Steam chambers and heat pipes with end cap heat sinks mounted on a rotor shaft for an electric machine

Abstract

This paper presents electric machines with heat pipes / steam chambers attached to the rotor shaft, which are thermally coupled to heat sinks integrated in an end cap, methods for manufacturing / using such machines, and vehicles equipped with such machines. An electric machine comprises an outer casing, a stator assembly attached to the casing, and a rotor assembly rotatably mounted alongside the stator assembly. The stator assembly comprises one or more stator windings attached to an annular stator core. The rotor assembly comprises one or more electromagnetic rotor windings attached to a cylindrical rotor core. A rotor power transmission circuit (rotor PTC) is electrically connected to the rotor assembly to electrify the rotor winding(s). A rotor shaft is attached to the rotor core and rotates in step with it.One or more heat pipes are attached to the outer surface of the rotor shaft and protrude axially between the rotor PTC and the rotor core. Each heat pipe passively extracts thermal energy from the rotor PTC and transfers it.

Description

Technical area

[0001] The present disclosure relates generally to electric machines. More specifically, aspects of this disclosure relate to thermal management systems for regulating the operating temperatures of separately excited motor (SEM) assemblies. introduction

[0002] Today's production vehicles, such as the modern automobile, are originally equipped with a powertrain that propels the vehicle and supplies the vehicle's on-board electronics. In motor vehicles, for example, the powertrain typically consists of a prime mover that transmits drive torque to the vehicle's drive system (e.g., differential, axle shafts, cam modules, wheels, etc.) via an automatic or manual transmission. Historically, motor vehicles were powered by a reciprocating internal combustion engine (ICE) due to their ready availability, relative light weight, and overall efficiency. These engines include compression-ignition (CI) diesel engines, spark-ignition (SI) gasoline engines, two-, four-, and six-stroke engines, and rotary engines, to name a few.Hybrid electric and fully electric vehicles (collectively referred to as “electric propulsion vehicles”), on the other hand, use alternative energy sources to power the vehicle, thus minimizing or eliminating dependence on a fossil fuel-based engine for traction power.

[0003] A fully electric vehicle (FEV)—colloquially referred to as an "electric car"—is an electric-powered vehicle configuration that completely eliminates the internal combustion engine and its peripheral powertrain components, instead using a rechargeable energy storage system (RESS) and a traction motor for vehicle propulsion. The engine assembly, fuel supply system, and exhaust system of an internal combustion engine vehicle are replaced in a battery-assisted FEV by one or more traction motors, rechargeable battery cells, and cooling and charging devices.

[0004] Hybrid electric vehicle (HEV) powertrains, on the other hand, utilize multiple traction sources to propel the vehicle, typically operating an internal combustion engine in conjunction with a battery- or fuel-cell-powered traction motor. Because electric vehicles are capable of drawing power from sources other than the engine, HEV engines can be fully or partially shut down while the vehicle is propelled by the electric motor(s). Description of the invention

[0005] A traction motor is an electrical machine that converts electrical energy into rotational mechanical energy to propel a vehicle, such as FEV and HEV automobiles. Many traction motors contain a fixed stator carrying multi-phase electromagnetic windings, such as copper hairpin or I-pin rods, and a rotatable rotor carrying a specialized pattern of magnets, such as core-mounted permanent magnets (PM) 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, radial flux or axial flux. In radial flux inner rotor designs, the rotor may be coaxially nested within the stator, while in axial flux rotary designs, the rotor and stator may be side by side as opposing, coaxial plates.The rotational excitation of the rotor assembly can be provided by a magnetic field generated by the current flow through multi-phase AC stator windings; this magnetic field emitted by the stator interacts with a counter magnetic field generated by permanent magnets or DC armature coils located in the rotor.

[0006] The rotor assemblies of many modern traction motors include a rotor core constructed from thin ferromagnetic discs stacked and laminated together to form a cylindrical body. Each rotor disc has multiple openings that, when aligned with the openings of adjacent discs, form rotor slots extending axially along the length of the rotor core. Permanent magnet or electrically excited magnetic elements, such as PM bars or copper coils, are inserted into these rotor slots and secured to the rotor core. Unlike permanent magnet motors, in which the rotor assembly supports internal or surface-mounted magnets, a separately excited motor (SEM) is generally characterized by armature windings in the rotor that interact electromagnetically with field windings in the stator to convert electrical energy into mechanical energy.The rotor core may be mounted on a motor shaft to deliver the drive-generating motor torque generated by the motor or to input the power-generating regenerative torque received from the motor.

[0007] During operation of a traction motor, the internal electrical and electromagnetic hardware can generate a significant amount of heat, for example, due to winding, friction, and hysteresis losses. An integrated motor cooling system can be employed to prevent undesirable overheating conditions within the motor. Active thermal management (ATM) systems, for example, use a central controller or dedicated control module to regulate the operation of a cooling circuit that circulates coolant through heat-generating engine components. Indirect liquid cooling systems, a heat-transferring coolant circulates through a network of internal channels and tubes within the motor casing. In contrast, direct liquid cooling—or "liquid immersion cooling" (LIC)—involves splashing, spraying, or immersing parts of the motor with a dielectric coolant that has a direct conduction.

[0008] Presented herein are electric machines having rotor shaft-mounted heat pipes and / or vapor chambers thermally coupled to heat sinks integrated into an end cap, methods of manufacturing and operating such machines, and vehicles equipped with such machines. As a non-limiting example, a novel separately excited motor design removes heat from the rotor power transfer circuit (rotor PTC) by attaching heat pipes and / or vapor chambers to the rotor shaft. The removed heat may be transferred axially from the PTC pack toward a longitudinal end of the rotor core and conducted into the larger heat sink of a rotor end cap. The rotor end cap may be equipped with fins that dissipate the transferred heat into an internal coolant volume of the drive unit (DU) housing.Spray or splash cooling can be used to remove heat from the pin fins while simultaneously removing thermal energy from the DU housing. A circular array of circumferentially spaced heat pipes / vapor chambers can be partially embedded in a polymer coating on the outer surface of the rotor shaft. Axially projecting pin fins can be molded onto an axial surface of the rotor end cap to transfer heat to the DU housing volume. End cap spray cooling and / or splash cooling can be used to increase the thermal conductivity of the end cap, thus facilitating heat removal from the PTC components.

[0009] Related benefits of at least some disclosed concepts include SEM architectures with reduced operating temperatures (e.g., at worst-case operating points (WCOP)), resulting in improved engine efficiency and extended engine performance limits (i.e., compared to comparable IPM designs). Unlike complex wave-fed ATM cooling concepts, which add significant cost, complexity, and failure points to the system, the disclosed SEM concepts utilize sealed heat pipes / vapor chambers and end-cap heat sinks to quickly and efficiently dissipate heat from selected engine components. Additional benefits include SEM systems eliminating the need for rare earth (RE) and heavy rare earth (HRE) elements, which can be vulnerable to price fluctuations and raw material shortages.Unlike many conventional SEM solutions that operate at lower peak currents and limit peak operating speeds to reduce motor temperatures, the disclosed SEM systems utilize both active and passive cooling features to dissipate heat and thus extend the peak performance limits of the SEM.

[0010] Aspects of this disclosure relate to rotor shaft-mounted vapor chambers and / or heat pipes for cooling the electrical PTC packages of electrical machines such as motors, generators, transformers, reactors, dynamometers, inverters, etc. In one example, an electric machine includes a protective outer casing, a stator assembly fixedly connected to the casing, and a rotor assembly rotatably mounted to the casing 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 mounted in the stator slot(s). Similarly, the rotor assembly includes a rotor core having at least one rotor slot and at least one electromagnetic rotor winding mounted in the rotor slot(s). A rotor power transfer circuit is mounted to the machine casing, e.g.,axially spaced from the rotor core and housed in a separate PTC compartment. The PTC is electrically connected to the rotor assembly, e.g., via the rotor shaft, to electrify the rotor winding(s) via a DC input. A rotor shaft is rigidly connected to the rotor core, e.g., via a key, spline, or hub, and rotates in unison with the core. At least one heat pipe is attached to an outer surface of the rotor shaft and projects axially along the shaft between the rotor PTC and the rotor core. Each heat pipe passively extracts heat energy from the rotor PTC and dissipates the extracted heat energy from the rotor PTC.

[0011] Further aspects of this disclosure relate to electric vehicles powered by SEM-type traction motors cooled by rotor shaft-mounted vapor 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 semi-autonomous vehicles, etc.), commercial vehicles, industrial vehicles, tracked vehicles, off-road and all-terrain vehicles, motorcycles, agricultural equipment, watercraft, aircraft, e-bikes, etc. In one example, a motor vehicle includes a vehicle body having a passenger compartment, a plurality of wheels attached to the vehicle body (e.g., via corner modules coupled to a unibody or body-on-frame chassis), and other standard original equipment.In electric vehicles, the vehicle is equipped with a rechargeable energy storage system (RESS) (e.g., a traction battery pack) that powers an electrified powertrain. The powertrain uses one or more SEM-type traction motor / generators (MGUs) that drive one or more wheels, either alone (e.g., in FEV powertrains) or in conjunction with an internal combustion engine (e.g., in HEV powertrains), to propel the vehicle.

[0012] Continuing the previous discussion, the traction motor includes a protective and insulated motor housing, a stator assembly fixedly mounted within the motor housing, and a rotor assembly rotatably mounted within 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. Conversely, the rotor assembly includes a cylindrical rotor core located within and circumscribed 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 rotor PTC is mounted within the motor housing, e.g., axially spaced from the rotor core and circumscribing the rotor shaft.The rotor PTC is electrically connected to the rotor assembly to selectively electrify the rotor windings. A rotor shaft circumscribes the rotor core and is connected to it for rotation in unison. Multiple heat pipes are attached to an outer surface of the rotor shaft and spaced circumferentially around it. Each heat pipe passively extracts heat energy from the rotor PTC and transfers the extracted heat energy out of the rotor PTC.

[0013] Aspects of this disclosure also relate to manufacturing workflows, computer-readable media, and control logic for manufacturing or using any of the disclosed PTC cooling systems, electric machines, and / or motor vehicles. In one example, a method of assembling an electric machine is presented. This representative method includes, in any order and in any combination with any of the options and features disclosed above and below, receiving a housing of the electric machine; attaching a stator assembly to the housing, the stator assembly including a stator core and an electromagnetic stator winding attached to the stator core;attaching a rotor assembly to the housing such that the rotor assembly is adjacent to and rotatable with respect to the stator assembly, the rotor assembly comprising a rotor core and an electromagnetic rotor winding attached to the rotor core; attaching a rotor power transfer circuit to the housing such that the rotor PTC is axially spaced from the rotor core and electrically connected to the rotor assembly to electrify the rotor winding; attaching a rotor shaft to the rotor core so that it rotates therewith; and attaching a heat pipe to an outer surface of the rotor shaft such that the heat pipe extends axially between the rotor PTC and the rotor core, the heat pipe being configured to passively extract thermal energy from the rotor PTC and to exhaust the thermal energy from the rotor PTC.

[0014] In all of the disclosed vehicles, methods, and electrical machines, the integrated thermal management system may utilize a single heat pipe or multiple heat pipes mounted on the outer surface of the rotor shaft and spaced circumferentially around the rotor shaft. Each heat pipe may be flush with the outer surface of the rotor shaft and substantially parallel to the rotor shaft. It is also contemplated that the rotor shaft may be provided with axially elongated slots recessed into the surface into which the heat pipes may be inserted. Alternatively, the entire heat pipe may be radially spaced from the rotor shaft, or one end of the heat pipe may be radially spaced from the rotor shaft and another end of the heat pipe may bear against the rotor shaft. The heat pipes may be parallel to each other and to the rotor shaft and, if desired, may be equidistant from each other around the rotor shaft.One or more of the heat pipes can be replaced by a flat or curved steam chamber.

[0015] In all of the disclosed vehicles, methods, and electrical machines, the outer surface of the rotor shaft may be fully or partially coated with a polymeric surface coating. It may be desirable for the surface coating to be formed as a one-piece, unitary structure from an electrically insulating thermoplastic polymer. In this case, each heat pipe is at least partially embedded in the polymeric surface coating. To improve thermal coupling between the PTC and tubes, a thermal interface material (TIM) may be inserted between and adjacent to the heat pipes and the rotor PTC. The TIM layer electrically isolates the PTC electrical components from the heat pipes. The rotor PTC contains multiple electrical components that enclose the rotor shaft.In this case, the heat pipes can extend through central cavities of the PTC and be thermally coupled to one or more electrical components of the PTC. In a contact-based rotor PTC, the PTC components can include a pair of (first and second) electric brushes, each coupled to a pair of (first and second) slip rings; in this case, the heat pipes can contact the slip rings. In a non-contact PTC, the components can include rectifiers, rectifier printed circuit boards (PCBs), electromagnetic couplings, matching capacitive plates, etc.

[0016] In all of the disclosed vehicles, methods, and electrical machines, each heat pipe may include a sealed, heat-conducting container (e.g., a copper or aluminum tube) containing a working fluid (e.g., water, acetone, methanol, or ammonia). The working fluid changes phases between liquid and gas to remove heat from the rotor PTC and conduct the removed heat outward through one or both axial ends of the PTC pack. A wick structure (e.g., a grooved, sintered, or screen-like wick) is located within the heat pipe container, which bears against, and if desired, covers, an interior surface of the container. The wick structure transports the liquid working fluid, e.g., by capillary action, to a proximal (first) axial end of the container. An elongated vapor channel may extend longitudinally through the center of the wick structure.The vapor channel directs the working fluid, when it has evaporated into a gas, to a distal (second) axial end of the sealed container; when the working fluid condenses into a liquid, the vapor channel directs the fluid into the wick structure.

[0017] In all of the disclosed vehicles, methods, and electrical machines, a left-hand (first) rotor end cap may be attached to one axial end of the rotor core and a right-hand (second) rotor end cap may be attached to the opposite axial end of the rotor core. A rotor end cap may abut a longitudinal end of the heat pipe(s) to capture the thermal energy extracted from the rotor PTC. The rotor end cap may be an annular, plate-like structure containing one or more heat pipe cavities, each of which is recessed into a radially inner surface of the rotor end cap and mates with the longitudinal end of the heat pipe. The rotor end cap may be fabricated with a set of end cap fins projecting axially from the rotor core; these end cap fins dissipate the extracted thermal energy transferred from the rotor PTC and captured by the rotor end cap.An optional active thermal management system can inject or spray a dielectric cooling fluid onto the end cap fins and, if desired, pump the heated cooling fluid away from the rotor assembly.

[0018] The above summary does not represent every embodiment or aspect of the present disclosure. Rather, the above summary merely provides an overview of some of the novel concepts and features set forth herein. The above features and advantages, as well as other features and related advantages of this disclosure, will be readily apparent from the following detailed description of illustrated examples and representative modes for carrying out the disclosure when considered in conjunction with the accompanying drawings and appended claims. Furthermore, this disclosure expressly includes all combinations and subcombinations of the elements and features set forth above and below. Brief description of the drawings Fig. 1 is a partially schematic side view of a representative motor vehicle having a rechargeable traction battery pack, a high voltage electrical system, and an SEM-based electrified powertrain with which aspects of this disclosure may be practiced. Fig. Figure 2 is a single-line schematic diagram showing a representative SEM drive system with which aspects of this disclosure may be practiced. Fig. 3 is a side cross-sectional view of a representative electric machine having rotor shaft mounted heat pipes and end cap integrated heat sinks for removing heat from a contact (brush) rotor PTC in accordance with aspects of the present disclosure. Fig. 4 is a side cross-sectional view of another representative electric machine having rotor shaft mounted heat pipes and end cap integrated heat sinks for heat removal from a non-contact (inductive) rotor PTC in accordance with aspects of the present disclosure. Fig. 5 is a side cross-sectional view of another representative electric machine having rotor shaft mounted heat pipes and end cap integrated heat sinks for heat dissipation from another non-contact (capacitive) rotor PTC in accordance with aspects of the present disclosure.

[0019] The present disclosure is susceptible to various modifications and alternative forms, and some representative embodiments of the disclosure are illustrated by way of example in the drawings and will be described in detail herein. It should be understood, however, that the novel aspects of this disclosure are not limited to the particular forms illustrated in the drawings enumerated above. Rather, this disclosure encompasses all modifications, equivalents, combinations, permutations, groupings, and alternatives falling within the scope of this disclosure, such as those encompassed by the appended claims. Detailed description

[0020] This disclosure may be embodied in many different forms. Representative embodiments of the disclosure are illustrated in the drawings and are described in detail herein, it being understood that these embodiments serve as examples of the disclosed principles and not as limitations on the general aspects of the disclosure. As such, elements and limitations described in, for example, the "Summary," "Introduction," "Description of the Invention," "Brief Description of the Drawings," and "Detailed Description" sections, but not expressly set forth in the claims, should not be construed as being incorporated into the claims, individually or collectively, by implication, inference, or otherwise. Furthermore, the mention of "first," "second," "third," etc.in the description or claims do not, per se, imply any serial or numerical limitation; unless expressly stated otherwise, these designations may be used to facilitate reference to similar features in the description and drawings and to distinguish between similar elements in the claims.

[0021] For the purposes of this detailed description, unless expressly excluded: the singular includes the plural and vice versa; the words "and" and "or" are both conjunctive and disjunctive; the words "each" and "all" mean "each and all"; and the words "including," "including," "comprising," "with," and the like each mean "including without limitation." In addition, words of approximation such as "approximately," "almost," "substantially," "generally," "nearly," and the like may be used herein to mean, for example, "at, near, or almost at," or "within 0-5% of," or "within acceptable manufacturing tolerances," or any logical combination thereof. Finally, directional adjectives and adverbs such as “forward”, “backward”, “inward”, “outward”, “starboard”, “port”, “vertical”, “horizontal”, “upward”, “downward”, “front”, “back”, “left”, “right”, etc.refer to a motor vehicle, e.g. to the forward direction of travel of a motor vehicle when the vehicle is operated on a horizontal driving surface.

[0022] With reference to the drawings, in which like reference numerals refer to like features in the several views, Fig. 1, a representative motor vehicle is illustrated, generally designated 10, and shown here for purposes of discussion as an electric sedan. The illustrated motor vehicle 10—also referred to herein for short as a "motor vehicle" or "vehicle"—is merely an exemplary application with which aspects of this disclosure may be practiced. Likewise, the incorporation of the present concepts into an FEV powertrain powered by a single RESS package and a single SEM traction motor should be understood as a non-limiting implementation of the disclosed features. It should be understood that aspects and features of this disclosure may be applied to other powertrain architectures, incorporated into any logically relevant motor vehicle type, and utilized for both automotive and non-automotive applications.Furthermore, only selected components of the motor vehicles, SEM drives, and HV electrical systems are shown and described in detail herein. Nevertheless, the vehicles, SEMs, and electrical systems discussed below may include numerous additional and alternative features and other available peripheral components to perform the various methods and functions of this disclosure.

[0023] The representative vehicle 10 of Fig. 1 is originally equipped with a central telecommunications and information unit 14 (“telematics”) that communicates wirelessly, e.g., via cell towers, satellite services, etc., with a remote cloud computing host service 24 (e.g., OnStar®). Fig. 1 include, by way of non-limiting examples, an electronic video display device 18, a microphone 28, audio speakers 30, and various user input controls 32 (e.g., buttons, knobs, switches, touchscreens, etc.). These hardware components 16 function as a human-machine interface (HMI), allowing the user to communicate with the telematics unit 14 and other components located both within and remote from the vehicle 10. For example, the microphone 28 allows occupants to input verbal commands. Conversely, the speakers 30 provide audible signals to the vehicle occupants and may be either a standalone speaker for the telematics unit 14 or part of an audio system 22.The audio system 22 is operatively connected to a network connection interface 34 and an audio bus 20 to receive analog information and reproduce it as sound through one or more speaker components.

[0024] The network connection interface 34 is communicatively coupled to the telematics unit 14. Suitable examples include twisted pair / fiber optic Ethernet switches, parallel / serial communication buses, local area network (LAN) interfaces, controller area network (CAN) interfaces, and the like. The network connection interface 34 enables the vehicle hardware 16 to send and receive signals with each other and with systems and subsystems both onboard and external to the vehicle body 12. This enables the vehicle 10 to perform various vehicle functions, such as modulating driveline power, activating a vehicle braking system, controlling the vehicle steering, regulating the charging and discharging of the vehicle batteries, and other automated functions.For example, the telematics unit 14 may receive and transmit signals from / to 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 braking system control module (BSCM) 60, and various other vehicle ECUs.

[0025] With further reference to Fig. 1, the telematics unit 14 is an in-vehicle computing device that provides a mix of services both individually and through its communication with other networked devices. This telematics unit 14 generally consists of one or more processors 40, each of which may be embodied as a discrete microprocessor, an application-specific integrated circuit (ASIC), or a dedicated control module. The vehicle 10 may provide centralized vehicle control via a central processing unit (CPU) 36 operatively 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, solid-state drive (SSD), hard disk drive (HDD), semiconductor memory, etc.

[0026] Long-range communication (LRC) capabilities with devices external to the vehicle may be provided via a cellular communication component, a navigation and location component (e.g., GPS transceiver), or a wireless modem, all shown collectively at 44. Short-range communication (SRC) may be provided via a short-range wireless communication device 46 (e.g., a Bluetooth® unit), a dedicated short-range communication (DSRC) component 48, and / or a dual antenna 50. It should be understood that the vehicle 10 may be implemented without one or more of the components listed above or may optionally include additional components and functionality as desired for a particular end application.The communication devices described above may provide data exchange as part of a periodic broadcast in a vehicle-to-vehicle (V2V) or vehicle-to-everything (V2X) communication system.

[0027] The CPU 36 receives sensor data from one or more sensing devices using, for example, photodetection, radar, laser, ultrasound, optics, infrared, or other suitable technologies, including short-range communication technologies (e.g., DSRC) or ultra-wide-band (UWB) radio technologies, to perform, for example, automated vehicle operation or a vehicle navigation service. According to the example shown, the vehicle 10 may be equipped with one or more digital cameras 62, one or more range sensors 64, one or more vehicle speed sensors 66, one or more vehicle dynamics sensors 68, and the necessary filtering, classification, fusion, and analysis hardware and software for processing raw sensor data.The type, placement, number, and interoperability of the distributed array of vehicle sensors can be tailored individually or collectively to a specific vehicle platform to achieve a desired level of autonomous vehicle operation.

[0028] To drive the motor vehicle 10, an electrified drive train can generate a traction torque and deliver it to one or more of the drive wheels 26 of the vehicle. The drive train is Fig. 1 by an electric traction motor 78 connected to a rechargeable energy storage system (RESS), which may be in the form of a chassis-mounted traction battery pack 70. The traction battery pack 70 may include one or more battery modules 72, each housing a group of electrochemical battery cells 74, such as lithium-ion or lithium polymer battery cells of the pouch, can, or prismatic type. One or more electric machines, such as a variable-speed, multi-phase SEM motor / generator (M) unit 78, receive electrical energy from, and optionally supply electrical energy to, one or more rechargeable battery units, such as the traction battery pack 70.A high-voltage electrical system with a power inverter module (PIM) 80 electrically connects the battery pack 70 to the motor / generator unit(s) 78 and modulates the transfer of electrical power between these units. The battery pack 70 can be configured so that the functions for module management, cell sensing, and module-to-host communication are integrated directly into each module 72 and are performed wirelessly via a wireless cell monitoring unit (CMU) 76.

[0029] In Fig. 2 illustrates a non-limiting example of an SEM drive system 200 suitable for electrically connecting and disconnecting a rechargeable battery assembly 202 to a high-voltage electrical source, such as an AC mains 201. Although different in appearance, it is intended that all features and options described herein relating to the traction motor of Fig. 1 and the electrical machines of the Fig. 3-5 individually or in any combination into the SEM drive system of Fig. 2 and vice versa. The SEM drive system 200 from Fig. 2, although not limited per se, may be characterized by a rechargeable battery assembly 202, a power factor correction (PFC) device 204, a traction inverter module (TIM) device 206, a power transfer circuit (PTC) 208, and a separately excited motor (SEM) unit 210.

[0030] The rechargeable battery assembly 202 may adopt any of the battery options described herein, including one or more battery packs or one or more battery modules, each containing one or more rechargeable battery cells 212 (e.g., liquid, polymer, or solid-state cell configurations in prismatic, pouch, or cylindrical cell form factors). Furthermore, each battery assembly 202 may include a series of solid-state relay contactors / switches (not shown) that independently respond to signals from a suitable controller / control module (e.g., EBCM) to control the electrical performance of the battery system. While in Fig. 2 only one battery assembly 202 and one motor 210 are shown for simplicity, the SEM drive system 200 may include any number of battery units, motor units, and associated electrical hardware without departing from the intended scope of this disclosure.

[0031] A 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 multiphase windings 214A, 214B, and 214C to transfer electrical energy between the SEM unit 210 and the battery assembly 202. In Fig. 2, the TIM device 206 (also referred to as the "inverter stage" or "inverter subcircuit") is directly electrically connected to and disposed 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. A DC battery output voltage is provided from the battery assembly 202 to the TIM 206 and the PTC 208 via positive and negative voltage bus bars 220A and 220B, with an optional DC bus capacitor 222 placed across the bars 220A and 220B.

[0032] Representative inverter topologies may include multiple inverters and corresponding motor control modules that can receive motor control commands and control inverter states to provide motor drive or regeneration functions. The TIM device 206 of Fig. 2 may include one or more pairs of series-connected electromechanical or semiconductor switches that collectively convert direct current from one or more energy storage devices (e.g., battery assembly 202) to alternating current to power one or more electrical machines (e.g., SEM unit 210) via radio-frequency circuits. According to the illustrated example, TIM device 206 includes six semiconductor switches S I1 , S I2 , S I3 , S I4 , S I5 and S I6 , which are arranged in three pairs 224A, 224B, and 224C of series-connected semiconductor TIM switches. These three switch pairs 224A, 224B, and 224C can be electrically connected in parallel. Each switch S I1 -S I6may 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 gallium nitride (GaN) device (WBG), or any other suitable switch having a corresponding gate to which a gate signal is applied to change the on / off state of the switch.

[0033] Each pair of semiconductor TIM switches 224A, 224B, and 224C may be electrically connected in series with each of the stator-supported field windings 214A, 214B, 214C of a SEM stator assembly 216. Power inverters, such as the TIM device 206 of Fig. 2, may use fast, controller-automated switching control techniques, such as pulse-width modulation (PWM) signals, to convert DC power supplied to the battery assembly 202 during discharge into AC power suitable for driving the SEM unit 210. A precharge circuit (not shown) may be used to charge a DC link capacitor 226 within the TIM device 206 at a controlled rate to equalize a voltage across the various switch pairs 224A-224C before contactors / switches within the battery assembly 202 are closed.

[0034] A multi-stage PFC device 204 is selectively electrically connected to the power source 201 and, once connected, is disposed between the power source 201 and the rest of the SEM drive system 200 (i.e., the battery assembly 202, the TIM 206, the PTC 208, and the SEM 210). This PFC device 204 (also referred to as a "PFC stage" or "PFC converter") provides power factor correction by shaping the input current, e.g., to comply with the harmonic limits of the system 200. Fig. 2, the PFC device 204 is directly electrically connected to and disposed between the power source 201 and the TIM device 206. This PFC device 204 may be disposed on the stator side of the SEM drive system 200, opposite the battery assembly 202. A PFC subcircuit may take on a variety of different topologies, including single- and multi-phase PFC designs, multi-stage (2-stage, 3-stage, ... N-stage) PFC designs, active and hybrid switching PFC designs, etc. A multi-phase PFC may be used for applications such as those described in Fig. 2 may be suitable, where the PFC is arranged on the stator side of the SEM in series with the multiphase windings of the motor.

[0035] A multi-stage PTC device 208 (also referred to as a "PTC stage" or "rotor PTC") is electrically connected on the output side to the rotor side of the SEM unit 210 and on the input side to both the battery assembly 202 and the PFC device 204. The PTC device 208 of Fig. 2 can provide a single-phase rotor excitation function for the SEM's rotor assembly 218, e.g., for optimized motor control and system charging. Fig. 2, the PTC device 208 is directly electrically connected to and disposed between the battery assembly 202 and the SEM rotor assembly 218. In the illustrated example, the PTC device 208 lacks a direct electrical connection to the stator assembly 216 of the SEM unit 210.

[0036] Between the TIM 206 and the PTC 208 is a separately excited motor unit 210, which is powered by the rechargeable battery assembly 202 to generate the output torque of the motor, e.g., to rotate the drive wheels 26 of Fig. 1 and thereby propel the vehicle 10 or to perform work in a non-automotive SEM propulsion application. Unlike polyphase PM electric motors, which rely on permanent magnets in the rotor, a wound-field synchronous SEM is generally characterized by armature windings in the rotor that electromagnetically interact with field windings in the stator to convert electrical energy into mechanical energy. As illustrated, the SEM unit 210 includes a rotor assembly 218 disposed coaxially with and rotatable with respect to a stator assembly 216. In radial-flow, inner-rotor designs, the stator assembly 216 includes an annular stator core 246 carrying a plurality of electromagnetic stator "field" windings 214A-214C. In contrast, the rotor assembly 218 includes a cylindrical rotor core 248 carrying one or more electromagnetic rotor “armature” windings 234.In this example, the rotor core 248 is rotatably mounted within a hollow center of the stator core 246 such that the stator assembly 216 circumscribes the rotor assembly 218.

[0037] The field windings 214A-214C and the armature windings 234 are powered by electrical energy supplied from the battery assembly 202; once energized, the stator-side field windings 214A-214C electromagnetically couple to the rotor-side armature winding 234 and drive it (the electromagnetic coupling is described in Fig. 2 by the S-shaped parallel lines connecting the stator 216 and the rotor 218). A motor output element, which may have the shape of a rotor shaft ( Fig. 4), may be splined, keyed, bolted, or otherwise rigidly connected to the rotor core 248 to rotate therewith and deliver motor torque. Although not limited per se, the stator and rotor cores 246, 248 may be fabricated as laminated core structures, each composed of a stack of iron or other ferrous sheets. Although the SEM unit 210 is illustrated and described as a radial flux electric machine, it may also adopt axial flux and transverse flux architectures within the scope of this disclosure.

[0038] Separately excited (induction) motors are not only an excellent alternative to many indoor permanent magnet (IPM) motors in terms of performance and efficiency, SEMs also eliminate the cost and relatively short life expectancy of rare earth (RE) and heavy rare earth (HRE) magnets. However, the additional power electronics used to excite the armature windings of an SEM unit generate heat that must be mitigated for the SEM unit to function optimally at all operating points. To regulate the operating temperatures of separately excited machines, the disclosed thermal management systems use rotor shaft-mounted heat pipes and / or vapor chambers to remove heat from the rotor's power transfer circuit, while the PTC delivers DC current to the rotor windings.The heat pipes / vapor chambers can be designed for direct (contact) or indirect (non-contact) heat extraction to cool the SEM efficiently and effectively. After dissipation, the heat pipes / vapor chambers can extract the heat generated by the PTC from the power electronics package and transfer the extracted heat to a larger thermal mass for dissipation. In contact-based power transfer circuits, heat can be extracted from the brushes and slip rings; in contactless power transfer circuits, heat can be extracted from the rectifier electronics and rotating capacitive plates.

[0039] To reduce the cost, complexity, and warranty issues associated with typical active thermal management of rotor PTCs, such as sump cooling or jet impingement, the disclosed passive thermal management systems utilize axial heat pipes / vapor chambers rigidly mounted on the outer surface of the rotor shaft to transfer heat away from the PTC's electrical components (e.g., slip rings and brushes). Heat pipes / vapor chambers are self-contained heat sink devices that do not utilize rotating seals, glycol pumps, or other moving parts that can fail during system operation.In addition, the heat pipes and vapor chambers mounted on the rotor shaft are closed, passive thermal management devices that do not interact or interfere with the stator, thus reducing system complexity while ensuring that operating speeds, inertial mass, and structural integrity of the rotor are maintained for high-speed operation.

[0040] Next, with reference to Fig. 3 shows another example of an electric machine 310, which is shown as a separately excited, radial flow, internal rotor motor unit cooled with rotor shaft-mounted heat pipes / vapor chambers, end cap integrated heat sinks, and optional spray or splash cooling of the ATM. As mentioned above, it is contemplated that all features and options described with respect to the traction motor 78 of Fig. 1 and the SEM unit 210 of Fig. 2, individually or in any combination into the electrical machine 310 of Fig. 3 and vice versa. The electric machine 310 of Fig. 3 is provided with a protective and insulated outer casing 302 (e.g., an integrated cast metal EDU casing) that provides the mechanical interface for mounting to a system support structure (e.g., a unibody or body-on-frame chassis) to show some non-limiting similarities. A multi-phase, field-wound, and AC-fed stator assembly 316 is rigidly mounted inside the casing 302, e.g., via an axial clamp ring 308. Spaced from the stator assembly 316 by an air gap is a single-phase, armature-wound, and DC-fed rotor assembly 318 that is rotatably mounted within the casing 302, e.g., via high-speed precision roller bearings 304. The rotor assembly 318 is fixed, e.g., B. via a key, a gear, a collar, a hub, etc., mounted on a power transmitting (motor or output) shaft 306 to rotate together with it.This shaft 306 serves to output the torque generated by the electric machine 310 and / or to receive the input torque generated by an external source.

[0041] Similar to the stator assembly 216 of Fig. 2 is the stator assembly 316 of Fig. 3 is constructed with a flux-permeable, layered, annular stator core 320 having a plurality of circumferentially spaced stator slots 321 radially aligned with and extending axially through the stator core 320. A corresponding set of electromagnetic conductors 326 (also referred to herein as a "stator winding" or "field winding") is wound through each axially elongated slot 321 of the stator core 320, which may be in the form of hairpin, I-pin, D-pin, or flat-ribbon copper conductors. The radially innermost ends of the slots 321 are divided by stator teeth that point toward the outer diameter (OD) of the rotor assembly 318. The stator teeth direct the magnetic flux generated by the stator windings 326 across the air gap to electromagnetically connect with the electromagnets carried by the rotor assembly 318 before completing the flux path back to the stator assembly 316.

[0042] Similar to the rotor assembly 218 of Fig. 2 is the rotor assembly 318 of Fig. 3 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 located within and circumscribed by the stator core 320 such that both cores 320, 322 are coaxial with the shaft 306. An electromagnetic conductor 328 (also referred to herein as a "rotor winding" or "armature winding") is wound through the axially extended rotor slots 323, which may be embodied as a single- or multi-strand winding of solid or litz-wire copper coils. The radially outermost ends of the slots 323 are divided by rotor teeth that face the inner circumference (ID) of the stator assembly 316.These rotor teeth conduct the magnetic flux generated by the rotor winding 328 across the air gap to establish an electromagnetic connection with the electromagnets carried by the stator assembly 316.

[0043] The operation of the SEM 310 from Fig. 3 is effected in part by a magnetic field generated by the rotor assembly 318 upon receipt of a direct current supplied by a suitable source of electrical energy, such as the traction battery pack 70 of Fig. 1 (e.g., for automotive applications) or the battery assembly 202 (e.g., for non-automotive applications). Since the rotor assembly 318 rotates during operation of the electric machine 310, the DC power supply to the rotor winding(s) 328 is provided via a rotating electromechanical interface, namely the rotor current transfer circuit 330. In a contact PTC configuration, this rotating interface may be characterized by a pair of electrically conductive (positive and negative) brushes 332A and 332B—a "stationary side" of the PTC—which each mate with a pair of electrically conductive (positive and negative) slip rings 334A and 334B—a "rotating side" of the PTC. The brushes 332A, 332B are rigidly mounted in a dedicated PTC compartment 312 ("dry area") of the housing 302 via a brush support assembly 314.Conversely, slip rings 334A, 334B are attached to the outer surface of rotor shaft 306 and extend circumferentially therearound, such that they are movably mounted within PTC compartment 312. Each brush 332A, 332B is electrically coupled to a corresponding (positive and negative) electrical lead 336A and 336B and slides against a corresponding slip ring 334A, 334B, thereby transferring direct current from the electrical power source to rotor assembly 318 and energizing armature winding(s) 328. A target position sensor 338, which may be in the form of a potentiometer, an inductive angle sensor, or a rotary encoder, actively monitors a rotational position of rotor shaft 306 and, thus, slip rings 334A, 334B.

[0044] For passive cooling of the electric machine 310, at least one heat pipe 340 is operatively connected to the rotor shaft 306 to harvest thermal energy from one or more of the heat-generating electrical components of the rotor PTC 330. According to the illustrated example, the rotor shaft 306 is an elongated, rectangular cylinder made of a rigid metallic or polymeric material as a one-piece structure. A single heat pipe 340 or a set of heat pipes 340 may be attached to an outer surface of the rotor shaft, projecting axially between the rotor PTC 330 and the rotor core 322. For high-speed, high-torque applications, multiple heat pipes 340 (e.g., four in the drawings) may be rigidly attached to the outer surface of the shaft and spaced circumferentially around the rotor shaft 306. These heat pipes 340 may be substantially parallel to each other and to the rotor shaft 306.As best seen in the inspection view on the top left side of . Fig. 3, the heat pipes 340 may be arranged around the rotor shaft 306 at substantially equal spacing from one another (e.g., approximately 90 degrees between adjacent heat pipes). In this arrangement, the heat pipes 340 orbit together about a rotational axis A during rotation of the rotor shaft 306. R1 .

[0045] The outer surface of the rotor shaft 306 may be fully or partially coated with a polymeric surface coating 358 to prevent inadvertent short circuiting between the positive and negative slip rings 334A, 334B during electrification of the rotor assembly 318 via the rotor PTC 330. To simplify design and manufacturing, this rotor shaft surface coating 358 may be formed as a one-piece, unitary structure made of an electrically insulating thermoplastic polymer (e.g., injection-molded liquid crystal polymer (LCP) resin). In this case, each heat pipe 340 is at least partially embedded in the polymeric surface coating 358, such that, for example, only a predefined contact area of ​​a radially outermost surface of the heat pipe 340 is exposed through the coating 358.Packaged in this manner, a radially innermost surface of each individual heat pipe 340 may be flush with the outer surface of the rotor shaft 306. Alternatively, a heat pipe 340 embedded in the coating may be radially spaced from the rotor shaft 306, or alternatively, the proximal (left) axial end of the heat pipe 340 may be radially spaced from the rotor shaft 306 and the opposite distal (right) axial end of the heat pipe 340 may be abutting the shaft 306. To electrically isolate the rotor PTC 330 from the heat pipes 340, an optional thermal interface material (TIM), such as acrylic polymer tape strips 364, may be disposed between each heat pipe 340 and the annular slip rings 334A, 334B. It is contemplated that the TIM tape strips 364 may be omitted from the SEM 310 if, for example, the heat pipes are made of or coated with an electrically non-conductive material.In addition, the heat pipes 340 may also help cool the polymer surface coating 358 of the rotor shaft 306.

[0046] The rotor PTC 330 contains several electrical components, such as the rotating electromechanical slip rings 334A, 334B of Fig. 3, which enclose the rotor shaft 306 and are thermally connected to the heat pipes 340. These slip rings 334A, 334B electrically connect the metal / graphite brushes 332A, 332B to the rotor winding 328, e.g., via drilled leads or surface-etched cables (not shown). Each heat pipe 340 extends through the central cavities of the PTC slip rings 334A, 334B and is thermally connected to them, directly or indirectly. In this arrangement, the heat pipes 340 are substantially orthogonal to the slip rings 334A, 334B and extend axially therefrom, protruding from the PTC space 312 and terminating near (but not touching) an axial end of the rotor core 322.

[0047] Although the use of shaft-mounted heat pipes is illustrated and described herein, the electric machine 310 may be Fig. 3, some or all of the heat pipes 340 may be replaced with thermal energy-dissipating vapor chambers. For example, a narrow, flat vapor chamber may replace any of the heat pipes 340; alternatively, a curved vapor chamber of greater width may replace multiple heat pipes 340. As a further option, the shaft-mounted heat pipes / vapor chambers described herein may be surface-mounted devices (as shown), surface-sunk devices (seated in corresponding channels recessed into the outer surface of the shaft), or subsurface devices (located in the internal slots of the rotor shaft). It is also contemplated that the SEM 310 assembly may include more or fewer heat pipes 340, which may take on different shapes, sizes, and locations than the configurations shown.

[0048] Each heat pipe 340 extends axially from a terminal end of the rotor shaft 306 to an axial end of the rotor core 322 and simultaneously extracts thermal energy generated by mating PTC components to transfer the extracted thermal energy from the PTC chamber 312. The heat pipes 340 act as thermodynamic conduits connecting the heat-generating components of the rotor PTC 330 to a convectively cooled rotor end cap 350 and a conductively cooled dielectric fluid 352 circulating through an internal coolant chamber (“wet area”) of the housing 302. As shown in the inset view on the lower left side of Fig. As best seen in Figure 3, each heat pipe 340 may be constructed with a hermetically sealed and heat-conducting container 342, which may be made as a rigid, hollow tube of copper or aluminum. The heat pipe container 342 contains a working fluid (in Fig. 3 by arrows 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 phases between liquid 344' and gas 344".

[0049] The working fluid 344 can flow freely through three adjacent sections of the container 342: a heat-absorbing “evaporation” section S 1E at a proximal end of the container 342; an intermediate “adiabatic” section S 2A in the middle of the container 342, which is a final end of the evaporation section S 1E flanked; and a heat-emitting “condensation” section S 3C at a distal end of the container 342, which is a terminal end of the “adiabatic” section S 2Aflanked. Inside the container 342 there is a wick structure 346, which draws the working fluid 344' in liquid phase, e.g. by capillary action, from the condensation section S 3C at the distal axial end of the container 342 to the evaporation section S 1E at the proximal axial end of the container 342. The wick structure 346 can take on a myriad of form factors, including a fine-fiber roving wick, a wound textile wick, an interwoven metal wire wick, a mesh screen wick, a sintered powder wick, etc. As illustrated, the wick structure 346 bears against and substantially covers an interior surface of the container 342.

[0050] An elongated steam channel 347 runs through the center of the heat pipe container 342 and the wick structure 346, which carries the gaseous working medium 344" from the evaporation section S 1Ewithin the PTC space 312 through the adiabatic section S 2A , which extends along the rotor shaft 206, and into the condensation section S 3C adjacent to the rotor core 322. As the working fluid 344 cools and condenses into a liquid, the vapor channel 347 directs the working fluid 344' into the wick structure 346. To facilitate manufacturing and simplify design, it may be desirable for all shaft-mounted heat pipes 340 to be substantially identical. Furthermore, each heat pipe 340 may be a fluid-tight, discrete unit that has no fluid connections, e.g., for fluid communication with the internal coolant chamber 303 of the housing 302.

[0051] During operation of the electric machine 310, the electrical components of the rotor PTC 330 generate frictional and resistive heat, particularly at high speeds (e.g., above 10,000 rpm). A portion of this heat generated by the PTC is transferred through the sealed containers 342 and into the wick structures 346 of the heat pipes 340. In particular, heat energy is dissipated through the proximal end of the heat pipe container 342—the evaporation section S 1E - evaporates part of the working fluid 344 enclosed in the container 342. When the working fluid 344 has evaporated by absorbing the heat generated by the PTC, the wick structure 346 directs the gas phase liquid 344" into the vapor channel 347. The gaseous working fluid 344" migrates axially, e.g., to the right into Fig. 3, through the steam channel 347 and condenses at the distal end of the heat pipe container 342 in the condensation section S 3C. When it condenses, the wick structure 346 draws the fluid 344 from the vapor channel 347. The liquid phase fluid 344' is drawn axially, e.g., to the left, under the force of capillary action, through the wick structure 346 to the evaporation section S 1E pulled to start the cycle again.

[0052] To assist in the dissipation of heat energy dissipated by the PTC 330 via the heat pipes 340, a heat-conducting rotor end cap 350 may be fixedly mounted on the PTC-facing axial end of the rotor core 322 in abutting relationship with the heat-dissipating longitudinal ends of the heat pipes 340. It may be desirable for this rotor end cap 350 to be fabricated with a circumferentially spaced set of heat pipe cavities 351 (e.g., one cavity per heat pipe) that form a thermal interface with the SEM heat pipes 340. Each heat pipe cavity 351 may be recessed into a radially inwardly facing surface of the rotor end cap 350 and receives a longitudinal tip of a corresponding heat pipe 340 therein. These cavities 351 help to increase the contact area between the end cap 350 and the heat pipes 340, thereby increasing the heat transfer rate between the adjacent structures.The rotor end cap 350 not only helps reduce winding losses and supports the rotor windings 328 for high-speed operation of the machine, but also serves as a heat sink to absorb and dissipate the heat absorbed by the heat pipes 340.

[0053] With further reference to Fig. 3, the rotor end cap 350 may be manufactured with a set of end cap fins 354 that serve to dissipate the heat accumulated by the end cap 350 from the rotor assembly 318 and the PTC 330 into the internal coolant chamber 303 of the housing 302. These heat-transferring end cap fins 354, located on an outwardly facing axial surface of the rotor end cap 350, may be pin-shaped, planar, or wave-shaped fins that project axially away from the rotor core 322 and into the internal coolant chamber 303 of the housing. The end cap fins 354 increase the total surface area of ​​the rotor end cap 350 exposed within the housing 302 to increase the dissipation of the extracted heat energy captured by the rotor end caps 350, e.g., through convective and, if desired, conductive heat transfer.

[0054] To assist in the removal of thermal energy from the machine housing 302, an optional active thermal management system (ATM) (in Fig. 3 by the oil pump 362), dielectric cooling fluid 352 may be circulated into and out of the housing 302 to cool the rotor end caps 350 and the end cap fins 354 by splashing or spraying. The cooling fluid 352 may be an electrically non-conductive, magnetically non-active oil that is sprayed onto the stator windings 326 and the rotor end caps 350, e.g., via spray nozzles in a stator end cap 360, to accelerate the heat dissipation action of the heat pipes 340 and the end cap 350. In addition to the enhanced convective cooling by the rotor end caps 350 and the end cap fins 354, the spray / splash cooling of the cooling fluid 352 provides immersion-type conductive heat transfer. 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 electric machine 310.For splash cooling, it may be desirable to have a set of rotor pin fins arranged in a helical, turbine-like pattern to excite the cooling liquid 352 and thereby create a desired splash effect during excitation of the rotor assembly 318.

[0055] During operation of an SEM 310 electric machine with a contact-based (brushed) rotor PTC 330, the interfaces where the brushes 332A, 332B meet their respective slip rings 334A, 334B generate heat due to sliding friction between the bristles and the surface, as well as electrical resistance to large currents. Heat pipes 340 may serve, at least in part, to dissipate the heat generated at the slip ring-brush interface and transfer the dissipated heat to a larger thermal mass, such as the rotor end cap 350. Cooling the rotor PTC 330 in this manner can help reduce the overall number / size of brushes while increasing the current density per brush, while minimizing wear and resistance of the brush PTC system.Additionally, the brush holder assemblies 314 may be manufactured as molded plastic components that are susceptible to high temperatures; effective heat removal from the PTC area can help extend the life of the brush holder assemblies 314 while increasing the peak currents through the PTC 330.

[0056] The passive and active thermal management features described above with respect to the contact rotor PTC configuration of Fig. 3 can also be used for heat dissipation of contactless rotor PTCs. As a non-limiting example, Fig. 4 an electrical machine 410 with an inductive contactless rotor PTC 430 is shown, while in Fig. 5 an electrical machine 410 with a capacitive contactless rotor PTC 530 is shown. Unless expressly stated otherwise, the above with reference to Fig. 3 described features and options to the SEM architectures of Fig. 4 and Fig. 5, whereby the same reference numerals are used to designate the same parts from Fig. 3 can be used. In Fig. 4, for example, the brushes 332A, 332B, slip rings 334A, 334B and the associated hardware of Fig. 3 is replaced by an electromagnetic induction coupling (rotating transformer) consisting of an annular outer "stationary" core 432 concentric with an annular inner "rotating" core 434 and the rotor shaft 306. The outer core 432 is rigidly mounted within the PTC chamber 312 and supports an outer induction coil 436 exposed through a radially inner surface of the core 432. The stationary core 432 surrounds the inner core 434, which is fixedly mounted on the rotor shaft 306 for co-rotation therewith and supports an inner induction coil 438 electromagnetically coupled to the outer induction coil 436. Operably connected to the inner core 434 are a rectifier PCB 470 and a complementary rectifier heat sink 472, which are also mounted on the rotor shaft 306 and co-rotate therewith.The heat pipes 340 are in thermal communication with the inner core 434 and the rectifier PCB 470 to extract and dissipate their heat. The rectifier PCB 470 contains power electronic components, such as rectifier diodes, that can generate a significant amount of heat. Passive cooling of these components using the heat pipes 340 (or vapor chambers) extends their lifespan, enables peak performance, and helps reduce component size.

[0057] In Fig. 5, the brushes 332A, 332B, the slip rings 334A, 334B and the associated hardware of Fig.3 is replaced by a rotating capacitive coupling consisting of an outer "stationary" capacitive plate 532 axially spaced from and opposed to an inner "rotating" capacitive plate 534. The outer capacitive plate 532 is rigidly mounted inside the PTC compartment 312 and concentric with the rotor shaft 306. The inner capacitive plate 534 is coaxial with the outer capacitive plate 532 and fixedly mounted on the rotor shaft 306 for rotation therewith. Connected to the inner capacitive plate 534 are a rectifier PCB 570 and a complementary rectifier heat sink 572, which are also mounted on the rotor shaft 306 and rotate therewith. The heat pipes 340 are thermally coupled to the capacitive plate 534 and the rectifier PCB 570 to extract and dissipate their heat.Passive cooling of these components using 340 heat pipes (or vapor chambers) can help extend their lifespan, enable higher performance, and reduce component size.

[0058] 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 construction and compositions disclosed herein; all modifications, changes, and variations apparent from the foregoing descriptions are intended to be within the scope of the disclosure as defined by the appended claims. Furthermore, the present concepts expressly include all combinations and subcombinations of the foregoing elements and features.

Claims

[1] Electrical machine, comprising: a housing; a stator assembly having a stator core attached to the housing and an electromagnetic stator winding mounted on the stator core; a rotor assembly having a rotor core rotatably mounted on the housing adjacent to the stator assembly and an electromagnetic rotor winding mounted on the rotor core; a rotor power transfer circuit, rotor PTC, mounted on the housing, axially spaced from the rotor core, and electrically connected to the rotor assembly to electrify the rotor winding; a rotor shaft attached to the rotor core for rotation therewith; and a heat pipe mounted on an outer surface of the rotor shaft and extending axially between the rotor PTC and the rotor core, the heat pipe configured to passively extract heat energy from the rotor PTC and transfer the heat energy out of the rotor PTC. [2] The electric machine of claim 1, wherein the heat pipe comprises a plurality of heat pipes mounted on the outer surface and spaced circumferentially around the rotor shaft. [3] An electric machine according to claim 2, wherein the heat pipes are adjacent to the outer surface and extend parallel to the rotor shaft. [4] An electric machine according to claim 2, wherein the heat pipes are parallel to each other and spaced at an equal distance from each other. [5] An electric machine according to claim 2, wherein the outer surface of the rotor shaft has a polymeric surface coating, and wherein the heat pipes are at least partially embedded in the polymeric surface coating. [6] The electric machine of claim 2, further comprising a thermal interface material, TIM, disposed between and electrically isolating the heat pipes and the rotor PTC. [7] The electric machine of claim 2, wherein the rotor PTC comprises a plurality of PTC electrical components surrounding the rotor shaft, and wherein the heat pipes extend through and are thermally coupled to central cavities of the PTC electrical components. [8] The electric machine of claim 7, wherein the PTC electrical components comprise first and second electrical brushes coupled to first and second slip rings, and wherein the heat pipes contact the first and second slip rings. [9] The electric machine according to claim 1, wherein the heat pipe includes a sealed container containing a working fluid configured to change phases between a liquid phase and a gas phase to thereby extract the thermal energy from the rotor PTC and transfer the thermal energy to the outside through an axial end of the rotor PTC. [10] The electric machine of claim 9, wherein the heat pipe further comprises a wick structure located inside the sealed container and configured to transfer the working fluid, when in the liquid phase, from a first axial end to a second axial end of the sealed container.

Images