WO2024148415A1

WO2024148415A1 - Switched reluctance motor drive system

Info

Publication number: WO2024148415A1
Application number: PCT/CA2023/050032
Authority: WO
Inventors: Jing Guo; Ehab Mohammed Mahmoud SAYED; Adam LEMPERT; Benjamin COSMAN; Ahmed S. ABDELRAHMAN; Christopher MAK; Berker Bilgin
Original assignee: Enedym Inc.
Priority date: 2023-01-12
Filing date: 2023-01-12
Publication date: 2024-07-18

Abstract

A motor drive system for driving at least one wheel of a motor vehicle is provided. The system may comprise a switched reluctance motor, an inverter and a phase plate. The switched reluctance motor may have a stator and a rotor. The stator may have (i) multiple stator poles and (ii) a stator coil winding around each of the stator poles. Each stator coil winding may have an input terminal and an output terminal. The rotor may be rotatably mounted with respect to the stator. The rotor may have a rotor output shaft and multiple rotor poles. The inverter may have a power outlet with a plurality of phases. The power outlet may have a positive terminal and a negative terminal for each phase. The phase plate may have at least first and second coil current transfer layers for each of the plurality of phases.

Description

SWITCHED RELUCTANCE MOTOR DRIVE SYSTEM

FIELD

[0001 ]This document relates to switched reluctance motor drive systems for motor vehicles.

BACKGROUND

[0002]The transportation sector is a significant contributor to global greenhouse gas emission. Internal combustion engines of motor vehicles burn fossil fuels like gasoline and diesel to drive the vehicles and generate greenhouse gas emissions in the process. The greenhouse gas emission of the transportation sector can be reduced by using electric motor drive systems instead of internal combustion engines in motor vehicles. The electric motor drive systems can provide a cleaner and more sustainable alternative to internal combustion engines. Increased adoption of electric motor drive systems in motor vehicles may require efficient, reliable, robust, and cost-effective electric motors.

SUMMARY

[0003]The following summary is provided to introduce the reader to the more detailed discussion to follow. The summary is not intended to limit or define any claimed or as yet unclaimed invention. One or more inventions may reside in any combination or sub-combination of the elements or process steps disclosed in any part of this document including its claims and figures.

[0004]According to some aspects, a motor drive system for driving at least one wheel of a motor vehicle is provided. The system may comprise a switched reluctance motor, an inverter, and a phase plate. The switched reluctance motor may have a stator and a rotor. The stator may have (i) multiple stator poles and (ii) a stator coil winding around each of the stator poles. Each stator coil winding may have an input terminal and an output terminal. The rotor may be rotatably mounted with respect to the stator. The rotor may have a rotor output shaft and multiple rotor poles. The inverter may have a power outlet with a plurality of phases. The power outlet may have a positive terminal and a negative terminal for each phase. Each of the stator coil windings of the stator may be associated with one of the phases of the power outlet. Each of the plurality of phases may be associated with at least two of the stator coil windings of the stator. The phase plate may have at least first and second coil current transfer layers for each of the plurality of phases. For each of the plurality of phases: the first coil current transfer layer may have two or more coil winding connectors that may be collectively electrically connected to the input terminals of the stator coil windings associated with that phase; the first coil current transfer layer may be electrically connected to the positive terminal for that phase of the power outlet; the second coil current transfer layer may have two or more coil winding connectors that may be collectively electrically connected to the output terminals of the stator coil windings associated with that phase; and the second coil current transfer layer may be electrically connected to the negative terminal for that phase of the power outlet.

[0005] According to some aspects, a motor vehicle is provided. The motor vehicle comprises at least one wheel; and a switched reluctance motor drive system. The switched reluctance motor drive system may be in accordance with an embodiment described herein. The rotor output shaft of the switched reluctance motor drive system may be drivingly coupled to the at least one wheel.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]The drawings included herewith are for illustrating various examples of articles, methods, and apparatuses of the present specification and are not intended to limit the scope of what is taught in any way. In the drawings:

[0007] FIG. 1 is a schematic illustration of a motor vehicle equipped with an example motor drive system, in accordance with an embodiment.

[0008] FIG. 2 is an exploded view of the motor drive system of FIG. 1 .

[0009] FIG. 3 is an exploded view of the mechanical construction of an example stator assembly of the switched reluctance motor of the motor drive system of FIG. 2.

[0010]FIG. 4 is an image showing attachment of example stator windings to stator poles of the switched reluctance motor of FIG. 3. [0011] FIG. 5 is an exploded view of the mechanical construction of an example rotor assembly of the switched reluctance motor of FIG. 3.

[0012] FIG. 6 is a schematic view of an example stator and rotor pole configuration of the switched reluctance motor of FIG. 3.

[0013] FIG. 7 is an exploded view of the mechanical construction of the inverter of the motor drive system of FIG. 2.

[0014] FIG. 8 is a top view of an example inverter housing of the inverter of FIG. 7.

[0015] FIG. 9 is a schematic view of the example phase plate of the motor drive system of FIG. 2.

[0016] FIG. 10 is an exploded view of an assembly of the motor drive system of FIG. 1.

[0017] FIG. 11 is a perspective view of an example integrated system housing of the motor drive system of FIG. 1 .

[0018] Fig. 12 is a perspective view of another example integrated system housing of the motor drive system of FIG. 1 .

[0019] FIG. 13 is a schematic view showing the multiple layers of an example power board of the inverter of FIG. 7.

DETAILED DESCRIPTION

[0020] Numerous embodiments are described in this application and are presented for illustrative purposes only. The described embodiments are not intended to be limiting in any sense. The invention is widely applicable to numerous embodiments, as is readily apparent from the disclosure herein. Those skilled in the art will recognize that the present invention may be practiced with modification and alteration without departing from the teachings disclosed herein. Although particular features of the present invention may be described with reference to one or more particular embodiments or figures, it should be understood that such features are not limited to usage in the one or more particular embodiments or figures with reference to which they are described. [0021 ]The terms “an embodiment,” “embodiment,” “embodiments,” “the embodiment,” “the embodiments,” “one or more embodiments,” “some embodiments,” and “one embodiment” mean “one or more (but not all) embodiments of the present invention(s),” unless expressly specified otherwise.

[0022]The terms “including,” “comprising” and variations thereof mean “including but not limited to,” unless expressly specified otherwise. A listing of items does not imply that any or all of the items are mutually exclusive, unless expressly specified otherwise. The terms “a,” “an” and “the” mean “one or more,” unless expressly specified otherwise.

[0023]As used herein and in the claims, two or more parts are said to be “coupled”, “connected”, “attached”, “joined”, “affixed”, or “fastened” where the parts are joined or operate together either directly or indirectly (i.e. , through one or more intermediate parts), so long as a link occurs. As used herein and in the claims, two or more parts are said to be “directly coupled”, “directly connected”, “directly attached”, “directly joined”, “directly affixed”, or “directly fastened” where the parts are connected in physical contact with each other. As used herein, two or more parts are said to be “rigidly coupled”, “rigidly connected”, “rigidly attached”, “rigidly joined”, “rigidly affixed”, or “rigidly fastened” where the parts are coupled so as to move as one while maintaining a constant orientation relative to each other. None of the terms “coupled”, “connected”, “attached”, “joined”, “affixed”, and “fastened” distinguish the manner in which two or more parts are joined together.

[0024] Further, although method steps may be described (in the disclosure and I or in the claims) in a sequential order, such methods may be configured to work in alternate orders. In other words, any sequence or order of steps that may be described does not necessarily indicate a requirement that the steps be performed in that order. The steps of methods described herein may be performed in any order that is practical. Further, some steps may be performed simultaneously.

[0025]As used herein and in the claims, a group of elements are said to ‘collectively’ perform an act where that act is performed by any one of the elements in the group, or performed cooperatively by two or more (or all) elements in the group. [0026] As used herein and in the claims, a first element is said to be “received” in a second element where at least a portion of the first element is received in the second element unless specifically stated otherwise.

[0027]Some elements herein may be identified by a part number, which is composed of a base number followed by an alphabetical or subscript-numerical suffix (e.g., 112a, or 112i). Multiple elements herein may be identified by part numbers that share a base number in common and that differ by their suffixes (e.g., 112i , 1122, and 112s). All elements with a common base number may be referred to collectively or generically using the base number without a suffix (e.g., 112).

[0028]There can be several challenges in using electric motor drive systems instead of internal combustion engines in motor vehicles. For example, in two-wheeled motor vehicles, the electric motor drive system may be located in a compact and harsh operating environment with a wide ambient temperature range and high vibrations. When electric motor drive systems include a permanent magnet (PM) machine (e.g., an electric motor having permanent magnets on the rotor), the harsh operating environment may cause irreversible demagnetization and/or damage of the permanent magnets. Electric motor drive systems including PM machines may have limited operating temperatures to prevent irreversible demagnetization of the permanent magnets. Additionally, spinning the rotor of PM machines, where the magnets are located, induces electromotive force (EMF) in the stator winding. This EMF may cause faults at a converter side of the PM machine unless the EMF is tightly controlled, especially at higher operating speeds of the PM machine. Furthermore, the winding used in PM machines is typically a distributed winding, and therefore faults occurring in one phase can affect other phases as well, thereby impacting the reliability and fault tolerance capability of the PM machine. Additionally, although the permanent magnets may represent a small fraction of the PM machine mass/volume, their cost may reach up to 40 % of the overall PM machine cost.

[0029] Described herein are motor drive systems that include a switched reluctance motor that can be used for driving a wheel of a motor vehicle. The switched reluctance motor may not include any permanent magnets on the rotor. This can increase the tolerance of the motor drive system to harsh operating environments. The ability to operate without permanent magnets on the rotor may also increase the fault tolerance capability and reliability of the motor drive system. The absence of permanent magnets may also enable a reduction in cost of the motor drive system (e.g. , a reduction in cost of around 40% for an example motor drive system for a two-wheeled motor vehicle) and an avoidance of any supply chain issues associated with the rare-earth materials generally used to manufacture the permanent magnets.

[0030] Referring now to FIG. 1 , shown therein is a schematic illustration of a motor vehicle 10 equipped with a motor drive system 100, in accordance with an embodiment. As shown, motor vehicle 10 may have multiple wheels 14 (two wheels 14a and 14b shown in FIG. 1 ), an energy source 18, a vehicle control unit (VCU) 22, an energy connection 26, a communication link 30, a gearbox assembly 34, and a gearbox coupling 38.

[0031] Motor vehicle 10 can include any vehicle having one or more wheels. For example, motor vehicle 10 may be a two-wheeled motor vehicle such as a motorcycle, a scooter, a moped, or a motorized bicycle. In other examples, motor vehicle 10 may be a four-wheeled motor vehicle such as a car or a truck. In some examples, motor vehicle 10 may be a micromobility device such as electric skateboards, electric pedal assisted bicycles, segways, motorcycles, scooters, or electric unicycles.

[0032] Energy source 18 can have any design suitable to store energy and provide the stored energy to motor drive system 100. For example, energy source 18 may include lead-acid batteries or lithium (e.g., lithium-ion or lithium-polymer) batteries. In some embodiments, energy source 18 may include a single battery or cell. In other embodiments, energy source 18 may include a battery pack having multiple batteries or cells. Energy source 18 may provide input energy to motor drive system 100 using energy connection 26. In some embodiments, energy source 18 may provide a DC voltage of 20V to 240V (e.g., 35V to 59V) and a maximum DC current of 100A to 500A (e.g., 150A to 250A, such as 200A) to motor drive system 100.

[0033] In some embodiments, energy source 18 may provide smaller DC voltages and currents (e.g., 20V to 35V and a maximum current of 100 to 150A) for smaller motor vehicles requiring less power and having smaller available volume for energy source 18. An energy source 18 with these characteristics may be lighter and smaller, and therefore better suited for smaller motor vehicles, which will tend to carry lighter loads across shorter distances and have lower power requirements. [0034] In some embodiments, energy source 18 may provide larger DC voltages and currents (e.g., 40V to 250V and a maximum current of 200A to 500A) for larger motor vehicles requiring greater power and having larger available volume for energy source 18. An energy source 18 with these characteristics may be larger and heavier, but better suited for larger motor vehicles, which tend to carry heavier loads for longer distances and therefore have greater power requirements.

[0035] Energy connection 26 may have any design suitable to transmit electrical energy from energy source 18 to motor drive system 100. For example, energy connection 26 may include one or more electrical cables, wires or circuit traces connected between energy source 18 and motor drive system 100.

[0036]VCU 22 can have any design suitable to control the operation of the motor vehicle 10. For example, VCU 22 may provide control inputs to motor drive system 100 to control the torque provided to drive wheels 14. In some embodiments, VCU 22 may generate the control inputs in response to input signals received at VCU 22. The input signals received at VCU 22 can be vehicle control signals provided by an operator of the motor vehicle 10, for example, an acceleration signal provided by the operator. In some embodiments, the input signals received at VCU 22 can be provided by one or more sensors of the motor vehicle, for example, a speed signal provided by a speed sensor 42 mounted on wheel 14a. VCU 22 may provide the control inputs to motor drive system 100 using communication link 30.

[0037]Communication link 30 may have any design suitable to transmit communication signals between VCU 22 and motor drive system 100. In some embodiments, communication link 30 may include a wired connection between the VCU 22 and motor drive system 100. A wired connection may provide enhanced signal reliability, particularly when there may be wireless signal interference. In other embodiments, communication link 30 may include a wireless network connection between the VCU 22 and motor drive system 100. A wireless network connection may provide flexibility in the placement of the VCU 22, and avoid the cost and complexity of wiring the VCU 22 to the motor drive system 100.

[0038]The gearbox assembly 34 and gearbox coupling 38 may have any design suitable to connect and convert the output mechanical energy from motor drive system 100 into torque at drive wheel(s) 14. In some embodiments, motor vehicle 10 may not include a gearbox assembly 34 and gearbox coupling 38, and the motor drive system 100 may be directly coupled to wheel(s) 14. FIG. 1 shows the output of the motor drive system 100 coupled to a single wheel 14a of motor vehicle 10. In some embodiments, the output of the motor drive system 100 may be coupled to multiple wheels 14 of motor vehicle 10.

[0039] In some embodiments (e.g., in some two-wheeled motor vehicles), motor vehicle 10 may impose tight space constraints on the motor drive system 100. For example, the axial length limit from a front-end cover 194 to a rear-end cover 196 of the motor drive system 100 may be 135mm or less and an outer diameter limit (excluding any cooling fins located on the exterior of the motor drive system 100) may be 170mm or less. Motor drive system 100 may be designed with an axial length 102 from a front-end cover 194 to a rear-end cover 196 of 100-135mm (such as 130- 135mm) and an outer diameter 104 (excluding any cooling fins located on the exterior of the motor drive system 100) of 130-170mm (such as 160-170mm). As one example, motor drive system 100 may have an axial length 102 from a front-end cover 194 to a rear-end cover 196 of 132mm and an outer diameter 104 of 170mm. In other embodiments, motor vehicle 10 may impose different space constraints on the motor drive system 100. For example, a motor drive system 100 with an axial length 102 larger than 135mm (e.g., 135-175mm) and an outer diameter 104 larger than 170mm (e.g., 170-175mm) may be used in larger motor vehicles 10 requiring larger output power and including larger available volume for the motor drive system 100. In some embodiments, the motor drive system 100 may have an axial length 102 from a frontend cover 194 to a rear-end cover 196 that is 70-100% of the maximum axial length limit, and an outer diameter 104 of 70-100% of the maximum outer diameter limit. As another example, a motor drive system 100 with an axial length 102 from a front-end cover 194 to a rear-end cover 196 smaller than 130mm (e.g., 100-130mm) and an outer diameter 104 smaller than 165mm (e.g., 120-165mm) may be used in smaller motor vehicles 10 requiring smaller output power but imposing even tighter space constraints for the motor drive system 100.

[0040] In some embodiments, motor drive system 100 may have a weight from 4-1 Okg. For example, motor drive system 100 may have a weight of 8.5kg. In some embodiments, motor drive system 100 may have a weight smaller than 7kg (e.g., 4- 7kg) to reduce the total weight of motor vehicle 10 and improve the driving range provided by the energy storage capacity of energy source 18. In other embodiments, motor drive system 100 may have a weight larger than 9kg (e.g., 9-1 Okg) to provide larger output power but at the cost of a shorter driving range due to the increased weight.

[0041] In some embodiments, motor drive system 100 may provide a maximum continuous output power of at least 1-8KW, a maximum peak output power of at least 2-1 OkW and a maximum overload output power of at least 3-12kW. In some embodiments (e.g., for larger motor vehicles 10 with larger weight, larger available volume for motor drive system 100 and requiring larger output power), motor drive system 100 may provide a maximum continuous output power of at least 6KW, maximum peak output power of at least 9kW and a maximum overload output power of at least 11.25kW. In other embodiments (e.g., for smaller motor vehicles 10 with smaller weight, smaller available volume for motor drive system 100 and requiring smaller output power), motor drive system 100 may provide a maximum continuous output power of at least 2KW, maximum peak output power of at least 3kW and maximum overload output power of at least 3.75kW.

[0042] In some embodiments, motor drive system 100 may operate at a maximum operating speed of at least 10,000-14, OOOrpm and provide a maximum rated torque of at least 10-18Nm and a maximum peak torque of at least 18-34Nm. For example, motor drive system 100 may operate at a maximum operating speed of at least 12, OOOrpm, and provide a maximum rated torque of at least 12-16Nm (e.g., 14Nm) and a maximum peak torque of at least 22-30Nm (e.g., 26Nm). In other embodiments, motor drive system 100 may operate at other speeds and provide different rated torques and different peak torques based on the requirements of motor vehicle 10 and design of components like the gearbox assembly 34. For example, in some embodiments (e.g., for larger motor vehicles 10 with larger weight and requiring a larger torque), motor drive system 100 may operate at higher speeds (e.g., a maximum operating speed of at least 14, OOOrpm) and provide a higher maximum rated torque of at least 16-18Nm (e.g., 17Nm) and a higher maximum peak torque of at least 30-34Nm (e.g., 32Nm). In some embodiments (e.g., for smaller motor vehicles with tighter space constraints and requiring smaller torque), motor drive system 100 may operate at lower speeds (e.g., a maximum operating speed of at least 10.OOOrpm) and provide a lower maximum rated torque of at least 10-14Nm (e.g., 12Nm) and a lower maximum peak torque of at least 18-24Nm (e.g. , 20Nm).

[0043] In some embodiments, the peak system efficiency of the motor drive system 100 may be at least 85-92%. For example, the peak system efficiency of the motor drive system may be at least 87-90% (e.g., 88%). In some embodiments, the design of the motor drive system 100 may be optimized for considerations like cost, weight and volume and the motor drive system 100 may have a lower peak system efficiency of at least 85-87%. In some embodiments, the design of the motor drive system 100 may be optimized for peak system efficiency to maximize the driving range for a given energy source 18 at higher cost and system complexity, and the motor drive system 100 may have a higher peak system efficiency of at least 90-92%.

[0044] Referring now to FIG. 2, shown therein is an exploded view of the motor drive system 100 of FIG. 1. As shown in FIG. 2, motor drive system 100 may include a switched reluctance motor 106, an inverter 108 and a phase plate 112. In some embodiments, the switched reluctance motor 106, inverter 108 and phase plate 112 may be integrated into a single enclosure to provide a compact design and reduce the volume and weight of the motor drive system 100. In other embodiments, the switched reluctance motor 106 and the inverter 108 may be provided in separate enclosures. This may enable a higher degree of customization by enabling a larger variety of combinations of different designs of the switched reluctance motor 106 and the inverter 108.

[0045]The switched reluctance motor 106 can have any design suitable to receive electrical energy from inverter 108 and provide output mechanical energy that can be coupled to wheel 14 of motor vehicle 10. Inverter 108 can have any design suitable to receive DC electrical energy from energy source 18 (e.g., via energy connection 26) and provide electrical energy to switched reluctance motor 106. Phase plate 112 can have any design suitable to provide electrical connections between the inverter 108 and switched reluctance motor 106 in a compact manner to enable efficient utilization of the available volume in motor vehicle 10. Below, some preferred embodiments of switched reluctance motor 106 (including particular designs for inverter 108 and phase plate 112) are described, which have a variety of advantages.

[0046] Reference is next made to FIGS. 2 to 6. FIG. 3 is an exploded view of the mechanical construction of a stator assembly 116 of the switched reluctance motor 106. FIG. 4 is an image showing attachment of an example stator coil winding to a stator pole of the switched reluctance motor 106. FIG. 5 is an exploded view of the mechanical construction of a rotor assembly 120 of the switched reluctance motor 106. FIG. 6 is a schematic view of an example stator and rotor pole configuration of the switched reluctance motor 106.

[0047] As shown in FIG. 3, the stator assembly 116 may include a motor housing 124, a front coil retaining ring 128, a stator core 132 (also referred to herein as stator 132), an alignment pin 136, a back coil retaining ring 140, slot insulation 144, stator coil windings 148, a phase connection carrying plate 152, and a back bearing carrying plate 156.

[0048]The motor housing 124 can have any design suitable to provide an enclosure for the other components of the stator assembly 116. An exterior surface of the motor housing 124 may optionally have multiple cooling fins to improve heat dissipation away from stator assembly 116. The cooling fins are described in greater detail herein with reference to FIGS. 11 and 12. In other embodiments, motor housing 124 does not having cooling fins.

[0049] In some embodiments, motor housing 124 may have a mounting diameter 160 of 170-220mm and a motor housing length 164 of 90-120mm. For example, motor housing 124 may have a mounting diameter 160 of 190-200mm (e.g., 195mm) and a motor housing length 164 of 100-105mm (e.g., 102mm). In some embodiments, motor housing 124 may have a larger mounting diameter 160 (e.g., 200-210mm) and/or larger motor housing length 164 of 105mm-110mm (e.g., for motor drive systems requiring larger power output at the cost of larger size and weight). In some embodiments, motor housing 124 may have a smaller mounting diameter 160 (e.g., 180-190mm) and/or smaller motor housing length 164 of 95mm-100mm (e.g., for motor drive systems requiring smaller size and weight at the cost of smaller power output). [0050] In some embodiments, the stator core 132 may be made of lamination sheets instead of a single solid piece of material. This may help to reduce eddy current losses. For example, stator core 132 may be made of laminated steel. In some embodiments, the lamination sheets may be stacked together by bonding, welding, interlocking, or a combination of these processes. In other embodiments, the stator core 132 may be made of a single solid piece of steel material or soft magnetic composites instead of lamination sheets. This may reduce the manufacturing cost, but may result in reduced efficiency due to eddy current losses or reduced output torque due to lower magnetic flux density.

[0051] Stator core 132 may have multiple stator poles 168 (e.g., stator core 132 shown in FIG. 6 has 18 stator poles 132, two of which are labelled 168a and 168b in FIG. 6). The number of stator poles 132 may be selected in combination with the number of rotor poles to ensure proper operation of the switched reluctance motor 106. In some embodiments, stator core 132 may have at least 6 stator poles, such as 6-48 stator poles. For example, switched reluctance motor 106 may include an 18/12 pole configuration with 18 stator poles and 12 rotor poles. In other examples, other pole configurations (e.g., 6/4, 12/8, 24/16) may be used depending on various factors including torque density and torque ripple, end winding length, and heat dissipation from the winding towards the motor housing. For example, a higher number of stator poles can provide lower torque ripple and can reduce the end winding length.

[0052] In some embodiments, stator core 132 may have a stator core inner diameter 184 of 90-120mm, a stator core outer diameter 188 of 135-180mm and a stator core length 192 of 40-60mm. For example, stator core 132 may have a stator core inner diameter 184 of 104-108mm (e.g., 106mm), a stator core outer diameter 188 of 155- 165mm (e.g., 160mm) and a stator core length 192 of 50-52mm (e.g., 51 mm). In some embodiments, stator assembly 116 may include a larger stator core 132 to provide larger output power at a cost of larger size and weight (e.g., stator core inner diameter 184 of 112-116mm, stator core outer diameter 188 of 165-175mm and stator core length 192 of 52-55mm). In some embodiments, stator assembly 116 may include a smaller stator core 132 to provide a smaller size and weight at a cost of smaller output power (e.g., stator core inner diameter 184 of 100-104mm, stator core outer diameter 188 of 145-155mm and stator core length 192 of 48-50mm). [0053] Alignment pin 136 can have any design suitable to prevent rotation of the stator core 132 with respect to the motor housing 124. In the illustrated example, alignment pin 136 is formed as a thin rod attached to the motor housing 124 and which extends along the entire length of the stator core 132. Stator assembly 116 may have any number of alignment pins 136. For example, stator assembly 116 may have 1 to 4 alignment pins 136. In the illustrated example, stator assembly 116 has one alignment pin 136.

[0054] Stator coil windings 148 may include concentrated windings with a stator coil winding around each stator pole/tooth of stator core 132. For an example, an 18/12 pole configuration with 18 stator poles, stator coil windings 148 may include a total of 18 stator coil windings, with one stator coil winding around each of the 18 stator poles. The stator coil windings may be organized into groups, where all the stator coil windings of one group are connected to the same phase of the input provided from the inverter. In some embodiments, there may be an equal number of stator coil windings in each group. For example, if a 3-phase input is provided from inverter 108 to the stator coil windings 148, the total of 18 stator coil windings may be organized into three groups with six stator coil windings in each group of the stator coil windings. The six stator coil windings in each group may be connected in series, in parallel, or in series/parallel combination.

[0055]The concentrated winding configuration may significantly reduce the electromagnetic interaction between the multiple phases and may also enhance the fault tolerance capability and reliability of the switched reluctance motor 106. The use of the concentrated winding configuration may also reduce the required length of the winding and can reduce the weight and volume of stator coil windings 148 compared with PM machines.

[0056] Each stator coil winding of stator coil windings 148 may include multiple turns and/or multiple strands. In some embodiments, the number of turns for each stator coil winding may be 3-40 and the number of strands may be 1-10. For example, the number of turns for each stator coil winding may be 6-26 and the number of strands may be 1-6. The number of turns may be selected based on required torque-speed characteristics at continuous, peak, and overload operating conditions while meeting the required efficiency targets. The number of strands may be selected based on current density limits and to reduce the proximity losses while keeping the fill factor at a manufacturable level.

[0057] In some embodiments, each of the stator coil windings may be attached to its associated stator pole by a thermally conductive adhesive paste 172 to enhance the thermal performance of the switched reluctance motor 106 by reducing the thermal resistance between the stator coil winding and the stator housing. Further, any gaps between the attached stator coil windings and the associated stator pole may be filled with a vacuum resin infusion 176 to further reduce the thermal resistance. In other embodiments, the thermally conductive adhesive paste and/or the vacuum resin infusion may not be used.

[0058]The front coil retaining ring 128 and the back coil retaining ring 140 can have any design suitable to mechanically retain the stator coil windings 148 in position relative to stator core 132. In some embodiments, slot insulation 144 may provide additional electrical insulation between the stator coil windings 148 and the stator core 132. For example, slot insulation 144 may be provided as an insulating slot liner or an insulating powder coating. In other embodiments, the stator assembly 116 may not include slot insulation 144.

[0059]The phase connection carrying plate 152 can have any design suitable to mechanically support and carry the phase plate 112. The phase plate 112 is described in further detail herein with reference to FIG. 9. The back bearing carrying plate 156 can have any design suitable to support a back bearing of the rotor. In the illustrated example, the back bearing carrying plate 156 is formed as a thin plate with a through hole located in the center of the plate to support the back bearing of the rotor.

[0060] As shown in FIG. 5, the rotor assembly 120 may include a finger disc spring 204, an O-ring 208, a front bearing 212, a rotor output shaft 216, a front rotor retaining ring 220, a rotor core 224 (also referred to herein as rotor 224), a back rotor retaining ring 228, a retaining nut 232, and a back bearing 236. The rotor assembly 120 may be rotatably mounted with respect to the stator assembly 116.

[0061] In some embodiments, the rotor core 224 may be made of lamination sheets instead of a single solid piece of material to reduce eddy current losses. For example, rotor core 224 may be made of laminated steel. In some embodiments, the lamination sheets may be stacked together by bonding, welding, interlocking, or using a mechanical retention mechanism. In other embodiments, the rotor core 224 may not be made of lamination sheets.

[0062] The rotor core 224 may not have any coils, permanent magnets, commutators, or brushes. Rotor core 224 may have multiple rotor poles 240 (e.g., rotor core 224 shown in FIG. 6 has 12 rotor poles 240, two of which are labelled 240a and 240b in FIG. 6). In some embodiments, rotor core 224 may have at least 4 rotor poles, such as 4-32 rotor poles. The number of rotor poles 240 may be selected in combination with the number of stator poles 168, as described herein above, to ensure proper operation of the switched reluctance motor 106.

[0063] In some embodiments, rotor core 224 may have a rotor core outer diameter 244 of 90-120mm and a rotor core length 248 of 40-60mm. For example, rotor core 224 may have a rotor core outer diameter 244 of 103-107mm (e.g., 105.2mm) and a rotor core length 248 of 50-54mm (e.g., 52.4mm). In some embodiments, rotor assembly 120 may include a larger rotor core 224 to provide larger output power at a cost of larger size and weight (e.g., rotor core outer diameter 244 of 107-112mm and rotor core length of 54-58mm). In some embodiments, rotor assembly 120 may include a smaller rotor core 224 to provide a smaller size and weight at a cost of smaller output power (e.g., rotor core outer diameter 244 of 100-103mm and rotor core length of 47- 50mm).

[0064]The front bearing 212 and back bearing 236 can have any suitable design based on the maximum operating speed, radial loading and axial loading of the motor drive system 100. In the illustrated example, the front bearing 212 and back bearing 236 are radial ball bearings.

[0065]The rotor output shaft 216 may be drivingly coupled to one or more wheels 14 of motor vehicle 10 (e.g., via gearbox assembly 34). The rotor output shaft can have any design suitable to transfer the output mechanical energy of the motor drive system 100 that provides the driving torque to a wheel 14 of motor vehicle 10. In the illustrated example, the rotor output shaft 216 is formed as a shaft that is rotatably coupled to the rotor core 224. [0066] In some embodiments, rotor output shaft 216 may have a rotor shaft length 252 of 110-160mm. For example, rotor output shaft 216 may have a rotor shaft length 252 of 110-135mm (e.g., 133.08mm). In some embodiments, rotor assembly 120 may have other rotor shaft lengths (e.g., 120-130mm, 135-140mm) depending on the size, volume, weight, and power constraints for the motor drive system 100.

[0067] Referring next to FIG. 7, shown therein is an exploded view of the mechanical construction of the inverter 108 of FIG. 2. As shown in FIG. 7, the inverter 108 may include a power outlet 260, a power-stage printed circuit board (PCB) 268 (also referred to herein as power board 268), power switching devices 272, DC capacitors 276, gate-driver board 280, control board 284, and inverter housing 288.

[0068] Power outlet 260 can have any design suitable to provide multi-phase output power to the switched reluctance motor 106. For example, the power outlet 260 may have a positive conductor (e.g., wire) and a negative conductor (e.g., wire) for each phase. In some embodiments, power outlet 260 may have a pair of mating sockets 264a and 264b to provide the positive and negative connections for each phase of the output power. For example, three pairs of mating sockets for a three-phase output are shown in FIG. 7. In other examples, different number of mating sockets may be present, e.g., four pairs of mating sockets for a four-phase output. In other embodiments, power outlet 260 may not have mating sockets to provide the output conductor connections. For example, power outlet 260 may include connections pins that provide the positive and negative connections for each phase of the output power.

[0069] Each of the stator coil windings may be associated with one of the phases of the power outlet 260. For example, each of the stator coil windings belonging to the same group of stator coil windings (as described herein above) may be associated with the same phase of the power outlet 260. Each of the plurality of phases of the power outlet 260 may be associated with at least two of the stator coil windings.

[0070] Reference is now made to FIG. 7 and FIG. 13. FIG. 13 is a schematic view showing the multiple layers of power board 268. In some embodiments, power board 268 may have multiple current conducting layers 352 that are each electrically connected to the power outlet 260. Each of the multiple current conducting layers 352 may conduct a portion of the total current (e.g., an equal portion of the total current). Power board 268 may include 2 to 20 current conducting layers 352. In some embodiments, each of the current conducting layers 352 may conduct an equal portion of the total current. The amount of current each layer carries depends on the total current and the number of layers, so it may be different from one application to another. For example, power board 268 may include seven current conducting layers 352, each conducting 1/7 of the total current. In other examples, power board 268 may have a lower number of current conducting layers 352 (e.g., 2-6). A lower number of current conducting layers 352 may provide a reduction in design and manufacturing complexity of the power board 268 at the cost of higher current density in each layer potentially reducing reliability and lifetime of the power board 268. In other examples, power board 268 may have a higher number of current conducting layers 352 (e.g., 8- 12). A higher number of current conducting layers 352 may provide a reduction in current density in each layer, but at the cost of a higher design and manufacturing complexity of the power board 268. In other embodiments, power board 268 may not have multiple current conducting layers.

[0071] In embodiments where the power board 268 has multiple current conducting layers 352, at least one of the multiple current conducting layers (e.g., current conducting layer 352a) may have a current sensor 304. Current sensor 304 can have any design suitable to sense the electrical current through that current conducting layer. For example, current sensor 304 can be a semiconductor-based integrated circuit. For a power board 268 with multiple current conducting layers 352, current sensor 304 may only sense the portion of the current flowing through one layer (e.g., 1/7 of the total current for a power board 268 with seven current conducting layers). Therefore, current sensor 304 can be smaller size compared with a current sensor 304 needed to sense the total combined current flowing through the multiple current conducting layers 352. In some embodiments, current sensor 304 may have a measuring range from 20-200A. For example, current sensor 304 may have a measuring range from 50-120A. In other examples, current sensor 304 may have different measuring ranges (e.g., 20-80A, 40-100A, 80-200A) based on the number of current conducting layers 352 and the current that has to be measured.

[0072] In some embodiments, the power board 268 may also have a non-conductive shielding layer 356 in addition to multiple current conducting layers 352. The non- conductive shielding layer 356 may be disposed between the current conducting layer 352a having the current sensor 304 and the other current conducting layers (352b and 352c in the illustrated example) to provide electromagnetic interference shielding to current sensor 304. In some embodiments, the non-conductive shielding layer 356 has electrical conductivity less than 10% of the electrical conductivity of the current conducting layers 352. In other embodiments, the power board 268 may not have a non-conductive shielding layer.

[0073]The power board 268 may have multiple power switching devices 272 surfacemounted on the power board 268 in a first arrangement and multiple DC capacitors 276 mounted on the power board 268 in a second arrangement around the first arrangement. Power switching devices 272 may have any design suitable to provide switching operation. For example, power switching devices may include power MOSFETs with/without diode utilization. Power MOSFETs may provide an advantage over diodes by reducing power losses and enhancing efficiency. The circuit routing on power board 268 may be optimized to balance circuit trace impedance and minimize switching transient differences. Each power switching device in the circuit topology may be replaced by parallel switching devices to reduce switching power losses and thermal stresses associated with the high currents of the power board 268.

[0074] Gate driver board 280 can have any design suitable to provide the gate driving signals to control the multiple power switching devices 272. The gate drive circuits of gate driver board 280 may be optimized to drive the parallel switching devices 272 simultaneously. For example, the gate drive circuits of gate driver board 280 may include gate drive ICs capable of providing sufficient drive current to drive the parallel switching devices 272 simultaneously.

[0075] Control board 284 can have any design suitable to control operations of the inverter 108. Control board 284 may receive control signals from VCU 22. In response control board 284 may control the operation of switched reluctance motor 106. Control board 284 may also monitor the operation status of switched reluctance motor 106. For example, control board 284 may receive position information of the rotor assembly 120 from a position sensor. The position sensor may be a hall-effect compact absolute encoder that may have a shorter axial length and provides a more compact design compared with other types of position sensors. Control board 284 may also detect any system faults during operation. For example, control board 284 may provide overtemperature, over-current and over-voltage protection of motor drive system 100.

[0076] Inverter housing 288 can include any design suitable to provide an enclosure for the other components of inverter 108. For example, inverter housing 288 may include a polymer or metal shell sized to surround the other components of inverter 108. Inverter housing 288 may also include a heatsink, for example, a ring-shaped heatsink as shown in FIG. 7. In some embodiments, inverter housing 288 may have an inverter housing axial length 292 of 10-60mm. For example, inverter housing 288 may have an inverter housing axial length 292 of 20-40mm (e.g., 35mm). In some embodiments, inverter housing 288 may have a different housing axial length 292 (e.g., 15-30mm, 35-55mm) based on the size of the other components and/or heat dissipation requirements of inverter 108. In some embodiments, inverter housing 288 may have an inverter housing diameter 296 (excluding the inverter housing mounts) of 120-220mm. For example, inverter housing 288 may have an inverter housing diameter 296 (excluding the inverter housing mounts) of 160-180mm (e.g., 170mm). In some embodiments, inverter housing 288 may have a different inverter housing diameter 296 (e.g., 130-160mm, 170-200mm) based on the size of the other components and/or heat dissipation requirements of inverter 108.

[0077] Reference is next made to FIGS. 7 and 8. FIG. 8 is a top view of an example inverter housing 288. Inverter housing 288 may have multiple potted slots 308 corresponding to the arrangement of the DC capacitors 276 of inverter 108. The potting may improve the reliability of inverter 108 by protecting the DC capacitors 276 from shock, vibration, water, and/or corrosive agents. The potting may also improve the heat dissipation from the capacitors.

[0078] Referring next to FIG. 9, shown therein is a schematic view of phase plate 112. Phase plate 112 can have any design suitable to provide electrical connections between the inverter 108 and switched reluctance motor 106 in a compact manner to enable efficient utilization of the available volume in motor vehicle 10. Phase plate 112 may have a pair of coil current transfer layers 312 (one pair of coil current transfer layers 312a and 312b are labelled in FIG. 9) for each of the multiple phases. For example, for a three-phase electrical current, phase plate 112 may have three pairs of coil current transfer layers 312. [0079] Coil current transfer layer 312 may include copper busbars or PCBs. Each of the coil current transfer layers 312 may have two or more coil winding connectors 316 that can be electrically connected to terminals of the stator coil windings. For example, coil winding connectors 316 of coil current transfer layer 312a of a given phase can be electrically connected to the input terminals of the stator coil windings associated with the given phase. The coil winding connectors 316 of coil current transfer layer 312b of the given phase can be electrically connected to the output terminals of the stator coil windings associated with the given phase. For a 3-phase electrical current and 18/12 pole configuration example described herein above, each of the coil current transfer layers 312 of a given phase can have six coil winding connectors 316 that can be electrically connected to the terminals of the six stator coil windings of the given phase. In other examples, coil current transfer layer 312 may have higher (e.g., 7-20) or lower (e.g., 2-5) number of coil winding connectors 316.

[0080] Each coil current transfer layer 312 may be coupled to a connector 318. The connector 318 can have any design suitable to provide an electrical connection between the coil current transfer layer 312 and a conductor of the power outlet of the inverter. In some embodiments, connector 318 may include a copper pin 322 that can be coupled to the coil current transfer layer 312 and connect with a mating socket of the power outlet of the inverter. The copper pins may not be all of the same length. The length of each copper pin 322 may correspond to the distance between the power outlet of the inverter and the specific coil current transfer layer 312 that the copper pin 322 is coupled to. For example, the copper pin 322 connecting the coil current transfer layer 312 farthest from the power outlet of the inverter may be longer than all the other copper pins 322. In other embodiments, connector 318 may not include a copper pin. For example, connector 318 may be made using other materials and/or other shapes.

[0081] Coil current transfer layer 312a may provide an electrical connection between the positive terminal for a given phase of the power outlet and the input terminals of the stator coil windings associated with the given phase. Coil current transfer layer 312b may provide an electrical connection between the negative terminal for the given phase of the power outlet and the output terminals of the stator coil windings associated with the given phase. [0082]The thickness of the coil current transfer layer 312 may have to be less than the skin depth to avoid eddy current losses due to skin effect. In some embodiments, the thickness of each coil current transfer layer 312 may be 0.4-1 mm. For example, the thickness of each coil current transfer layer 312 may be 0.6-0.8mm (e.g., 0.6mm). In some embodiments, the thickness of each coil current transfer layer 312 may be larger (e.g., 0.7-0.9mm) to reduce current density at the cost of larger size. In some embodiments, the thickness of each coil current transfer layer 312 may be smaller (e.g., 0.5-0.6mm) to reduce size at the cost of higher current density.

[0083] Referring next to FIG. 10, shown therein is an exploded view of an assembly of the motor drive system 100. A ring assembly 320 may be disposed between the power board 268 and the back bearing carrying plate 156. The motor drive system 100 may use fasteners 332 to fasten the assembly together by fastening the inverter housing 288 (including the inverter heatsink) against the motor housing 124. A good contact between the fastened surfaces (power board 268 of inverter housing 288 and the back bearing carrying plate 156 of the motor housing 124) can apply a compressive pressure on the contact surface between the power switching devices 272 and the heatsink of the inverter to provide a good thermal contact. This may avoid the need for mounting screws typically used to mount the power switching devices onto the power board and then mount the power board to the housing. The through holes required for the mounting screws reduce the available electrical conduction area on the power board. The use of the fasteners and the associated compressive pressure can provide a good thermal contact without sacrificing electrical conduction area on the power board. This can enable higher currents and/or lower current density for the power board. The stacking distance between the power board 268 and the back bearing carrying plate 156 may need to be carefully controlled to enable the good thermal contact using compressive pressure. However, there may be wide tolerances associated with the manufacturing of the power boards. A spring ring 324 of ring assembly 320 can accommodate the manufacturing tolerance of the power boards and provide the required compressive pressure for the good thermal contact. In some embodiments, a flat ring 328 may be included between spring ring 324 and power board 268 to increase the uniformity of the compressive pressure. The flat ring 328 may be made of insulating materials, e.g., FR4, to prevent short circuit across the power board. In other embodiments, the spring ring 324 and/or the flat ring 328 may not be included.

[0084] Referring next to FIGS. 11 and 12, shown therein are perspective views of example integrated system housing 340 for motor drive system 100. The integrated system housing 340 can have any design suitable to provide an enclosure for the components of the motor drive system 100 including the switched reluctance motor 106, the inverter 108 and the phase plate 112. The integrated system housing 340 may be completely sealed to provide ingress protection. The exterior surface of the integrated system housing 340 may include multiple cooling fins 344. Multiple cooling fins 344 can have any design suitable to dissipate heat away from the integrated system housing 340. The multiple cooling fins 344 may be designed to align with the direction of air flow when the motor vehicle is moving in a forward direction. Multiple cooling fins 344 may include any suitable number of fins based on the size and heat dissipation requirements. In some embodiments, the integrated system housing 340 may include 4-20 fins. In the illustrated example, the integrated system housing 340 includes 7 fins. In some embodiments, integrated system housing 340 may include a larger number of fins (e.g., 12-18) to provide larger heat dissipation at the cost of larger size and weight. In some embodiments, integrated system housing 340 may include a smaller number of fins (e.g., 4-6) to reduce size and weight at the cost of smaller heat dissipation capacity. The fins may be arranged in uniform or variable fin density. Multiple cooling fins 344 may include wave-shaped fins (e.g., cooling fins 344b shown in FIG. 12) designed to increase turbulence of the cooling air flow, thereby enhancing the convective heat transfer coefficients. In other embodiments, multiple cooling fins 344 may not include wave-shaped fins.

[0085] In some embodiments, the motor drive system 100 may not have an integrated system housing 340. The switched reluctance motor and the inverter may be housed in separate housings (e.g., motor housing 124 and inverter housing 288). In such embodiments, the exterior surfaces of the motor housing 124 and/or inverter housing 288 may have multiple cooling fins 344.

[0086]While the above description provides examples of the embodiments, it will be appreciated that some features and/or functions of the described embodiments are susceptible to modification without departing from the spirit and principles of operation of the described embodiments. Accordingly, what has been described above has been intended to be illustrative of the invention and non-limiting and it will be understood by persons skilled in the art that other variants and modifications may be made without departing from the scope of the invention as defined in the claims appended hereto. The scope of the claims should not be limited by the preferred embodiments and examples, but should be given the broadest interpretation consistent with the description as a whole.

ITEMS

[0087] Item 1 : A motor drive system for driving at least one wheel of a motor vehicle, the system comprising: a switched reluctance motor having: a stator having (i) multiple stator poles and (ii) a stator coil winding around each of the stator poles, each stator coil winding having an input terminal and an output terminal; and a rotor rotatably mounted with respect to the stator and having a rotor output shaft and multiple rotor poles; an inverter having a power outlet with a plurality of phases, the power outlet having a positive terminal and a negative terminal for each phase, each of the stator coil windings of the stator is associated with one of the phases of the power outlet, and each of the plurality of phases is associated with at least two of the stator coil windings of the stator; and a phase plate having at least first and second coil current transfer layers for each of the plurality of phases, wherein for each of the plurality of phases: the first coil current transfer layer has two or more coil winding connectors, the coil winding connectors being collectively electrically connected to the input terminals of the stator coil windings associated with that phase, the first coil current transfer layer being electrically connected to the positive terminal forthat phase of the power outlet, the second coil current transfer layer has two or more coil winding connectors, the coil winding connectors being collectively electrically connected to the output terminals of the stator coil windings associated with that phase, and the second coil current transfer layer being electrically connected to the negative terminal for that phase of the power outlet.

[0088] Item 2: The motor drive system of any preceding item, wherein: the inverter has a power-stage printed circuit board (PCB) having multiple current conducting layers, each of the current conducting layers being electrically connected to the power outlet of the inverter; and wherein at least one current conducting layer of the multiple current conducting layers has a current sensor.

[0089] Item 3: The motor drive system of any preceding item, wherein: the power-stage PCB has a non-conductive shielding layer disposed between the at least one current conducting layer having the current sensor and other current conducting layers.

[0090] Item 4: The motor drive system of any preceding item, wherein: the switched reluctance motor is enclosed in a motor housing, the inverter is enclosed in an inverter housing, and an exterior surface of at least one of the motor housing and the inverter housing has multiple cooling fins.

[0091] Item 5: The motor drive system of any preceding item, wherein: one or more of the multiple cooling fins are wave-shaped fins.

[0092] Item 6: The motor drive system of any preceding item, wherein: each of the stator coil windings are attached to associated stator pole by a thermally conductive adhesive paste.

[0093] Item 7: The motor drive system of any preceding item, wherein: a volume between each of the stator coil windings and the associated stator pole is filled with a vacuum resin infusion.

[0094] Item 8: The motor drive system of any preceding item, wherein: the power-stage PCB further has multiple power switching devices surface-mounted on the powerstage PCB in a first arrangement; and multiple DC capacitors mounted on the powerstage PCB in a second arrangement around the first arrangement.

[0095] Item 9: The motor drive system of any preceding item, wherein the inverter further has a ring-shaped heatsink having multiple potted slots corresponding to the second arrangement.

[0096] Item 10: The motor drive system of any preceding item, wherein: the rotor further has a first bearing mounted at a first end of the rotor output shaft and the switched reluctance motor further has a bearing carrying plate attached to the first bearing; a ring assembly disposed between the power-stage PCB and the bearing carrying plate, wherein a first surface of the ring assembly is in contact with the bearing carrying plate and a second surface of the ring assembly is in contact with the powerstage PCB; and multiple fasteners coupling the bearing carrying plate with the ringshaped heatsink, wherein the coupling applies compressive pressure between the multiple power switching devices of the power-stage PCB and the ring-shaped heatsink.

[0097]ltem 11 : The motor drive system of any preceding item, wherein: the ring assembly has at least one of (i) a spring ring having the first surface and a flat ring having the second surface or (ii) a rubber ring having the first surface and the second surface.

[0098]ltem 12: The motor drive system of any preceding item, wherein: the stator has 18 poles and the rotor has 12 poles.

[0099] Item 13: The motor drive system of any preceding item, wherein: the motor vehicle is a two-wheeled motor vehicle.

[0100] Item 14: The motor drive system of any preceding item, wherein: the motor vehicle is a micro-mobility device.

[0101] Item 15: A motor vehicle comprising: at least one wheel; and the motor drive system of any preceding item, wherein the rotor output shaft is drivingly coupled to the at least one wheel.

Claims

WE CLAIM:

1. A motor drive system for driving at least one wheel of a motor vehicle, the system comprising: a switched reluctance motor having: a stator having (i) multiple stator poles and (ii) a stator coil winding around each of the stator poles, each stator coil winding having an input terminal and an output terminal; and a rotor rotatably mounted with respect to the stator and having a rotor output shaft and multiple rotor poles; an inverter having a power outlet with a plurality of phases, the power outlet having a positive terminal and a negative terminal for each phase, each of the stator coil windings of the stator is associated with one of the phases of the power outlet, and each of the plurality of phases is associated with at least two of the stator coil windings of the stator; and a phase plate having at least first and second coil current transfer layers for each of the plurality of phases, wherein for each of the plurality of phases: the first coil current transfer layer has two or more coil winding connectors, the coil winding connectors being collectively electrically connected to the input terminals of the stator coil windings associated with that phase, the first coil current transfer layer being electrically connected to the positive terminal for that phase of the power outlet, the second coil current transfer layer has two or more coil winding connectors, the coil winding connectors being collectively electrically connected to the output terminals of the stator coil windings associated with that phase, and the second coil current transfer layer being electrically connected to the negative terminal for that phase of the power outlet.

2. The motor drive system of claim 1 , wherein the inverter has a power-stage printed circuit board (PCB) having multiple current conducting layers, each of the current conducting layers being electrically connected to the power outlet of the inverter; and wherein at least one current conducting layer of the multiple current conducting layers has a current sensor.

3. The motor drive system of claim 2, wherein the power-stage PCB has a non- conductive shielding layer disposed between the at least one current conducting layer having the current sensor and other current conducting layers.

4. The motor drive system of claim 1 , wherein the switched reluctance motor is enclosed in a motor housing, the inverter is enclosed in an inverter housing, and an exterior surface of at least one of the motor housing and the inverter housing has multiple cooling fins.

5. The motor drive system of claim 4, wherein one or more of the multiple cooling fins are wave-shaped fins.

6. The motor drive system of claim 1 , wherein each of the stator coil windings are attached to associated stator pole by a thermally conductive adhesive paste.

7. The motor drive system of claim 6, wherein a volume between each of the stator coil windings and the associated stator pole is filled with a vacuum resin infusion.

8. The motor drive system of claim 2, wherein the power-stage PCB further has: multiple power switching devices surface-mounted on the power-stage PCB in a first arrangement; and multiple DC capacitors mounted on the power-stage PCB in a second arrangement around the first arrangement.

9. The motor drive system of claim 8, wherein the inverter further has a ringshaped heatsink having multiple potted slots corresponding to the second arrangement.

10. The motor drive system of claim 8, wherein the rotor further has a first bearing mounted at a first end of the rotor output shaft and the switched reluctance motor further has: a bearing carrying plate attached to the first bearing; a ring assembly disposed between the power-stage PCB and the bearing carrying plate, wherein a first surface of the ring assembly is in contact with the bearing carrying plate and a second surface of the ring assembly is in contact with the power-stage PCB; and multiple fasteners coupling the bearing carrying plate with the ring-shaped heatsink, wherein the coupling applies compressive pressure between the multiple power switching devices of the power-stage PCB and the ring-shaped heatsink.

11 . The motor drive system of claim 10, wherein the ring assembly has: at least one of (i) a spring ring having the first surface and a flat ring having the second surface or (ii) a rubber ring having the first surface and the second surface.

12. The motor drive system of claim 1 , wherein the stator has 18 poles and the rotor has 12 poles.

13. The motor drive system of claim 1 , wherein the motor vehicle is a two-wheeled motor vehicle.

14. The motor drive system of claim 1 , wherein the motor vehicle is a micro-mobility device.

15. A motor vehicle comprising: at least one wheel; and the motor drive system of claim 1 , wherein the rotor output shaft is drivingly coupled to the at least one wheel.