Eddy Current Repulsion Motor

Abstract

To provide a lightweight electric motor that generates larger torque with a smaller size.SOLUTION: An alternating current (130) flowing through a plurality of stator coils (118) of an electric motor (108) is controlled based on a position of a rotor (116) in an electric motor (108). When the alternating current (130) flows through at least one stator coil (136) among stator coils (118), repulsive force (140) is adapted to be generated between a rotor and at least one stator coil (136).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates generally to electric motors, and more particularly to electric motors that use alternating current. [Background technology]

[0002] An electric motor is a device that converts electrical power into mechanical power. Electric motors are used in a variety of applications. For example, but not limited to, electric motors are used to drive fans, pumps, tools, disk drives, drills, and other types of equipment. Electric motors are used in a variety of environments. For example, electric motors are used in applications on fixed and mobile platforms, such as aircraft and other vehicles.

[0003] Electric motors may be used in aircraft to perform a variety of functions, for example, but not limited to, electric motors in aircraft may be used to operate flight control surfaces, raise and lower landing gear, open and close valves, and perform other functions on the aircraft.

[0004] When using electric motors in aircraft, factors such as weight and space are important considerations. Current electric motors employ rotors that contain ferromagnetic materials. Ferromagnetic materials are dense. Therefore, the weight of the rotors can make the electric motor unduly heavy. The weight of the rotors can also affect the responsiveness, speed, and power density of the electric motor.

[0005] For example, electric motors may take too long to start and stop, the iron in the rotor creates a large moment of inertia compared to other lighter materials, which reduces responsiveness, and electric motors may be limited in maximum speed by centrifugal stress, commutation voltage limitations, or a combination of these.

[0006] Electric motors are also expensive, for example due to materials and parts that make them expensive.

[0007] Also, assembly costs are high. For example, manufacturing an electric motor involves winding coils, stacking laminated iron sheets with insulating layers, and other steps that are taken to assemble the electric motor. The steps of assembling the various parts add to the cost of the electric motor.

[0008] The manufacturing precision required for electric motors also adds to costs. For example, electric motors can be very sensitive to the air gap distance between the rotor and stator coils. Thus, the number of parts and the various operations required to assemble the parts to create an electric motor can make the costs too high.

[0009] Brushless direct current (DC) motors are a type of electric motor that use permanent magnets. These permanent magnets are usually constructed of samarium cobalt or neodymium iron boron. These types of magnets are more expensive to manufacture and more difficult to machine and assemble.

[0010] Brushless DC motors include the weight of bearings, which are selected to prevent wear and tear caused by the heat generated by the windings. The moment of inertia of this type of motor is often very large, reducing responsiveness. The weight and heat of the windings can also limit the speed of a brushless DC motor.

[0011] A reluctance motor is an electric motor that contains non-permanent magnet poles mounted on a ferromagnetic rotor. Torque is generated using magnetic reluctance. Because reluctance motors do not use permanent magnets, this type of motor is less expensive than brushless DC motors.

[0012] However, reluctance motors also typically use stacked laminations in both the rotor and stator. The use of laminations and ferromagnetic materials in the rotor and flux return paths can result in excessive weight.

[0013] Also, because only attractive forces are generated between the stator and rotor, this type of motor has limited responsiveness. Additionally, fast commutation in this type of motor requires high voltages to stop and reverse direction. Reluctance motors have a fixed speed for a particular supply voltage, and speed is also limited by centrifugal stresses in the rotor.

[0014] An induction motor is an alternating current (AC) electric motor in which the current in the rotor to generate torque is obtained by electromagnetic induction from the magnetic field generated by windings in the stator. Induction motors are less expensive than other permanent magnet electric motors. Induction motors are also easier to control than other types of electric motors, and therefore require relatively simple control circuits.

[0015] However, induction motors are relatively heavy due to their squirrel-cage rotor design, which uses stacked laminations, windings, or large conductive materials. Due to the weight of the rotor, induction motors can be less responsive than desired, especially when reversing direction.

[0016] It would therefore be desirable to provide a method and apparatus that takes into account at least some of the problems discussed above, as well as other possible problems. For example, it would be desirable to provide a method and apparatus that overcomes the technical problems related to the weight of electric motors. As another example, it would be desirable to provide a method and apparatus that overcomes the technical problems related to the cost of electric motors. It would be desirable to provide a method and apparatus that overcomes the technical problems related to the responsiveness and speed of electric motors. Summary of the Invention

[0017] One embodiment of the present disclosure provides an apparatus. The apparatus includes a rotor, a plurality of stator coils, and a current control system. The rotor includes a conductive material and is rotatable about an axis. The stator coil is disposed adjacent to the rotor such that an alternating current flows through the stator coil to generate eddy currents in the rotor. The current control system controls an alternating current through the stator coil based on a position of the rotor. When an alternating current flows through the at least one stator coil, the at least one stator coil creates an alternating magnetic field and generates eddy currents in the rotor such that a repulsive force between the at least one stator coil and the rotor rotates the rotor about the axis.

[0018] A further exemplary embodiment of the present disclosure provides a dual frequency electric motor. The dual frequency electric motor includes a rotor, stator coils, and a current control system. The rotor is rotatable about an axis and includes a core formed of a ferromagnetic material and layers surrounding the core, the layers being non-ferromagnetic conductive material. The stator coils are connected to an AC current source and a DC current source. The current control system controls the AC and DC currents flowing through the stator coils based on a rotor position. At least one of the stator coils generates an AC magnetic field when an AC current flows through the at least one stator coil, thereby generating an AC magnetic field that couples the at least one stator coil and the stator coil to the rotor. A repulsive force is generated between the at least one stator coil and the rotor, and when a direct current flows through the at least one stator coil, a unidirectional magnetic field is formed, generating an attractive force between the at least one stator coil and the rotor, causing the rotor to rotate around the axis.

[0019] A further exemplary embodiment of the present disclosure provides a method of controlling an electric motor, the method including controlling an alternating current through a plurality of stator coils of the electric motor based on a rotor position such that an alternating current through at least one of the stator coils generates a repulsive force between a rotor of the electric motor and the at least one stator coil.

[0020] A further exemplary embodiment of the present disclosure provides a method of controlling an electric motor, comprising: transmitting a direct current to at least one stator coil of the electric motor when a rotor of the electric motor is in a first position relative to at least one of the stator coils, such that an attractive force between the at least one stator coil and the rotor causes the rotor to rotate about an axis; and transmitting an alternating current to the at least one stator coil of the electric motor when the rotor is in a second position relative to the at least one stator coil, such that a repulsive force between the at least one stator coil and the rotor causes the rotor to rotate about an axis.

[0021] The features and functions can be achieved independently in various embodiments of the present disclosure or may be combined in other embodiments, further details of which will be understood with reference to the following description and drawings. [Brief description of the drawings]

[0022] The novel features believed characteristic of the illustrative embodiments are set forth in the appended claims, however the illustrative embodiments, as well as the preferred mode of use, together with their objects and advantages, will be best understood by reference to the following detailed description of exemplary embodiments of the present disclosure taken in conjunction with the accompanying drawings, in which:

[0023] [Figure 1] FIG. 1 is a block diagram of an electric motor environment in accordance with an illustrative embodiment. [Diagram 2] FIG. 1 is a block diagram of a current control system in accordance with an example embodiment. [Diagram 3] 1 is a diagram of an electric motor having a rotor in accordance with an example embodiment; [Figure 4] FIG. 1 illustrates operation of an electric motor in accordance with an example embodiment. [Diagram 5] FIG. 1 illustrates the operation of an electric motor using repulsive forces in accordance with an illustrative embodiment. [Figure 6]FIG. 1 illustrates the operation of an electric motor using repulsive forces in accordance with an illustrative embodiment. [Figure 7] FIG. 1 illustrates the operation of an electric motor using repulsive forces in accordance with an illustrative embodiment. [Figure 8] FIG. 1 illustrates the operation of an electric motor using repulsive forces in accordance with an illustrative embodiment. [Figure 9] FIG. 1 illustrates a diagram of a dual frequency electric motor in accordance with an illustrative embodiment. [Figure 10] FIG. 1 illustrates an operation of a dual frequency electric motor in accordance with an example embodiment. [Figure 11] FIG. 1 illustrates an operation of a dual frequency electric motor in accordance with an example embodiment. [Figure 12] FIG. 1 is a block diagram of a power supply for a dual frequency electric motor in accordance with an example embodiment. [Figure 13] FIG. 1 is a block diagram of a power supply for a dual frequency electric motor in accordance with an example embodiment. [Figure 14] FIG. 1 is a block diagram of a power supply for a dual frequency electric motor in accordance with an example embodiment. [Figure 15] 1 is an illustration of a rotor of an electric motor in accordance with an illustrative embodiment; [Figure 16] 5 is a flowchart of a process for controlling an electric motor in accordance with an example embodiment. [Figure 17] 1 is a flowchart of a process for controlling a dual frequency electric motor in accordance with an example embodiment. [Figure 18] 1 is an illustration of an aircraft manufacturing and service method in accordance with an illustrative embodiment; and FIG. [Figure 19] FIG. 1 is a block diagram of an aircraft in which an illustrative embodiment may be implemented. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The illustrative embodiments recognize and take into account one or more problems, such as the use of ferromagnetic materials in the rotor and the number of parts in the rotor and other portions of the electric motor, which may not provide the desired responsiveness and may be too costly, and also that it would be desirable to provide an electric motor whose speed is not limited by centrifugal stresses that may be generated in the rotor.

[0025] The illustrative embodiments recognize and take into account that it is desirable to provide a lightweight electric motor that generates greater torque in a smaller size than currently available electric motors. For example, it is desirable to achieve high acceleration and high power density in electric flight control actuators that may be located on the wings of an aircraft, such as an unmanned aerial vehicle.

[0026] The illustrative embodiments also recognize and take into account the desire for smaller and faster electric motors for medical applications and research. An electric motor having a desired torque that is smaller than currently available electric motors would be useful for medical equipment such as prosthetics and implantable devices. For research, electric motors that provide a desired level of rotational speed are desired for medical equipment such as centrifuges.

[0027] It is recognized and taken into account in the illustrative embodiments that weight, space, and speed are factors for electric motors used in vehicles. In electric and hybrid electric vehicles, especially high performance versions of these types of vehicles, the size, weight, and speed of the electric motor are considerations when designing the vehicle.

[0028] Thus, it is recognized and taken into consideration in the illustrative embodiments that it would be desirable to provide an electric motor that reduces at least one of the amount of ferromagnetic material or the number of parts. As used herein, when the phrase "at least one" is used in conjunction with a list of items, it means that various combinations of one or more of the listed items may be used, and that only one of each item in the list may be required. That is, "at least one" means that any number of items in any combination may be used from the list, but not all items on the list are required. An item may be a particular object, thing, or category.

[0029] For example, without limitation, "item A, item B, or item C" may include item A, item A and item B, or item B. This example may further include item A, item B, and item C, or item B and item C. Of course, any combination of these items may exist. In some example embodiments, "at least one" may be, for example, without limitation, 2 item A, 1 item B, and 10 item C; 4 item B and 7 item C; or any other suitable combination.

[0030] It is recognized and taken into account in the exemplary embodiment that one manner in which a reduction in the amount of ferromagnetic material or part count is achieved involves a reduction in the weight of the rotor, thereby alleviating limitations in responsiveness, speed, and power density. Magnetic fields at frequencies that cause generation within the material are used in a manner that reduces the weight of the rotor in an electric motor.

[0031] It is recognized and taken into account in the illustrative embodiments that induced currents flow in a direction opposite to the change that created the induced current. Also, currents flowing in opposite directions tend to magnetically repel each other; that is, they create magnetic fields that repel each other. Thus, induced currents, known as "eddy currents," are typically repelled by the current that is causing the "eddy currents."

[0032] In one exemplary embodiment, the apparatus includes a rotor, a stator coil, and a current control system. The rotor includes a conductive material and is rotatable about an axis. The stator coil is disposed adjacent to the rotor such that eddy currents are generated in the rotor when an alternating current is applied to the stator coil. The current control system controls the alternating current applied to the stator coil based on a position of the rotor. When an alternating current is applied to the at least one stator coil, the at least one stator coil creates an alternating magnetic field and generates eddy currents in the rotor such that a repulsive force between the at least one stator coil and the rotor rotates the rotor about the axis.

[0033] 1, a block diagram of an electric motor environment is shown in accordance with one illustrative embodiment. Electric motor environment 100 is an example of an environment in which illustrative embodiments may be implemented.

[0034] Electric motor environment 100 may be any environment in which electric motor system 102 provides mechanical power 104 to platform 106. For example, electric motor environment 100 may include, without limitation, a manufacturing environment, a research environment, a medical environment, a military environment, a transportation environment, or any other suitable environment in which mechanical power 104 is needed or desired for platform 106.

[0035] For example, platform 106 may be selected from the group consisting of a mobile platform, a fixed platform, a land-based structure, a water-based structure, and a space-based structure. More specifically, platform 106 may be selected from the group consisting of a surface ship, a tank, a personnel carrier, a train, a spacecraft, a space station, a satellite, a submarine, an automobile, a power plant, a bridge, a dam, a house, a manufacturing facility, a building, and other suitable platforms. In one exemplary embodiment, platform 106 may be a human body.

[0036] Electric motor system 102 may be configured to provide mechanical power 104 for any suitable application in electric motor environment 100. For example, but not limited to, the applications may include driving fans, pumps, tools, disk drives, drills, any other suitable type of device, or various combinations of devices. For example, but not limited to, if platform 106 is in the form of an aircraft, the applications of electric motor system 102 may include operating flight control surfaces, raising and lowering landing gear, and performing various other functions or combinations of functions on the aircraft.

[0037] In this illustrative example, electric motor system 102 includes a number of various components. As shown, electric motor system 102 includes electric motor 108, sensor system 110, current control system 112, and power supply 114.

[0038] Electric motor 108, in this exemplary embodiment, generates mechanical power 104. Electric motor 108 includes a rotor 116 and a stator coil 118.

[0039] As shown, rotor 116 is comprised of an electrically conductive material 120 and is rotatable about an axis 122. In an exemplary embodiment, electrically conductive material 120 is at least one selected from an electrically conductive ferromagnetic material 124 or an electrically conductive non-ferromagnetic material 126.

[0040] The conductive ferromagnetic material 124 is at least one selected from iron, iron oxide, nickel, samarium cobalt, or some other suitable material. In this embodiment, the conductive non-ferromagnetic material 126 is at least one selected from aluminum, copper, gold, intercalated graphene, lead, nickel, silver, tin, titanium, zinc, or some other suitable material.

[0041] The stator coils 118 are positioned adjacent to the rotor 116. In an exemplary embodiment, the stator coils 118 are positioned adjacent to the rotor 116 such that they are capable of generating a sufficient level of repulsive force 140 to rotate the rotor 116 from any of its resting positions.

[0042] This is the location where eddy currents 128 are generated in rotor 116 when alternating current 130 flows through stator coil 118. In this illustrative example, alternating current 130 flows through windings 132 within stator coil 118. Windings 132 are conductive wires coiled and stacked within stator coil 118.

[0043] In an exemplary embodiment, the first frequency of the alternating current 130 is independent of the second frequency of rotation of the rotor 116. That is, the first frequency is not related to the second frequency. For example, the first frequency is an integer multiple or a rational product of the first and second frequencies. In one exemplary embodiment, the frequency of the alternating current 130 is greater than or equal to about 10 kHz.

[0044] Here, the frequency can be selected based on the desired location of the eddy currents 128. For example, the frequency may be selected based on whether it is desired to generate the eddy currents 128 near the surface or deep inside the rotor 116. In an exemplary embodiment, the further the eddy currents 128 are generated from the shaft 122, the greater the torque.

[0045] The sensor system 110 determines a position 134 of the rotor 116. The position 134 is transmitted by the sensor system 110 to the current control system 112 as shown.

[0046] In one exemplary embodiment, the sensor system 110 is a rotary encoder that indicates the position 134 of the rotor 116. The rotary encoder may be attached to at least one of the rotor 116 or a shaft on which the rotor 116 is mounted. In one exemplary embodiment, the rotary encoder may be one selected from a mechanical encoder, an optical encoder, a magnetic encoder, a capacitive encoder, or other suitable encoding system.

[0047] In another exemplary embodiment, the sensor system 110 is a group of position sensing coils that respond to eddy currents 128 in the rotor 116 based on the position 134 of the rotor 116 (or respond to the eddy currents 128 in the rotor 116 based on the position 134 of the rotor 116). The position 134 of the rotor 116 is determined by the group of position sensing coils.

[0048] If there are position sensing coils, an AC current is continuously sent through each of the position sensing coils. As the rotor 116 rotates, eddy currents 128 are induced in the rotor 116 by the position sensing coils. The eddy currents 128 become stronger as the rotor 116 approaches the position sensing coils. As a result, the AC current flowing through the position sensing stator coils decreases. In this way, The position of the rotor 116 can be determined by changes in the AC current flowing through the position sensing coils, caused by eddy currents 128 .

[0049] The AC current sent to the position sensing coils is weak compared to the AC current 130. The AC current is set such that repulsive force 140 is not generated or is small enough that it does not undesirably affect the rotation of rotor 116.

[0050] This type of implementation of the sensor system 110 does not require optical components that can be blocked by dirt and other debris that can occur in rotary encoders. In this manner, the position 134 of the rotor 116 can be determined based on changes in the current flowing through the position sensing coils due to the effect of eddy currents 128.

[0051] In this exemplary embodiment, the current control system 112 controls the flow of alternating current in the stator coils 118 based on the position 134 of the rotor 116. The current control system 112 may be in the form of a commutator. As described below, the current control system 112 may connect the appropriate stator coils 118 to the power source 114 when the position 134 of the rotor 116 is at a selected position relative to the stator coils 118.

[0052] When an AC current 130 flows through a stator coil 136 of the stator coils 118, the stator coil 136 creates an AC magnetic field 138, which generates eddy currents 128 in the rotor 116, and the repulsive force 140 between the stator coil 136 and the rotor 116 causes the rotor 116 to rotate about the axis 122.

[0053] More specifically, the eddy currents 128 create an AC magnetic field 144. The AC magnetic field 138 from the stator coils 136 interacts with the AC magnetic field 144 from the ends 142 of the rotor 116 to create a repulsive force 140.

[0054] In the illustrated embodiment, when the position 134 of the rotor 116 is such that an end 142 of the rotor 116 is adjacent to the stator coils 136 , the current control system 112 sends an alternating current 130 to the stator coils 136 .

[0055] Referring to Figure 2, a block diagram of a current control system is shown, according to one exemplary embodiment. In the exemplary embodiments, the same reference numerals may be used in more than one drawing. Thus, the use of the same reference numerals in different drawings represents the same elements in different drawings.

[0056] As described below, eddy current 128 can be implemented in a variety of ways. In one exemplary embodiment, current control system 112 includes a controller 200 and a number of switches 202.

[0057] 1. The stator coils 118 are indirectly connected to the power source 114 via the switches 202. Here, each of the switches 202 is connected to a corresponding one of the stator coils 118.

[0058] For example, when at least one switch 204 of the switches 202 is in a closed position, the switch 204 passes the AC current 130 to the stator coils 136. When the switch 204 is in an open position 208, no AC current 130 flows through the stator coils 136.

[0059] The control unit 200 controls the switch 202 based on the position 134 of the rotor 116. 1. In other words, the control unit 200 turns the switch 202 on and off based on the position 134 of the rotor 116. The position 134 of the rotor 116 is determined by the sensor system 110 shown in FIG.

[0060] In this exemplary embodiment, when an AC current 130 flows through a stator coil 136 of the stator coils 118, the stator coil 136 creates an AC magnetic field 138. The AC magnetic field 138 induces eddy currents 128 in the rotor 116, and a repulsive force 140 between the stator coil 136 and the rotor 116 causes the rotor 116 to rotate about the axis 122. More specifically, the eddy currents 128 create an AC magnetic field 144. The AC magnetic field 138 from the stator coil 136 interacts with the AC magnetic field 144 from the end 142 of the rotor 116 to create the repulsive force 140.

[0061] The control unit 200 is configured to switch the AC current 130 flowing through the stator coil 136 of the stator coil 118 that is in an aligned state with the end 142 of the rotor 116. In the illustrated embodiment, the state in which the end 142 of the rotor 116 has passed the center of the stator coil 136 is selected as this aligned state.

[0062] In addition to position, the controller 200 may turn off the flow of AC current 130 to the stator coils 136 when the AC current 130 is at or near zero in an alternating current (AC) cycle. In this manner, the commutation voltage may be reduced. This reduction allows for the use of higher currents, which translates into higher torque. The use of higher currents may be achieved without expensive or heavy high voltage components. Additionally, the pattern of turning the AC current 130 on and off may be achieved using a different phase angle relative to the rotor than electric motors that utilize magnetic attraction.

[0063] In an exemplary embodiment, the control unit 200 may be implemented by software, hardware, firmware, or a combination thereof. When using software, the operations performed by the control unit 200 may be implemented by program code configured to run on hardware, such as a processor unit. When using firmware, the operations performed by the control unit 200 are implemented by program code and data, stored in persistent memory, and executed on a processor unit. When using hardware, the hardware includes circuitry that operates to perform the operations in the control unit 200.

[0064] In an example embodiment, the hardware may be in the form of a circuit system, an integrated circuit, an application specific integrated circuit (ASIC), a programmable logic device, or any other suitable type of hardware configured to perform a given number of processes. For example, the controller 200 may include at least one of a solid state circuit, a silicon controlled rectifier (SCR), a triode for alternating current circuit (TRIAC), or any other suitable type of circuit.

[0065] In the case of a programmable logic device, the device may be configured to perform a predetermined number of operations. The device may be later reconfigured or may be permanently configured to perform a predetermined number of operations. Programmable logic devices include, for example, programmable logic arrays, programmable array logic, field programmable logic arrays, field programmable gate arrays, and other suitable hardware devices. Additionally, the process may be performed by organic elements interspersed with inorganic elements, or may be entirely composed of organic elements excluding humans. For example, the process may be realized as a circuit in organic semiconductors.

[0066] In another exemplary embodiment, the current control system 112 may include electric brushes 210 and electrical contacts 212. In this exemplary embodiment, the stator coils 118 have a first end connected to the power source 114. The electric brushes 210 are connected to a second end of the stator coils 118.

[0067] 1. The electrical contacts 212 are connected to the power source 114. The electrical brushes 210 may contact the electrical contacts 212 depending on the position of the rotor 116.

[0068] The electrical contacts 212 rotate as the rotor 116 rotates, and are arranged in a pattern 214 such that the electrical brushes 210 contact the electrical contacts 212 at different locations on the rotor 116 as the electrical contacts 212 rotate about the axis 122, thereby controlling the flow of AC current 130 in the stator coils 118.

[0069] The electrical contacts 212 are associated with the rotor 116. For example, the association may be a direct association, with the electrical contacts 212 being provided on the rotor 116. In another example, the association may be an indirect association, with the electrical contacts 212 being provided on a shaft coupled to the rotor 116.

[0070] The use of electric brushes 210 and electrical contacts 212 is low cost and can reduce the use of electrical circuitry in the electric motor system 102. As a result, costs can be reduced with this type of configuration.

[0071] Thus, the illustrative embodiments provide one or more technical solutions to overcome the technical problems associated with the weight of electric motors, for example, lighter weight materials may be used in electric motor 108 instead of materials used in currently used electric motors.

[0072] As another example, the illustrative embodiments provide a technical solution that overcomes technical problems related to the cost of electric motors. For example, electric motor 108 can be manufactured using fewer components, which reduces component and assembly costs. For example, rotor 116 of electric motor 108 does not need to use laminations or heavy materials.

[0073] Additionally, the illustrative embodiments may provide one or more technical solutions to overcome technical problems with electric motor response and speed. Response and speed limitations due to high inertia may be mitigated. Spot and speed limitations due to rotor stresses may also be mitigated according to the illustrative embodiments. For example, rotor 116 may be a simpler design than currently used rotors to achieve a desired level of performance.

[0074] The illustration of electric motor environment 100 and various components in Figures 1 and 2 is not intended to impose physical or architectural limitations on the manner in which an example embodiment may be implemented. Other components in addition to or in place of the illustrated components may be used. Some components may not be required. Additionally, the blocks in the figures represent functional components. One or more of these blocks may be combined, divided, or combined and divided into different blocks when implemented in an example embodiment.

[0075] For example, the sensor system 110 may detect the position 134 of the rotor 116 in addition to or in addition to the position 134 of the rotor 116. Alternatively, other information may be determined. For example, the sensor system 110 may determine at least one selected from the temperature, speed, torque, magnetic field levels, or any other desired information regarding the electric motor 108.

[0076] In this embodiment, the power supply 114 provides an alternating current 130 to the stator coils 118. The provision of the alternating current 130 is under the control of the current control system 112. The alternating current 130 may be provided directly or indirectly. For example, the alternating current 130 may be provided directly by a wire or indirectly by wireless electromagnetic coupling to the stator coils 118.

[0077] As another example, each stator coil 118 may have a resonant frequency that is different from the other stator coils. The resonant frequency is the frequency at which the stator coil responds to a given magnitude of alternating current. In an exemplary embodiment, the resonant frequency may be set using a capacitor connected in parallel with the stator coil.

[0078] In this embodiment, the control unit 200 includes a power transmitter configured to transmit power to the stator coils 118 by wireless electromagnetic coupling to the stator coils 118. The transmitted power becomes an alternating current 130 flowing through the stator coils 118.

[0079] In another exemplary embodiment, if the current control system 112 is an analog current control system, the sensor system 110 may be omitted. If electrical brushes and electrical contacts are provided, the position 134 of the rotor 116 can be determined without the sensor system 110.

[0080] The operation of an electric motor according to an exemplary embodiment will now be described with reference to Figures 3-8, which illustrate how repulsive forces can be used to rotate the rotor of an electric motor.

[0081] Referring first to Figure 3, an electric motor having a rotor is shown in accordance with an exemplary embodiment. In this exemplary embodiment, electric motor 300 includes rotor 302 and stator coils 304.

[0082] As shown, rotor 302 has arm 301 and arm 303 extending from axis 312. In this exemplary embodiment, rotor 302 does not include a magnetic material. Rotor 302 is comprised of an electrically conductive material in the form of an electrically conductive non-ferromagnetic material. In this example, rotor 302 is comprised of aluminum.

[0083] In this exemplary embodiment, stator coils 304 include stator coil 306, stator coil 308, and stator coil 310. Any number of stator coils 304, greater than or equal to two, may be used in electric motor 300.

[0084] As shown, rotor 302 is in a rest position, which in this example is a starting position, and the desired direction of rotation of rotor 302, in this example, is in the direction of arrow 314 about axis 312.

[0085] In this illustrative example, end 316 of arm 301 of rotor 302 is shown in a starting position relative to stator coils 306. A series of movements activates and deactivates stator coils 304, causing rotor 302 to rotate.

[0086] In this starting position of the rotor 302, the alignment between the end 316 of the arm 301 of the rotor 302 and the stator coil 306 is such that the center line 320 of the end 316 is aligned with the center line 320 of the stator coil 306. 06。 That is, the end 316 passes past the center of the stator coil 306. In this example embodiment, the offset is measured in degrees. The offset may be, for example, 1° or 2°.

[0087] A centerline is a line that divides an object in half, such as rotor 302 or stator coil 306. As shown, stator coil 308 has centerline 322, and stator coil 310 has centerline 324. The centerlines in these illustrated examples are imaginary lines and are not actually visible on the structure.

[0088] As a result of the offset shown in this example, when the electric motor begins to operate, rotor 302 rotates in the direction of arrow 314. The amount of offset between centerline 318 and centerline 320 can be varied depending on the amount of repulsive force desired to be generated when alternating current is applied to stator coils 306.

[0089] 4, an operation of an electric motor is illustrated in accordance with an exemplary embodiment. As illustrated, when an alternating current 400 is applied to the stator coils 306, the stator coils 306 are turned on.

[0090] The flow of the AC current 400 generates an AC magnetic field 404. The generation of the AC magnetic field 404 generates eddy currents 402 at the end 316 of the rotor 302. The eddy currents 402 generate an AC magnetic field 406.

[0091] In this exemplary embodiment, the AC 400 may have a relatively high frequency compared to other currently available AC motors, for example, a frequency of 10 kHz or higher.

[0092] The magnetic fields due to these two currents generate a repulsive force 408. Then, as shown in the figure, the repulsive force 408 causes the rotor 302 to rotate in the direction of the arrow 314.

[0093] As shown, the repulsive force 408 has two components: a tangential force 410 and a radial force 412. These components are associated with the rotation of the rotor 302. The tangential force 410 creates a torque that causes the rotor 302 to rotate.

[0094] 5, an operation of a repulsive electric motor is illustrated in accordance with an exemplary embodiment. In this example, the rotor 302 rotates until the centerline 320 of the rotor 302 is aligned with the centerline 324 of the stator coils 310.

[0095] In this position, the stator coils 306 are turned off, i.e., the AC current 400 shown in Figure 4 no longer flows through the stator coils 306. Thus, the AC magnetic field 404 shown in Figure 4 is also no longer present.

[0096] An example embodiment of the operation of a repulsive electric motor is shown in Figure 6. As shown, the rotor 302 rotates from the position shown in Figure 5 to the position shown in Figure 6 due to the moment of inertia of the rotor 302.

[0097] In the figure, the rotor 302 has rotated to a state where a center line 320 of an end 317 of the rotor 302 has passed a center line 324 of the stator coil 310. In other words, the alignment state between the end 317 of the rotor 302 and the stator coil 310 is such that an offset has occurred between the center line 324 of the stator coil 310 and the center line 320 of the end 317.

[0098] When the end 317 and the stator coil 310 are aligned in this manner, the stator coil An AC current 600 is sent to the rotor 310, turning on the stator coil 310. That is, when the end 317 of the rotor 302 rotates to a position past the center line 324 of the stator coil 310, the AC current 600 is sent to the stator coil 310. When the AC current 600 flows through the stator coil 310, an AC magnetic field 602 is formed.

[0099] The AC magnetic field 602 causes eddy currents 402 to flow in the end 317 of the rotor 302. Then, the eddy currents 402 in turn cause an AC magnetic field 604 to be formed in the end 317 of the rotor 302.

[0100] The AC currents 600 and eddy currents 402 in the stator coils 310 result in a repulsive force 408 due to the interaction of AC magnetic field 602 and AC magnetic field 604. This results in a torque being applied to rotor 302, causing rotor 302 to rotate in the direction of arrow 314.

[0101] 7, which illustrates the operation of an electric motor using repulsive forces, according to an example embodiment. The rotor 302 rotates until the centerline 320 of the end 316 is aligned with the centerline 322 of the stator coil 308. In this position, the stator coil 310 is turned off.

[0102] Referring to Figure 8, an operation of an electric motor using repulsive forces is illustrated in accordance with an example embodiment. As illustrated, rotor 302 rotates from the position illustrated in Figure 7 to the position illustrated in Figure 8 due to the moment of inertia in rotor 302.

[0103] In this figure, a centerline 320 of rotor 302 is in a predetermined alignment with a centerline 322 of stator coil 308. This alignment is such that centerline 320 is offset from centerline 322.

[0104] In this aligned state, an AC current 800 is passed through the stator coils 308, turning them on and creating an AC magnetic field 802 by the stator coils 308. This causes eddy currents 402 to flow at the ends 316 of the rotor 302. The eddy currents 402 create an AC magnetic field 804.

[0105] In this manner, alternating current 800 and eddy currents 402 generate a repulsive force 408. Repulsive force 408 causes rotor 302 to rotate in the direction of arrow 314. This rotation of rotor 302 returns rotor 302 to the position shown in FIG.

[0106] In the illustrated example, the stator coils 304 are turned on and off in a predetermined pattern so that torque is always present in the direction of arrow 314. As described above, the alignment of the end 316 and the stator coils 304 during operation of the electric motor 300 is such that there is an offset between the centerline 320 of the end 316 of the rotor 302 and the centerline of the stator coils 304. In the illustrative example, the offset is measured in degrees. The number of degrees may vary depending on the embodiment.

[0107] Electric motor 300, as illustrated in Figures 3-8, is illustrated for purposes of illustrating one embodiment of electric motor 108, as shown in block diagram form in Figure 1. This illustration of electric motor 300 is not intended to limit the manner in which electric motor 108 may be implemented in other illustrative embodiments.

[0108] Although the stator coils 304 include three stator coils as shown in the electric motor 300, other numbers of stator coils 304 may be used in other exemplary embodiments. For example, in other exemplary embodiments, two, five, seven, or other numbers of stator coils may be used. A stator coil 304 may be used in the electric motor 300 .

[0109] In this example embodiment, the number of stator coils may depend on the configuration of rotor 302. As shown, rotor 302 has two elongated members extending from axis 312 in the form of arm 301 and arm 303. In other example embodiments, the number of arms may be different.

[0110] In selecting the number of stator coils 304 and arms of the rotor 302, the number of stator coils 304 can be selected in various ways. For example, the number of stator coils 304 can be selected to be greater than two and different from the number of arms of the rotor 302 multiplied by 0.5, 1, or 2. Using a ratio of 0.5, 1, or 2 may result in the rotor 302 being in a position where the repulsive forces of the stator coils 304 are symmetrical. These ratios are undesirable for the rotor 302 because, if positions where the repulsive forces are symmetrical exist, the torque applied to the rotor 302 would be substantially zero at these positions.

[0111] If the rotor 302 stops in one of these positions, the rotor 302 cannot start moving again. For example, a configuration with four stator coils 304 and two rotor 302 arms is less desirable.

[0112] In one preferred embodiment, the number of stator coils 304 and the number of arms of rotor 302 differ by one, i.e., are consecutive numbers. For example, if rotor 302 has nine arms, ten stator coils may be used as stator coils 304.

[0113] In another example of a preferred configuration, the number of stator coils 304 is a multiple of 3. For example, if the rotor 302 has four arms, six stator coils are used as the stator coils 304. Using a multiple of three stator coils 304 allows the motor to operate with three commutator phases.

[0114] 3, the rotor 302 of the electric motor 300 has its centerline 320 slightly past the centerline 318 of the stator coils 306, which is the starting position for the electric motor 300 when it begins operation from a dead stop. In controlling the operation of the electric motor 300, regardless of the starting position of the rotor 302, current is sent to the stator coils 304 to rotate the rotor 302 from a dead stop in the direction of arrow 314, or in the opposite direction if desired. For example, if the centerline 320 of the end 316 is aligned with the centerline 318 of the stator coils 306, then rotor 302 can be rotated in the direction of arrow 314 by sending alternating current through stator coils 306, 308 with a slight overlap.

[0115] In the illustrated embodiment, sending slightly overlapping alternating currents to the stator coils 304 may be done so that two or more stator coils in the stator coils 304 are turned on. For example, when the centerline 320 of the end 316 of the rotor 302 is aligned with the centerline 318 of the stator coil 306, the stator coil 310 is left turned on.

[0116] Thus, when the rotor 302 starts with the centerlines aligned, it does not get stuck in that position or rotate in an undesired direction. Once the centerline 320 of the end 316 of the rotor 302 rotates a few degrees past the centerline 318 of the stator coil 306, the stator coil 310 is turned off.

[0117] The same pattern of motion applies when the centerline 320 of the end 316 of the rotor 302 coincides with the centerline 322 of the stator coil 308. In this position, the stator coil 306 is turned on. The rotor 302 rotates several degrees while remaining in the on-state. As the end 316 of the rotor 302 passes the stator coils 310, a similar sequence takes place.

[0118] Alternative patterns of turning on the stator coils 304 may cause the rotor 302 to rotate in a direction opposite to that of the arrow 314. That is, the rotor 302 may rotate in either a clockwise or counterclockwise direction. Additionally, the amount of current and / or the duration of the current sent to one or more of the stator coils 304 may be used to change at least one of the speed, torque, or direction of rotation of the rotor 302.

[0119] A sensor may also be used to measure the rotational speed, which may be used to eliminate the overlap when the rotor 302 of the electric motor 300 rotates above a threshold speed. In this way, once the rotor 302 begins to rotate, the power spikes required to send current to two of the stator coils 304 as described above are reduced or eliminated.

[0120] 9, a dual frequency electric motor is shown in accordance with an example embodiment. A top cross-sectional view of a dual frequency electric motor 900 is shown. In this example embodiment, the dual frequency electric motor 900 includes a rotor 902 and a stator coil 904. The dual frequency electric motor 900 uses both repulsive and attractive forces to rotate the rotor 902. By using both repulsive and attractive forces, a 100 percent duty cycle can be achieved for each stator coil and the torque generated by the dual frequency electric motor 900 can be increased.

[0121] In this illustrative embodiment, rotor 902 has arm 905 and arm 906 extending from axis 908. As seen in this cross-sectional view, rotor 902 includes a core 910 and a layer 912. Layer 912 is a coating formed on core 910.

[0122] In this exemplary embodiment, core 910 comprises an electrically conductive ferromagnetic material, which in this embodiment is at least one selected from iron, iron oxide, nickel, or samarium cobalt.

[0123] Layer 912 comprises an electrically conductive non-ferromagnetic material, which in this embodiment is at least one selected from aluminum, copper, gold, intercalated graphene, lead, silver, tin, titanium, or zinc.

[0124] In this exemplary embodiment, stator coils 904 include three stator coils. More specifically, stator coils 904 include stator coil 914, stator coil 916, and stator coil 918.

[0125] As described below, two frequencies are used to operate the dual frequency electric motor 900. In this exemplary embodiment, a first frequency is used to generate an attractive force and a second frequency is used to generate a repulsive force in the dual frequency electric motor 900. This type of motor, which uses at least one of an attractive or repulsive force to rotate the rotor 902, is also referred to as a dual frequency electric motor.

[0126] In selecting the thickness of layer 912, layer 912 has an electrical skin depth (δ), which depends on the conductivity and permeability of the material and the frequency of the applied magnetic field. In this exemplary embodiment, the skin depth is the distance between the outer surface and the critical surface through which current flows. The skin depth determines the current density (J) at a depth (d) according to the following formula:

number

number

[0127] The coating thickness of layer 912 is selected to be less than one skin depth at low frequency and more than one skin depth at high frequency. The low frequency may be a commutation frequency of about 30-100 Hz. The low frequency may be as low as direct current. The high frequency may be an alternating current (AC) frequency at which eddy current motors operate. The frequency may be about 10 kHz. In this exemplary embodiment, the thickness of layer 912, which is an aluminum coating, is about 1.5 millimeters.

[0128] 10, an operation of a dual frequency electric motor is illustrated in accordance with an exemplary embodiment. As shown in the figure, rotor 902 rotates about axis 908 in the direction of arrow 1000.

[0129] As the end 1004 of the arm 905 of the rotor 902 approaches the stator coil 914, a direct current 1006 is sent to the stator coil 914. The direct current 1006 flows through the stator coil 914, causing the stator coil 914 to form a unidirectional magnetic field 1008. In this illustrative example, the unidirectional magnetic field 1008 has a frequency of about 30 Hz. This varying frequency is within the strength of the unidirectional magnetic field 1008.

[0130] At this frequency, the skin depth of the unidirectional magnetic field 1008 is approximately 14 millimeters. At a frequency of 0 Hz, the skin depth is infinite. Thus, almost all of the magnetic flux of the unidirectional magnetic field 1008 passes through the layer 912, which is approximately 1.5 millimeters.

[0131] The unidirectional magnetic field 1008 creates an attractive force 1010 on the core 910. The attractive force 1010 attracts the ends 1004 of the arms 905 of the rotor 902 to the stator coils 914. This attractive force on the core 910 causes the rotor 902 to rotate in the direction of the arrow 1000 about the axis 908.

[0132] 11, an operation of a dual frequency electric motor is shown in accordance with an example embodiment, with the end 1004 of the arm 905 of the rotor 902 rotating past the stator coils 914. At this position of the rotor 902, the DC current 1006 of FIG. 10 is turned off and an AC current 1100 flows through the stator coils 914.

[0133] An alternating current 1100 flowing through the stator coils 914 produces an alternating magnetic field 1102. In this exemplary embodiment, the alternating magnetic field 1102 has a frequency of about 10 kHz. At this frequency, the skin depth of the aluminum in layer 912 is about 0.8 millimeters. A large portion of the AC magnetic field 1102 is blocked by eddy currents 1104 flowing in layer 912.

[0134] The eddy currents 1104 generate an AC magnetic field 1106. The interaction of these magnetic fields creates a repulsive force 1108 between the stator coils 914 and the ends 1004 of the arms 905 of the rotor 902, causing the rotor 902 to rotate in the direction of the arrow 1000 about the axis 908. This pattern of DC current 1006 and AC current 1100 in the stator coils 914 can be applied to the stator coils 916 and 918 when the ends 1004 of the rotor 902 are in a similar position relative to the stator coils 916 and 918.

[0135] The dual frequency electric motor 900 shown in Figures 9-11 is shown to illustrate one embodiment of the electric motor 108 shown in block diagram form in Figure 1. As described above, the dual frequency electric motor 900 uses an attractive force 1010 in addition to a repulsive force 1108 to rotate the rotor 902.

[0136] 12, a block diagram of a power supply for a dual frequency electric motor is shown in accordance with an example embodiment, illustrating one manner of powering a dual frequency electric motor, such as the dual frequency electric motor 900 shown in FIG.

[0137] In this illustrative example, power supply 1200 includes a DC current source 1202 and an AC current source 1204. Power supply 1200 is an example embodiment of power supply 114 shown in block diagram form in Figure 1. Power supply 1200 provides both DC current 1210 and AC current 1212 to a stator coil 1206 in a dual frequency electric motor 1208. Each source has a different frequency.

[0138] In this illustrative example, current control system 1214 is an example of an embodiment of current control system 112 shown in block diagram form in Figure 1. As shown, current control system 1214 includes a controller 1216, a selector switch 1218, and a selector switch 1220. Current control system 1214 is an example of an embodiment of current control system 112 shown in block form in Figure 1.

[0139] The controller 1216 may be implemented by hardware, software, or a combination thereof. The controller 1216 may take the form of rectifying electronics. The controller 1216 selects the frequency by controlling a selector switch 1220 to select either the DC current source 1202 or the AC current source 1204. In this exemplary embodiment, the frequency of the AC current source 1204 is approximately 10 kHz.

[0140] Current from the selected source is sent to a selector switch 1218. The controller 1216 controls the selector switch 1218 to send the selected current to a particular one of the stator coils 1206. In an illustrative example, current may be sent to more than one of the stator coils 1206, depending on the embodiment.

[0141] In this example embodiment, a substantially 100 percent torque duty cycle is available from each stator coil in stator coils 1206. This configuration provides a greater average torque for a given size electric motor than the 50 percent duty cycle from each stator coil in a reluctance motor.

[0142] 13, a block diagram of a power supply for a dual frequency electric motor is shown in accordance with an exemplary embodiment. In this exemplary embodiment, power supply 130 0 is a DC current source 1302. The current control system 1304 includes a controller 1306, a selector switch 1308, and a selector switch 1310.

[0143] As shown, a capacitor 1312 is connected in parallel with a stator coil 1314 of an electric motor 1316 and a selector switch 1310. The current control system 1304 is an example of an embodiment of the current control system 112 shown in block diagram form in FIG.

[0144] In operation, the controller 1306 controls the selector switch 1310 to route current from the DC current source 1302 to the selector switch 1308. The controller 1306 also controls the selector switch 1308 to select which of the stator coils 1314 is to be connected to the DC current source 1302. The DC current source 1302 supplies current until the end of the rotor is closest to the selected coil. While the DC current source 1302 is connected, it also charges the capacitor 1312.

[0145] When the rotor ends are in closest proximity, the controller 1306 shuts off the DC current source 1302 and connects the capacitor 1312 to the stator coils using the selector switch 1308. This completes a circuit between the selected one of the stator coils 1314 and the capacitor 1312. Current flows through the capacitor 1312.

[0146] The stator coil and capacitor 1312 form an LC (inductor capacitor) tank circuit that oscillates to send an AC current to the coil, which generates eddy currents in the rotor, creating a repulsive force that causes the rotor to rotate.

[0147] The value of the capacitor 1312 is selected by the following formula using the frequency (ω0) at which the skin effect in the conductive coating of the rotor is sufficient and the inductance of the coil (L). This determines the value of the capacitance (C) of the capacitor 1312.

number

[0148] In this example, the frequency at which the skin effect is sufficient in the conductive coating of the rotor (ω0 ) may be selected as a frequency at which the skin depth is less than half the thickness of the layer covering the rotor core.

[0149] In an exemplary embodiment, each of the stator coils 1314 is connected to a capacitor 1312. In another exemplary embodiment, instead of using a single capacitor as shown in FIG. 13, i.e., capacitor 1312 for all of the stator coils 1314, each stator coil may have a capacitor.

[0150] 14, there is shown a block diagram of a power supply for a dual frequency electric motor in accordance with an illustrative embodiment, in which a stator coil 1400 is connected to a set of capacitors 1402.

[0151] As used herein, the term "set" when used with respect to an item means one or more items. For example, set of capacitors 1402 is one or more capacitors. For example, multiple capacitors may be connected in series, parallel, or a combination thereof to achieve a desired level of capacitance.

[0152] As shown, a set of capacitors 1402 are connected to a first end 1406 of the stator coil 1400 and a second end 1408 of the stator coil 1400. The first end 1406 is further connected to a DC current source 1410 via a switch 1412. The second end 1408 is connected to the DC current source 1410.

[0153] In this configuration, a set of capacitors 1402 are connected in parallel with a stator coil 1400 and a DC current source 1410. In this exemplary embodiment, the stator coil 1400 and the set of capacitors 1402 form a resonant LC (inductor capacitor) tank circuit.

[0154] When the switch 1412 is in the closed position, the DC current source 1410 applies a DC voltage to both the stator coil 1400 and the set of capacitors 1402. With the switch 1412 in the closed position, current flows in the direction of the arrow 1414 through the stator coil 1400. During this time, the set of capacitors 1402 is charged. Also, an attractive force is generated by the unidirectional magnetic field 1008 formed by the stator coil 1400 in FIG. 8, and a DC current from the DC current source 1410 flows through the stator coil 1400.

[0155] When switch 1412 is in the open position, the stator coil 1400 is isolated from the DC current source 1410. Current continues to flow in the direction of arrow 1414, draining charge from the set of capacitors 1402 and then charging the set of capacitors 1402 with the opposite polarity and a higher voltage than the DC current source 1410.

[0156] The resonant LC tank circuit formed by the stator coil 1400 and a set of capacitors 1402 then oscillates, causing a current to flow in the direction of arrow 1416. The current oscillation decays over time. This current oscillation induces eddy currents in the rotor, which in turn generate a repulsive force that causes the rotor to rotate.

[0157] This configuration, with each stator coil having a set of capacitors, uses more capacitors than the configuration shown in Figure 13, which uses one capacitor for multiple stator coils. By associating a set of capacitors with each of the stator coils, fewer switches are used.

[0158] Both of the power supply configurations shown in Figures 13 and 14 can obtain a duty cycle of torque greater than 50 percent but less than 100 percent from each stator coil. This type of performance is better than a reluctance motor, but less than the dual frequency electric motor 1208 shown in Figure 12, which uses a power supply 1202 with a DC current source 1202 and an AC current source 1204.

[0159] The dual frequency electric motor system of Figures 9-14 is illustrated for the purposes of illustrating one embodiment of a dual frequency electric motor as electric motor 108 shown in block diagram form in Figure 1. This illustration is not intended to limit the embodiment of other dual frequency electric motors.

[0160] For example, other than the two arms shown in rotor 902 of dual frequency electric motor 900 may be used. For example, rotor 902 may be implemented with three arms, four arms, or other numbers of arms. The number of stator coils 904 may also vary based on the configuration of rotor 902.

[0161] 15, an electric motor rotor is illustrated in accordance with an exemplary embodiment. The illustrated rotor 1500 is an implementation of rotor 116 shown in block diagram form in FIG. This is an example of a form.

[0162] Rotor 1500 is rotatable about axis 1502. Rotor 1500 has three arms: arm 1504, arm 1506, and arm 1508. As can be seen, the arms taper in width as they extend away from axis 1502.

[0163] Rotor 1500 may also be comprised of two or more materials. In this example, rotor 1500 includes core 1510. Core 1510 may be comprised of a material that has a high ratio of tensile strength to density. This allows rotor 1500 to rotate the tip of the arm at a faster speed than currently used rotors.

[0164] For example, the ratio of tensile strength to density may be selected to provide a density-to-strength ratio at least similar to that of beryllium, which has a density-to-strength ratio of approximately 200,000 Pascals / (Kg / m 3 ).

[0165] Since stresses in the rotor are primarily radial, the core 1510 may be comprised of a material with anisotropic tensile strength. This type of material can provide the rotor 1510 with a higher radial tensile strength to density ratio. For example, a standard unidirectional carbon fiber reinforced plastic (CFRP) with about 60% fiber volume has a tensile strength of at least about 937,500 Pascals / (Kg / m 3 ) radial strength ratio to density is obtained.

[0166] The core 1510 material may be electrically conductive. The core 1510 material may also have a desirable level of thermal conductivity relative to materials currently used in rotors. High thermal conductivity facilitates the transfer of heat generated by eddy currents near the tip of the rotor 1500 to other portions of the rotor 1500. This allows the rotor 1500 material to be maintained at a temperature that provides a desired level of strength. For example, beryllium and aluminum have substantially higher thermal conductivity than iron or steel. Beryllium has a thermal conductivity of 175 W / (m·K) and aluminum has a thermal conductivity of 220 W / (m·K). In comparison, iron and steel have thermal conductivities of 16-60 W / (m·K), which are typical of these materials and alloys.

[0167] The rotor 1500 further includes a layer 1512 that covers some or all of the core 1510. The layer 1512 may be electrically conductive and may be formed using an electrically conductive, non-ferromagnetic material. For example, if the core 1510 is non-conductive, the thickness of the layer 1512 may be selected to be approximately twice the skin depth for the frequency of the alternating current and the material used for the layer 1512.

[0168] With such a design and material selection, rotor 1500 can rotate faster than currently used rotors that have solid iron arms that are not tapered and are uniform in width and thickness. In this way, faster and lighter electric motors can be manufactured.

[0169] The depiction of rotor 1500 in FIG. 15 is not intended to limit the use of other rotors in the electric motor 108 shown in block diagram form in FIG. 1. For example, other rotors may have two arms, six arms, seven arms, or other numbers of arms. In yet other example embodiments, the layer on the core may not cover the entire core. For example, the core may be exposed in the vicinity of the axis of rotation while the core may be covered in the layer in the vicinity of the ends of the arms.

[0170] Additionally, rotor 1500 may rotate using repulsive forces or both repulsive and attractive forces. The materials of core 1510 and layers 1512 may be selected based on whether rotor 1500 is rotated using repulsive forces or both repulsive and attractive forces.

[0171] Referring now to Figure 16, a flow chart of a process for controlling an electric motor is shown, according to an example embodiment. The process shown in Figure 16 may be implemented in the electric motor environment 100 shown in Figure 1. In particular, various steps may be implemented using the electric motor system 102 shown in Figure 1.

[0172] The process begins by identifying a rotor position in the electric motor (step 1600). In this exemplary embodiment, the position of the ends of the rotor arms is identified.

[0173] The process controls AC current through stator coils of the electric motor based on a rotor position in the electric motor (step 1602), and returns to step 1600. In step 1602, the flow of AC current is controlled such that when AC current flows through at least one of the stator coils, a repulsive force is generated between the rotor and the at least one stator coil.

[0174] This process is repeated while the electric motor is running. Further, control of the flow of alternating current may be performed to vary at least one of the speed, the amount of torque, the direction of rotation, or some other suitable parameter.

[0175] Referring to Figure 17, a flow chart of a process for controlling a dual frequency electric motor is shown in accordance with an example embodiment. The process shown in Figure 17 may be implemented using the dual frequency electric motor 900 shown in Figure 9.

[0176] The process begins by identifying rotor positions in an electric motor (step 1700). These positions include a first position and a second position for at least one of the stator coils of the electric motor.

[0177] The process includes sending a direct current to a stator coil of an electric motor when the rotor of the electric motor is in a first position relative to the at least one stator coil (step 1702). At step 1702, an attractive force between the stator coil and the rotor causes the rotor to rotate about an axis.

[0178] The process sends an alternating current to the stator coil (step 1704) when the rotor is in a second position relative to the at least one stator coil of the electric motor, and returns to step 1700. At step 1704, repulsive forces between the stator coil and the rotor cause the rotor to rotate about its axis.

[0179] In this manner, both attractive and repulsive forces are utilized to operate an electric motor, which may provide improved speed, torque, duty cycle, or other parameters over currently used electric motors.

[0180] The flowcharts and block diagrams in the various embodiments described above illustrate the structure, functionality, and operation of some possible implementations of the apparatus and methods in one exemplary embodiment. In this regard, each block in the flowchart or block diagram may be a module. The blocks may represent at least one of a program, a segment, a function, or a portion of an operation or step. For example, one or more of the blocks may be embodied as program code, hardware, or a combination of program code and hardware. If implemented in hardware, the hardware may take the form of, for example, integrated circuits that are manufactured or configured to perform one or more steps in the flowcharts or block diagrams. If implemented as a combination of program code and hardware, the hardware may be embodied in firmware.

[0181] In some alternative aspects of the illustrative embodiments, the functions shown in the blocks may be performed in an order different from that shown in the figures. For example, in some cases, two blocks shown in succession may be performed substantially concurrently or in the reverse order, depending on the functionality involved. Also, other blocks may be added to the blocks shown in the flowcharts or block diagrams.

[0182] An example embodiment of the disclosure will be described in Figure 18 with reference to an aircraft manufacturing and service method 1800 and in Figure 19 with reference to an aircraft 1900. Referring initially to Figure 18, a block diagram of an aircraft manufacturing and service method is shown in accordance with an example embodiment. During pre-production, aircraft manufacturing and service method 1800 includes specification and design 1802 and material procurement 1804 of the aircraft 1900 shown in Figure 19.

[0183] During production, component and subassembly manufacturing 1806 and system integration 1808 of the aircraft 1900 shown in Figure 19 takes place. The aircraft 1900 then goes through certification and delivery 1810 and enters service 1812. While in customer use 1812, the aircraft 1900 is scheduled for routine maintenance and service 1814, which may include modifications, reconfigurations, refurbishments, and other maintenance or upkeep.

[0184] Each process of aircraft manufacturing and service method 1800 may be performed or carried out by a system integrator, a third party, an operator, or any combination thereof. In these examples, the operator may be a customer. For purposes of illustration, a system integrator may include, but is not limited to, an aircraft manufacturer and any number of major system subcontractors. A third party may include, but is not limited to, any number of vendors, subcontractors, and suppliers. An operator may be an airline, a leasing company, a military entity, a service organization, etc.

[0185] 19, a block diagram of an aircraft in which illustrative embodiments may be implemented is shown. In this example, aircraft 1900 may be produced by aircraft manufacturing and service method 1800 as shown in FIG. 18 and may include an airframe 1902 with a number of systems 1904 and an interior 1906. Examples of systems 1904 include one or more of a drive train 1908, an electrical system 1910, a hydraulic system 1912, and an environmental system 1914, and may also include any number of other systems. Additionally, although an aerospace application is shown as an example, various illustrative embodiments may be applied to other industries, such as the automotive industry.

[0186] Apparatus and methods embodied herein may be employed in at least one stage of aircraft manufacturing and service method 1800 shown in Figure 18. In one example embodiment, components or subassemblies of an example embodiment electric motor system may be manufactured in component and subassembly manufacturing 1806 in Figure 18 similar to components and subassemblies manufactured in service 1812 of aircraft 1900 shown in Figure 18. In another example embodiment, an example embodiment electric motor system may be used in equipment used to manufacture components or subassemblies of aircraft 1900.

[0187] One or more apparatus embodiments, method embodiments, or combinations thereof may be used during use 1812 of the aircraft 1900. For example, an electric motor system according to example embodiments may operate within the aircraft 1900 during use 1812 of the aircraft 1900. For example, the electric motor system may be used for flight control actuators that move control surfaces, such as flaps, ailerons, and control surfaces. Additionally, the size of the electric motor may provide a desired level of torque to enable use of the electric motor within a space, such as a wing, vertical stabilizer, horizontal stabilizer, or other suitable location of the aircraft.

[0188] Additionally, the electric motor system in the example embodiment may control valves of fluid systems within aircraft 1900. By using various example embodiments, the speed of assembly of aircraft 1900 may be substantially increased, or the cost of aircraft 1900 may be reduced, or both.

[0189] One or more illustrative embodiments provide electric motors that have higher levels of torque for acceleration than currently used electric motors. The increased amount of torque is particularly useful in aircraft where spaces such as space within an aircraft's wings require smaller sized motors, but higher levels of torque than currently used motors are desirable. The increased amount of torque provided by the electric motors of various illustrative embodiments is also useful in robotics manufacturing, as well as other applications where torque is a desired factor in selecting an electric motor.

[0190] The electric motors shown and described in the exemplary embodiments may provide a desired level of torque or at least one of rotational output over a wide range of speeds. Additionally, the electric motors described in the exemplary embodiments may provide a desired level of responsiveness with respect to starting, stopping, and changing speed or direction. The electric motors achieve these characteristics in a configuration that is at least one of smaller, lighter, and less expensive than electric motors currently in use.

[0191] Additionally, the electric motors of the example embodiments are lighter and have fewer parts than reluctance motors, and the rotors of the example embodiments can be used at higher speeds than rotors in reluctance motors, as a result of the rotor being designed to have a higher weight to weight ratio than rotors currently used in reluctance motors because the commutation voltage does not rise with motor speed.

[0192] Additionally, acceleration is increased compared to current electric motors because the rotor material selected in the exemplary embodiment provides a lower moment of inertia compared to reluctance motors, and the controller of the exemplary embodiment is less costly because the circuitry used switches AC current instead of DC current.

[0193] The electric motor of the exemplary embodiment is more efficient than currently used induction motors. In the exemplary embodiment, the frequency of rotation of the electric motor is decoupled from the frequency of the alternating current. For example, the frequency of rotation is on the order of tens of Hertz, while the frequency of the alternating current is on the order of tens of kilohertz.

[0194] The electric motors of the example embodiments have advantages over brushless DC motors, such as the absence of permanent magnets. The electric motors of the example embodiments can achieve the same or better power density without the use of permanent magnets. Thus, the electric motors of the example embodiments are simpler, resulting in lower assembly costs as well as lower material costs compared to brushless DC motors.

[0195] The present disclosure also includes examples according to the following appendices.

[0196] Supplementary Note 1. A rotor (116) including a conductive material (120), the rotor (116) being rotatable about an axis (122); A plurality of stator coils (118); a current control system (112) for controlling an AC current (130) flowing through the stator coils (118) based on a position (134) of the rotor (116); The stator coil (118) is disposed adjacent to the rotor (116) such that eddy currents (128) are generated in the rotor (116) when an alternating current (130) flows through the stator coil (118); When an alternating current (130) flows through at least one stator coil (136), the at least one stator coil (136) forms an alternating magnetic field (138) and induces eddy currents (128) in the rotor (116), such that a repulsive force (140) between at least one of the stator coils (118) and the rotor (116) causes the rotor (116) to rotate about the axis (122).

[0197] Addendum 2. The apparatus of Addendum 1, wherein when the position (134) of the rotor (116) is such that an end (142) of the rotor (116) is adjacent to the at least one stator coil (136), the current control system (112) sends the alternating current (130) to the at least one stator coil (136).

[0198] Addendum 3. The apparatus of Addendum 1, wherein the conductive material (120) is at least one selected from a conductive ferromagnetic material (124) or a conductive non-ferromagnetic material (126).

[0199] Clause 4. The apparatus of clause 3, wherein the conductive ferromagnetic material (124) is at least one selected from iron, iron oxide, nickel, or samarium cobalt.

[0200] Clause 5. The apparatus of clause 3, wherein the conductive non-ferromagnetic material (126) is at least one selected from aluminum, copper, gold, intercalated graphene, lead, silver, tin, titanium, or zinc.

[0201] Appendix 6. The apparatus of Appendix 1, wherein each of the stator coils (118) has a resonant frequency different from the other ones of the stator coils (118), and further comprising a power source (114) configured to transmit power to the stator coils (118) by wireless electromagnetic coupling to the stator coils (118), the transmitted power being an alternating current (130) flowing through the stator coils (118).

[0202] Addendum 7. The current control system (112) includes a plurality of switches (202) connected to the stator coils (118), wherein at least one switch (204) of the switches (202) transmits the AC current (130) to the at least one stator coil (136) when the at least one switch (204) is in a closed position; and a control circuit for controlling the AC current (130) flowing through the stator coils (118) based on the position (134) of the rotor (116), the control circuit for controlling the AC current (130) flowing through the stator coils (118) based on the position (134) of the rotor (116). and a control unit (200) for controlling a rotor (116) and a control circuit (202) for controlling the rotor (116) and the at least one stator coil (118) to generate an alternating current (130) when the alternating current (130) flows through the at least one stator coil (136) of the stator coils (118), such that the repulsive force (140) between the at least one stator coil (136) and the rotor (116) rotates the rotor (116) about the axis (122).

[0203] Addendum 8. The apparatus of Addendum 7, wherein the control unit (200) is configured to switch the alternating current (130) flowing through at least one stator coil (136) among the stator coils (118) with which an end (142) of the rotor (116) is aligned at the position (134) of the rotor (116).

[0204] Clause 9. The apparatus of clause 7, further comprising a rotary encoder indicating the position (134) of the rotor (116).

[0205] Addendum 10. The apparatus of Addendum 7, wherein the control unit (200) includes at least one of a solid-state circuit, a silicon-controlled rectifier, or a triac (TRIAC).

[0206] Addendum 11. The apparatus of Addendum 7, further comprising a group of position sensing coils responsive to the eddy currents (128) in the rotor (116) based on the position (134) of the rotor (116), and the control unit (200) uses the group of position sensing coils to determine the position (134) of the rotor (116).

[0207] Appendix 12. The apparatus of Appendix 1, wherein a first end of the stator coil (118) is connected to a source of alternating current, and the current control system (112) includes electric brushes (210) connected to a second end of the stator coil (118) and electrical contacts (212) arranged about the shaft (122), the electrical contacts (212) being connected to a power source (114) and arranged in a given pattern (214) such that as the electrical contacts (212) rotate about the shaft (122), the electric brushes (210) contact the electrical contacts (212) at various positions on the rotor (116) to control the alternating current (130) flowing through the stator coil (118).

[0208] Addendum 13. The apparatus of Addendum 1, wherein the rotor (116) includes a core (910) including a ferromagnetic material and a layer (912) disposed on the core (910), the layer (912) including a conductive non-ferromagnetic material (126), and the current control system (112) selectively attracts and repels the rotor (116) by controlling the DC current (1210) and the AC current (1212) flowing through the stator coil (118).

[0209] Addendum 14. The apparatus of Addendum 13, further comprising a capacitor (1312) connected in parallel to the stator coil (118) and the DC current source (1302), the capacitor (1312) generating the AC current (130) from a charge stored in the capacitor (1312).

[0210] Addendum 15. The apparatus of Addendum 1, wherein the stator coil (118) is positioned adjacent to the rotor (116) such that the repulsive force (140) is sufficient to rotate the rotor (116) from any rest position of the rotor (116).

[0211] Clause 16. The apparatus of clause 1, wherein the first frequency of the alternating current (130) is independent of a second frequency of rotation of the rotor (116).

[0212] Clause 17. The apparatus of clause 16, wherein the first frequency of the alternating current (130) is greater than or equal to about 10 kHz.

[0213] Clause 18. The apparatus of clause 1, wherein the eddy currents (128) generate a repulsive force (140) when interacting with the alternating magnetic field (138), the tangential force of the repulsive force (140) generating a torque that rotates the rotor (116) about the axis (122). .

[0214] Appendix 19. A rotor (116) rotatable about an axis (122), the rotor (116) including a core (910) formed of a ferromagnetic material and a layer (912) surrounding the core, the layer (912) including an electrically conductive non-ferromagnetic material (126); and a current control system (112) configured to control the AC current (130) and the DC current (1202) flowing through the stator coils (118) based on a position (134) of the rotor (116). At least one stator coil (136) of the stator coils (118) generates an AC magnetic field (138) when the AC current (130) flows through the at least one stator coil (136). to generate a repulsive force (140) between the at least one stator coil (136) and the rotor (116), and, when a direct current (1210) is passed through the at least one stator coil (136), to generate a unidirectional magnetic field (1008) to generate an attractive force (1010) between the at least one stator coil (136) and the rotor (116) to rotate the rotor (116) about the axis (122).

[0215] Clause 20. The dual frequency electric motor (900) of clause 19, further comprising a capacitor connected in parallel to the stator coils (118) and the DC current source (1410), the capacitor (1402) being the AC current source (1204) when the DC current source (1410) is disconnected from the stator coils (118), and each stator coil (136) of the stator coils (118) having a pair of capacitors (1402) connected in parallel or in series.

[0216] Clause 21. The dual frequency electric motor (900) of clause 19, wherein the electrically conductive ferromagnetic material (124) is at least one selected from iron, iron oxide, nickel, or samarium cobalt.

[0217] Addendum 22. The dual frequency electric motor (900) of Addendum 19, wherein the conductive non-ferromagnetic material (126) is at least one selected from aluminum, copper, gold, intercalated graphene, lead, nickel, silver, tin, titanium, or zinc.

[0218] Addendum 23. The method includes controlling an alternating current (130) flowing through a plurality of stator coils (118) of an electric motor; The method of controlling an electric motor (108), wherein the control of the AC current is based on a position (134) of the rotor (116) such that when an AC current (130) flows through at least one stator coil (136) of the stator coils (118), a repulsive force (140) is generated between a rotor (116) of the electric motor and the at least one stator coil (136).

[0219] Clause 24. The method of clause 23, further comprising determining the position (134) of the rotor (116).

[0220] Addendum 25. The method of Addendum 24, wherein the determination of the position (134) of the rotor (116) is performed using at least one of a rotary encoder, contacts associated with the rotor (116), or a position sensing coil.

[0221] Addendum 26. The rotor (116) includes a core (910) formed of a ferromagnetic material and a layer (912) encasing the core (910), the layer (912) including an electrically conductive non-ferromagnetic material (126); 24. The method of claim 23, further comprising controlling a direct current (1210) flowing through the at least one stator coil (136) such that an attractive force (1010) between the at least one stator coil (136) and the rotor (116) causes the rotor (116) to rotate about an axis (122).

[0222] CLAIM 27. Sending a direct current (1210) to at least one stator coil (136) of an electric motor (108) when a rotor (116) of the electric motor (108) is in a first position relative to at least one stator coil (136) of the stator coils (118), such that an attractive force (1010) between the at least one stator coil (136) and the rotor (116) rotates the rotor (116) about an axis (122); 23. A method of controlling an electric motor (108), comprising: sending an alternating current (130) to the at least one stator coil (136) of the electric motor (108) when the rotor (116) is in a second position relative to the at least one stator coil (136), wherein a repulsive force (140) between the at least one stator coil (136) and the rotor (116) causes the rotor (116) to rotate about the axis (122).

[0223] Clause 28. The method of clause 27, further comprising determining positions of the rotor (116) including the first position and the second position.

[0224] The description of various exemplary embodiments has been presented for purposes of illustration and description, and is not intended to be exhaustive or to be limited to the implementation in the form disclosed. Various exemplary embodiments describe components that perform operations or steps. In the exemplary embodiments, the components may be configured to perform the described operations or steps. For example, the components may have a structural configuration or design that enables the components to perform the operations or steps described in the exemplary embodiments as being performed by the components.

[0225] Also, many modifications or variations will be apparent to those skilled in the art. Moreover, various exemplary embodiments may provide different features than other preferred embodiments. The selected embodiments have been chosen and described in order to best explain the principles and practical applications of the embodiments and to enable those skilled in the art to understand the disclosure for the various embodiments with various modifications suited to the particular applications envisioned.

Claims

1. a rotor including a core made of an electrically conductive ferromagnetic material and a layer of an electrically conductive non-ferromagnetic material surrounding the core, the rotor being rotatable about an axis; a plurality of stator coils connected to an AC current source and a DC current source; a current control system for controlling AC and DC currents flowing through the stator coils based on the position of the rotor; 1. A dual frequency electric motor configured such that when an AC current flows through at least one of the stator coils, the at least one stator coil creates an AC magnetic field generating a repulsive force between the at least one stator coil and the rotor, and when a DC current flows through the at least one stator coil, the at least one stator coil creates a unidirectional magnetic field generating an attractive force between the at least one stator coil and the rotor.

2. A dual frequency electric motor as described in claim 1, further comprising a capacitor connected in parallel to the plurality of stator coils and the DC current source, wherein when the DC current source is disconnected from the plurality of stator coils, the capacitor functions as the AC current source.

3. 3. The dual frequency electric motor of claim 1 or 2, wherein the electrically conductive ferromagnetic material is at least one selected from iron, iron oxide, nickel, or samarium cobalt.

4. A dual frequency electric motor as described in any of claims 1 to 3, wherein the conductive non-ferromagnetic material is at least one selected from aluminum, copper, gold, intercalated graphene, lead, silver, tin, titanium, or zinc.

5. A method for producing an electric motor comprising: supplying a direct current to at least one stator coil in an electric motor having a rotor and a plurality of stator coils; and supplying an alternating current to the at least one stator coil, comprising: providing a direct current to the at least one stator coil when the rotor is in a first position relative to the at least one stator coil to generate an attractive force between the at least one stator coil and the rotor to rotate the rotor about an axis; supplying alternating current to the at least one stator coil when the rotor is in a second position relative to the at least one stator coil to generate a repulsive force between the at least one stator coil and the rotor, causing the rotor to rotate about the axis.

6. The method of claim 5, further comprising determining a position of the rotor including the first position and the second position.

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