Cooling configurations for electric motors

Abstract

An example electric motor includes: a housing; a stator disposed within the housing; and a plurality of cooling channels formed in either the housing or the stator, or in both the stator and the housing.

Description

Cooling Configurations for Electric MotorsCROSS REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to U.S. Provisional Application No. 63 / 701,060 filed on September 30, 2024, the entire contents of which are herein incorporated by reference as if fully set forth in this description.BACKGROUND

[0002] Electric motors, particularly multi-phase alternating current (AC) motors, generate significant heat during operation. Typically, output power of such motors is limited by ability to conduct heat to the external environment of the motor. Thus, it may be desirable to configure the motors with effective cooling strategies to maintain performance and prevent damage.

[0003] Some cooling methods rely on having cooling channels in a housing or cooling jacket of the electric motor. Fluid flows through such channels, absorbing heat generated by the electric motor. Typically, cooling fluid does not contact the components of the motor. Rather, there is a barrier between the motor components and the fluid flowing through a housing or cooling jacket. Thus, such methods might not adequately address the cooling needs of high power density motors.

[0004] Thus, there is a need for an enhanced cooling system for critical components of the motor. It is with respect to these and other considerations that the disclosure made herein is presented.SUMMARY

[0005] The present disclosure describes implementations that relate to cooling configurations for electric motors.

[0006] In a first example implementation, the present disclosure describes an electric motor. The electric motor includes: a housing; a stator disposed within the housing; and a plurality of internal grooves formed in the housing, wherein at least a portion of each internal groove is cut into an inner surface of the housing such that coolant flowing through the portion of an internal groove of the plurality of internal grooves is in direct contact with an exterior surface of the stator without barriers therebetween.

[0007] In a second example implementation, the present disclosure describes an electric motor including: a housing; a stator disposed within the housing; a plurality of housing cooling channels embedded in in the housing; and a plurality of stator cooling channels embedded in the stator, wherein (i) coolant flows through the plurality of housing cooling channels in a first direction, then communicated to the plurality of stator cooling channels, flowing in a second direction, or (ii) coolant flows through the plurality of stator cooling channels in the first direction, then communicated to the plurality of housing cooling channels, flowing in the second direction.

[0008] In a third example implementation, the present disclosure describes an electric motor having: a housing; a stator disposed within the housing, wherein the stator comprises a plurality of stator teeth projecting radially inward from a yoke of the stator; and a plurality of stator cooling channels embedded in one or both of: (i) the yoke, or (ii) at least some of the plurality of stator teeth, such that coolant flowing through the plurality of stator cooling channels is in direct contact with an interior surface of the stator.

[0009] In a fourth example implementation, the present disclosure describes a vehicle. The vehicle includes: a propeller; and the electric motor of any of first, second, or third example implementations having a rotor and a motor shaft coupled to the rotor, wherein the motor shaft is coupled to and configured to drive the propeller.

[0010] In a fifth example implementation, the present disclosure describes a method of operating the electric motor of any of first, second, or third example implementations or the vehicle of the fourth example implementation.

[0011] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, implementations, and features described above, further aspects, implementations, and features will become apparent by reference to the figures and the following detailed description.BRIEF DESCRIPTION OF THE FIGURES

[0012] Figure 1 is a block diagram of a vehicle, according to exemplary embodiments of the present invention.

[0013] Figure 2 illustrates a cooling system for an electric motor, according to exemplary embodiments of the present invention.

[0014] Figure 3 A illustrates a partial perspective view of an electric motor, according to exemplary embodiments of the present invention.

[0015] Figure 3B illustrates a cross-sectional side view of the electric motor of Figure 3A, according to exemplary embodiments of the present invention.

[0016] Figure 4 illustrates a partial perspective view of an electric motor, according to exemplary embodiments of the present invention.

[0017] Figure 5 illustrates a partial perspective view of an electric motor having a mixed cooling configuration, according to exemplary embodiments of the present invention.

[0018] Figure 6 illustrates a partial front view of an electric motor, according to exemplary embodiments of the present invention.

[0019] Figure 7 illustrates a partial front view of an electric motor, according to exemplary embodiments of the present invention.

[0020] Figure 8 illustrates a partial front view of an electric motor, according to exemplary embodiments of the present invention.

[0021] Figure 9 illustrates a partial front view of an electric motor, according to exemplary embodiments of the present invention.

[0022] Figure 10 illustrates a partial front view of an electric motor, according to exemplary embodiments of the present invention.

[0023] Figure 11 illustrates a partial front view of an electric motor, according to exemplary embodiments of the present invention.DETAILED DESCRIPTION

[0024] Disclosed herein are systems, vehicles, and assemblies relating to thermal management system for electric motors. Tn one embodiment, a dual-strategy cooling system for an electric motor that employs both direct and indirect cooling configurations for enhanced thermal performance and motor efficiency is disclosed. In this embodiment, cooling channels in both a housing or cooling jacket of the motor and in the stator of the electric motors are used.

[0025] In another embodiment, direct cooling configurations are disclosed involving various cooling channel configurations formed in the stator of the electric motor to enhance cooling of the electric motors are disclosed. In another embodiment, cooling configurations involving using internal grooves in the housing to allow coolant to directly contact the stator of the motor are disclosed.

[0026] The disclosed systems, assemblies, and motors may be utilized in any device or application that utilizes a motor. For example, the motor may be used to power or drive a vehicle, including but not limited to a ground vehicle (i.e., an automobile), a sea vehicle (such as a boat), or a flying craft (such as an aerial, floating, soaring, hovering, airborne, aeronautical aircraft, airplane, plane, spacecraft, a helicopter, an airship, or an unmanned aerial vehicle, a vertical take-off and landing (VTOL) craft, or a drone). The disclosed embodiments of the present invention may be utilized in any of these applications in order to obtain advantages such as compactness, light weight, enhanced power density, and higher efficiency.

[0027] Figure 1 is a block diagram of a vehicle 100, according to an exemplary embodiment of the present invention. In some embodiments, and as noted above, the vehicle 100 may be a VTOL, which may or may not use electric power to hover, takeoff, and / or land. It should be understood that in other embodiments, the vehicle 100 may be any other type of vehicle that may be able toutilize the advantages of the present invention, such as a ground vehicle (i.e., an automobile), a sea vehicle (such as a boat), or a flying craft (such as an aerial, floating, soaring, hovering, airborne, aeronautical aircraft, airplane, plane, spacecraft, a helicopter, an airship, or an unmanned aerial vehicle, or a drone).

[0028] In some embodiments, the vehicle 100 may include one or more propellers or rotors used to drive the vehicle 100. Each propeller may be configured, for examples, as tiltrotors, lift rotors, or any other type of rotors. In other embodiments, the vehicle 100 may include one or more turbine engines, one or more tires, one or more ski-structures, or the like instead of the one or more propellers used to drive the vehicle.

[0029] For example, a first propeller 102 may be driven by a gearbox 106, which in turn is driven by one or more motors such as propeller motor 108, propeller motor 110, and propeller motor 112. Similarly, a second propeller 104 is driven by a gearbox 114, which in turn is driven by one or more motors such as propeller motor 116, propeller motor 118, and propeller motor 120. In some embodiments, the motors may be electric motors.

[0030] The vehicle 100 also may include multiple lift rotors, such as multiple lift rotors that can facilitate vertical takeoff and landing of the vehicle 100. For example, the vehicle 100 can include a lift rotor 122, a lift rotor 124, a lift rotor 126, and a lift rotor 128.

[0031] The lift rotor 122 is driven by a gearbox 130, which in turn is driven by a motor 132. The lift rotor 124 is driven by a gearbox 134, which in turn is driven by a motor 136. The lift rotor 126 is driven by a gearbox 138, which in turn is driven by a motor 140. The lift rotor 128 is driven by a gearbox 142, which in turn is driven by a motor 144.

[0032] Any of the propellers or lift rotors described herein may be a tilting propeller. In some embodiments, the tilting propellers may also be referred to as a tilting prop, rotor, or proprotor, depending on their design details.

[0033] In one embodiment, each of the motors described above may include one or more respective motor controllers (e.g., including inverters) integrated therewith. For example, the lift motor 132 has one or more motor controllers 146 integrated therewith.

[0034] In some embodiments, the various motors of the vehicle 100 may be electric motors driven by electric power provided by a plurality of batteries. As depicted in in Figure 1, the vehicle 100 can have “n” battery modules 148, such as battery module 150, battery module 152, battery module 154, and battery module 156. In an example, the battery modules can be Lithium-ion (Li-Ion) batteries. Each battery module can include a housing or enclosure that houses a plurality of battery cells arranged in rows and columns.

[0035] The battery modules 148 are configured to store electric power, and provide electric power to the various electric motors when commanded by respective energy management systems of the vehicle 100. Particularly, in an example implementation, the vehicle 100 can have a plurality (“m”) of energy management systems (EMSs) 158 that are in communication with the battery modules 148. The EMSs 158 are configured as electronic regulators that monitor and control the charging and discharging of the battery modules 148.

[0036] In an example, the EMSs 158 are configured to measure voltages of the battery modules 148 and stop charging them when a desired voltage is reached. Further, the EMSs 158 can be configured to monitor parameters that affect life and / or performance of the battery modules 148 as well as ensuring safe operation of the battery modules 148. Safe operation includes, as examples,operating below a threshold temperature to elongate the life of the battery modules 148, preclude overheating, preclude failure of the battery modules 148, etc.

[0037] The EMSs 158 can monitor and control parameters of the battery modules 148. For example, the EMSs 158 monitor and control main power voltage, battery or cell voltage, charging and discharge rates of the battery modules 148, temperatures of the battery modules 148 or their individual cells, health of the battery modules 148 or their individual cells, coolant temperature and flow for air or liquid cooling parameters of a cooling system of the battery modules 148 or their individual cells, etc.

[0038] The vehicle 100 may further include multiple contactor control units (CCUs), such as CCU 160, CCU 162, CCU 164, and CCU 166, which are electrically coupled to the battery modules 148, and are in communication with the EMSs 158. In one embodiment, as illustrated in Figure 1, each CCU is coupled to a respective battery module of the battery modules 148. A contactor is an electrically-controlled switch used for switching an electrical power circuit. A CCU controls the actuation of the contactor to allow power flow to and from the respective battery module. For example, the EMSs 158 control the power flow to and from the battery modules 148 based on power demand from the various electric motors, and accordingly control the CCUs to enable power flow from particular battery modules as desired.

[0039] The vehicle 100 may be configured to include a distributed electric propulsion system configured to provide the vehicle 100 with the required energy to power the multiple propellers and lift rotors via an electric transmission system. Particularly, the vehicle 100 can include a redundant distribution module 168 in communication with the EMSs 158, and the redundant distribution module 168 is electrically coupled to the battery modules 148 via the respective CCUs,and is configured to provide electric power, via transmission lines, to the multiple electric motors of the vehicle 100.

[0040] The EMSs 158 along with the redundant distribution module 168 can provide for redundancy in the vehicle 100 such that if, for example, one propeller or one lift rotor fails, power can be distributed to other propellers or lift rotors to maintain operation of the vehicle 100.

[0041] In applications where high power density electric motors are used, such as in the vehicle 100, output power of such electric motors is limited by the ability to conduct heat to the external environment of the motors to cool them. Thus, to increase the power density of an electric motor, it may be desirable to have cooling arrangements that enhance removal of heat from the electric motor.

[0042] Figure 2 illustrates a cooling system 200 for an electric motor 202, according to exemplary embodiments of the present invention. The electric motor 202 may be a three-phase AC electric motor, for example. The configuration of the electric motor 202 provided in Figure 2 is an example embodiment of an electric motor provided for illustration only and is not meant to be limiting. The cooling configurations described below may be implemented with other electric motor configurations.

[0043] The electric motor 202 includes a housing 204, which may be formed as an assembly of a first housing portion 206 and a second housing portion 208. Particularly, the first housing portion 206 may include attachment ears or bosses such as boss 207, and the second housing portion 208 may include respective attachment ears or bosses such as boss 209. Fasteners may then be inserted and screwed into the mating bosses to couple the first housing portion 206 to the second housing portion 208.

[0044] In an embodiment, the electric motor 202 may be configured as a permanent magnet motor having a stator 210, a rotor 212, and a plurality of magnets 214 radially interposed therebetween and attached to the rotor 212. Other types of motors may be used.

[0045] In an embodiment, the electric motor 202 also includes an inverter 216 integrated therewith and disposed in the second housing portion 208. In other embodiments, the inverter 216 might not be integrated with the electric motor 202 within the housing 204, but may rather be disposed externally and electrically coupled to the wire windings of the stator 210.

[0046] The inverter 216 may be configured to power the electric motor 202. Particularly, the inverter 216 may convert direct current (DC) power provided from a battery (e.g., any of the battery modules 148) to AC power provided to wire windings of the stator 210. In some embodiments, a rotating magnetic field is then generated, which interacts with the plurality of magnets 214, causing them and the rotor 212 to rotate. The rotor 212 may be supported by a first bearing 217 to facilitate rotation of the rotor 212 relative to the first housing portion 206.

[0047] The rotor 212 may have splines 218 formed in an interior peripheral surface thereof to facilitate coupling a motor shaft (not shown) to the rotor 212 via a spline arrangement. The motor shaft may be supported by a second bearing 220 to facilitate rotation of the motor shaft relative to the second housing portion 208. The motor shaft may extend from the housing 204 to drive any of the propellers or lift rotors described above with respect to Figure 1.

[0048] The inverter 216 may be mounted to a coldplate 222 disposed within the second housing portion 208. In some embodiments, the coldplate 222 is a component that cools the inverter 216 and other power electronics by transferring heat from the inverter 216 as. This way, the coldplate 222 may help to improve stable performance and reduce overheating, and the coldplate 222 may have a precise heat dissipation configuration to avoid excessive temperature differences in theelectric motor 202. The coldplate 222 may also configured to have a light weight to avoid reducing the energy density of the electric motor 202.

[0049] The cooling system 200 may further include one or more cooling pumps such as pump 224. The pump 224 may be mounted to the housing 204 and may be driven by the electric motor 202, or may be mounted remotely from the electric motor 202 and driven by an independent mechanism.

[0050] The cooling system 200 further includes a heat exchanger 226 (e.g., a radiator). The cooling system 200 may also include several fluid lines (e.g., tubes, hoses, or pipes) that facilitate transfer of coolant between the components of the electric motor 202, the inverter 216, the pump 224, and the heat exchanger 226.

[0051] In some embodiments, the pump 224 is configured to operate as a positive pressure source of coolant that draw coolant from a sump or reservoir and circulate the coolant throughout the cooling system 200 (e.g., through the heat exchanger 226, the housing 204 and / or the stator 210, and the coldplate 222 to which the inverter 216 is mounted). The reservoir may be a separate tank or accumulator (a volume of fluid which is under pressure by a piston or bladder). The reservoir may provide a way to collect the coolant, provides extra capacity if a small leakage occurs, provide positive pressure upstream the pump 224, and provide volume to support expansion and contraction of the coolant because of variations in temperature during operation of the electric motor 202.

[0052] In one embodiment, the reservoir may be a separate component that is fluidly coupled to the pump 224. In another embodiment, the reservoir may be integrated into the heat exchanger226.

[0053] Any type of coolant pumps may be used. For example, the pump 224 can be piston, gerotor, gear, vane, or centrifugal pumps.

[0054] Any type of heat exchanger may be used. For example, the heat exchanger 226 may have a shell and tube configuration, plate and frame configuration, a finned tube configuration, depending on the design and fluid flow configuration. The heat exchanger 226 may have one or more cores to increase reliability and provide redundancy. In examples, the cores may target different coolant temperature ranges through the fluidic network of the cooling system 200.

[0055] During operation of the electric motor 202, the pump 224 may draw cold coolant from the heat exchanger 226 via fluid lines, then displace the coolant under pressure through cooling channels in the housing 204 and / or in the stator 210. Various cooling arrangements in the housing 204 and / or the stator 210 are disclosed herein to enhance cooling efficiency.

[0056] In an example embodiment, rather than embedding cooling channels within a housing or a cooling jacket of a motor, the cooling channels may be formed as internal grooves, e.g., grooves formed in the interior surface of the housing. This way, coolant is in direct contact with the stator, without barriers therebetween, thereby enhancing cooling efficiency.

[0057] Figure 3A illustrates a partial perspective view of an electric motor 300, and Figure 3B illustrates a cross-sectional side view of the electric motor 300, according to exemplary embodiments of the present invention. The electric motor 300 is an example embodiment of the electric motor 202 described above.

[0058] The electric motor 300 has a housing 302 in which a stator 304 is disposed. The housing 302 has a plurality of internal grooves, such as internal groove 306, at least a portion of which being formed in the interior surface of the housing 302. In some embodiments, at least a portionof the internal groove 306 is cut into the inner surface of the housing 302. A dielectric coolant 308 (e.g., Paratherm LR, Slytherm 800, or Shell Diala) may be provided by the pump 224 through the internal groove 306.

[0059] As shown, the coolant flowing in the internal groove 306 is in direct contact with an exterior surface of the stator 304, without barriers therebetween. Thus, cooling efficiency may be enhanced compared to other systems. In some embodiments, in addition to the internal grooves in the housing 302, cooling channels may also be embedded in the stator 304 for enhanced cooling.

[0060] Figure 4 illustrates a partial perspective view of an electric motor 400, according to exemplary embodiments of the present invention. The electric motor 400 is an example embodiment of the electric motor 202 described above.

[0061] The electric motor 400 may have a housing 402 in which a stator 404 is disposed. Similar to the housing 302 described above, the housing 402 has a plurality of internal grooves, such as internal groove 406, internal groove 408, and internal groove 410. The internal grooves 406-410 are formed or cut in the inner surface of the housing 402. In an embodiment, the plurality of internal grooves are formed in a circular array around the inner surface of the housing 402.

[0062] The stator 404 has a plurality of poles or teeth such as stator tooth 412, stator tooth 414, and stator tooth 416 protruding or projecting radially inward (toward the magnets and rotor of the electric motor which are not shown in Figure 4 to reduce visual clutter in the drawing). Thus, slots, such as slot 418, are formed between the stator teeth. Coils or wire windings of the stator 404 may then be wrapped around at least some of the stator teeth of the stator 404 such that the wire windings traverse or are disposed in the slots of the stator 404.

[0063] In addition to the internal grooves of the housing 402, the electric motor 400 includes stator cooling channels, such as stator cooling channel 420, stator cooling channel 422, and stator cooling channel 424, formed or embedded in respective teeth of the stator 404. Particularly, the stator cooling channel 420 is formed in the stator tooth 412, the stator cooling channel 422 is formed in the stator tooth 414, and the stator cooling channel 424 is formed in the stator tooth 416.

[0064] The electric motor 400 further includes a manifold 426 that distributes and routes fluid between the various cooling channels of the electric motor 400. The manifold 426 may be formed, at least partially, in the housing 402. For example, the manifold 426 may include a fluid distribution groove or fluid distribution channel 428 that is in fluid communication with the internal grooves 406, 408, 410 of the housing 402 as depicted.

[0065] The manifold 426 may further include connecting channels, such as connecting channel 430, that fluidly couple the fluid distribution channel 428 to the stator cooling channels 420, 422, 424. For example, the connecting channel 430 fluidly couples the fluid distribution channel 428 to the stator cooling channel 422. In an embodiment, as shown in Figure 4, the connecting channels are arcuate in shape.

[0066] In operation, a dielectric coolant may be provided by the pump 224 through the stator cooling channels 420, 422, 424, upward in Figure 4 as indicated by the arrows. The dielectric coolant is in direct contact with the interior surface of the stator 404 and absorbs heat therefrom. The coolant is then provided to the fluid distribution channel 428, and then provided to the internal grooves 406, 408, 410 of the housing 402.

[0067] Coolant then flows, downward in Figure 4 as shown by the arrows, through the internal grooves 406, 408, 410 of the housing 402, in direct contact with the exterior surface of the stator 404, thus further absorbing heat from the stator 404. As shown in Figure 4, the coolant flowingthrough the internal grooves 406, 408, 410 is in direct contact with the stator 404 without barriers therebetween.

[0068] Thus, the cooling arrangements of the electric motor 300 and the electric motor 400 involve direct cooling of the stators 304, 404 as the coolant is in direct contact with the stators 304, 404 during operation. In other embodiments, a mixed cooling arrangement involving both direct (through channels in the stator) and indirect (through channels embedded in the housing) may be used.

[0069] Figure 5 illustrates a partial perspective view of an electric motor 500 having a mixed cooling configuration, according to exemplary embodiments of the present invention. The electric motor 500 is an example embodiment of the electric motor 202 described above.

[0070] The electric motor 500 may have a housing 502 inside which a stator 504 is disposed. The electric motor 500 may also have a rotor 506 disposed within the stator 504 as shown. The electric motor 500 may further include a plurality of permanent magnets 508 mounted to a surface of the rotor 506, such that the plurality of permanent magnets 508 are radially interposed between the stator 504 and the rotor 506.

[0071] The stator 504 has a plurality of teeth such as stator tooth 510, stator tooth 512, stator tooth 514, stator tooth 516, stator tooth 518, stator tooth 520, and stator tooth 522 projecting radially inward such that slots, such as slot 524 and slot 526, are formed therebetween. Coils or wire windings such as wire windings 528 and wire winding 530 of the stator 504 are wrapped around at least some of the teeth of the stator 504, such that the wire windings are disposed in the slots of the stator 504. For example, the wire winding 530 is wrapped around the stator tooth 510, and is disposed in the slots 524, 526.

[0072] In the example embodiment of Figure 5, between each two stator teeth around which respective wire windings are wrapped, a stator tooth is circumferentially interposed therebetween without a wire winding wrapped thereabout. For example, the stator tooth 512 is circumferentially interposed between the stator tooth 510 (around which the wire winding 530 is wrapped) and the stator tooth 514 (around which one of the wire windings 528 is wrapped). No wire winding is wrapped around the stator tooth 512.

[0073] The housing 502 includes a plurality of housing cooling channels, such as housing cooling channel 532, housing cooling channel 534, and housing cooling channel 536, embedded in in the housing 502. Additionally, the stator 504 may have a plurality of stator cooling channels disposed in respective stator teeth that do not have wire windings wrapped thereabout. Particularly, the stator 504 may include stator cooling channel 538 formed in the stator tooth 512, stator cooling channel 540 formed in the stator tooth 516, and stator cooling channel 542 formed in the stator tooth 520.

[0074] In other embodiments, stator cooling channels may additionally or alternatively be added to stator teeth around which wire windings are disposed. Also, in other embodiments, stator cooling channels may additionally or alternatively be added to a yoke 544 portion of the stator 504.

[0075] In an embodiment, a dielectric coolant may be provided by the pump 224 through the stator cooling channels 538, 540, 542 to flow in a first direction. The dielectric coolant is in direct contact with the stator 504 and absorbs heat therefrom. The coolant can then be routed (e g., via a manifold or distribution channels, not shown) to the housing cooling channels 532, 534, 536 of the housing 502. The coolant then flows through the housing cooling channels 532, 534, 536 of the housing 502 in a second direction (opposite the first direction), indirectly absorbing excess heat that istransferred from the stator 504 to the housing 502 by conduction. In other embodiments, coolant may be provided by the pump 224 first through the housing cooling channels 532, 534, 536 flowing in the first direction, then routed to the stator cooling channels 538, 540, 542 to flow in the second direction.

[0076] Thus, the cooling arrangement of the electric motor 500 involves a dual cooling strategy or mix of direct and indirect cooling of the stator 504 for enhanced thermal performance and motor efficiency. In this configuration, the primary or direct cooling may be achieved through the stator cooling channels 538, 540, 542, which are dedicated for coolant flow, and embedded within the stator 504. The geometry of the stator cooling channels 538, 540, 542 may be selected to minimize its effect on magnetic flux and maximize the cooling effectiveness by strategically placing them to flow close (e.g., in the stator teeth) to the wire windings, effectively removing heat from the most thermally critical areas.

[0077] The secondary or indirect cooling, may be achieved by circulating coolant through housing cooling channels 532, 534, 536 embedded within the housing 502. The housing cooling channels 532, 534, 536 are not only responsible for dissipating additional heat that is conducted to the housing 502 itself but may also serve as a fluid distribution system. This configuration may improve the uniform supply of coolant to all the stator cooling channels 538, 540, 542, thereby enhancing the overall cooling efficiency. This dual cooling embodiment may allow the electric motor 500 to operate at desired or optimal temperatures under varying load conditions, increasing both the efficiency and lifespan of the electric motor 500.

[0078] In an example embodiment, temperature sensors may be placed within the stator 504 (e.g., proximate to the wire windings) and the housing 502 to continually monitor temperatures, and providing temperature information to a controller of the pump 224. The controller may thendynamically adjust the flow rates of the coolant as desired to achieve a desired or optimal operating temperature for the stator 504.

[0079] Thus, the embodiment of Figure 5 may provide several advantages over conventional cooling arrangements. For example, the combination of direct and indirect cooling methods may provide comprehensive thermal management, rendering components such as the stator 504 effectively cooled. Further, the housing cooling channels, in addition to their cooling functionality, may also operate as a fluid distribution system, which may provide consistent and even coolant delivery to the stator cooling channels, improving the cooling process.

[0080] By maintaining lower operating temperatures, this cooling configuration may reduce thermal losses, leading to improved motor efficiency and power output. Further, this dual cooling configuration may minimize thermal stress on motor components, and may reduce the temperature gradient within the electric motor 500, thereby reducing the risk of failure and extending the operational life of the electric motor 500.

[0081] Also, this dual cooling configuration may provide an added layer of redundancy. If one cooling method experiences reduced efficiency, the other cooling method may compensate, providing continual motor cooling.

[0082] In other embodiments, rather than using a mixed cooling arrangement involving both direct (through channels in the stator) and indirect (through channels embedded in the housing), only direct cooling may be used. In these embodiments, the shape and location of the stator cooling channels may be selected to target specific areas of the stator, particularly the hot spots in stator wire windings, rendering the cooling system more effective in maintaining a uniform temperature distribution.

[0083] Figure 6 illustrates a partial front view of an electric motor 600, according to exemplary embodiments of the present invention. The electric motor 600 is an example embodiment of the electric motor 202 described above.

[0084] The electric motor 600 may have a stator 602. The electric motor 600 may also have a rotor 604 disposed within the stator 602 as shown. The electric motor 600 may further include a plurality of permanent magnets 606 mounted to a surface of the rotor 604.

[0085] The stator 602 has a plurality of teeth such as stator tooth 608, stator tooth 610, and stator tooth 612 projecting radially inward from a yoke 613 of the stator 602. Slots, such as slot 614, slot 616, slot 618, and slot 620, are formed between the stator teeth. Coils or wire windings such as wire winding 622 and wire winding 624 of the stator 602 are wrapped around at least some of the teeth of the stator 602, such that the wire windings traverse or are disposed in the slots of the stator 602. For example, the wire winding 622 is wrapped around the stator tooth 608, and is thus disposed in the slots 614, 616, whereas the wire winding 624 is wrapped around the stator tooth 612, and is thus disposed in the slots 618, 620.

[0086] In the example embodiment of Figure 6, between each two stator teeth around which respective wire windings are wrapped, a stator tooth is circumferentially interposed therebetween without a wire winding wrapped thereabout. For example, the stator tooth 610 is circumferentially interposed between the stator tooth 608 (around which the wire winding 622 is wrapped) and the stator tooth 612 (around which one of the wire windings 624 is wrapped). No wire winding is wrapped around the stator tooth 610.

[0087] The stator 602 includes a plurality of stator cooling channels formed in both the yoke 613 and the stator teeth. Particularly, in the example embodiment of Figure 6, the yoke 613 may have yoke cooling channel 626, yoke cooling channel 628, yoke cooling channel 630, and yoke coolingchannel 632. As shown in an embodiment of Figure 6, the yoke cooling channels 626, 628 are disposed on respective sides of the stator tooth 608 close to peripheries of the wire winding 622. Similarly, the yoke cooling channels 630, 632 are disposed on respective sides of the stator tooth 612 close to peripheries of the wire winding 624. Also, the yoke cooling channels 628, 630 are disposed on respective sides of the stator tooth 610.

[0088] Additionally, the stator teeth also have respective teeth cooling channels. For example, the stator tooth 608 has tooth cooling channel 634, the stator tooth 610 has tooth cooling channel 636, and the stator tooth 612 has tooth cooling channel 638.

[0089] In operation, a dielectric coolant may be provided by the pump 224 through the yoke cooling channels 626, 628, 630, 632 and the tooth cooling channels 634, 636, 638. The dielectric coolant is in direct contact with the stator 602 and absorbs heat therefrom.

[0090] The configuration (e.g., shape and location) of the cooling channels of the stator 602 may enhance cooling effectiveness. As shown in an embodiment of Figure 6, the yoke cooling channels 626, 628, 630, 632 extend horizontally or laterally along the yoke 613, and are located close to the wire windings 622, 624, which may represent the hot or critical spots of the electric motor 600. The tooth cooling channels 634, 636, 638 generally extend vertically or transversely in their respective stator teeth. Further, the tooth cooling channel 634 extends, at least partially, within the wire winding 622, and the tooth cooling channel 638 extends, at least partially, within the wire winding 624. This way, the tooth cooling channels are advantageously located close to hot areas of the stator 602 and may enhance cooling efficiency.

[0091] Other variations of the shape and location of the cooling channels may be implemented in other embodiments.

[0092] Figure 7 illustrates a partial front view of an electric motor 700, according to exemplary embodiments of the present invention. The electric motor 700 is an example embodiment of the electric motor 202 described above. Common components between the electric motor 600 and the electric motor 700 are designated with the same reference numbers.

[0093] In an embodiment of Figure 7, the yoke cooling channels and their associated teeth cooling channels form a generally T-shaped channel. Particularly, the yoke 613 has a yoke cooling channel 702 that is generally horizontal / lateral or extends along the yoke 613, while the associated or corresponding stator tooth 608 has a tooth cooling channel 704 that is vertical / transversal or extends along the stator tooth 608. Thus, the yoke cooling channel 702 and the tooth cooling channel 704 form a T-shape. In this example embodiment, the yoke cooling channel 702 and the tooth cooling channel 704 are disconnected, so the T-shape is incomplete.

[0094] Similarly, the yoke 613 has a yoke cooling channel 706 that is generally horizontal / lateral, while the corresponding stator tooth 610 has a tooth cooling channel 708 that is vertical / transversal. Thus, the yoke cooling channel 706 and the tooth cooling channel 708 form a T-shape, which may be disconnected or incomplete. Similarly, the yoke 613 has a yoke cooling channel 710 that is generally horizontal / lateral, while the corresponding stator tooth 612 has a tooth cooling channel 712 that is vertical / transversal. Thus, the yoke cooling channel 710 and the tooth cooling channel 712 form a T-shape, which may be disconnected or incomplete.

[0095] The tooth cooling channels 704, 712 extend, at least partially, within the respective wire windings. This way, the tooth cooling channels are advantageously located close to critical areas of the stator 602 and may enhance cooling efficiency.

[0096] Figure 8 illustrates a partial front view of an electric motor 800, according to exemplary embodiments of the present invention. The electric motor 800 is an example embodiment of theelectric motor 202 described above. Common components between the electric motor 600 and the electric motor 800 are designated with the same reference numbers.

[0097] In an embodiment of Figure 8, the yoke 613 might not have cooling channels, while each stator tooth may have a set of two tooth cooling channels, that may be parallel to each other. Particularly, the stator tooth 608 has a tooth cooling channel 802 and a tooth cooling channel 804 that extend along the stator tooth 608 and may be parallel to each other. The tooth cooling channel 802 and the tooth cooling channel 804 are laterally spaced from each other, such that each of the tooth cooling channels 802, 804 is disposed proximate to a respective lateral end of the stator tooth 608. Both of the tooth cooling channels 802, 804 extend, at least partially, within the wire winding 622 to enhance cooling effectiveness.

[0098] Similarly, the stator tooth 610 has a tooth cooling channel 806 and a tooth cooling channel 808 that extend along the stator tooth 610 and may be parallel to each other. The tooth cooling channel 806 and the tooth cooling channel 808 are laterally spaced from each other, such that each of the tooth cooling channels 806, 808 is disposed proximate to a respective lateral end of the stator tooth 610. Notably, the tooth cooling channel 806 is disposed proximate to the wire winding 622, while the tooth cooling channel 808 is disposed proximate to the wire winding 624 to enhance cooling effectiveness.

[0099] The stator tooth 612 has a tooth cooling channel 810 and a tooth cooling channel 812 that extend along the stator tooth 612 and may be parallel to each other. The tooth cooling channel 810 and the tooth cooling channel 812 are laterally spaced from each other, such that each of the tooth cooling channels 810, 812 is disposed proximate to a respective lateral end of the stator tooth 612. Both of the tooth cooling channels 810, 812 extend, at least partially, within the wire winding 624 to enhance cooling effectiveness.

[0100] Figure 9 illustrates a partial front view of an electric motor 900, according to exemplary embodiments of the present invention. The electric motor 900 is an example embodiment of the electric motor 202 described above. Common components between the electric motor 600 and the electric motor 900 are designated with the same reference numbers.

[0101] In an embodiment of Figure 9, the yoke 613 and the stator teeth that have wire windings wrapped thereabout might not have cooling channels, while each stator tooth that is circumferentially interposed between stator teeth with wire windings have a T-shaped tooth cooling channel. Particularly, the stator tooth 610 has a tooth cooling channel 902 that is T-shaped.

[0102] As depicted, the tooth cooling channel 902 has a horizontal or lateral portion 904 and a vertical or transversal portion 906, intersecting with the lateral portion 904, thus forming a complete T shape.

[0103] In other embodiments, the other stator teeth (e.g., the stator teeth 608, 612) may also have T-shaped stator cooling channels similar to the tooth cooling channel 902. Further, the shape may be varied to increase the flow area of the cooling channels.

[0104] Figure 10 illustrates a partial front view of an electric motor 1000, according to exemplary embodiments of the present invention. The electric motor 1000 is an example embodiment of the electric motor 202 described above. Common components between the electric motor 600 and the electric motor 1000 are designated with the same reference numbers.

[0105] In an embodiment of Figure 10, the yoke 613 might not have cooling channels, while the stator teeth may all have respective stator cooling channels. For example, the stator tooth 610 has a tooth cooling channel 1002 that is generally T-shaped.

[0106] As depicted in Figure 10, the stator cooling channel 1002 has a horizontal or lateral portion 1004 and a vertical or transversal portion 1006, intersecting with the lateral portion 1004 at an intersection or neck portion 1008. In comparison with the tooth cooling channel 902 of the electric motor 900, the stator cooling channel 1002 has the neck portion 1008, which is enlarged to increase the coolant flow area, thereby enhancing cooling efficiency.

[0107] In an embodiment of Figure 10, the other stator teeth also have similarly configured cooling channels. For example, the stator tooth 608 has stator cooling channel 1010, and the stator tooth 612 has stator cooling channel 1012. The stator cooling channels 1010, 1012 are configured similar to the tooth cooling channel 1002. The transversal portions of the stator cooling channels 1010, 1012 extend, at least partially, within the wire windings 622, 624, respectively, to enhance cooling effectiveness.

[0108] Figure 11 illustrates a partial front view of an electric motor 1100, according to exemplary embodiments of the present invention. The electric motor 1100 is an example embodiment of the electric motor 202 described above. Common components between the electric motor 600 and the electric motor 1100 are designated with the same reference numbers.

[0109] In an embodiment of Figure 11, the yoke 613 has yoke cooling channels that extend laterally to substantially cover a width of a respective wire winding. For example, the yoke 613 has a yoke cooling channel 1102 that extends laterally to substantially cover a width of the wire winding 622. The term “substantially” is used herein to indicate coverage of about 90% or more of the width of the wire winding.

[0110] Similarly, the yoke 613 has a yoke cooling channel 1104 that extends laterally to substantially cover a width of the wire winding 624. In an embodiment, the cooling effectiveness may be enhanced as the width of the yoke cooling channels 1102, 1104 is increased compared toother yoke cooling channels described above, increasing flow area and proximity to the entire width of the wire winding, not just a portion thereof.

[0111] In an embodiment of Figure 11, the stator teeth that have wire windings wrapped thereabout might not have cooling channels, while each stator tooth that is circumferentially interposed between stator teeth with wire windings have a respective stator cooling channel. For example, the stator tooth 610 has a tooth cooling channel 1106 that is a vertical or transversal channel.

[0112] The embodiments of Figures 6-11 involving various direct cooling configurations may provide several advantages. In these direct cooling configurations, the coolant directly contacts the stator 602, providing efficient heat transfer and reducing the temperature of the stator 602 more effectively. This may help maintain desired or optimal operating temperatures, which may be needed for high-performance electric motors. Also, maintaining a lower stator temperature may reduce resistive losses in the wire windings, contributing to an improvement in overall motor efficiency.

[0113] These direct cooling configurations may also involve targeting specific areas of the stator 602, particularly the hot spots in stator wire windings, rendering the cooling system more effective in maintaining uniform temperature distribution in the stator 602. This may allow for higher power output for the electric motors 700, 800, 900, 1000, 1100, without the risk of overheating. Further, with these cooling configurations, the electric motors may be more compact and may have higher power density, rendering the electric motors suitable for high performance applications such as electric VTOL vehicles and electric cars, among others.

[0114] Also, with these direct cooling embodiments, lower operating temperatures may be achievable to reduce thermal stress on the stator materials, which may lead to a longer lifespan andhigher reliability of the motor components. Further, insulation degradation may be prevented, reducing the risk of demagnetization of the magnets, as both insulation degradation and demagnetization may be accelerated by high temperatures.

[0115] Additionally, the coolant flowing in channels formed in the stator may have dampening effect, particularly, reducing vibrations and noise, leading to quieter motor operation. This may be particularly beneficial in passenger vehicles where noise reduction may be desirable.

[0116] Further, in example embodiments, the same coolant used to cool other components of the vehicle (e.g., inverters, controllers, etc.) may be also used for cooling the electric motors described above. Integrating motor cooling with the overall thermal management system of a vehicle may improve overall system efficiency and reduce complexity.

[0117] It should be understood that features of the various cooling embodiments described above may be used in combination, and are not meant to be limited to the illustrated configuration as an isolated implementation. For example, the T-shaped cooling channels of Figures 7, 9-10 may be used in lieu of the teeth cooling channels of Figures 6, 8, 11. Further, the stator cooling channels described with respect to Figure 4 may be configured to be similar to any of the stator cooling channels described with respect to Figures 7-11, and so on.

[0118] The detailed description above describes various features and operations of the disclosed systems with reference to the accompanying figures. The illustrative implementations described herein are not meant to be limiting. Certain aspects of the disclosed systems can be arranged and combined in a wide variety of different configurations, all of which are contemplated herein.

[0119] Further, unless context suggests otherwise, the features illustrated in each of the figures may be used in combination with one another. Thus, the figures should be generally viewed ascomponent aspects of one or more overall implementations, with the understanding that not all illustrated features are necessary for each implementation.

[0120] Additionally, any enumeration of elements, steps, or blocks in this specification or the claims is for purposes of clarity. Thus, such enumeration should not be interpreted to require or imply that these elements, steps, or blocks adhere to a particular arrangement or are carried out in a particular order.

[0121] Further, devices or systems may be used or configured to perform functions presented in the figures. In some instances, components of the devices and / or systems may be configured to perform the functions such that the components are actually configured and structured (with hardware and / or software) to enable such performance. In other examples, components of the devices and / or systems may be arranged to be adapted to, capable of, or suited for performing the functions, such as when operated in a specific manner.

[0122] By the term “substantially” or “about” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those with skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0123] The arrangements described herein are for purposes of example only. As such, those skilled in the art will appreciate that other arrangements and other elements (e.g., machines, interfaces, operations, orders, and groupings of operations, etc.) can be used instead, and some elements may be omitted altogether according to the desired results. Further, many of the elements that are described are functional entities that may be implemented as discrete or distributed components or in conjunction with other components, in any suitable combination and location.

[0124] While various aspects and implementations have been disclosed herein, other aspects and implementations will be apparent to those skilled in the art. The various aspects and implementations disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope being indicated by the following claims, along with the full scope of equivalents to which such claims are entitled. Also, the terminology used herein is for the purpose of describing particular implementations only, and is not intended to be limiting.

[0125] Implementations of the present disclosure can thus relate to one of the enumerated example embodiments (EEEs) listed below.

[0126] EEE 1 is an electric motor comprising: a housing; a stator disposed within the housing; and a plurality of internal grooves formed in the housing, wherein at least a portion of each internal groove is cut into an inner surface of the housing such that coolant flowing through the portion of an internal groove of the plurality of internal grooves is in direct contact with an exterior surface of the stator without barriers therebetween.

[0127] EEE 2 is the electric motor of EEE 1, wherein the plurality of internal grooves are formed in a circular array around the inner surface of the housing.

[0128] EEE 3 is the electric motor of any of EEEs 1-2, wherein the stator has a plurality of stator teeth projecting radially inward, wherein wire windings of the stator are wrapped around at least some stator teeth of the plurality of stator teeth of the stator, and wherein the stator further comprises: a plurality of stator cooling channels respectively embedded in at least some stator teeth of the stator, such that coolant flowing through the plurality of stator cooling channels is in direct contact with an interior surface of the stator.

[0129] EEE 4 is the electric motor of EEE 3, further comprising: a fluid distribution channel that is in fluid communication with the internal grooves of the housing; and a plurality of connecting channels that fluidly couple the fluid distribution channel to the plurality of stator cooling channels.

[0130] EEE 5 is the electric motor of EEE 4, wherein the plurality of connecting channels are arcuate in shape.

[0131] EEE 6 is an electric motor comprising: a housing; a stator disposed within the housing; a plurality of housing cooling channels embedded in in the housing; and a plurality of stator cooling channels embedded in the stator, wherein (i) coolant flows through the plurality of housing cooling channels in a first direction, then communicated to the plurality of stator cooling channels, flowing in a second direction, or (ii) coolant flows through the plurality of stator cooling channels in the first direction, then communicated to the plurality of housing cooling channels, flowing in the second direction.

[0132] EEE 7 is the electric motor of EEE 6, wherein the stator has a plurality of stator teeth projecting radially inward, wherein wire windings of the stator are wrapped around at least some stator teeth of the plurality of stator teeth of the stator, and wherein the plurality of stator cooling channels are embedded in the respective stator teeth of the plurality of stator teeth.

[0133] EEE 8 is the electric motor of EEE 7, wherein between each two stator teeth around which respective wire windings are wrapped, a stator tooth is circumferentially interposed therebetween without a wire winding wrapped thereabout, and wherein the plurality of stator cooling channels are disposed in respective stator teeth without wire windings wrapped thereabout.

[0134] EEE 9 is an electric motor comprising: a housing; a stator disposed within the housing, wherein the stator comprises a plurality of stator teeth projecting radially inward from a yoke ofthe stator; and a plurality of stator cooling channels embedded in one or both of: (i) the yoke, or (ii) at least some of the plurality of stator teeth, such that coolant flowing through the plurality of stator cooling channels is in direct contact with an interior surface of the stator.

[0135] EEE 10 is the electric motor of EEE 9, further comprising: a plurality of wire windings respectively wrapped around at least some of the stator teeth of the stator, wherein between each two stator teeth around which respective wire winding is wrapped, a stator tooth is circumferentially interposed therebetween without a wire winding wrapped thereabout, and wherein respective stator teeth without wire windings wrapped thereabout comprise respective stator cooling channels of the plurality of stator cooling channels.

[0136] EEE 11 is the electric motor of any of EEEs 9-10, wherein respective stator teeth having respective wire windings wrapped thereabout comprise respective stator cooling channels of the plurality of stator cooling channels, such that the respective stator cooling channels extend, at least partially, within the respective wire windings.

[0137] EEE 12 is the electric motor of any of EEEs 9-11, wherein a stator cooling channel of the plurality of stator cooling channels is configured to have a yoke cooling channel formed laterally in the yoke and a tooth cooling channel formed transversely in a respective stator tooth.

[0138] EEE 13 is the electric motor of any of EEEs 9-12, wherein a stator cooling channel of the plurality of stator cooling channels is configured to have a lateral portion and a transversal portion, intersecting with the lateral portion.

[0139] EEE 14 is the electric motor of EEE 13, wherein the lateral portion intersects with the transversal portion at an neck portion that is enlarged to increase a coolant flow area through the stator cooling channel.

[0140] EEE 15 is the electric motor of any of EEEs 9-14, wherein respective stator teeth of the stator have two tooth cooling channels that are parallel and laterally spaced from each.

[0141] EEE 16 is the electric motor of any of EEEs 9-15, further comprising: a plurality of wire windings respectively wrapped around at least some of the stator teeth of the stator, wherein the stator cooling channels comprise: a yoke cooling channel formed proximate to a respective stator tooth having a wire winding wrapped thereabout, wherein the yoke cooling channel extends laterally to substantially cover a width of the wire winding.

[0142] EEE 17 is a vehicle comprising: a propeller; and the electric motor of any of EEEs 1-16 having a rotor and a motor shaft coupled to the rotor, wherein the motor shaft is coupled to and configured to drive the propeller.

[0143] EEE 18 is a method of operating the electric motor of any of EEEs 1-16 or the vehicle ofEEE 17.

Claims

CLAIMSWhat is claimed is:1 . An electric motor comprising: a housing; a stator disposed within the housing; and a plurality of internal grooves formed in the housing, wherein at least a portion of each internal groove is cut into an inner surface of the housing such that coolant flowing through the portion of an internal groove of the plurality of internal grooves is in direct contact with an exterior surface of the stator without barriers therebetween.

2. The electric motor of claim 1, wherein the plurality of internal grooves are formed in a circular array around the inner surface of the housing.

3. The electric motor of claim 1, wherein the stator has a plurality of stator teeth projecting radially inward, wherein wire windings of the stator are wrapped around at least some stator teeth of the plurality of stator teeth of the stator, and wherein the stator further comprises: a plurality of stator cooling channels respectively embedded in at least some stator teeth of the stator, such that coolant flowing through the plurality of stator cooling channels is in direct contact with an interior surface of the stator.

4. The electric motor of claim 3, further comprising: a fluid distribution channel that is in fluid communication with the internal grooves of the housing; anda plurality of connecting channels that fluidly couple the fluid distribution channel to the plurality of stator cooling channels.

5. The electric motor of claim 4, wherein the plurality of connecting channels are arcuate in shape.

6. An electric motor comprising: a housing; a stator disposed within the housing; a plurality of housing cooling channels embedded in in the housing; and a plurality of stator cooling channels embedded in the stator, wherein (i) coolant flows through the plurality of housing cooling channels in a first direction, then communicated to the plurality of stator cooling channels, flowing in a second direction, or (ii) coolant flows through the plurality of stator cooling channels in the first direction, then communicated to the plurality of housing cooling channels, flowing in the second direction.

7. The electric motor of claim 6, wherein the stator has a plurality of stator teeth projecting radially inward, wherein wire windings of the stator are wrapped around at least some stator teeth of the plurality of stator teeth of the stator, and wherein the plurality of stator cooling channels are embedded in the respective stator teeth of the plurality of stator teeth.

8. The electric motor of claim 7, wherein between each two stator teeth around which respective wire windings are wrapped, a stator tooth is circumferentially interposed therebetweenwithout a wire winding wrapped thereabout, and wherein the plurality of stator cooling channels are disposed in respective stator teeth without wire windings wrapped thereabout.

9. An electric motor comprising: a housing; a stator disposed within the housing, wherein the stator comprises a plurality of stator teeth projecting radially inward from a yoke of the stator; and a plurality of stator cooling channels embedded in one or both of: (i) the yoke, or (ii) at least some of the plurality of stator teeth, such that coolant flowing through the plurality of stator cooling channels is in direct contact with an interior surface of the stator.

10. The electric motor of claim 9, further comprising: a plurality of wire windings respectively wrapped around at least some of the stator teeth of the stator, wherein between each two stator teeth around which respective wire winding is wrapped, a stator tooth is circumferentially interposed therebetween without a wire winding wrapped thereabout, and wherein respective stator teeth without wire windings wrapped thereabout comprise respective stator cooling channels of the plurality of stator cooling channels.

11. The electric motor of claim 9, wherein respective stator teeth having respective wire windings wrapped thereabout comprise respective stator cooling channels of the plurality of stator cooling channels, such that the respective stator cooling channels extend, at least partially, within the respective wire windings.

12. The electric motor of claim 9, wherein a stator cooling channel of the plurality of stator cooling channels is configured to have a yoke cooling channel formed laterally in the yoke and a tooth cooling channel formed transversely in a respective stator tooth.

13. The electric motor of claim 9, wherein a stator cooling channel of the plurality of stator cooling channels is configured to have a lateral portion and a transversal portion, intersecting with the lateral portion.

14. The electric motor of claim 13, wherein the lateral portion intersects with the transversal portion at an neck portion that is enlarged to increase a coolant flow area through the stator cooling channel.

15. The electric motor of claim 9, wherein respective stator teeth of the stator have two tooth cooling channels that are parallel and laterally spaced from each.

16. The electric motor of claim 9, further comprising: a plurality of wire windings respectively wrapped around at least some of the stator teeth of the stator, wherein the stator cooling channels comprise: a yoke cooling channel formed proximate to a respective stator tooth having a wire winding wrapped thereabout, wherein the yoke cooling channel extends laterally to substantially cover a width of the wire winding.

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