Electric machine comprising dielectric layer arranged between stator and housing

Abstract

A multi-phase multi-pole permanent magnet motor / generator (electric machine) is described and includes a rotor disposed on a rotor shaft within an annular stator, the rotor being arrangeable in a housing with an inserted insulator system. The insulator system is arranged to mitigate and isolate common mode current in the shaft bearing system by insulating the stator core from an electrically grounded return path of the electric drive source. The electric machine includes a rotor rotatably disposed within a stator, and the stator is fixed to a housing with an insulator system interposed between the stator and the housing.

Description

Technical Field

[0001] introduction

[0002] The invention relates to a drive unit for a vehicle, an electric machine and a method for assembling a permanent magnet electric machine. Background Art

[0003] Electrical multiphase rotating motor / generators, such as permanent magnet (PM) machines, may be used as torque generating devices on vehicles.

[0004] In an electric machine, traction torque or reaction torque can be generated by multiple alternating current (AC) waveforms passing through three or more phase leads. A power inverter can be configured to generate multiple AC waveforms that operate at the same frequency and amplitude, but have a time offset or phase shift between different phases. In a vehicle or other system using an electric machine, a power inverter generates a phased AC waveform that is transmitted to each stator winding of a rotating electric machine to induce a changing magnetic field. This magnetic field causes the rotor to rotate, which in turn provides the motor output torque or regenerative torque. The motor output torque can be utilized and directed to perform useful work, for example, to propel the vehicle.

[0005] Under some operating conditions, common-mode electrical power may be generated and transmitted through the bearings of a rotating electrical machine. This may result in bearing degradation, which may be in the form of grooves, pitting, or other effects. This bearing degradation may lead to problems related to noise and vibration, may cause bearing failures that may require repair, and / or may reduce the useful life of the rotating electrical machine. Summary of the invention

[0006] A multi-phase, multi-pole permanent magnet electric motor / generator (motor) is described and includes a rotor disposed on a rotor shaft within an annular stator, which can be arranged in a housing with an interposed insulator system. The insulator system is arranged to mitigate and isolate common mode currents in a shaft bearing system by insulating the stator core from an electrical ground return path of an electric drive source. Insulating the stator core from a housing (e.g., a drive unit housing) reduces common mode currents. Reducing common mode currents from the stator core system reduces or eliminates common mode currents and deleterious effects associated therewith.

[0007] Aspects of the present disclosure may include a drive unit for a vehicle, the drive unit including an electric machine disposed in a housing; and an insulator system. The electric machine includes a rotor rotatably disposed within a stator, and the stator is fixed to the housing, wherein the insulator system is interposed between the stator and the housing. The rotor is rotatably or otherwise coupled to an element of a drive train.

[0008] Another aspect of the present disclosure may include that the insulator system is a dielectric layer disposed between the stator and the housing; wherein the dielectric layer electrically isolates the stator from the housing.

[0009] Another aspect of the present disclosure may include that the dielectric layer is fabricated from a polymer material.

[0010] Another aspect of the present disclosure may include a dielectric layer disposed between the stator core and the housing having an impedance greater than a predetermined minimum resistance threshold; wherein the magnitude of the predetermined resistance threshold minimizes common mode electrical power transferred through the bearing system.

[0011] Another aspect of the present disclosure may include a dielectric layer arranged between the stator core and the housing having an impedance greater than a predetermined minimum resistance threshold at a predefined excitation frequency; wherein the magnitude of the predetermined resistance threshold and the magnitude of the predefined excitation frequency minimize the common mode electrical power transmitted through the bearing system.

[0012] Another aspect of the present disclosure may include that a dielectric layer disposed between the stator and the housing has an impedance greater than a hard short circuit.

[0013] Another aspect of the present disclosure may include that the dielectric layer disposed between the stator and the housing is a dielectric spacer, wherein the dielectric spacer is interposed between the stator and the housing.

[0014] Another aspect of the present disclosure may include that the stator is a plurality of laminated plates arranged in a stack, wherein the stack has a first end and a second end. The insulator system includes a dielectric spacer; and the stator is secured to a housing, including a first end of the plurality of laminated plates arranged in a stack secured to the housing, wherein the dielectric spacer is interposed between the stator and the housing.

[0015] Another aspect of the present disclosure may include a stator including a plurality of laminated plates arranged in a stack; wherein the plurality of laminated plates arranged in a stack have a plurality of mounting bosses; wherein the stator is secured to a housing via a plurality of fasteners, the plurality of fasteners being arranged in the plurality of mounting bosses and coupled to the housing; and wherein the insulator system includes a plurality of dielectric fastener packers. The stator is secured to the housing via the plurality of fasteners, wherein the plurality of dielectric fastener packers are interposed therebetween.

[0016] Another aspect of the present disclosure may include coupling the rotor to a rotatable element of a driveline to transfer tractive torque to the drive wheels.

[0017] Another aspect of the present disclosure may include an electric machine arranged in a housing. The electric machine includes a rotor, a stator, and an insulator system, wherein the rotor is rotatably arranged in the stator, and the stator includes a stator core and a plurality of field windings. The insulator system is interposed between the stator core and the housing.

[0018] Another aspect of the present disclosure may include that the electric machine is a multi-phase permanent magnet electric machine.

[0019] Another aspect of the present disclosure may include a method for assembling a permanent magnet electric machine, the method comprising inserting a rotor into a hole defined by a stator core, including inserting a plurality of concentrically disposed spacers between the rotor and the stator core; inserting the stator core into a housing, including inserting a dielectric sleeve between the stator core and the housing; securing the stator core to the housing; and removing the plurality of concentrically disposed spacers from between the rotor and the stator core.

[0020] Another aspect of the present disclosure may include inserting a dielectric insulator system between the stator core and the housing prior to inserting the stator core into the housing, wherein the dielectric insulator system includes a plurality of dielectric fastener encapsulators and dielectric spacers.

[0021] The present disclosure also provides the following technical solutions:

[0022] 1. A drive unit for a vehicle, the drive unit comprising:

[0023] an electric motor disposed in the housing; and

[0024] Insulator systems;

[0025] Wherein, the motor comprises a rotor rotatably disposed within a stator;

[0026] wherein the stator is fixed to the housing, wherein the insulator system is interposed between the stator and the housing; and

[0027] Wherein, the rotor is coupled to a transmission system.

[0028] 2. A drive unit according to technical solution 1, wherein the insulator system is inserted between the stator and the housing, including the insulator system being a dielectric layer arranged between the stator and the housing; wherein the dielectric layer electrically isolates the stator from the housing.

[0029] 3. The drive unit according to technical solution 2, wherein the dielectric layer arranged between the stator and the housing is made of a polymer material.

[0030] 4. A drive unit according to Technical Solution 2, wherein the dielectric layer arranged between the stator and the housing has an impedance greater than a predetermined minimum resistance threshold; wherein the size of the predetermined minimum resistance threshold is selected to minimize the common-mode electrical power transmitted through the bearing system.

[0031] 5. A drive unit according to technical solution 2, wherein the dielectric layer arranged between the stator and the housing has an impedance greater than a predetermined minimum resistance threshold at a predetermined excitation frequency; wherein the size of the predetermined minimum resistance threshold is selected to minimize the common-mode electric power transmitted through the bearing system.

[0032] 6. A drive unit according to Technical Solution 2, wherein the dielectric layer arranged between the stator and the housing has an impedance greater than a predetermined minimum resistance threshold; wherein the magnitude of the predetermined minimum resistance threshold is greater than a hard short circuit.

[0033] 7. The drive unit according to technical solution 2, wherein the dielectric layer arranged between the stator and the housing includes a dielectric spacer; wherein the dielectric spacer is inserted between the stator and the housing.

[0034] 8. The drive unit according to technical solution 1, wherein:

[0035] The stator comprises a plurality of laminated plates arranged as a stack;

[0036] The plurality of laminated plates arranged in the stack have a first end and a second end;

[0037] The insulator system includes a dielectric spacer; and

[0038] The stator is fixed to the housing with the insulator system interposed between the stator and the housing, and the first end of the plurality of laminated plates arranged as the stack is fixed to the housing with the dielectric spacer interposed between the stator and the housing.

[0039] 9. The drive unit according to technical solution 1, wherein:

[0040] The stator has a plurality of mounting bosses;

[0041] The stator is secured to the housing via a plurality of fasteners disposed in the plurality of mounting bosses and coupled to the housing;

[0042] The insulator system includes a plurality of dielectric fastener packages; and

[0043] The stator is secured to the housing via the plurality of fasteners, wherein the plurality of fasteners secure the stator to the housing with the plurality of dielectric fastener encapsulators interposed therebetween.

[0044] 10. The drive unit according to technical solution 1, wherein the rotor is coupled to the transmission system, including the rotor being coupled to a rotatable element of the transmission system to transmit traction torque to a drive wheel.

[0045] 11. A motor, comprising:

[0046] rotor, stator, housing, bearing system and insulator system;

[0047] wherein the stator and the bearing system are arranged in the housing;

[0048] wherein the rotor is rotatably arranged in the stator by means of the bearing system;

[0049] Wherein, the stator comprises a stator core and a plurality of field windings; and

[0050] Therein, the insulator system is interposed between the stator core and the housing.

[0051] 12. An electric motor according to technical solution 11, wherein the insulator system is inserted between the stator core and the housing, including that the insulator system is a dielectric layer arranged between the stator core and the housing; wherein the dielectric layer electrically isolates the stator core from the housing.

[0052] 13. According to the electric motor of technical solution 12, the dielectric layer arranged between the stator core and the housing is made of a polymer material.

[0053] 14. An electric motor according to Technical Solution 12, wherein the dielectric layer arranged between the stator core and the housing has an impedance greater than a predetermined minimum resistance threshold; wherein the size of the predetermined minimum resistance threshold minimizes the common-mode electric power transmitted through the bearing system.

[0054] 15. The electric motor according to technical solution 12, wherein the dielectric layer arranged between the stator core and the housing includes a dielectric spacer; wherein the dielectric spacer is inserted between the stator core and the housing.

[0055] 16. The motor according to technical solution 11, wherein:

[0056] The insulator system includes a dielectric spacer; and

[0057] The stator core is fixed to the housing, with the dielectric spacer interposed between the stator core and the housing.

[0058] 17. The motor according to technical solution 11, wherein:

[0059] The stator core is secured to the housing via a plurality of fasteners disposed in the plurality of mounting bosses and mechanically coupled to the housing;

[0060] The insulator system includes a plurality of dielectric fastener packages; and

[0061] The stator core is secured to the housing via the plurality of fasteners, wherein the plurality of fasteners secure the stator to the housing with the plurality of dielectric fastener encapsulators interposed therebetween.

[0062] 18. An electric motor according to Technical Solution 11, wherein the electric motor comprises a multi-phase permanent magnet motor.

[0063] 19. A method for assembling a permanent magnet electric machine, the method comprising:

[0064] inserting a dielectric insulator system between the stator core and the housing of the permanent magnet electric machine before inserting the stator core into the housing;

[0065] inserting a dielectric sleeve between the housing and the stator core;

[0066] inserting the stator core into the housing, including inserting a dielectric sleeve between the stator core and the housing;

[0067] fixing the stator core to the housing; and then

[0068] The dielectric sleeve is removed from between the rotor and the stator core.

[0069] 20. A method according to technical solution 19, wherein, before the stator core is inserted into the housing, the dielectric insulator system is inserted between the stator core and the housing, including inserting a plurality of dielectric fastener encapsulators and dielectric spacers between the stator core and the housing.

[0070] The above features and advantages and other features and advantages of the present teachings are apparent from the following detailed description of some of the best modes and other embodiments for carrying out the present teachings as defined in the appended claims when considered in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] One or more embodiments will now be described by way of example with reference to the accompanying drawings, in which:

[0072] Figure 1 is a schematic illustration of a system according to the present disclosure, the system including a multi-phase multi-pole permanent magnet motor / generator (motor), a DC power supply, an inverter, and a controller.

[0073] Figure 2 A side view of an embodiment of an electric machine including an insulator system according to the present disclosure is shown.

[0074] Figure 3 An isometric view of an embodiment of a stator and insulator system for an electric machine according to the present disclosure is shown.

[0075] Figure 4 An isometric view of an embodiment of an insulator system for an electric machine according to the present disclosure is shown.

[0076] Figure 5 An equivalent circuit of an embodiment of a stator and insulator system for an electric machine according to the present disclosure is schematically shown.

[0077] Figure 6 Schematically illustrated is an isometric view of an embodiment of a stator and insulator system for an electric machine including an assembly spacer tool according to the present disclosure.

[0078] The drawings are not necessarily to scale and present somewhat simplified representations of various preferred features of the present disclosure as disclosed herein, including, for example, specific dimensions, orientations, locations, and shapes. The details associated with such features will be determined in part by the specific intended application and use environment. DETAILED DESCRIPTION

[0079] As described and shown herein, the parts of the disclosed embodiments can be arranged and designed in various configurations. Therefore, the following detailed description is not intended to limit the scope of the disclosure claimed for protection, but only represents its possible embodiments. In addition, although many specific details are recorded in the following description to provide a full understanding of the embodiments disclosed herein, some embodiments can be implemented without some of these details. In addition, for the purpose of clarity, some technical materials understood in the relevant art are not described in detail to avoid unnecessarily obscuring the disclosure. In addition, the disclosure as illustrated and described herein can be implemented without the presence of elements not specifically disclosed herein.

[0080] As used herein, the term "system" refers to mechanical and electrical hardware, software, firmware, electronic control components, processing logic and / or processor devices, alone or in combination, including but not limited to: application specific integrated circuits (ASICs), electronic circuits, processors (shared, dedicated or groups) that execute one or more software or firmware programs, (multiple) memory devices that electrically store software or firmware instructions, combinational logic circuits, and / or other components that provide the described functionality.

[0081] As used herein, the term "electrical machine" refers to an electrical motor / generator device that includes a rotor and a stator disposed in a housing that is capable of converting electrical power into mechanical power (e.g., rotational torque) and / or capable of converting mechanical power (e.g., rotational torque) into electrical power through electromagnetic action. In one embodiment, the electromagnetic motor / generator includes a rotor that rotates relative to the stator to achieve work. In one embodiment, the electromagnetic motor / generator includes a rotor that translates relative to the stator to achieve work.

[0082] Referring to the drawings, wherein like reference numerals refer to like or similar parts throughout the several views. Figure 1 The system 100 is schematically shown, which includes a multi-phase multi-pole rotating permanent magnet electric motor / generator (motor) 200, which is arranged in a housing 230 to generate torque and transmit the torque to an actuator 120 to achieve work, and a controller 130 executes a control routine to control and manage its operation. In one embodiment, the system 100 is disposed on a vehicle (not shown). When disposed on a vehicle, the vehicle may include, but is not limited to, a mobile platform in the form of a commercial vehicle, an industrial vehicle, an agricultural vehicle, a passenger car, an airplane, a boat, a train, an all-terrain vehicle, a personal mobility device, a robot, etc., to achieve the purposes of the present disclosure. Alternatively, the system 100 may be an element of a stationary system.

[0083] The system 100 further includes an inverter 104 and a DC power source 102. The DC power source 102 is connected to the inverter 104 via a high voltage DC bus 103, and the inverter 104 is connected to the motor 200 via a plurality of power lines 106.

[0084] The inverter 104 includes a plurality of semiconductor switches (not shown) arranged and controllable to convert DC electric power to AC electric power and to convert AC electric power to DC electric power using a pulse width modulation signal 108 or another control technique. The inverter 104 is arranged and controllable to convert DC electric power originating from the DC power source 102 to AC electric power to actuate the motor 200 via electromagnetic action. When operating in a torque generating mode, the motor 200 is controllable to rotate and generate mechanical torque, which is transmitted to the actuator 120 via a rotatable member 112 and a gear train 114. When operating in a power generating mode, the motor 200 is controllable to generate AC electric power from the mechanical torque originating from the actuator 120 via electromagnetic action, which is converted by the inverter 104 to DC electric power for storage in the DC power source 102. In one embodiment, the actuator 120 includes a wheel that transmits torque to the ground as part of a traction propulsion system to achieve forward motion. The DC power source 102 may be in the form of a rechargeable electrochemical battery device, a fuel cell, a supercapacitor, and / or other electrical energy storage / generation technology.

[0085] The controller 130 may be implemented as one or more digital computing devices and may include one or more processors 134 and a memory 132. A control routine 136 may be stored as an executable instruction set in the memory 132 and executed by one of the processors 134 of the controller 130. The controller 130 communicates with the inverter 104 to control its operation in response to execution of the control routine 136 to operate the motor 200.

[0086] The term "controller" and related terms such as microcontroller, control module, module, control, control unit, processor and similar terms refer to one or various combinations of the following: application specific integrated circuit(s) (ASIC), field programmable gate array (FPGA), electronic circuit(s), central processing unit(s), such as microprocessor(s) and associated memory component(s) in the form of transient and / or non-transitory memory component(s) and storage devices (read-only, programmable read-only, random access, hard disk drive, etc.). The non-transitory memory component(s) can store machine-readable instructions in the form of one or more software or firmware programs or routines, combinational logic circuit(s), input / output circuit(s) and devices, signal conditioning and buffering circuits, and other components accessible by one or more processors to provide the described functionality. The input / output circuit(s) and devices include analog / digital converters and related devices to monitor inputs from sensors, where such inputs are monitored at a preset sampling frequency or in response to a triggering event. Software, firmware, programs, instructions, control routines, code, algorithms and similar terms refer to controller executable instruction sets, including calibrations and look-up tables.

[0087] Figure 2 , Figure 3 and Figure 4 , and continue to refer to reference Figure 1 Elements of an embodiment of system 100 are described, schematically illustrating various elements of an embodiment of an electric machine 200 , including a stator assembly 210 and a rotor assembly 220 , disposed within a housing 230 with an insulator system 240 interposed therebetween.

[0088] The electric machine 200 is shown in the context of a radial axis 13 and a longitudinal axis 12 , wherein the longitudinal axis 12 is defined by a rotor shaft 224 .

[0089] The rotor assembly 220 includes a cylindrical rotor core 222 disposed on a rotor shaft 224 and disposed within a cylindrical opening formed by the stator body 210, wherein the rotor assembly 220 is coaxial with the rotor opening formed in the stator 210. The rotor shaft 224 is disposed on a bearing system 250, which is fixed to the housing 230 to facilitate rotation of the rotor assembly 220 within the stator assembly 210 and the housing 230. The bearing system 250 may be constructed of a sleeve bearing, a ball bearing, a tapered bearing, or other bearing arrangement. Other elements of the motor 200, such as end caps, electrical connections, etc., are included but not shown.

[0090] The stator assembly 210 includes a stator core 212 and a plurality of field windings 215. The stator assembly 210 is configured as a distributed electric winding assembly arranged to provide a rotating electric field that provides a rotating magnetic field in the plurality of field windings 215 by applying a multi-phase alternating current. The plurality of field windings 215 are electrically connected to a reference rectifier via a plurality of power lines 106. Figure 1 Inverter 104 is described. In one embodiment, the polyphase AC power is a three-phase AC power.

[0091] A plurality of field windings 215 are arranged circumferentially. The electrical windings are electrically connected to the inverter 104, which is controlled by the controller 130 to generate a rotating electric field that induces a magnetic field adjacent to the rotor 220 and interacts with the magnetic fields of the permanent magnets arranged in the rotor assembly 220 to generate a mechanical torque that is transmitted to the rotor shaft 224. The rotating electrical machine 200 can be controlled to operate as a torque motor and / or an electrical generator.

[0092] In one embodiment, the stator core 212 is constructed as a plurality of laminated plates arranged as a stack having a first end 213 and a second end 214. The plurality of laminated plates arranged as a stack have a plurality of mounting bosses 216 arranged around the periphery of the stator core 212. Each of the mounting bosses 216 includes a hole 215 into which a fastener 217 can be inserted. Alternatively, the stator core 212 can be manufactured from a soft magnetic composite (SMC) material having similar features. Alternatively, the stator core 212 can be manufactured from other materials using another manufacturing technique, thereby bringing features similar to those of the laminated stack.

[0093] The stator core 212, and therefore the stator assembly 210, is secured to the housing 230 via fasteners 217 coupled to bosses 232 that are attached to the housing 230. In one embodiment, each of the fasteners 217 may be configured as a threaded screw having a head portion 218 and an elongated shaft portion 219 that has threads on the end and is capable of interacting with a threaded portion of one of the bosses 232 in the housing 230. Alternatively, the plurality of fasteners 217 may be configured as latches (e.g., quarter-turn latches), cam locks, compression latches, rivets, etc., or other fastener configurations having a head portion 218 and a shaft portion 219 that are arranged to interact with a corresponding boss configuration in the housing 230.

[0094] The insulator system 240 is interposed between the stator core 212 of the stator 210 and the housing 230 .

[0095] The insulator system 240 includes one or more dielectric spacers 242 and a plurality of dielectric fastener encapsulators 244 .

[0096] The one or more dielectric spacers 242 and the plurality of dielectric fastener encapsulators 244 function to electrically isolate the elements of the stator 210 , stator core 212 , and field winding 215 from the housing 230 .

[0097] The dielectric spacer(s) 242 are interposed between the stator core 212 of the stator 210 and the housing 230 .

[0098] A plurality of dielectric fastener packers 244 are arranged in the plurality of mounting bosses 216 and coupled to the housing 230. A plurality of fasteners 217 fix the stator core 212 of the stator 210 to the housing 230 with the plurality of dielectric fastener packers 244 interposed therebetween.

[0099] In one embodiment, each of dielectric fastener encapsulators 244 includes a washer portion 245 that is interposed between head portions 218 of fasteners 217 .

[0100] Each of the dielectric fastener encapsulators 244 may include a sleeve portion 246 that is interposed between the shaft portion 219 of the fastener 217 and an edge of the mounting boss 216 that defines the aperture 215 .

[0101] The dielectric fastener encapsulator 244 is used to isolate the fastener 217 from the mounting boss 216 by ensuring there is a dielectric material therebetween and ensuring there is a minimum distance therebetween to provide electrical decoupling.

[0102] The dielectric fastener encapsulator 244 serves to isolate the fastener 217 by ensuring a minimum distance between the shaft portion 219 and the edge of the mounting boss 216 and a minimum distance or gap between the fastener head 218 of the fastener 217 and the surface of the mounting boss 216 .

[0103] Bolt insulation can also be achieved by using non-conductive brackets, or mounting interfaces that can also serve as vibration dampeners.The end brackets can be made of dielectric materials and / or isolated by means of dielectric layers.

[0104] The insulator system 240 is provided with a dielectric layer that is arranged between the stator 210 and the housing 230 to electrically isolate the stator 210 from the housing 230. The dielectric spacer(s) 242 and the plurality of dielectric fastener encapsulators 244 are formed of a dielectric material. A dielectric material is a material that supports an electric charge but does not conduct the charge to a large extent. The dielectric property of a material is a measure of the potential for charge movement to occur within the material in response to an external electric field. Examples of dielectric materials include plastics / polymers, including glass-filled polymers. In one embodiment, the dielectric layer associated with the insulation system 240 arranged between the stator 210 and the housing 230 is made of a polymer material. In one embodiment, a dielectric layer associated with an insulation system 240 disposed between the stator 210 and the housing 230 has an impedance greater than a predetermined resistance threshold at a predefined excitation frequency, wherein the magnitude of the predetermined resistance threshold and the magnitude of the predefined excitation frequency are determined to avoid (i.e., minimize or eliminate) the generation and / or transmission of common-mode electrical power through bearings of the rotating electrical machine, which common-mode electrical power may cause degradation of the bearings, which may be in the form of grooves, pitting, or other effects.

[0105] In one embodiment, a dielectric layer associated with the insulation system 240 disposed between the stator 210 and the housing 230 has an impedance greater than a predetermined minimum resistance threshold.

[0106] In one embodiment, the predetermined minimum resistance threshold is greater than a hard short.

[0107] In one embodiment, the predetermined minimum resistance threshold is greater than 1 ohm.

[0108] In one embodiment, the predetermined minimum resistance threshold is greater than 1 milliohm.

[0109] In one embodiment, the predetermined minimum resistance threshold is 1 Ohm at an excitation frequency on the order of 1 MHz.

[0110] In one embodiment, the predetermined minimum resistance threshold is 100 Ohms at an excitation frequency on the order of 1 MHz.

[0111] The thickness and gaps of the elements of insulation system 240 are determined so that the impedance between stator core 212 and housing 230 is at least a predetermined minimum resistance threshold. To increase the impedance, thicker insulation and / or larger gaps may be used.

[0112] During operation, the electromagnetic force induced in the field winding 215 introduces a magnetic flux acting on a permanent magnet arranged in or on the rotor assembly 220, thereby applying a torque to rotate the rotor assembly 220 around the rotor shaft 224 within the stator 210. Alternating current (AC) motors can be generally divided into AC induction motors and AC synchronous motors. In a rotating magnetic field type AC synchronous motor, in which the stator is provided with an armature winding and the rotor assembly is provided with a magnet winding, the rotor assembly is turned into an electromagnet by excitation of the magnet winding of the rotor assembly, and the rotor assembly is rotated by applying multi-phase alternating current to the stator. In applications in which the electric power is derived from a DC power supply, the multi-phase alternating current is generated by a power inverter.

[0113] The field winding 215 of the stator 210 is arranged with a certain number of electrical phases and a certain number of electrical turns per phase. Depending on the specific arrangement, the number of electrical phases may be between 3 and 6, and the number of layers of conductors may be between 4 and 12.

[0114] Stator 210 includes a plurality of stamped ferrous laminates, each of which is formed of electrical steel and is a disc-shaped device of uniform thickness and each having a centrally located inner bore sized to accommodate an outer diameter of rotor assembly 220 .

[0115] Specific geometric design parameters associated with the rotor assembly 220 and the stator assembly 210 of the electric machine 200 are selected to achieve electric motor operating parameters including high drive cycle efficiency, for example, a peak efficiency greater than 90% over a wide operating region, high torque density, a wide peak power range, and a maximum speed of 21,000 rpm or more.

[0116] Figure 5 Schematically shows the reference Figure 2 , Figure 3 and Figure 4 An equivalent circuit of an embodiment of an electric machine 200 is depicted, including a stator 210 having a core 212 and a field winding 215, a rotor 220, a housing 230, an insulator system 240, and a bearing system 250. The equivalent circuit includes a plurality of capacitive couplings 260 between the field winding 215 of the stator 210 and the housing 230, which may result in the generation of common-mode electrical power that may be transmitted through the bearing system 250 of the rotating electric machine 200, thereby causing degradation thereof.

[0117] The plurality of capacitive couplings 260 include a first capacitive coupling C between the housing 230 and the field winding 215. WF 261. A second capacitive coupling between the housing 230 and the field winding 215 may occur via the rotor 220 and include a parallel arrangement and also with the rotor-housing capacitance C WR 265 The first variable capacitor C arranged in series B1 262. Second variable capacitor C RF 263. The third variable capacitor C B2 264.

[0118] The increased impedance 241 due to the insulation system 240 additionally increases the overall impedance between the field winding 215 of the stator 210 and the housing 230 .

[0119] Figure 6 Schematically illustrated is an isometric view of an embodiment of a stator and insulator system for an embodiment of an electric machine 200, including an assembly spacer tool 610. During assembly of the electric machine 200, the dielectric insulator system 240 is inserted between the stator core 211 of the electric machine 200 and the housing 230 before the stator 210 including the stator core 210 is inserted into the housing 230. Additionally, during the portion of the electric machine assembly including securing the stator core to the housing, an assembly spacer tool 260 is inserted between the housing 230 and the stator core 212. The assembly spacer tool 260 may be in the form of a plurality of dielectric spacers or dielectric sleeves.

[0120] The assembly spacer tool 260 is utilized to center the stator 210 within the housing 230 and prevent physical contact between the housing 230 and the stator core 212. When the assembly spacer tool 260 is in the form of a plurality of spacers, in one embodiment, it may be removed prior to assembling the rotor 220. When the assembly spacer tool 260 is in the form of a dielectric sleeve, it may be left in place after assembly.

[0121] The assembly spacer tool 260 is utilized to maintain concentricity between the stator 210 and the housing 230 during assembly and to prevent physical contact between the stator 210 and the housing 230. In embodiments where the assembly spacer tool 260 is removed after assembly, in one embodiment, the assembly spacer tool 260 is made of metal. Alternatively, in embodiments where the assembly spacer tool 260 remains in its place after assembly, the assembly spacer tool 260 is made of a dielectric material.

[0122] Embodiments of multi-phase, multi-pole permanent magnet electric machines described herein include a rotor disposed within an annular stator on a rotor shaft and arranged in a housing with an interposed insulator system. The insulator system is arranged to mitigate and isolate common mode currents in the shaft bearing system by insulating the stator core from an electrical ground return path. Insulating the stator core from a housing (e.g., a drive unit housing) can reduce common mode currents. Reducing common mode currents from the stator core system reduces or eliminates common mode currents and the harmful effects associated therewith. In addition, embodiments of the electric machines described herein are configured to simultaneously achieve operating parameters related to torque, speed, power, efficiency, packaging, and other limitations while meeting other performance criteria such as torque density, high drive cycle efficiency, protection from permanent demagnetization, and minimum torque ripple.

[0123] The specific description and drawings or illustrations are supportive and descriptive of the present teaching, but the scope of the present teaching is limited only by the claims. Although some of the best modes and other embodiments for implementing the present teaching have been described in detail, there are various alternative designs and embodiments for implementing the present teaching defined in the appended claims.

Claims

1. A drive unit for a vehicle, the drive unit comprising: a motor disposed in the housing; and Insulator systems; Wherein, the motor comprises a rotor rotatably disposed within a stator; wherein the stator is fixed to the housing, wherein the insulator system is interposed between the stator and the housing; and Wherein, the rotor is coupled to a transmission system.

2. The drive unit according to claim 1, wherein: The insulator system being interposed between the stator and the housing includes the insulator system being a dielectric layer disposed between the stator and the housing; wherein the dielectric layer electrically isolates the stator from the housing.

3. The drive unit according to claim 2, wherein: The dielectric layer arranged between the stator and the housing is made of a polymer material.

4. The drive unit according to claim 2, wherein: The dielectric layer disposed between the stator and the housing has an impedance greater than a predetermined minimum resistance threshold; wherein the magnitude of the predetermined minimum resistance threshold is selected to minimize common mode electrical power transferred through the bearing system.

5. The drive unit according to claim 2, wherein: The dielectric layer disposed between the stator and the housing has an impedance greater than a predetermined minimum resistance threshold at a predefined excitation frequency; wherein the magnitude of the predetermined minimum resistance threshold is selected to minimize common mode electrical power transferred through the bearing system.

6. The drive unit according to claim 2, wherein: The dielectric layer disposed between the stator and the housing has an impedance greater than a predetermined minimum resistance threshold; wherein the predetermined minimum resistance threshold has a magnitude greater than a hard short circuit.

7. The drive unit according to claim 2, wherein: The dielectric layer disposed between the stator and the housing includes a dielectric spacer; wherein the dielectric spacer is interposed between the stator and the housing.

8. The drive unit according to claim 1, wherein: The stator comprises a plurality of laminated plates arranged as a stack; The plurality of laminated plates arranged in the stack have a first end and a second end; The insulator system includes a dielectric spacer; and The stator is fixed to the housing with the insulator system interposed between the stator and the housing, and the first end of the plurality of laminated plates arranged as the stack is fixed to the housing with the dielectric spacer interposed between the stator and the housing.

9. The drive unit according to claim 1, wherein: The stator has a plurality of mounting bosses; The stator is secured to the housing via a plurality of fasteners disposed in the plurality of mounting bosses and coupled to the housing; The insulator system includes a plurality of dielectric fastener packages; and The stator is secured to the housing via the plurality of fasteners, wherein the plurality of fasteners secure the stator to the housing with the plurality of dielectric fastener encapsulators interposed therebetween.

10. The drive unit according to claim 1, wherein: Coupling the rotor to the driveline includes coupling the rotor to a rotatable element of the driveline to transfer tractive torque to drive wheels.

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