at a frequency range between about 60 Hz to about 1200 Hz. According to a preferred embodiment, and to minimize the size and weight of the components, a frequency of about 400 Hz is used for the AC voltage. A lower AC voltage frequency, for example about 60 Hz, would facilitate production and manufacturing of the self aligningpower transfer system100, but the size of the components is inversely proportional to the AC frequency. Also, losses due to radiated effects increase with lower frequencies, or decrease with higher frequencies. Although frequencies above 400 Hz could also be used, as they become smaller components that operate at those frequencies are generally more expensive and create additional engineering difficulties.
• According to a further exemplary embodiment, self aligningpower transfer system100 uses a special semi-permeable magnetic membrane336 (FIG. 16) over the surfaces of the primary and secondary induction coils303,301 that efficiently transfers the magnetic field from theprimary induction coil303 through an air gap to thesecondary induction coil301 with minimum loss. Self aligningpower transfer system100 includes afloor mounting station102 that houses theprimary induction coil303, and other components, and that can self-align theprimary induction coil303 to thesecondary induction coil301 in thevehicle124 as the vehicle automatically aligns with thefloor mounting station102. Alignment of the primary and secondary induction coils303,301 increases the efficiency of the power transfer from the floor mounting station102 (i.e., the primary induction coil303) to the vehicle and thesecondary induction coil301.
• Referring back now toFIG. 1, station computer control and communications module (station module)132 is linked to one or more of the other components infloor mounting station102 by a floor mounted station data/control computer bus (station bus)142, and vehicle computer control and communications module (vehicle module)134 is linked to one or more of the other components invehicle unit108 by a vehicle unit data/control computer bus (vehicle bus)148. According to an exemplary embodiment,buses142,148 can by any type of command/control/communication buses commonly used in the computer industry such as a universal serial bus (USB), a serial buses, a parallel bus, or any of a multitude of other buses known for transmitting and receiving commands and/or data. According to still another exemplary embodiment,station module132 andvehicle module134 communicate with each other, either wirelessly, via an electrical/mechanical connection (i.e., wired connectors), or a combination of both. If the communication path is at least partially wireless, it can be in the form of infra-red, radio-frequency (RF), microwave, laser, light emitting diode (LED), or even ultra-sonic wireless communications, among other types. In operation, both station andvehicle modules132,134 monitor the status of the components in their respective units (floor mountedstation unit102, and vehicle unit108), and data/information can be transmitted to thestation module132, which can store the data, or transmit it to a central unit (not shown) for further processing and reporting needs. Alternatively,station module132 collects and utilizes the collected data to monitor and keep track of the performance ofvehicle124 as well as the components ofvehicle unit108.
• According to a preferred embodiment,station module unit132, through the use ofcommunication devices135,137, automatically alignsstation induction coil303 withvehicle induction coil301 through use of feedback control. According to alternative embodiments,floor mounting station102 guides the vehicle into an optimum docking position that is within a range of control offloor mounting station102.Station module unit132 provides indications to the operator ofvehicle124 to affect such position. Oncevehicle124 has achieved a near alignment position,station module132 provides a low level amount of power to stationinduction coil303, andvehicle module unit134 provides a dummy load forvehicle induction coil301 so that its output power can be measured. The measured output power is then communicated back tostation module unit132 viacommunication modules135,137, and the efficiency is measured.Station module unit132 positions thestation induction coil303 until a maximum power efficiency is achieved. Once maximum power transfer efficiency is achieved,station module132 provides maximum input power tostation induction coil303 andvehicle module unit134 allows the output power to be sent tovehicle control unit112 to rechargebattery114. A detailed discussion of automation of the self-alignment procedure is set forth below.
• Referring now toFIGS. 1 and 3,AC input power101 entersfloor mounting station102 and is received by station electronic power transfer control unit (station control unit)104.Station control unit104 includescircuit breakers118, andcontrol contactors146.Control contactors146 are simply high power switches that safely handle switching of high voltage AC such as 240 VAC. The power then enters rectifier andfilter unit120 which rectifies the input power to produce a direct current voltage and filters it. According to an exemplary embodiment, rectifier andfilter unit120 is a full wave rectification device which forms a better utilization factor of input power than half-wave rectification devices which are more commonly used for low-power devices. The filters in therectifier filter unit120 reduce high and low frequencies that might otherwise induce physical and electrical noise into the self-aligningpower transfer system100 andvehicle124. Rectifier andfilter unit120 is composed of an inductive-capacitance (LC) section.Unit120 may also be a power factor correcting (PFC) device producing the required DC voltage for use by themedium frequency inverter122. Rectifier andfilter unit120 is preferably a single phase or a three phase bridge rectifier and filter or PFC in which the 240 VAC, 60 Hz input power is changed to a direct current (DC) voltage with less than about 5% ripple for use bymedium frequency inverter122.
• Following rectifier and filter orPFC unit120 is amedium frequency inverter124, which creates a substantially sinusoidal voltage or square wave voltage with a pre-selected frequency. According to various embodiments, the pre-selected frequencies of the input power tovehicle induction coil301 range from about 60 Hz to about 1200 Hz. Medium frequency as used herein refers to a range of frequencies in power usage from about 120 to about 1200 Hz. Frequencies below 120 are referred to as low frequencies and frequencies at or above about 1200 Hz are referred to as high frequencies.Medium frequency inverter122 is a full bridge insulated gate bipolar transistor (IGBT), or MOSFET inverter that uses four high voltage IGBT's or MOSFET's, two designated as high side IGBT's or MOSFET's and the other two as low side IGBT's or MOSFET's. According to a preferred exemplary embodiment, to keep the total power losses low and the total conversion efficiency high,medium frequency inverter122, which can be characterized as a dc-ac inverter circuit, combines low and high side IGBT's or MOSFET's to generate a single-phase wave at any frequency between about 120 and about 1000 Hz.Capacitor126 andstation induction coil201,301 are tuned to substantially maximize power transfer.
• A powerresonant capacitor126 is connected with themedium frequency inverter122.Resonant capacitor126 effectively supplies reactive power to the system in the form of a resonant LC circuit which includes the primary ofprimary station coil303.
• Input electrical power entersstation induction coil303 between 100-240 VAC and at medium frequencies and creates a changing magnetic flux field in the ferro-magnetic core ofstation induction coil303, according to known electromagnetic principles. The magnetic field flows across an air gap and is coupled to the ferro-magnetic core ofvehicle induction coil301. The magnetic field reenters thestation induction coil303 through the air gap and alternates as the changing input power alternates in a substantially sinusoidal fashion. As an alternate embodiment,vehicle induction coil301 may be a coil composed of conductive material without a ferro-magnetic core. A resultant output voltage is produced according to known electromagnetic and transformer principles.
• As voltage is induced in thevehicle induction coil301, atrigger tuning circuit128, along with silicon controlledrectifier136, switches in and outcircuit capacitor138, and thereby controls the voltage regulation of vehicle induction coil output voltage (induction coil output voltage). Alternatively the frequency and/or duty cycle ofpower system122 is changed to maintain voltage regulation. Awireless communications system135 and137 provides this alternative control feature.Capacitor138 forms a coil tuning system with the reactance ofvehicle induction coil301 to substantially maximize power transfer. Induction coil output voltage is coupled tocharger114 ofvehicle124 through atransfer switch130.Transfer switch130 isolates conduction cable340 (FIG. 2) from the self aligning inductivepower transfer system100, or isolates self aligning inductivepower transfer system100 from the conductive cables.Battery116 can then be charged for use to driveelectric engine144.Conduction cable340 can be coupled tovehicle conduction receptacle106, which carries conducted power fromstation unit108 tovehicle124,charger114, and ultimatelybattery116.
• InFIG. 8 is shown a high-noise, low-efficiency power transfer system (first PTS)200, using a gapped transformer with anair gap221a,221bbetweenprimary induction coil203 andsecondary induction coil201.
• It is known in the power transformer arts that a magnetic field is created when current flows through a conductor. In most cases, the conductor is a wire, and in the case of a transformer, the wire is wrapped around a ferro-magnetic core, usually formed of ferro-magnetic iron. Wrapping the wire causes the magnetic field to be concentrated within the ferro-magnetic iron core.
• It is further well known that a changing or alternating magnetic field will induce a charging or alternating current in a conductor, if that conductor is cut by the changing or alternating magnetic field. This generally explains how power transformers operate: a magnetic field is created by the AC input current to the transformer, the AC magnetic field travels throughout the ferro-magnetic iron core around which the input power wires are wrapped, and a voltage is induced on the secondary, or output wires that are also wrapped around the same ferro-magnetic iron core.
• Iffirst PTS200, shown inFIG. 8, were built conventionally, that is, with noair gaps221a,221b, then it would operate as any normal electrical power transformer. However,first PTS200 can be used to induce electric power in the form of a magnetic field acrossair gaps221a,221bsuch that the electric power can be transmitted wirelessly to a different location, and no physical interface (i.e., connectors) is needed to transmit the electric power. As discussed above, one particular exemplary embodiment that makes use of such wirelessly transmitted power is an electric vehicle. Referring again toFIG. 8,first PTS200 includessecondary induction coil201 andprimary induction coil203.Secondary induction coil201 is made up ofsecondary core202 andsecondary windings206 andsecondary core202 comprisesfirst pole214, with a cross sectional area224 (FIG. 9), andsecond pole216, with a cross sectional area226.Primary induction coil203 is made up ofprimary core204, andprimary windings208, andprimary core204 comprisesfirst pole218 with a crosssectional area228, andsecond pole220 with a crosssectional area230.
• Secondary induction coil201 is located invehicle124 that requires recharging of itsrechargeable batteries116. As discussed in greater detail below,primary induction coil201 is preferably located in floor mounting station (FMS)102, or some other suitable enclosure, and whensecondary induction coil201 is proximately located relative toprimary induction coil203, an indication will alert the operator ofvehicle124. Thefloor mounting system102 applies a suitable AC voltage to primary input voltage leads (primary leads)212a,212bof the transformer. According to an exemplary embodiment,floor mounting station102, which is discussed in greater detail below, contains suitable logic and electronic and/or mechanical controls that facilitate switching on-and-off of power toprimary induction coil203. According to a preferred embodiment, the logic and control circuitry offloor mounting station102 only allows power to be applied toprimary induction coil203 whensecondary induction coil201 is located at a close enough distance such that effective proximity inductive transfer of electrical power can occur.
• As those of ordinary skill in the art can appreciate, regardless of how closesecondary induction coil201 is located toprimary induction coil203, anair gap221a,221bwill exist between the two poles of the two cores of the two induction coils. That is, as shown inFIG. 8,air gap221aexists between first pole ofsecondary coil214 and first pole ofprimary core218, and air gap221bexists between second pole ofsecondary coil214 and second pole ofprimary core218. There is a reactance and permeability factor that must be taken into account when analyzing the flow of magnetic fields through open space such asair gaps221a,221b. The permeability and reactance of air are fixed quantities, and for purposes of this discussion, can be presumed to act as an impedance to the transfer ofmagnetic fields232a,232bthroughair gaps221a,221b.
• Ifsecondary induction coil201 is located at the proper position for effective proximity inductive transfer of electrical power to occur,floor mounting station102 provides input power toprimary induction coil203. When input power it applied toprimary core204, via primary input voltage leads (primary leads)212a,212b,magnetic flux field232a,232bexists throughoutsecondary core202 andprimary core204, and through first andsecond air gaps221a,221b. Because of the air gaps,magnetic field232a,232bwill tend to flow in a bulging, outward manner betweenfirst pole218 of primary core andfirst pole214 of secondary core, and in a substantially same manner with respect to second pole ofprimary core220 and second core ofsecondary core216. The bulging, outward flow ofmagnetic field232a,232breduces the efficient transfer of electrical energy betweenprimary core204 andsecondary core202. As a result, a significantly greater amount of input power is required for a given amount of output power. For example, if the efficiency is reduced by 50%, then if 1000 watts of charging power was required to rechargebattery116 ofvehicle124, then at least 2,000 watts of power input toprimary induction coil203 would be required. This would necessitate larger windings to compensate for the additional heat that would have to be dispersed, as well as greater cooling requirements to dissipate the larger amounts of heat that would be generated.
• FIG. 9 illustrates a first pole cross sectional surface area of the secondary core of the gapped transformer as shown inFIG. 8, andFIG. 10 shows a first core cross sectional surface area of the secondary core of the gapped transformer ofFIG. 8. One reason for the ineffective transfer ofmagnetic flux field232a,232bacrossair gap221a,221bis that the ratio of cross sectional area offirst pole224 of secondary core to the cross sectional area of secondary winding223 is substantially unitary, or that is, about 1. An improvement to the design and shape offirst PTS200 is shown inFIGS. 11-16.
• FIG. 14 illustrates a low-noise high-efficiency power transfer system (second PTS)300, using a gapped transformer with anair gap321a,321bbetweenprimary induction coil303 andsecondary induction coil301 according to a preferred embodiment.FIG. 11 is a side view of a novel flared C shapedsecondary core302 ofsecond PTS300 according to an exemplary embodiment,FIG. 12 is a bottom view of the flared C shapedsecondary core302 ofsecond PTS300 further illustrating cross sectional area of thefirst pole324 of secondary core and cross sectional area of thesecond pole326 of secondary core, andFIG. 13 is a cross sectional view along line13-13 ofFIG. 11, showing cross sectional area of the secondary winding323 ofsecondary core302 ofsecond PTS300.FIG. 15 is a front perspective view of the secondary C shaped secondary core as shown in F.11. According to an exemplary embodiment,first pole314 ofsecondary core302 and second pole ofsecondary core302, as shown inFIG. 15, are notably larger thanfirst pole214 ofsecondary core202 and second pole ofsecondary core202 offirst PTS200. The shape of secondary core302 (and similarly, primary core304) is preferably a C shape with flared portions at the top and bottom portions of the C. This flaring provides a larger surface area formagnetic field332a,332bto flow through and into, and which leads directly to the increased efficiency and low noise effects ofsecond PTS300.
• The relative permeability of iron is generally in the thousands and there is a direct relationship between the permeability value and the ability of the magnetic field to flow. Thus, the higher the permeability, the easier the magnetic field will flow. That is why most transformers are fabricated from iron. Conversely, the lower the permeability, the less able the magnetic field can flow. Air is generally thought to have a relative permeability value of about 1. Therefore, any air gap between the primary andsecondary cores202,204;302,304, will negatively affect the ability of the magnetic field to flow. In other words, the magnetic field will flow thousands of times better in the iron than through the air.
• Second PTS300 comprises vehicle (secondary)induction coil301, and station (primary)induction coil303.Secondary induction coil301 includessecondary core302 andsecondary windings306, andsecondary core302 comprisesfirst pole314 with a crosssectional area324, andsecond pole316 with a crosssectional area326.Primary induction coil303 includesprimary core304, andprimary windings308, andprimary core304 has afirst pole318 with a crosssectional area328 and asecond pole320 with a crosssectional area330.
• Operation ofsecond PTS300 is similar to that offirst PTS200. Notably however, the ratio of cross sectional area of first pole of secondary core324 (seen inFIG. 12) to cross sectional area of secondary winding323 (seen inFIG. 13) is between about 2.0 to about 5.0. Preferably, the ratio of cross sectional area of first pole ofsecondary core324 to cross sectional area of secondary winding323 is about 3.2. Increasing the ratio of the area of the pole area to the winding area ofsecondary core302 andprimary core304 leads tomagnetic field332a,332bbeing substantially contained within a volume of space essentially defined by the boundaries of the pole areas of the cores as seen inFIG. 14.
• The flux density of the magnetic field is directly proportional to the area of the iron that the magnetic field is traveling through. In the air gap between primary andsecondary cores302,304, the low permeability of the air acts as an impediment to the flow of the magnetic field. As a result an increase in fringing occurs. The magnetic field seeks a different path through which to flow, and therefore diverges greatly from its intended path, straight across the air gap. It has been determined that if the flux density can be decreased in that the air gap area by increasing the pole area relative to the cross sectional area of the winding area, then the amount of fringing is decreased dramatically, and more of the magnetic field finds its way across the air gap. Thus, the overall charging efficiency of the second PTS increases substantially. The ratio of the pole cross sectional area to that of the winding cross sectional area is preferably about 3.2.
• As a result of the increase in ratio of pole to winding areas, a greater majority ofmagnetic flux332a,332bis contained and can flow unimpeded betweensecondary core302 andprimary core304 and the power transfer efficiency between the power input toprimary core304 and power output fromsecondary core302 increases to between about 80% to about 95%. According to a preferred embodiment, the power transfer efficiency is about 90%.
• At least one additional benefit is derived from the flared C shape of secondary andprimary cores304,302 of second PTS300: induced noise is reduced dramatically. As discussed in greater detail above, a preferred frequency for the AC voltage is within the medium range of frequencies on the order of 400 Hz. Use of amedium frequency inverter122 reduces the size of the components. In addition, use of frequencies in the medium range is widely used in the aircraft industry, and therefore power supply/transformer components are readily available and competitively priced. One drawback to medium frequencies is that they are substantially close to a pure “A” note (440 Hz) and are most discernable, in a negative manner, even in very noisy environments.
• Second PTS300 substantially reduces inducted noise by containingmagnetic field232a,232b, as discussed in greater detail below, within the larger area of itspoles314,316,318, and320. As a result, inducted oscillations of different components of self-aligningPTS100 andvehicle124 were reduced, on the order of at least several decibels (dB's). According to an exemplary embodiment, induced noise was reduced between a first range of dB's and induced noise was reduced between a second range of dB's.
• Thepole areas214,216,218, and220 ofvehicle core202 andstation core204 need not be substantially flat, asFIGS. 17 and 18 illustrate. As discussed above, increasing the ratio of area between the pole and winding sections of the core increases the capability of magnetic flux field232 to travel acrossair gaps221a,221b. The ratio of area can be increased without altering the overall dimensions ofpole areas214,216,218, and220 ofvehicle core202 andstation core204, as shown inFIG. 17. InFIG. 17, which is a front view ofvehicle core202 andstation core204 according to an alternate exemplary embodiment, the outer dimensions of the pole sections remain the same as shown inFIGS. 11-15, but the surface area, the cross sectional area of the first and second poles of thevehicle core202 andstation core204 has increased substantially because of the modified U shape of the pole surfaces. The ratio of area of the pole to core winding areas now increases by a first percentage. Other configurations are possible. Such alternative configurations of the pole surfaces will necessitate a modified approach to docking betweenvehicle124 andfloor mounting station102 as will be discussed in greater detail below.
• Referring now toFIGS. 17 and 18, an alternate embodiment of the core pole areas is shown. As discussed above, adding area to the first pole ofsecondary core214 and first pole ofprimary core218 permits an easier flow of magnetic flux field232 across the small gap betweenvehicle core202 andstation core204, substantially increasing its efficiency and substantially decreasing induced noise/hum invehicle124. The arrangement ofpole areas214′ and218′ increases the surface area because of the trapezoid extension and recess formed in the twocores202,204. Similarly, the extension and recess could be square, triangular, circular, oval, parabolic or any of a multitude of shapes. Each such change in configuration adds more surface area than if a flat surface were used, with the length and width constraints of the cross-sectional area of the winding222. By way of example only, for a square extension and recess as shown inFIGS. 19 and 20, and expressing the same in percentages of length and width, an increase in area of 60% can be obtained.
• Some gap between thecores302,304 is desirable to prevent them from sliding across each other and thereby causing undue wear to the surface of each core. The larger thegap221a,221b, the less efficient will be the transfer ofmagnetic fields232a,232bbetween thecores302,304. Themagnetic fields232a,232btend to fan out at the edges ofcores302,304 acrossgaps221a,221b, as shown inFIG. 8. To reduce or alleviate this issue, and increase the efficiency of the system, thecores302,304 are substantially coated with a semi-permeable resin or epoxy material in the form of a semi-permeablemagnetic membrane336 that includes a magnetic material embedded therein. In one implementation, the magnetic material embedded within the resin or epoxy material is a ferromagnetic material, such as iron or steel.
• FIG. 17 shows a view ofvehicle induction coil301 as would be seen bystation induction coil303. Although onlyvehicle induction coil301 is shown, a similar arrangement would be used forstation induction coil303.Secondary core302 includes secondary winding306 as discussed above. First andsecond poles314,316 are coated with the semi-permeablemagnetic membrane336.
• The semi-permeablemagnetic membrane336 forms a hermetic coating over first andsecond poles314,316 to prevent corrosion. Semi-permeable magnetic membrane includes aferromagnetic material337 such as iron or steel filings embedded therein.Ferromagnetic material337 may be formed of powdered transformer steel or similar material.Ferromagnetic material337 is mixed into an epoxy binder and applied to first andsecond poles314,316 to form the semi-permeablemagnetic membrane336.
• Ferromagnetic material337 generally comprises about 30% to 90% or more of the semi-permeablemagnetic membrane336. In general, less than about 30% offerromagnetic material337 would not sufficiently increase efficiency, while greater than about 75% may become brittle. In one implementation, semi-permeablemagnetic membrane336 includes 71% powdered iron as theferromagnetic material337.
• When implemented as powdered iron, a general implementation would include a distribution of sizes of the individual granules. The distribution includes about 70% to 75% being +325 mesh, less than about 16% being +100 mesh, with the balance of up to about 30% pan sieve. In one example, iron powder size distribution is as follows:

• 	+60 Mesh US Std Sieve	0.0 wt %
  	+100 Mesh US Std Sieve	10.3 wt %
  	+325 Mesh US Std Sieve	72.0 wt %
  	+Pan Sieve	17.7 wt %

• There are several types of resins or epoxies that can be used with specific formulations. Furthermore, the filings can be aligned or they can be placed randomly. There are several sizes of the filings, several methods of preparation, and several methods of applying the semi-permeable magnetic membrane to the poles.
• The semi-permeablemagnetic membrane336 is applied to bothprimary core304 andsecondary core302 to fill the gap between thecores302,304. Semi-permeablemagnetic membrane336 reduces friction on each core when they come into contact, thereby saving wear on thecores302,304.Ferromagnetic material337 embedded in semi-permeablemagnetic membrane336 permits an appreciable increase in transfer of the magnetic field and therefore the power transfer efficiency. A 24 V drop was noted without use offerromagnetic material337 in semi-permeablemagnetic membrane336.
• FIGS. 22A and 22B illustrate a first decrease in the fringing of magnetic flux field232 when a semi-permeablemagnetic membrane336 is used withfirst power transformer200 according to one embodiment, andFIGS. 23A and 23B illustrate a second decrease in fringing of magnetic flux field332 when a semi-permeablemagnetic membrane336 is used withsecond power transformer300.FIGS. 22A and 22B illustrate the effect of use ofmembrane336 withsecondary core202 andprimary core204. InFIG. 22A, there is nomembrane336 and there is significant fringing of magnetic flux field232 as discussed in detail above. InFIG. 22B, membrane336 (not drawn to scale) is added to the first pole ofprimary core218 and the first pole ofsecondary core214, andmagnetic flux field232a′ is significantly reduced. The reduction inmagnetic flux field232a′ is between about a first range, and the reduction inmagnetic flux field232a′ is about a second percentage.
• FIGS. 23A and 23B illustrate the effect ofmembrane336 withsecondary core302 andprimary core304. InFIG. 23A, there is nomembrane336 and there is significant fringing of magnetic flux field332 as discussed in detail above. InFIG. 23B, membrane336 (not drawn to scale) is added to first pole ofprimary core318 and first pole ofsecondary core314, andmagnetic flux field332a′ is significantly reduced. According to an exemplary embodiment, the reduction inmagnetic flux field332a′ is between about a second range, and according to a preferred embodiment, the reduction inmagnetic flux field332a′ is about a third percentage.
• Referring now toFIG. 24, there is shown a floor mounting station (FMS)102 that can be used with either of the first or second self or automatic aligningpower transfer system100,200 according to a preferred embodiment of the present invention. As briefly discussed above,floor mounting station102 can automatically self-align itself tovehicle124 when an operator ofvehicle124 approaches thefloor mounting station102 to begin rechargingbattery116. Self-aligning offloor mounting station102 is accomplished by a three quadrant operating mechanism supported by a plurality of springs, slides, enclosures and rollers that allowsinterface plate406aoffloor mounting station102 to freely and independently move in lateral, longitudinal and vertical directions asvehicle124 moves in proximity to thefloor mounting station102. Status indicator lights ontower402 offloor mounting station102 indicate several different statuses offloor mounting station102, and proximity sensors allow charging to begin whenvehicle124 is in the proper position.
• Thefloor mounting station102 includestower402,indicators140a-d,floor mounting fixture404,interface plate406ahaving aguide plate408 thereon,station unit enclosure410, front mounting receptacles416,rear mounting receptacle418,indicator panel420, springs422, plate anchor430, andinner enclosure414, among other components. TheFMS102 further includeselectronics enclosure150, and stationunit communication device137.Electronic enclosure150 housesstation control unit104. First or secondpower transfer systems200,300 that are part of floor mounting station102 (and not part of vehicle124), and stationunit communication device137 are generally housed instation unit enclosure410. Also shown as part offloor mounting station102 are certain components of firstpower transfer system200 and secondpower transfer system300, for example,primary induction coil203,303, hermeticepoxy sealing case334, and semi-permeablemagnetic membrane336.
• As seen inFIGS. 24-32,floor mounting station102 is generally a rectangular shaped device with a low profile and a column-like tower402.Tower402 needs only be tall enough such that it can reasonably be seen by an operator ofvehicle124 which is to be positioned relative to the system. Thestation unit102 and first and secondpower transfer system200,300 are designed to accommodate different brands of motor vehicles or other types electrically powered devices to be recharged. Moreover, the position of thetower402 onfloor mounting station102 can be changed as necessary to accommodate different vehicles asFIGS. 6 and 24 illustrate. InFIG. 24,tower402 is centrally located onfloor mounting station102 whereas inFIG. 6,tower402 is located along a left side offloor mounting station102 as viewed by an operator ofvehicle124 and is therefore substantially directly in front of the vehicle operator. In this case, according to a preferred embodiment,vehicle124 is an automobile, and the location oftower402 greatly improves docking so that near perfect alignment is achieved.
• As seen inFIG. 24,interface plate406aresides on an upper portion ofstation unit enclosure410, and houses the station unit components of first and secondpower transfer system200,300, which includesprimary induction coil203,303, and hermeticepoxy sealing case334, and semi-permeablemagnetic membrane336.FIG. 25 is a top view of the floor mounting system as shown inFIG. 24. While the secondpower transfer system300 and its components will be described, both first and secondpower transfer system200,300 are substantially interchangeable, and both can be used with the different exemplary embodiments offloor mounting station102 as discussed herein.
• Vehicle induction coil301 is mounted on thevehicle124 and positioned in such a way as to be able to get as close as possible to stationinduction coil303 on theinterface plate406aof thestation102 when recharging is desired. Theinduction coil303 is mounted tofirst interface plate406asuch that first and second poles ofprimary core318,320 are flush with an upper surface offirst interface plate406aas shown inFIGS. 24,25, and27. First and second poles ofstation core318,320 and first and second poles ofvehicle core314,316 are covered with semi-permeablemagnetic membrane336 to facilitate transfer of electric power inductively fromstation unit102 tovehicle124. When thevehicle124 is properly positioned with respect to thestation unit102, the semi-permeablemagnetic membranes336 of first and second poles ofstation core318,320 and first and second poles ofvehicle core314,316 may be very close together or touching each other. At such a positioning betweenvehicle124,floor mounting station102, the first and second poles ofstation core318 and first and second poles ofvehicle core314,316 are in magnetic conjunction so that a substantially efficient transfer of electrical power can take place betweenfloor mounting station102 andvehicle124.
• Referring now toFIGS. 26,27, and28,FIG. 26 is a front cut-away perspective view offloor mounting station102 as shown inFIG. 24,FIG. 27 is a cut-away side view offloor mounting station102, andFIG. 28 is a partial cut-away side view offloor mounting station102.FIG. 26 illustrates a pair of front mountingreceptacles416a,416bwhich provide a mounting location forsprings422a,422bas shown inFIGS. 27 and 28 which are then attached on a lower surface offirst interface plate406a. For purposes of this discussion, reference shall be made to an upper and lower surface offirst interface plate406awhere the upper surface is that surface located closest tovehicle124 and the lower surface is that surface located closest to or withinstation unit enclosure410. A top portion offirst interface plate406ais that portion offirst interface plate406athat is closest to tower402 and a lower portion offirst interface plate406ais that portion offirst interface plate406athat is located farthest away fromtower402, and to which is attachedrear mounting receptacle418 as shown inFIGS. 27 and 28. It will be appreciated that while two mounting receptacles are shown, other configurations will work equally well.
• In operation,station unit102 allows thevehicle induction coil301 to come in as close proximity as possible to stationinduction coil303. To facilitate a sufficient proximity ofvehicle induction coil301 andstation induction coil303,station unit102 is constructed such thatfirst interface plate406aretainsstation induction coil303 at plate inclination angle θ. Preferably, the plate inclination angle θ is a relatively shallow or small angle such that a smooth almost frictionless interface exists betweenvehicle induction coil301 andstation induction coil303. Use ofsprings422a,422bat first and second mountingreceptacles416a,416bprovidefirst interface plate406awith the ability to rotate about rear mountingreceptacle418 in the direction of arrow A as shown inFIG. 27, such that asvehicle124 andvehicle induction coil301encounter station unit102 andstation induction coil303,first interface plate406agently rotates downwardly.Springs422a,422bpushfirst interface plate406awithstation induction coil301 gently upwardly, so thatstation induction coil303 andvehicle induction coil301 can make sufficient contact while substantially minimizing shock, vibration, and mechanical damage.
• Also shown inFIG. 27 is anelectronics enclosure150 which housesstation control unit104 which is electrically connected to stationinduction coil303. The electronics are electrically connected or wirelessly connected toindicators140 and/orindicator panel420.Station unit enclosure410 is fixed to the floor or ground viafloor mounting fixture404 andbolt432.
• As discussed above,first interface plate406acan rotate about rear mountingreceptacle418 in the direction of arrow A, becausefirst interface plate406ais mounted to rear mountingreceptacle418 via a pin that can rotate as shown by arrow B. Referring now toFIG. 28, it can be seen that rear mountingreceptacle418 can also rotate in the direction of arrow C which further allows rotation offirst plate406ain the direction of arrows D and E as shown inFIG. 28.Springs422a,422ballow thefirst plate406ato rotate in the direction of arrows D and E, but such rotation would be constrained with the use of rotatingrear mounting receptacle418. According to an alternate embodiment,rear mounting receptacle418 can be replaced withspring422 and still operate in a substantially similar manner. Thus, the combination of rotatingrear mounting receptacle418 and front mountingreceptacles416a,416bwithsprings422 providesfirst interface plate406awith the means to move in two dimensions: up and down as shown by arrow A inFIG. 27 and to the left and right as shown by arrows D and E, inFIG. 28 in order to self-align thestation induction coil303 on thefirst interface plate406awith thevehicle induction coil301.
• Attention is now directed toFIGS. 29 and 30.FIG. 29 is a partial top view ofvehicle124 approachingfloor mounting station102 as shown inFIG. 24, andFIGS. 30A and 30B illustrate angles of approach betweenvehicle124 andfloor mounting station102 as shown inFIGS. 24 and 29. As discussed above, the combination of rotatingrear mounting receptacle418 and front mountingreceptacles416a,416bwithsprings422 providesfirst interface plate406awith the means to move laterally and vertically in order to self-alignfirst interface plate406aandstation induction coil303 withvehicle induction coil301. Self-alignment, however, is accomplished by interaction betweenvehicle induction coil301 as it approachesstation unit102 and self-alignfirst interface plate406aso thatvehicle induction coil301 andstation induction coil303 are proximately close together.Plate guide408 comprises left plate guide arm409a, rightplate guide arm409b, and plate guide backwall411. Both first and second plate guidearms409a,409bare formed at a plate guide angles Φ_1,2with respect to plate guide backwall411. As discussed in greater detail below, the length of first and second plate guidearms409a,409band plate guide angle Φ directly determine the limitations in terms of distances in which self-alignment can still occur.
• Various design considerations are taken into account in the design ofplate guide408, the length of plate guidearms409a,409b, and the angles of left and right plate guide arms409a, b. If plate guide angle Φ is too large and/or the length of plate guidearms409a,409bis too long, then there will not be enough range of motion insprings422 and rear mountingreceptacle418. In other words, if plate guide angle Φ is too large,vehicle124 can approachfloor mounting station102 at too large of an angle for first interface plate406 to compensate for self-alignment, and it will not occur. Moreover, limiting plate guide angle Φ means that there is a limitation on the angle thatvehicle124 can make in approaching first interface plate406, which is referred to as approach angle Ω. Approach angle Ω is shown inFIGS. 30A, and30B.
• As seen inFIG. 30A (which shows only enough detail offloor mounting station102 necessary for an explanation of approach angle Ω), ifvehicle124 is approaching such that it is to the left ofstation unit102, the left-front corner LF ofvehicle induction coil301 will be aligned just to the right or inner part of the end-most portion of left plate guide arm409a. Ifvehicle124 was any further to the left ofstation unit102, a front portion ofvehicle induction coil301 would impact left plate guide arm409a, and no self-alignment could take place. A similar situation occurs whenvehicle124 approaches from the right side ofstation unit102 wherein, as shown inFIG. 30B, the right-front corner RF ofvehicle induction coil301 will be aligned just to the left, or inner, part of the end-most portion of rightplate guide arm409b
• FIG. 31 is a partial top view of an alternate embodiment of the second interface plate406bthat is used with first and secondpower transfer system200,300 andFIG. 32 is a side view of second interface plate406b. Second interface plate406boperates in a manner similar tofirst interface plate406a, and all other components offloor mounting station102 not shown inFIGS. 31 and 32 are substantially the same as discussed above. Second interface plate406bdiffers fromfirst interface plate406ain that it is connected to enclosure upper surface412a,412band not to the inner floor surface ofstation unit enclosure410 byseveral springs422 and plate anchors430 as shown inFIG. 31. The arrangement of plate anchors430 and springs422 and their connection to second interface plate406bprovides second interface plate406bwith the ability to move in three dimensions and to rotate as shown inFIGS. 31 and 32. However, even with additional degrees of movement, there are limitations on the angles of movement and the approach angle ofvehicle124 as discussed above with respect to thefirst interface plate406a. That is, there is a plate guide angle, now referred to as second plate guide angle Φ, and there is an approach angle Ω, now referred to as second approach angle Ω.
• Tower401 containsindicators140a-dand anindicator panel420 that housesindicators140a-das shown inFIG. 27.Indicators140a-dcan be one or more of many different types of colored indicators such as light emitting diodes (LEDs), incandescent bulbs, florescent bulbs, neon lamps, plasma panels, light commanding diodes (LCDs), fiber optic cables, or even white/clear-colored indicators, with colored plastic or glass coverings.
• By way of example,indicator140acan be colored red and indicates “STOP”, meaning thatvehicle124 is in position.Indicator140bcan be colored yellow to indicate “CHARGING”, meaning self aligningpower transfer system100 is chargingvehicle124.Indicator140cis colored green and indicates “READY”, meaningfloor mounting station102 andvehicle unit108 have communicated with each other and that self aligningpower transfer system100 is ready to begin charging. Indictor104dcan be colored blue to indicate “STOPPED CHARGING”, meaning that charging is completed. Of course, the colors and messages/meanings can be altered and configured to fit specific situations, and/or design choices
• Not shown but part ofstation unit108 is a proximity detector which can be a separate sensor or a particular function that is carried out bystation communication module134 andvehicle communication module132. Proximity detection determines whenvehicle124 is in position and ready to accept electrical power. The proximity detector also determines whenvehicle124 has pulled away from or is no longer in close proximity tostation unit108 so that if charging is still occurring, controls can be implemented to turn off power tostation induction coil203,303.
• Communications between thevehicle124 and the self-aligningpower transfer system100 can take the form of wireless communications such as via radio frequency (RF) or microwave frequencies (or higher), infra-red, laser, and ultra-sonic signals or in a wired fashion by a physical connection betweenvehicle124 andvehicle unit108, andfloor mounting station102. Communications and other electrical specifications are discussed in greater detail in “Surface Vehicle Recommend Practice,” published by The Engineering Society for Advancing Mobility Land Sea Air and Space, Society of Automotive Engineers (SAE), document J1772, issued in October of 1996, rev. November 2001 and the “2008 National Electrical Code Handbook,” Article 625, “Electric Vehicle Charging System,” both of which are incorporated herein by reference.
• FIG. 33 is a flow diagram of method500 illustrating operation of the self-aligning inductive ACpower transfer system100 according to another embodiment. Method500 begins whenvehicle124 pulls into a parking spot, and engagesfloor mounting station102. Indecision step502, one or more sensors determine proximity ofvehicle124 and communicates that thevehicle124 has properly mated with self-aligning power transfer system100 (“Yes” path from decision step502).Stop indicator140ais lit (step504). Alternatively, ifvehicle124 has not properly mated with self-aligningpower transfer system100,decision step502 preventsstop indicator140afrom lighting (step506, “No” path from decision step502). Method500 continues to check the proximity detector function, until proximity is detected. Followingdecision step502, method500 proceeds to decision step508, and the balance of the flow chart.
• FIG. 7 is a system architecture block diagram600 for the self-aligning inductive ACpower transfer system100 according to a further embodiment. Substantially all of the components shown inFIG. 7 have been discussed in greater detail above, and therefore shall not be repeated again. However, there are some components ofsystem architecture600 that have not been addressed. For example, additional inputs602a-jto stationcomputer132 can be incorporated into self-alignmentpower transfer system100. A non-exhaustive list of additional inputs can further include proximity detect602a(discussed above), charge current602b, stop button602c, over travel limit602d, station pole over-temperature602e, heat sink over-temperature602f, infra-red system status602g, station pole proximity detect602h, pilot voltage602i, and load shed602j. Additional outputs can be produced byvehicle computer134 for use by self-alignment system100 and for observation by an operator of self-alignmentpower transfer system100. These include, for example, system ready light604a(discussed above), stop light604b(discussed above), charging light604c(discussed above), safety contactor604d, P2 generation604e, pilot voltage pulse width604f, and station plugtransfer switch604g, among others.
• Charge current602bcan be an input tostation computer132 to monitor and track the amount of current that is being transferred tovehicle124. A separate charge current can also be monitored byvehicle computer134 and the two values can be compared. Over travel limit602dcan be detected bystation computer132 to detect whenvehicle124 is misaligned withstation unit102. Station pole over-temperature602eis an indication of the temperature of either one or both of first and second poles of primary and/orsecondary cores314,316,318,320. Heat sink over-temperature602fis an indication of the temperature of a heat sink for one or both ofvehicle core302 andstation core304, or ofstation unit102 itself. Infra-red system status602gis an induction of the operating status of vehicle andstation communication devices137,136 respectively. Station pole proximity detect602his an indication of proximity between one or both first and second poles ofsecondary core314,316 with first and second poles ofprimary core318,320.
• Additional outputs can be produced for observation by an operator of self-alignmentpower transfer system100. These can include, for example, system ready light604a, stop light604b, and charging light604c.
• FIG. 34 is a block diagram of a multiple-user floor mounted station system700 according to an exemplary embodiment. Multiple floor mounted system700 allows multiple users to charge their vehicles or other devices that userechargeable batteries116, simultaneously. Thus, for example, multiple floor mounted station system can be used at parking lots and garages, convenience stores, shopping centers, malls, and housing developments, among other places. Vendors can charge user fees for recharging vehicles and an appropriately designed user interface that takes different modes of payments (cash, credit cards, electronic tag systems) could be used to collect the user-charging fees.
• Multiple floor mounted station system700 can simultaneously charge one ormore vehicles124 at a time. The multiple charging system700 operates similarly to a stand-alone charging system102. As shown inFIG. 34, there are several floor mountedstations102 interconnected byAC input power101, and intra-floor mountedstation communication cable152. Each individual floor mountedstation102 operates similarly to that as described above, except that with two or more floor mountedstations102 connected together in the configuration of multiple floor mounted station system700 as shown inFIG. 34, one of themultiple stations102 must be designated a master and the rest as slaves. The master floor mountedstation102 of multiple floor mounted station system700 can communicate with its slaves either wirelessly or through awired communication cable152, as shown inFIG. 34 using RS232, USB, or other types of communication. Communication can be performed from the master to all slaves and visa-versa, or from the master to slave1, then from slave1 toslave2, and so on. In either case, the master floor mountedstation102 must be informed of all of the slave floor mountedstations102 that it is responsible for, and this can be done manually via switches or electronically. For example, there can be a protocol built into floor mountedstation102 that whencommunication cable152 is hooked into afirst station102, it automatically begins searching forother stations102 and attempts to determine which one is the master.
• The master floor mountedstation102 of the multiple system700 collects data for billing and/or maintenance purposes and can communicate with a base station by cellular, internet or other landline/wireless communication system. The master floor mounted station of the multiple station system700 controls current load distribution between and among its slaves. By way of example, assume that there are 10stations102 in a multiple floor mounted station system700, each providing a total of 50 Amps current for recharging. However, the electrical service that multiple station system is connected to is rated only for 400 Amps. If ten vehicles are simultaneously recharging, the maximum current load for the electrical circuit will be exceeded, and either the breaker will trip, or a catastrophic failure and fire could result. According to the invention, the master floor mountedstation102 can detect that the tenth vehicle is ready to begin charging and can communicate to its slaves to decrease their respective output charging current to 40 Amps (or less) until further notified. Information about each slave's charging current is automatically communicated to the master, or the master can periodically request status updates, or a combination thereof can occur. As soon as one of the slave's vehicle discontinues charging, themaster station102 authorizes maximum charging current from the balance of the slave stations. A preferential payment system can be implemented that allows a user to pay more for the express purpose of receiving a maximum charging current from its chargingstation102 even if the charging current provided byother stations102 are severely degraded.
• There are several advantages to the design and implementation of self-alignmentpower transfer system100 according to the various embodiments discussed herein. For example, it is advantageous to provide inductive power transfer to a vehicle that is universal in nature, and wherein the voltage ratio of the station and vehicle unit is matched to supply the proper charging voltage and power required by the vehicle.
• A further advantage is to eliminate the problems associated with handling dirty, wet, dangerous frayed cords and exposed live contacts since there are no live contacts which the operator can access. The invention provides a very convenient method of inductive power transfer that requires that the operator need only to drive up to and over a self-aligning station unit to initiate power transfer. Coupling of the vehicle with the charging station is safe and tamper proof while power is transferred to the vehicle. The invention further provides high power, high efficiency, low audible noise power transfer to the vehicle that is durable, reliable and economical. This is accomplished by the use of a transformer gap composed of semi-permeable magnetic material.
• While the preferred forms and embodiments of the present invention have been illustrated and described, it will be readily apparent to those skilled in the art that various changes and modifications may be made without deviating from the inventive concepts set forth above.

Claims (30)

1. A power transformer, comprising:

a first core including first, second, and third pole areas; and

a second core including first, second, and third pole areas, and wherein

the first core and the second core are separated by first, second, and third air gaps,

the first air gap separating the first pole of the first core and the first pole of the second core, the second air gap separating the second pole of the first core and the second pole of the second core, and the third air gap separating the third pole of the first core and the third pole of the second core.

2. The power transformer according toclaim 1, wherein

the first core further comprises a first winding area wrapped about a first conductive material connected with a primary voltage source;

the second core further comprises a second winding area wrapped about a second conductive material configured to provide current;

the first, second, and third poles of the first core, and the first, second, and third poles of the second core are substantially similar in size and shape;

the first and second windings are substantially similar in cross sectional area; and

a ratio of surface area of the first pole to the cross sectional area of the first winding area is between about a 2.0 and about 5.0.

3. The power transformer according toclaim 2, wherein the ratio of surface area of the first pole to the cross sectional area of the first winding area is about 3.2.

4. The power transformer according toclaim 1, wherein power input to the primary core is inductively coupled through the first, second, and third air gaps to the second core.

5. The power transformer according toclaim 1, wherein the first core and the second core are shaped like a flared “C”.

6. A system for charging a rechargeable battery, comprising:

a power transformer including

a first core, the first core including first, second, and third pole areas; and

a second core, the second core including first, second, and third pole areas, and wherein

the first core and the second core are separated by first, second, and third air gaps,

the first air gap separating the first pole of the first core and the first pole of the second core, the second air gap separating the second pole of the first core and the second pole of the second core, and the third air gap separating the third pole of the first core and the third pole of the second core; and

a semi-permeable magnetic membrane comprising an epoxy binder and a ferromagnetic material embedded within the epoxy binder, wherein

the semi-permeable magnetic membrane coats each of the first, second, and third poles on the first core, and

the semi-permeable magnetic membrane coats each of the first, second, and third poles on the second core,

the first core is electrically connected to a primary voltage source, and

the second core is located apart from the first core until recharging occurs and further is electrically connected to the rechargeable battery.

7. The system for recharging according toclaim 6, wherein the ferromagnetic material includes at least one of iron and steel.

8. The system for recharging according toclaim 6, wherein the semi-permeable magnetic material comprises a mixture of between 30% and 90% iron or steel filings in an epoxy binder.

9. An inductively coupled battery recharging system, comprising:

a first inductive winding coupled to an exterior power source and including

a first core,

a first winding area of the first core including a first winding cross sectional area A_WC1;

a first pole section of the first core including a first pole sectional area A_C1P1, a second pole section of the first core including a second pole sectional area A_C1P2, and a third pole section of the first core including a third pole section area A_C1P3, wherein A_C1P1, A_C1P2, and A_C1P3are substantially similar in shape and size; and

a second inductive winding coupled to a rechargeable battery and including

a second core,

a second winding area of the second core including a second winding cross sectional area A_WC2;

a first pole section of the second core including a first pole sectional area A_C2P1, and a second pole section of the second core includes a second pole sectional area A_C2P2, and a third pole section of the second core including a third pole sectional area A_C2P3, wherein A_C2P1and A_C2P2and A_C2P3are substantially similar in shape and size, A_WC1and A_WC2are substantially similar in shape and size, and A_C1P1and A_C1P2and A_C1P3and A_C2P1and A_C2P2and A_C2P3are substantially similar in shape and size, and further wherein,

when the ratio of the area of the pole of the core to the area of the winding of the core is between 2.0- and 5.0, both a first magnetic flux area formed between the first pole of the first core and the first pole of the second core, and a second magnetic flux area formed between the second pole of the first core and the second pole of the second core, and a third magnetic flux area formed between the third pole of the first core and the third pole of the second core are substantially contained, respectively, within a first volume formed by the cross sectional areas of the first pole of the first core and the first pole of the second core, and the second pole of the first core and the second pole of the second core, and the third pole of the first core and the third pole of the second core.

10. An inductively coupled battery recharging system as defined inclaim 1, wherein the ratio of the area of the pole of the core to the area of the winding of the core is about 3.2.

11. An inductively coupled battery recharging system as defined inclaim 9, and further comprising a semi-permeable magnetic material comprising an epoxy binder and a ferromagnetic material embedded within the epoxy binder for coating said first and second poles on said first and second cores, respectively.

12. An inductively coupled battery recharging system as defined inclaim 11, wherein the ferromagnetic material includes at least one of iron and steel.

13. An inductively coupled battery recharging system as defined inclaim 11, wherein the semi-permeable magnetic material comprises a mixture of between 30% and 90% of at least one of iron and steel filings in an epoxy binder.

14. A method for increasing the efficiency of energy transfer in a transformer having at least two cores, each core having at least two poles, comprising the steps of

embedding a ferromagnetic material into an epoxy binder to provide a semi-permeable magnetic material; and

applying the semi-permeable magnetic material to the at least two poles of each core.

15. The method of claim, wherein said embedding step comprises forming a mixture of between 30% and 90% of at least one of iron and steel filings in the epoxy binder.

16. Apparatus for inductively charging a battery in a vehicle, comprising

(a) a fixture; and

(b) a transformer including

(1) a primary coil mounted on said fixture; and

(2) a secondary coil mounted on the vehicle,

whereby when the vehicle is positioned adjacent to said fixture and said secondary coil is opposite said primary coil and power is supplied to said primary coil, inductive power is transmitted to said secondary coil to charge the vehicle battery.

17. Apparatus as defined inclaim 16, wherein said fixture includes a movable interface plate, said primary coil being mounted on said interface plate.

18. Apparatus as defined inclaim 17, and further comprising means for displacing said interface plate to position said primary coil proximate to said secondary coil.

19. Apparatus as defined inclaim 18, wherein said displacing means comprises a guide plate mounted on said interface plate, said guide plate engaging a member on said vehicle and being displaced relative to said vehicle member to displace said interface plate laterally and longitudinally relative to the vehicle to align said primary and secondary coils.

20. Apparatus as defined inclaim 19, wherein said interface plate is pivotally connected with said fixture.

21. Apparatus as defined inclaim 20, wherein said displacing means further comprises a spring for pivoting said interface plate vertically to position said primary coil proximate to said secondary coil.

22. Apparatus as defined inclaim 18, and further comprising a first control module connected with said fixture and a second control module connected with said second coil said first control module controlling the operation of said first coil and said second control module controlling the operation of said second coil.

23. Apparatus as defined inclaim 22, and wherein said first and second control modules include wireless communication devices for sending information between said first and second control modules.

24. Apparatus as defined inclaim 23, wherein said first control module is connected with said displacing means to control the movement of said interface plate.

25. Apparatus as defined inclaim 24, wherein said displacing means moves said interface plate laterally, longitudinally and vertically to position said first coil proximate to said second coil.

26. Apparatus as defined inclaim 25, wherein said communication devices transmit information between said first and second modules relating to the strength of the magnetic field generated by said coils in order to position said interface plate in a position where energy transferred from said first coil to said second coil is maximized.

27. A method for inductively charging a battery in a vehicle, comprising the steps of

(a) connecting the secondary coil of a transformer with the vehicle battery and the primary coil of a transformer with a fixture;

(b) positioning the vehicle adjacent to the fixture;

(c) aligning the primary coil with the secondary coil to maximize the inductive transfer of power from said primary coil to said secondary coil, thereby to deliver power to the battery.

28. A method as defined inclaim 25, wherein said aligning step includes the steps of

(a) supplying a low level of AC current to said primary coil to induce AC current in the secondary coil;

(b) measuring the AC current induced in the secondary coil to determine the efficiency of the inductive transfer of power between said coils;

(c) positioning said primary coil to maximize the efficiency of the inductive transfer of power.

29. A method as defined inclaim 28, and further comprising the step of transmitting a signal corresponding to the level of induced current in the secondary coil to the fixture to control the positioning of said primary coil.

30. A method as defined inclaim 29, and further comprising the step of rectifying the AC current supplied to the primary coil of the transformer.

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