Winding slot embedded steam chamber for motor and heat pipe with end cover radiator

Abstract

An electric machine having a winding slot embedded heat pipe / steam chamber and end cap integrated radiator, a method of making / using such an electric machine, and a vehicle equipped with such an electric machine are presented. An electric machine, such as a traction motor or generator, includes a housing, a stator assembly mounted to the housing, and a rotor assembly rotatably mounted adjacent the stator assembly. The stator assembly includes an annular stator core with one or more electromagnetic stator windings mounted on or in the stator core. The rotor assembly includes a cylindrical rotor core and one or more electromagnetic rotor windings mounted in rotor slots of the rotor core. One or more heat pipes are mounted in the rotor slots adjacent the rotor windings, and axially protrude from one or both axial ends of the rotor core. Each heat pipe extracts thermal energy from the rotor winding and transfers the thermal energy out of the rotor core.

Description

Technical Field

[0001] The present disclosure relates generally to electric machines. More specifically, aspects of the present disclosure relate to a thermal management system for regulating the operating temperature of a separately excited motor (SEM) assembly. Background Art

[0002] The motor vehicles currently produced, such as modern automobiles, are initially equipped with a powertrain that operates to propel the vehicle and provide power for the vehicle's onboard electronics. For example, in automotive applications, the vehicle powertrain is typically represented by a prime mover that transmits drive torque to the vehicle's final drive system (e.g., differential, axle, corner module, wheels, etc.) through an automatic or manually shifted power transmission. Due to the availability, relatively light weight, and overall efficiency of reciprocating piston internal combustion engine (ICE) assemblies, historically automobiles have been powered by reciprocating piston internal combustion engine assemblies. As some non-limiting examples, such engines include compression ignition (CI) diesel engines, spark ignition (SI) gasoline engines, two-stroke, four-stroke, and six-stroke architectures, and rotary engines. On the other hand, hybrid electric vehicles and all-electric vehicles (collectively referred to as "electric vehicles") utilize alternative power sources to propel the vehicle, and thus minimize or eliminate reliance on fossil fuel-based engines for traction power.

[0003] A full electric vehicle (FEV), commonly known as an "electric vehicle," is an electrically driven vehicle configuration that completely omits the internal combustion engine and the accompanying peripheral components of the powertrain system, instead relying on a rechargeable energy storage system (RESS) and a traction motor for vehicle propulsion. The engine components, fuel supply system, and exhaust system of an ICE-based vehicle are replaced by a single or multiple traction motors, rechargeable battery cells, and battery cooling and charging hardware in a battery-based FEV. In comparison, the powertrain of a hybrid electric vehicle (HEV) employs multiple traction power sources to propel the vehicle, most commonly operating an internal combustion engine component in conjunction with a battery-powered or fuel cell-powered traction motor. Because a hybrid electric-drive vehicle is able to obtain its power from a source other than the engine, the HEV engine can be fully or partially shut down when the vehicle is propelled by the electric motor. Summary of the invention

[0004] Traction motors are electric machines that convert electrical energy into rotational mechanical energy to propel a vehicle, such as FEV and HEV type automobiles. Many traction motors include a fixedly mounted stator carrying multi-phase electromagnetic windings, such as copper hairpin or I-shaped pin bars, and a rotatable rotor carrying a designed pattern of magnets, such as core-mounted permanent magnets (PMs), or electromagnetic armature windings, such as core-mounted copper coils. Traction motors can be classified as alternating current (AC) or direct current (DC), brushed or brushless, rotary or linear, and radial flux or axial flux. In a radial flux inner rotor design, the rotor can be coaxially nested within the stator, while an axial flux rotary design can juxtapose the rotor and stator as facing coaxial plates. The rotational excitation of the rotor assembly can be affected by a magnetic field generated by passing current through the multi-phase AC stator windings; the magnetic field emitted by the stator interacts with the mating magnetic field generated by the permanent magnets or DC armature coils carried by the rotor.

[0005] The rotor assembly of many modern traction motors includes a rotor core made of thin ferromagnetic disks that are stacked and laminated together into a cylinder. Each rotor disk has a plurality of openings that, when aligned with the openings of an adjacent disk, form rotor slots that extend axially through the length of the rotor core. Continuous state or electrically excited magnetic elements (e.g., PM rods or copper coils) are inserted into these rotor slots and fixed to the rotor core. Unlike permanent magnet motor structures in which the rotor assembly supports internal or surface mounted magnets, a separately excited motor (SEM) is typically represented by an armature winding supported by the rotor that electromagnetically cooperates with a field winding (field winding) supported by the stator to convert electrical energy into mechanical energy. The rotor core can be mounted on a motor shaft for outputting propulsion generating motor torque generated by the motor or for inputting power generating regenerative torque received by the motor.

[0006] During operation of the traction motor, the internal electrical and electromagnetic hardware can generate a large amount of heat, for example due to windage, friction, and hysteresis losses. An integrated motor cooling system can be employed to prevent undesirable overheating conditions in the motor. An active thermal management (ATM) system, for example, employs a central controller or a dedicated control module to regulate the operation of a cooling circuit that circulates a coolant fluid through heat-generating motor components. For an indirect liquid cooling system, a heat transfer coolant is circulated through a network of internal passages and tubes within the motor housing. In contrast, a direct liquid cooling system (or "liquid immersion cooling" (LIC)) utilizes a direct conduction dielectric liquid coolant to splash, spray, or immerse components of the motor in a direct conduction dielectric liquid coolant.

[0007] This article proposes a motor with winding slot embedded heat pipes and / or steam chambers and end cover integrated heat sinks, a method for manufacturing such a motor, a method for operating such a motor, and a vehicle equipped with such a motor. As a non-limiting example, a novel separately excited motor design extracts heat from the windings carried by the rotor by integrating heat pipes and / or steam chambers into each rotor pole and placing the pipes / chambers in the winding bundle. The extracted heat can be transferred axially to the opposite axial ends of the rotor core and to the larger thermal body (thermal body) of the rotor end cover. The rotor end cover can be manufactured with axial pin fins, which dissipate the transferred heat into the internal coolant volume of the drive unit (DU) housing. Spray or splash cooling can be used to extract heat from the pin fins and concomitantly bring thermal energy out of the DU housing. Each heat pipe / steam chamber can be embedded in the axial rotor slot gap and surrounded by the rotor winding. The axially protruding pin fins can be integrally formed into the rotor end cover, for example, to effectively dissipate heat to the DU housing volume. End cover spray cooling and / or splash cooling may be used to accelerate end cover thermal conductivity and thereby facilitate heat extraction from the rotor windings.

[0008] Ancillary benefits of at least some of the disclosed concepts include a SEM architecture with reduced winding temperatures (e.g., at worst case operating points (WCOP)), which results in enhanced motor efficiency and extended motor performance limits (i.e., beyond comparable IPM designs). Unlike complex shaft-fed ATM cooling designs that significantly increase cost, complexity, and system failure points, the disclosed SEM design uses sealed heat pipes / vapor chambers and end cap heat sinks to quickly and efficiently extract heat from the motor windings. Other attendant advantages may include a SEM system that eliminates the need for rare earth (RE) and heavy rare earth (HRE) materials, which may be susceptible to erratic price changes and commodity shortages. Unlike many conventional SEM solutions that choose to operate at lower peak rotor field currents and limit peak rotor field amplitudes to reduce motor temperatures, the disclosed SEM system uses both active and passive cooling features to extract winding heat caused by copper losses and, therefore, extend the SEM peak performance limits.

[0009] Aspects of the present disclosure relate to winding slot embedded steam chambers and / or heat pipes for cooling electromagnetic rotors and / or stator windings of electric machines, such as motors, generators, transformers, inductors, dynamometers, converters, and the like. In one example, the electric machine includes a protective housing, a stator assembly fixedly attached to the housing, and a rotor assembly rotatably attached to the housing adjacent to the stator assembly. The stator assembly includes a stator core having at least one stator slot and at least one electromagnetic stator winding installed in the stator slot. Similarly, the rotor assembly includes a rotor core having at least one rotor slot and at least one electromagnetic rotor winding installed in the rotor slot. At least one heat pipe is installed in one, some, or all of the rotor slots adjacent to the rotor winding. The heat pipe protrudes axially from one or two opposite axial ends of the rotor core. Each heat pipe passively extracts heat energy from the rotor winding and transfers the extracted heat energy away from the rotor core.

[0010] Additional aspects of the present disclosure relate to an electrically driven vehicle propelled by a SEM-type traction motor that is cooled by winding slot embedded steam chambers and / or heat pipes. As used herein, the terms "vehicle" and "motor vehicle" may be used interchangeably and synonymously to refer to any relevant vehicle platform, such as passenger cars (ICE, HEV, FEV, fuel cell, fully and partially autonomous, etc.), commercial vehicles, industrial vehicles, tracked vehicles, off-road and all-terrain vehicles, motorcycles, agricultural equipment, watercraft, aircraft, electric bicycles, etc. In one example, the motor vehicle includes a body with a passenger compartment, a plurality of wheels mounted to the body (e.g., via corner modules coupled to a unibody or body-on-frame chassis), and other standard original equipment. For electric drive vehicle applications, the vehicle is equipped with a rechargeable energy storage system (RESS) (e.g., a traction battery pack) and an electrified powertrain that employs one or more traction motor / generator units (MGUs) that operate alone (e.g., for an FEV powertrain) or in combination with an internal combustion engine assembly (e.g., for an HEV powertrain) to selectively drive one or more wheels to propel the vehicle.

[0011] Continuing with the previous discussion, the traction motor includes a protective and insulating motor housing, a stator assembly rigidly mounted inside the motor housing, and a rotor assembly rotatably mounted inside the motor housing adjacent to the stator assembly. The stator assembly includes an annular stator core having a series of circumferentially spaced stator slots in which a plurality of electromagnetic stator windings (e.g., copper hairpin winding bars) are mounted. In contrast, the rotor assembly includes a cylindrical rotor core nested within and surrounded by the annular stator core. The rotor core has a series of circumferentially spaced rotor slots in which a plurality of electromagnetic rotor windings (e.g., copper winding coils) are mounted. A single or a group of heat pipes are mounted in each rotor slot adjacent to the rotor winding in the slot and protrude axially from one or both axial ends of the rotor core. Each heat pipe includes a sealed tank containing a working fluid that changes phase between a liquid and a gas, thereby extracting heat energy from the rotor windings and transmitting the extracted heat energy out through the axial ends of the rotor core.

[0012] Aspects of the present disclosure also relate to manufacturing workflow processes, computer-readable media, and control logic for manufacturing or using any of the disclosed winding cooling systems, motors, and / or motor vehicles. In one example, a method for assembling a motor is presented. The representative method includes, in any order and in any combination of any of the options and features disclosed above and below: receiving a housing of the motor; attaching a stator assembly to the housing, the stator assembly comprising a stator core and an electromagnetic stator winding mounted in a stator slot of the stator core; attaching a rotor assembly to the housing so that the rotor assembly is adjacent to the stator assembly and can rotate relative to the stator assembly, the rotor assembly comprising a rotor core and an electromagnetic rotor winding mounted in a rotor slot of the rotor core; and installing a heat pipe in the rotor slot so that the heat pipe is adjacent to the rotor winding and protrudes axially from the axial end of the rotor core, wherein the heat pipe is configured to passively extract heat energy from the rotor winding and transfer the heat energy away from the rotor core.

[0013] For any of the disclosed vehicles, methods, and electric machines, the rotor assembly may include a rotor winding bundle mounted in a rotor slot. In this case, the heat pipe may include a plurality of heat pipes mounted in the rotor slot and embedded within the rotor winding bundle. As another option, the heat pipes in a given rotor slot may be stacked along a straight line extending radially relative to the rotor core. In this case, the heat pipes may be parallel to each other and radially spaced apart from each other. For a multi-slot, multi-bundle configuration, the electric machine may include a plurality of heat pipe stacks that are equally spaced apart from each other around the rotor core, with each heat pipe stack oriented at an oblique angle relative to its adjacent heat pipe stack.

[0014] For any of the disclosed vehicles, methods, and motors, each heat pipe may include a sealed heat-conducting tank (e.g., a copper tube or an aluminum tube) containing a working fluid (e.g., water, acetone, methanol, or ammonia). The working fluid changes phase between liquid and gas to extract heat from the rotor windings and transfers the extracted heat through one or both axial ends of the rotor core. Located inside the heat pipe tank is a core structure (e.g., a grooved, sintered, or sieve-type core) that abuts the inner surface of the tank and, if necessary, covers the inner surface of the tank. The core structure transports the liquid-phase working fluid to the center of the tank, for example, via capillary action. An elongated steam channel may extend longitudinally through the center of the core structure. The steam channel transfers the working fluid to the opposite axial ends of the sealed tank when the working fluid evaporates into a gas; when the working fluid condenses into a liquid, the steam channel transfers the fluid to the core structure.

[0015] For any of the disclosed vehicles, methods, and electric machines, a left (first) rotor end cap can be attached to one axial end of the rotor core, and a right (second) rotor end cap can be attached to the opposite axial end of the rotor core. Each end cap is adjacent to the longitudinal end of the heat pipe to receive therefrom the extracted heat energy transferred from the rotor core. The rotor end cap can be an annular plate-like structure comprising one or more heat pipe cavities, each heat pipe cavity being recessed into the inwardly facing axial surface of the rotor end cap and nesting the longitudinal end of the heat pipe therein. Each rotor end cap can be manufactured with a set of end cap fins that protrude axially away from the rotor core; these end cap fins dissipate the extracted heat energy transferred from the rotor core and received by the rotor end cap. An optional active thermal management system can splash or spray a dielectric coolant fluid onto the end cap fins and, if necessary, pump the heated coolant fluid away from the rotor assembly.

[0016] For any of the disclosed vehicles, methods, and electric machines, the rotor assembly may include a series of circumferentially spaced rotor slots, each extending axially through the rotor core and having an open terminal end. In this case, a set of rotor windings may be wound through each rotor slot and secured within each rotor slot. A single heat pipe or a set of heat pipes may be secured within each rotor slot, for example, extending through the center of the set of rotor windings in that slot. The heat pipes may be arranged as discrete tube stacks spaced circumferentially around the rotor core, embedded in the rotor windings, with each tube stack located in a corresponding one of the rotor slots.

[0017] The present invention also includes the following scheme:

[0018] Solution 1. A motor comprising:

[0019] case;

[0020] a stator assembly comprising a stator core attached to the housing and electromagnetic stator windings mounted in stator slots of the stator core;

[0021] a rotor assembly including a rotor core rotatably attached to the housing adjacent the stator assembly and an electromagnetic rotor winding mounted in rotor slots of the rotor core and configured to magnetically cooperate with the stator winding; and

[0022] A heat pipe is mounted in the rotor slot adjacent to the rotor winding and protrudes axially from an axial end of the rotor core, the heat pipe being configured to passively extract thermal energy from the rotor winding and transfer the thermal energy away from the rotor core.

[0023] Solution 2. The electric machine according to Solution 1, wherein the rotor winding comprises a rotor winding bundle installed in the rotor slot, and the heat pipe comprises a plurality of heat pipes installed in the rotor slot and embedded in the rotor winding bundle.

[0024] Option 3. An electric machine according to Option 2, wherein the heat pipes are stacked along a straight line extending radially relative to the rotor core.

[0025] Option 4. The electric machine according to Option 3, wherein the heat pipes are parallel to each other and radially spaced apart from each other.

[0026] Option 5. An electric machine according to Option 1, wherein the heat pipe includes a sealed tank containing a working fluid, and the working fluid is configured to change phase between a liquid phase and a gas phase, thereby extracting thermal energy from the rotor winding and transmitting the extracted thermal energy through the axial end of the rotor core.

[0027] Option 6. An electric machine according to Option 5, wherein the heat pipe further comprises a core structure, which is located within the sealed can and is configured to transfer the working fluid from an axial end of the sealed can to a central region of the sealed can when the working fluid is in a liquid phase.

[0028] Option 7. An electric motor according to Option 6, wherein the core structure is adjacent to the inner surface of the sealed can and defines an elongated central steam channel, and the elongated central steam channel is configured to allow the working fluid to reach the axial end of the sealed can through the steam channel when evaporating into the gas phase and to allow the working fluid to enter the core structure when condensing into the liquid phase.

[0029] Option 8. The electric machine according to Option 1 further includes a rotor end cover, which is attached to the axial end of the rotor core and adjacent to the longitudinal end of the heat pipe to receive the extracted heat energy transferred from the rotor core from the longitudinal end.

[0030] Solution 9. The electric machine according to Solution 8, wherein the rotor end cover includes a heat pipe cavity, which is recessed into the axial surface of the rotor end cover and in which the longitudinal end of the heat pipe is nested.

[0031] Embodiment 10. The electric machine according to embodiment 8, wherein the rotor end cap includes a plurality of end cap fins, the plurality of end cap fins protruding away from the rotor core and configured to dissipate extracted heat energy transferred from the rotor core and received by the rotor end cap.

[0032] Option 11. The electric machine according to Option 10 further includes an active thermal management (ATM) system configured to splash or spray coolant fluid onto the end cover fins.

[0033] Option 12. An electric motor according to Option 1, wherein the rotor slots include a plurality of rotor slots extending axially through the rotor core and circumferentially spaced around the rotor core, the rotor winding includes a plurality of rotor windings wound through the rotor slots, and the heat pipes include a plurality of heat pipes extending axially through the rotor slots substantially parallel to the rotation axis of the rotor core.

[0034] Option 13. An electric machine according to Option 12, wherein the heat pipes are arranged in a plurality of tube stacks spaced circumferentially around the rotor core, the plurality of tube stacks are embedded in the rotor winding, and each tube stack is located in a corresponding one of the rotor slots.

[0035] Solution 14. A motor vehicle, comprising:

[0036] Car body;

[0037] a plurality of wheels attached to the vehicle body;

[0038] a rechargeable energy storage system (RESS) attached to the vehicle body; and

[0039] a traction motor attached to the vehicle body, electrically connected to the RESS, and configured to drive one or more of the wheels to propel the motor vehicle, the traction motor comprising:

[0040] Motor housing;

[0041] a stator assembly rigidly mounted inside the motor housing, the stator assembly comprising an annular stator core and a plurality of electromagnetic stator windings mounted in circumferentially spaced stator slots of the stator core;

[0042] a rotor assembly rotatably mounted within the motor housing adjacent the stator assembly, the rotor assembly comprising a cylindrical rotor core nested within the annular stator core and a plurality of electromagnetic rotor windings mounted in circumferentially spaced rotor slots of the rotor core; and

[0043] A plurality of heat pipes are mounted in the rotor slots, embedded in the rotor windings and protruding axially from the axial ends of the rotor core, each of the heat pipes comprising a sealed tank containing a working fluid, the working fluid being configured to change phase between a liquid phase and a gas phase so as to thereby extract thermal energy from the rotor windings and transfer the extracted thermal energy out through the axial ends of the rotor core.

[0044] Solution 15. A method for assembling an electric machine, the method comprising:

[0045] a housing for receiving the motor;

[0046] attaching a stator assembly to the housing, the stator assembly comprising a stator core and electromagnetic stator windings mounted in stator slots of the stator core;

[0047] attaching a rotor assembly to the housing such that the rotor assembly is adjacent to and rotatable relative to the stator assembly, the rotor assembly including a rotor core and electromagnetic rotor windings mounted in rotor slots of the rotor core; and

[0048] Heat pipes are installed in the rotor slots such that the heat pipes are adjacent to the rotor windings and protrude axially from an axial end of the rotor core, wherein the heat pipes are configured to passively extract thermal energy from the rotor windings and transfer the thermal energy away from the rotor core.

[0049] Embodiment 16. The method according to Embodiment 15, wherein the rotor winding comprises a rotor winding bundle installed in the rotor slot, and the heat pipe comprises a plurality of heat pipes installed in the rotor slot and embedded in the rotor winding bundle.

[0050] Option 17. The method according to Option 16, wherein the heat pipes are stacked in a straight line extending radially relative to the rotor core, the heat pipes are parallel to each other and radially spaced apart from each other.

[0051] Option 18. A method according to Option 15, wherein the heat pipe includes a sealed tank containing a working fluid, and the working fluid is configured to change phase between a liquid phase and a gas phase to thereby extract thermal energy from the rotor winding and transfer the extracted thermal energy through the axial end of the rotor core.

[0052] Option 19. A method according to Option 18, wherein the heat pipe further comprises a wick structure, which is located within the sealed can and is configured to transfer the working fluid from an axial end of the sealed can to a central region of the sealed can when the working fluid is in the liquid phase.

[0053] Option 20. The method according to Option 15 further includes: attaching a rotor end cover to the axial end of the rotor core so that the rotor end cover is adjacent to the longitudinal end of the heat pipe to receive the extracted heat energy transferred from the rotor core from the longitudinal end.

[0054] The above summary of the invention does not represent every embodiment or every aspect of the present disclosure. On the contrary, the above summary of the invention only provides an overview of some novel concepts and features set forth herein. From the following specific embodiments of the illustrated examples and representative modes for implementing the present disclosure in conjunction with the accompanying drawings and the appended claims, the above features and advantages of the present disclosure and other features and accompanying advantages will be apparent. In addition, the present disclosure explicitly includes any and all combinations and sub-combinations of the elements and features presented above and below. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 is a partially schematic side view of a representative motor vehicle having a rechargeable traction battery pack, a high voltage electrical system, and a SEM-based electrified powertrain with which aspects of the present disclosure may be implemented.

[0056] Figure 2 is a schematic single-line diagram illustrating a representative SEM drive system in which aspects of the present disclosure may be implemented.

[0057] Figure 3 is a cross-sectional side view illustration of a representative electric machine having winding slot embedded heat pipes and end cap integrated heat sink according to aspects of the present disclosure.

[0058] Figure 4 yes Figure 3 An end view illustration of a rotor assembly of a representative electric machine is shown with the rotor end cap removed to better view the winding slot embedded heat pipes embedded within the electromagnetic windings carried by the rotor.

[0059] The present disclosure may have various modifications and alternative forms, and some representative embodiments of the present disclosure are shown in the accompanying drawings by way of example and will be described in detail herein. However, it should be understood that the novel aspects of the present disclosure are not limited to the specific forms illustrated in the drawings listed above. On the contrary, the present disclosure covers all modifications, equivalents, combinations, permutations, groupings and substitutions that fall within the scope of the present disclosure, such as those covered by the appended claims. DETAILED DESCRIPTION

[0060] The present disclosure allows for embodiments in many different forms. Representative embodiments of the present disclosure are shown in the accompanying drawings and will be described in detail herein, wherein it should be understood that these embodiments are provided as examples of the disclosed principles, rather than limitations on the broad aspects of the present disclosure. In this regard, elements and limitations described in the abstract, technical field, background technology, content of the invention, illustrations, and specific implementation sections but not explicitly set forth in the claims should not be incorporated into the claims individually or collectively by implication, inference, or otherwise. In addition, the descriptions of "first", "second", "third", etc. in the specification or claims are not themselves used to establish continuous or numerical limitations; unless otherwise specifically stated, these names can be used to facilitate reference to similar features in the specification and drawings, and to distinguish between similar elements in the claims.

[0061] For purposes of this Detailed Description, unless specifically disclaimed: the singular encompasses the plural, and vice versa; the words "and" and "or" shall be both conjunctive and disjunctive; the words "any" and "all" shall mean "any and all"; and the words "include," "comprising," "containing," "having," and the like shall each mean "including but not limited to." In addition, approximate words, such as "approximately," "almost," "substantially," "generally," "approximately / roughly," and the like, may each be used herein to mean, for example, "at, approximately, or nearly at," or "within 0-5% of ...," or "within acceptable manufacturing tolerances," or any logical combination thereof. Finally, directional adjectives and adverbs, such as front, rear, inboard, outboard, starboard, port, vertical, horizontal, upward, downward, front, rear, left, right, and the like, may be used relative to a motor vehicle, such as relative to a forward driving direction of a motor vehicle when the vehicle is operatively oriented on a level driving surface.

[0062] Referring now to the drawings, wherein like reference numerals represent like features throughout the several views, Figure 1A representative motor vehicle is shown, generally designated 10, and for purposes of discussion is depicted herein as a sedan-type electric drive vehicle. The illustrated vehicle 10 (also referred to herein as a "motor vehicle" or simply "vehicle") is merely an exemplary application in which various aspects of the present disclosure may be practiced. Likewise, the inventive concept incorporated into a FEV powertrain powered by a single-pack RESS and a single traction motor should be understood as a non-limiting implementation of the disclosed features. Therefore, it should be understood that aspects and features of the present disclosure may be applied to other powertrain architectures, incorporated into any logically related type of motor vehicle, and similarly used in automotive and non-automotive applications. In addition, only selected components of the motor vehicle, SEM drive, and HV electrical system are shown and described in additional detail herein. However, the vehicles, SEMs, and electrical systems discussed below may include many additional and alternative features, as well as other available peripheral components, for performing the various methods and functions of the present disclosure.

[0063] Figure 1 A representative vehicle 10 is initially equipped with a central stack telecommunications and information ("telematics") unit 14 that communicates with a remotely located cloud computing host service 24 (e.g., ) wireless communications. As a non-limiting example, Figure 1 Other in-vehicle hardware components 16 shown include an electronic video display device 18, a microphone 28, audio speakers 30, and various user input controls 32 (e.g., buttons, knobs, switches, touch screens, etc.). These hardware components 16 serve as a human / machine interface (HMI) that enables a user to communicate with the telematics unit 14 and other components located in the vehicle 10 and other components remote from the vehicle. The microphone 28, for example, provides a means for a passenger to input verbal commands. In contrast, the speaker 30 provides audio output to vehicle occupants and may be a separate speaker dedicated to the telematics unit 14, or may be part of the audio system 22. The audio system 22 is operably connected to the network connection interface 34 and the audio bus 20 to receive analog information via one or more speaker components and present it as sound.

[0064] Communicatively coupled to the telematics unit 14 is a network connection interface 34, suitable examples of which include a twisted pair / fiber optic Ethernet switch, a parallel / serial communications bus, a local area network (LAN) interface, a controller area network (CAN) interface, and the like. The network connection interface 34 enables the vehicle hardware 16 to send and receive signals to and from each other and to and from systems and subsystems onboard and offboard the vehicle body 12. This allows the vehicle 10 to perform various vehicle functions, such as adjusting powertrain output, activating the vehicle braking system, controlling vehicle steering, regulating the charging and discharging of the vehicle battery, and other automated functions. For example, the telematics unit 14 can send and receive signals to or from a powertrain control module (PCM) 52, an onboard charging module (OBCM) 54, an electronic battery control module (EBCM) 56, a steering control module (SCM) 58, a brake system control module (BSCM) 60, and various other vehicle ECUs.

[0065] Continue to refer Figure 1 , the telematics unit 14 is an onboard computing device that provides hybrid services both alone and through its communication with other networked devices. The telematics unit 14 typically includes one or more processors 40, each of which may be implemented as a discrete microprocessor, an application specific integrated circuit (ASIC), or a dedicated control module. The vehicle 10 may provide centralized vehicle control through a central processing unit (CPU) 36, which is operably coupled to an IC real time clock (RTC) 42 and one or more electronic storage devices 38, each of which may take the form of a CD-ROM, a solid state drive (SSD) memory, a hard disk drive (HDD) memory, a semiconductor memory, etc.

[0066] Long range communication (LRC) capability with off-board devices may be provided via a cellular communication component, a navigation and positioning component (e.g., a global positioning system (GPS) transceiver), or a wireless modem (all of which are collectively indicated as 44). Unit), dedicated short-range communication (DSRC) component 48 and / or dual antenna 50 to provide short-range communication (SRC). It should be understood that the vehicle 10 can be implemented without one or more of the above components, or can optionally include additional components and functions required for a specific end use. The above communication devices can provide data exchange as part of a periodic broadcast in a vehicle-to-vehicle (V2V) communication system or a vehicle-to-everything (V2X) communication system.

[0067] The CPU 36 receives sensor data from one or more sensing devices that use, for example, light detection, radar, laser, ultrasonic, optical, infrared, or other suitable technologies, including, for example, short-range communication technologies (e.g., DSRC) or ultra-wideband (UWB) radio technologies for performing automatic vehicle operation or vehicle navigation services. According to the illustrated example, the automobile 10 may be equipped with one or more digital cameras 62, one or more distance sensors 64, one or more vehicle speed sensors 66, one or more vehicle dynamic sensors 68, and any necessary filtering, classification, fusion, and analysis hardware and software for processing the raw sensor data. The type, arrangement, number, and interoperability of the distributed array of on-board sensors can be adapted to a given vehicle platform, either individually or collectively, for achieving a desired level of autonomous vehicle operation.

[0068] To propel the motor vehicle 10 , the electrified powertrain is operable to generate and transmit tractive torque to one or more of the vehicle's drive wheels 26 . Figure 1 , represented by an electric traction motor 78 connected to a rechargeable energy storage system (RESS), which may be in the nature of a chassis-mounted traction battery pack 70. The battery pack 70 may include one or more battery modules 72, each of which houses a group of electrochemical cells 74, such as lithium-ion or lithium-polymer cells of the pouch, can, or prismatic type. One or more electric machines, such as adjustable-speed multi-phase SEM motor / generator (M) units 78, draw power from one or more rechargeable battery cells (e.g., traction battery pack 70), and optionally deliver power to the one or more rechargeable battery cells (e.g., traction battery pack 70). An HV electrical system having a power inverter 80 electrically connects the battery pack 70 to the motor / generator unit 78 and regulates the current transfer between them. The battery pack 70 may be configured so that module management, battery cell sensing, and module-to-host communication functions are directly integrated into each module 72 and are wirelessly performed via a wirelessly enabled battery cell monitoring unit (CMU) 76.

[0069] Then go to Figure 2 , which shows a non-limiting embodiment of a SEM drive system 200 that can be adapted to electrically connect and disconnect a rechargeable battery assembly 202 to a high voltage power source (e.g., a utility AC grid 201). Although different in appearance, it is contemplated that reference herein to Figure 1 The electric traction motor 78 and Figure 3 Any features and options described for the motor 310 may be incorporated individually or in any combination Figure 2 Although not limiting in itself, Figure 2The SEM drive system 200 may be represented by the following components: a rechargeable battery cell / assembly 202 , a power factor correction (PFC) device 204 , a traction inverter module (TIM) device 206 , a power transfer circuit (PTC) device 208 , and a separately excited motor (SEM) unit 210 .

[0070] The rechargeable battery assembly 202 may employ any of the battery options described herein, including one or more battery packs or one or more battery modules containing one or more rechargeable battery cells 212 (e.g., prismatic, pouch, or cylindrical lithium-ion battery cells). In addition, each battery assembly may include a set of solid-state relay contactors / switches (not shown) that independently respond to signals from an appropriate controller / control module to manage the electrical output of the battery system. Although for simplicity of illustration, Figure 2 Only one battery assembly 202 and one motor 210 are shown, but the SEM drive system 200 may include any number of battery units, motor units, and related electrical hardware without departing from the intended scope of the present invention.

[0071] The DC-AC and AC-DC power inverter 206, which may be part of a traction inverter module (TIM), is connected to the SEM unit 210 via multi-phase windings 214A, 214B, and 214C to transfer power between the SEM 210 and the battery assembly 202. Figure 2 In the embodiment of the present invention, the TIM device 206 (also referred to as an "inverter stage" or "inverter sub-circuit") is directly electrically connected and interposed between the PFC device 204 and the SEM unit 210. In the illustrated example, the TIM device 206 has no direct electrical connection to the rotor assembly 218 of the SEM unit 210. The DC battery output voltage is transmitted from the battery 202 to the TIM 206 and the PTC 208 through the positive voltage bus rail 220A and the negative voltage bus rail 220B, respectively, wherein an optional fixed-type DC bus capacitor 222 ( Figure 2 ) is placed between busbars 220A, 220B.

[0072] A representative power inverter topology may incorporate multiple inverters and corresponding motor control modules operable to receive motor control commands and thereby control inverter states to provide motor drive or regeneration functionality. Figure 2The TIM device 206 may include one or more pairs of electromechanical switches or semiconductor switches connected in series, which cooperatively convert DC power from one or more energy storage devices (e.g., battery assembly 202) into AC voltage to power one or more motors (e.g., SEM unit 210) via high-frequency switching. According to the illustrated example, the TIM device 206 includes six semiconductor switches S I1 , S I2 , S I3 , S I4 , S I5 and S I6 , which are arranged as three pairs of solid-state TIM switches 224A, 224B, and 224C connected in series. The three switch pairs 224A, 224B, and 224C may be electrically connected in parallel with each other. Each switch S I1 -S I6 It can be implemented as a voltage controlled bipolar switching device in the form of an insulated gate bipolar transistor (IGBT), a metal oxide semiconductor field effect transistor (MOSFET), a wideband GaN device (WBG), or other suitable switch having a corresponding gate to which a gate signal is applied to change the on / off state of a given switch.

[0073] Each pair of solid-state TIM switches 224A, 224B, and 224C may be electrically connected in series to a respective one of the field windings 214A, 214B, 214C carried by the stator of the SEM stator assembly 216. A power inverter, such as Figure 2 The TIM device 206 may use a fast controller-automatic switch control technique, such as a pulse width modulation (PWM) signal, to convert the DC power provided during the discharge of the battery cell 202 into AC power suitable for driving the SEM unit 210. A pre-charge circuit (not shown) may be used to charge the DC link capacitor 226 within the TIM device 206 at a controlled rate to equalize the voltage across the various switch pairs 224A-224C before closing the contactors / switches within the battery cell 202.

[0074] A multilevel PFC device 204 is selectively electrically connected to the power source 201 and, once connected, is interposed between the power source 201 and the rest of the SEM drive system 200 (i.e., the battery unit 202, the TIM 206, the PTC 208, and the SEM 210). The PFC device 204 (also referred to as a "PFC stage" or "PFC converter") provides power factor correction by shaping the input current, for example, to meet the current harmonic limits of the system 200. Figure 2In the example, the PFC device 204 is directly electrically connected and inserted between the power supply 201 and the TIM device 204. In the illustrated example, the PFC device 204 is located on the stator side circuit or the rotor side circuit of the SEM drive system 200, whichever side is opposite to the side of the battery unit 202. The PFC subcircuit can adopt a variety of different topological structures, including single-phase and multi-phase PFC structures, multi-level (2-level, 3-level...N-level) PFC structures, active and hybrid switching PFC structures, etc. Multi-phase PFC can be applied to, for example Figure 2 Application shown, where the PFC is located on the stator side of the SEM in line with the multi-phase windings of the motor.

[0075] The multi-stage PTC device 208 (also referred to as a “PTC stage” or “rotor excitation circuit”) is electrically connected on its output side to the rotor side of the SEM unit 210 and on its input side to both the battery unit 202 and the PFC device 204 . Figure 2 The PTC device 208 can provide single-phase rotor excitation functionality to the rotor assembly 218 of the SEM, for example, to optimize motor control and system charging. Figure 2 2, the PTC device 208 is directly electrically connected to and interposed between the battery cell 202 and the SEM rotor assembly 218. In the illustrated example, the PTC device 208 has no direct electrical connection to the stator assembly 216 of the SEM cell 210.

[0076] The externally excited motor unit 210 is interposed between the TIM 206 and the PTC 208 and is powered by the rechargeable battery assembly 202 to generate a motor output torque, for example, to enable Figure 1 The drive wheels 12 are rotated, thereby propelling the vehicle 10 or performing work in non-automotive SEM drive applications. Unlike multi-phase PM electric motors that rely on permanent magnets carried by the rotor, synchronous wound-field SEMs are typically represented by armature windings carried by the rotor that electromagnetically cooperate with field windings carried by the stator to convert electrical energy into mechanical energy. As shown, the SEM unit 210 includes a rotor assembly 218 that is coaxial with and rotatable relative to the stator assembly 216. For a radial flux inner rotor design, the stator assembly 216 includes an annular stator core 246 that carries a plurality of electromagnetic stator "field" windings (field windings) 214A-214C. In contrast, the rotor assembly 218 includes a cylindrical rotor core 248 that carries one or more electromagnetic rotor "armature" windings 234. In this example, rotor core 248 is rotatably mounted within the hollow center of stator core 246 such that stator assembly 216 surrounds rotor assembly 218 .

[0077] The field windings 214A-214C and the armature winding 234 are excited by the power provided by the battery assembly 202; once excited, the field windings 214A-214C carried by the stator are electromagnetically coupled with the armature winding 234 carried by the rotor and drive the armature winding (at Figure 2 216 and 218). The electromagnetic coupling is represented by the S-shaped parallel lines connecting the stator assembly 216 and the rotor assembly 218. The motor output member, which may be in the nature of a rotor shaft (not shown), may be fixedly attached to the rotor core 248 by splines, keys, bolts or other means to rotate in unison therewith and output motor torque therefrom. Although not limiting in themselves, the stator and rotor cores 246, 248 may be manufactured as laminated core constructions, each laminated core construction consisting of a stack of iron plates or other iron-containing plates. Although illustrated and described as a radial flux motor, the SEM unit 210 may employ axial flux and transverse flux architectures within the scope of the present invention.

[0078] Next go to Figure 3 , shows another example of an electric machine 310, which is represented as a radial flux inner rotor type separately excited motor unit, which is cooled by winding slot embedded heat pipes or steam chambers, end cover integrated heat sinks, and spray or splash ATM cooling. As described above, it is conceivable that with reference to Figure 1 The traction motor 78 and Figure 2 Any features and options described for the SEM unit 210 may be incorporated into the Figure 3 As some non-limiting similarities, Figure 3 The electric motor 310 is assembled with a protective and insulative housing 302 (e.g., a cast metal integrated electric drive unit (EDU) housing) that provides a mechanical interface for mounting to a system support structure (e.g., a body-on-frame or non-body-on-frame chassis). A multi-phase, field-wound (electromagnetic windings), and AC-fed stator assembly 316 is rigidly mounted within the housing 302, for example, via an axial clamping ring 308. Separated from the stator assembly 316 by an air gap is a single-phase, armature-wound (armature windings), and DC-fed rotor assembly 318, which is rotatably mounted within the housing 302, for example, via high-speed precision roller bearings 304. The rotor assembly 318 is securely mounted on a power transmission (motor or output) shaft 306, for example, by a key, spline, collar, hub, etc., to rotate in unison therewith. The shaft 306 is used to output torque generated by the electric motor 310 and / or receive input torque generated by an external source.

[0079] Similar to Figure 2 The stator assembly 216, Figure 3The stator assembly 316 is constructed of a flux permeable stacked laminated annular stator core 320 having a plurality of circumferentially spaced stator slots 321 that are radially aligned with and extend axially through the stator core 320. A corresponding set of electromagnetic "field" conductors 326 are wound through each axially elongated slot 321 of the stator core 320, which can be in the nature of hairpins, I-pins, D-pins, or flat bar copper conductors. Separating the radially innermost ends of the slots 321 are stator teeth that point toward the outer diameter (OD) periphery of the rotor assembly 318. The stator teeth direct the magnetic flux generated by the stator windings 326 through the air gap to electromagnetically link with the electromagnets carried by the rotor assembly 318 before completing the flux path back to the stator assembly 316. Similar to Figure 2 The rotor assembly 218, Figure 3 The rotor assembly 318 is constructed with a magnetically permeable, stacked, laminated cylindrical rotor core 322 having a plurality of circumferentially spaced rotor slots 323 radially recessed into and extending axially through the rotor core 322. The rotor core 322 is nested within and surrounded by the stator core 320 such that both cores 320, 322 are coaxial with the shaft 306. Wrapped through the axially elongated rotor slots 323 are electromagnetic "armature" conductors 328, which may be in the nature of single-filar or multi-filar winding components having solid or stranded copper coils.

[0080] In order to passively cool the rotor assembly 318 during operation of the electric machine 310, at least one heat pipe 340 is installed in one or more of the rotor slots 323 to extract thermal energy from the windings 328 carried by the rotor. According to the illustrated example, each rotor slot 323 is an open-facing, axially elongated channel that is recessed radially inward into the outer diameter surface of the rotor core 322 and in which a corresponding bundle of rotor windings 328 (e.g., a cluster of winding segments of a single-filar winding or a multi-filar winding) is securely nested. A single heat pipe 340 or a group of heat pipes 340' can be embedded in each rotor slot 323, embedded in the bundle of rotor windings 328 in that slot 232. For high-speed, high-torque applications, multiple heat pipes 340 (e.g., five in the figure) can be stacked one on top of another along a straight line extending radially relative to the rotor core 322, such as Figure 4 The overall height of the tube stack 340' may be substantially equal to the radial depth of the slot 323. When stacked in this manner, as shown in FIG. Figure 3 As best shown in FIG. 1 , the individual heat pipes 340 may be parallel to each other and radially spaced apart from each other. The linear heat pipe stacks 340' may be circumferentially spaced apart around the rotor core 322, i.e., positioned equidistant from each other, with each stack 340' oriented at an oblique angle (e.g., approximately 45 degrees) relative to its immediately adjacent stack 340'.

[0081] Although shown and described herein as using slot embedded heat pipes, Figure 3 The motor 300 may replace any or all of the heat pipes 340 with a thermal energy dissipating steam chamber. For example, a single planar steam chamber may replace each stack 340' of heat pipes 340 within a given rotor slot 323. As another option, the slot-embedded heat pipes and steam chambers described herein may be adapted to be integrated into one or more of the stator slots 321 to passively cool the stator assembly 316. It is also contemplated that the rotor assembly 318 may include more or fewer heat pipes 340, which may take alternative shapes, sizes, and packaging locations that differ from the illustrated construction. The disclosed rotor-mounted heat pipes and steam chambers are closed, passive thermal management devices that do not interact with or interfere with the stator, and therefore reduce system complexity while ensuring that rotor operating speeds, inertial mass, and structural integrity are maintained for high-speed operation.

[0082] For higher speed operation, the heat pipes 340 may be encapsulated within optional slot wedge jackets 334 that help hold the rotor windings 328 in place during energization of the rotor assembly 318. It may be desirable to manufacture each slot wedge jacket 334 as a one-piece unitary structure from a thermally conductive polymer (e.g., high density polyethylene (HDPE) or aromatic polyimide) that is wrapped around or overmolded onto a respective stack 340' of heat pipes 340. In addition to helping maintain winding placement, the slot wedge jackets 334 may also preclude direct physical contact between the electromagnetic windings 328 and the heat pipes 340 (e.g., to prevent damage to the winding insulation).

[0083] Each heat pipe 340 protrudes axially from one or both opposing axial ends of the rotor core 322, thereby extracting heat energy generated by the adjacent rotor windings 328 and transferring the extracted heat energy away from the rotor core 328. The heat pipes 340 effectively act as thermodynamic conduits that interface the slot-embedded windings 328 with the convection-cooled rotor end caps 350, 352 and the conductively-cooled dielectric fluid 332 that circulates through the internal coolant chamber of the housing 302. Figure 4 As best seen in the illustration of FIG. 1 , each heat pipe 340 can be constructed with a hermetically sealed and thermally conductive can 342, which can be manufactured as a rigid hollow tube formed of copper or aluminum. The heat pipe can 342 contains a working fluid (in Figure 4 The working fluid may be a refrigerant (represented by arrow 344), such as water, acetone, methanol, ammonia, or a mixture of water and refrigerant, which converts thermal energy (heat) into mechanical energy (and vice versa) by changing phase between liquid 344' and gas 344".

[0084] The working fluid flows freely through five different sections along the length of the tank 342: a central "evaporator" section S 1E ; In the evaporator section S1E A pair of (first and second) "insulating" sections S on the left and right end sides 2A and S 3A ; and in the "insulation" section S 2A and S 3A The outer pair (first and second) of "condensation" sections S 4C and S 5C Enclosed within the tank 342 is a fluid wicking (wick) structure 346 that draws the liquid phase working fluid 344' from the condensing section S at the axial end of the tank 342, for example, via capillary action. 4C and S 5C The evaporator section S transported to the center of the tank 342 1E The wick structure 346 can take a variety of form factors, including fine fiber rovings, wound fabrics, entangled wires, meshes, sintered powder cores, etc. As shown, the wick structure 346 presses against and (if necessary) substantially covers the inner surface of the tank 342. An elongated vapor passage 347 extends through the center of the tank 342 and the wick structure 346, which allows the vapor phase working fluid 344" to be discharged from the evaporator section S 1E Through the insulation section S 2A and S 3A And reaches the condensation section S 4C and S 5C . When the working fluid 344 condenses, the vapor channel 347 allows the working fluid 344' to be transferred to the wick structure 346 when it condenses into a liquid. For ease of manufacturing and simplicity of design, it may be desirable that all of the slot-embedded heat pipes 340 are substantially identical in structure to one another. In addition, each heat pipe 340 can be a fluid-tight, discrete unit that lacks, for example, a fluid port for exchanging fluid with an internal coolant chamber of the housing 302.

[0085] During operation of the motor 310, the rotor windings 328 will generate a significant amount of heat, especially during high speed operation (e.g., 10,000+RPM). A portion of this winding generated heat will be transferred through the sealed can 342 and into the core structure 346 of the heat pipe 340. The thermal energy from this heat tends to be concentrated at the axial center of the harness; the thermal energy is conducted through the central region of the heat pipe can 342 (i.e., the central "evaporator" section S 1E ), thereby causing a portion of the working fluid 344 sealed in the tank 342 to evaporate. When the working fluid 344 is evaporated by the heat generated by the absorption device, the wick structure 346 is used to transfer the gas phase fluid 344" into the vapor channel 347. The gas phase working fluid 344" moves axially outward, for example, to Figure 4 The left and right sides of the condensation section S 4C and S 5CThe liquid phase fluid 344′ is pulled inwardly by capillary forces and reaches the evaporator section S through the wick structure 346. 1E to restart the cycle.

[0086] To help dissipate the thermal energy exhausted from the rotor core 322 via the heat pipes 340, a pair of (first and second) rotor end caps 350 and 352 are respectively securely mounted to the opposing (first and second) axial faces of the rotor core 322 in abutting relation with the opposing (first and second) longitudinal ends of the heat pipes 340. It may be desirable for each rotor end cap 350, 352 to be fabricated with circumferentially spaced sets of heat pipe cavities 351 and 353 (e.g., one cavity per heat pipe) that interface with the rotor-borne stack 340' of heat pipes 340. Each cavity 351, 353 may be recessed into the axially inward surface of the rotor end caps 350, 352 and nest the longitudinal tip of the corresponding heat pipe 340 therein. These cavities 351, 353 increase the contact surface area between the end caps 350, 352 and the heat pipes 340, thereby increasing the rate of conductive heat transfer between the interfacing structures. In addition to helping to minimize windage losses and ensuring that the windings 328 are supported for high speed machine operation, the end caps 350, 352 also act as heat sinks.

[0087] Each rotor cap 350, 352 may be manufactured with a respective set of cap fins 354 and 356 to help dissipate accumulated heat from the caps 350, 352, and thus from the rotor assembly 318, into the internal coolant chamber of the housing 302. Located on the outboard-facing surfaces of the rotor caps 350, 352, these cap fins 354, 356 project axially away from the rotor core 322 and into the internal coolant chamber of the housing. The pin fins 354, 356 increase the total surface area of ​​the rotor assembly 318 exposed within the housing 302 to increase the dissipation of the extracted thermal energy received by the rotor caps 350, 352, for example, via convection and, if desired, conductive heat transfer.

[0088] To help remove the heat energy generated by the windings from the machine housing 302, an active thermal management (ATM) system (in Figure 3The dielectric coolant fluid 332 is circulated in and out of the housing 302 (represented by an oil pump 360 in FIG. 1 ) to splash cool or spray cool the rotor end caps 350, 352 and the end cap fins 354, 356. The coolant fluid 332 may be a non-conductive, magnetically inactive oil that is sprayed, for example, via spray nozzles in the stator end caps 360 and 362 onto the stator windings 326 and the rotor end caps 350, 352 to accelerate the effect of dissipating heat from the rotor field windings. The spraying / splashing of the coolant fluid 332 provides immersion-type conductive heat transfer in addition to the enhanced convective cooling provided by the rotor end caps 350, 352 and the end cap fins 354, 356. The spray / splash cooling for the rotor assembly 318 may also be directed to the stator assembly 316 to further improve the peak performance of the motor 310. For splash cooling embodiments, it may be desirable that a set of rotor pin fins be arranged in a spiral turbine-like pattern to energize coolant fluid 332 and thereby create a desired splash effect during energization of rotor assembly 318 .

[0089] Various aspects of the present disclosure have been described in detail with reference to the illustrated embodiments; however, those skilled in the art will recognize that many modifications may be made thereto without departing from the scope of the present disclosure. The present disclosure is not limited to the precise configuration and composition disclosed herein; any and all modifications, changes and variations apparent from the above description are within the scope of the present disclosure as defined by the appended claims. Furthermore, the concepts of the present invention expressly include any and all combinations and sub-combinations of the aforementioned elements and features.

Claims

1. A motor, comprising: case; a stator assembly comprising a stator core attached to the housing and electromagnetic stator windings mounted in stator slots of the stator core; a rotor assembly including a rotor core rotatably attached to the housing adjacent the stator assembly and an electromagnetic rotor winding mounted in rotor slots of the rotor core and configured to magnetically cooperate with the stator winding; as well as A heat pipe is mounted in the rotor slot adjacent to the rotor winding and protrudes axially from an axial end of the rotor core, the heat pipe being configured to passively extract thermal energy from the rotor winding and transfer the thermal energy away from the rotor core.

2. The motor according to claim 1, wherein: The rotor winding includes a rotor winding bundle installed in the rotor slot, and the heat pipe includes a plurality of heat pipes installed in the rotor slot and embedded in the rotor winding bundle.

3. The motor according to claim 2, wherein: The heat pipes are stacked along a straight line extending radially relative to the rotor core.

4. The motor according to claim 3, wherein: The heat pipes are parallel to each other and radially spaced apart from each other.

5. The motor according to claim 1, wherein: The heat pipe includes a sealed can containing a working fluid configured to change phase between a liquid phase and a gas phase to extract thermal energy from the rotor windings and transfer the extracted thermal energy out through an axial end of the rotor core.

6. The motor according to claim 5, wherein: The heat pipe further includes a wick structure located within the sealed can and configured to transfer the working fluid from an axial end of the sealed can to a central region of the sealed can when the working fluid is in a liquid phase.

7. The motor according to claim 6, wherein: The core structure is adjacent to the inner surface of the sealed can and defines an elongated central steam channel, which is configured to allow the working fluid to reach the axial end of the sealed can through the steam channel when evaporating into the gas phase and to allow the working fluid to enter the core structure when condensing into the liquid phase.

8. The electric machine of claim 1, further comprising a rotor end cap attached to an axial end of the rotor core and adjacent to a longitudinal end of the heat pipe to receive the extracted heat energy transferred from the rotor core from the longitudinal end.

9. The electric machine according to claim 8, wherein: The rotor cover includes a heat pipe cavity recessed into an axial surface of the rotor cover and nesting the longitudinal ends of the heat pipes therein.

10. The electric machine according to claim 8, wherein: The rotor cap includes a plurality of cap fins that protrude away from the rotor core and are configured to dissipate extracted thermal energy transferred from the rotor core and received by the rotor cap.

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