Separately excited electric machine with rotor cooling system

Abstract

Cooling system for a separately excited electrical machine, comprising: Rotor windings arranged radially around a rotor shaft and having a plurality of gaps between bundles of metal wires; and a cooling device arranged in the plurality of gaps and configured to directly cool the rotor windings.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a separately excited electric machine having a rotor cooling system that directs coolant through gaps between the rotor windings. BACKGROUND AND OVERVIEW

[0002] Electric motors are used in vehicles to generate motive power and in a variety of other applications. Rare-earth magnets are used in some electric motors because permanent magnet motors can achieve high efficiency. To further increase motor efficiency, cooling systems have been incorporated into certain motors.

[0003] US 8,022,582 B2 by Dames et al. discloses a liquid-cooled permanent magnet rotor. The rotor cooling system directs oil through a rotor shaft and then to radial passages located near the end of the rotor shaft to cool the rotor.

[0004] The inventors have recognized several disadvantages of the Dames liquid-cooled permanent magnet motor and other earlier permanent magnet motors. For example, the use of permanent magnets in Dames motors, as well as in other motors, can have environmental and economic disadvantages. Furthermore, separately excited electric motors have different temperature gradients compared to permanent magnet motors, where heat is generated in the permanent magnets. Consequently, the cooling challenges of separately excited electric motors differ from those of permanent magnet motors. For example, the losses in the rotor windings of the separately excited motor can be higher than the electrical losses in other motor types, such as permanent magnet motors.In addition, separately excited electric motors can have smaller shaft diameters than other motors, which further complicates motor cooling challenges due to the reduction in rotor shaft size, which leads to a reduction in the rotor shaft cooling channel.

[0005] Considering the aforementioned disadvantages of previous motors, the inventors developed a cooling system for a separately excited electric machine to at least partially overcome these disadvantages. The cooling system for a separately excited electric machine comprises, for example, rotor windings arranged radially outside a rotor shaft and having a plurality of gaps between metal wire bundles. The cooling system for a separately excited electric machine additionally comprises a cooling device arranged in the gaps and configured to directly cool the rotor windings. In this way, the rotor is effectively cooled to increase the operating efficiency of the machine by utilizing the previously unused space in the metal wire bundles of the rotor windings.More specifically, the electric machine is capable of achieving the targeted efficiencies for a wide range of applications and vehicle platforms, particularly through the use of materials that are easier to obtain than rare earth magnets.

[0006] In one example, the cooling device may include a plurality of cooling tubes. In such an example, the cooling tubes may be in fluid communication with a rotor shaft cooling channel. Furthermore, in such an example, the cooling tubes may be in fluid communication with the rotor end winding enclosures. In this way, the operating efficiency of the machine is further increased by cooling the rotor end windings.

[0007] It should be understood that the above summary is intended to introduce, in simplified form, a selection of concepts that are further explained in the detailed description. It is not intended to identify the most important or essential features of the claimed subject matter, the scope of which is clearly defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that address the disadvantages noted above or elsewhere in this disclosure. SHORT DESCRIPTION OF THE CHARACTERS Fig. 1 is an illustration of an exemplary system with a separately excited electric machine with a cooling system. Fig. 2 shows a cross-sectional view of an example of a cooling system with cooling tubes. Fig. Figure 3 shows a cross-section of an example of a cooling system in which the coolant is passed directly through gaps in the wire bundles in the rotor windings. Fig. Figure 4 shows a cross-sectional view of an example of a heat pipe cooling system. Fig. 5-6 show further cross-sectional views of various examples of a cooling system with cooling tubes. Fig. Figure 7 shows another cross-section of an example of a cooling system in which the coolant is passed directly through gaps in the wire bundles in the rotor windings. Fig. Figures 8-9 show a cross-section of another example of a cooling system in a rotor. Fig. 10 shows another cross-sectional view of the cooling system used in Fig. 3 is shown. DETAILED DESCRIPTION

[0008] Described herein is a separately excited electric machine having a rotor cooling arrangement for achieving increased efficiency. The rotor cooling arrangement includes a cooling device arranged in gaps in the rotor windings to directly cool the rotor windings. The cooling device may take a number of different forms in various embodiments. For example, the cooling device may be in the form of a plurality of cooling tubes through which coolant is pumped. The cooling device may also be in the form of a plurality of heat pipes. In the heat pipe example, the heat pipes may be cooled by coolant sprayed or circulated around the rotor end windings. In other embodiments, the coolant may flow directly through the gaps in the rotor windings that are closed at one end.

[0009] Fig. 1 shows an example of an electric drive 100 with a separately excited electric machine system 102. The electric drive 100 may, for example, be integrated into an electric drivetrain 103 of a vehicle 105. In such an example, the electric machine included in the electric drive may be a traction motor. However, it is understood that the electric drive 100 may be used in a variety of fields, including, but not limited to, industrial machinery, agricultural systems, mining systems, and the like.

[0010] The separately excited electric machine system 102 includes a separately excited electric machine 104 (e.g., a separately excited synchronous motor (EESM)) electrically coupled to an inverter 108 via electrical connections 107 (e.g., wires, busbars, combinations thereof, and the like).

[0011] In the electric drive 100, an inverter 108 is electrically coupled to the separately excited electric machine 104. The inverter 108 can be electrically connected to an energy storage device 110 (e.g., one or more traction batteries, capacitor(s), fuel cell(s), combinations thereof, and the like). Thus, during propulsion and regeneration mode, electrical energy can flow between the inverter and the energy storage device if the separately excited electric machine 104 is configured as a motor-generator.

[0012] The separately excited electric machine 104 includes a stator 112 and a rotor 114. The rotor 114 includes a rotor shaft 118 and a rotor core 120 with separately excited rotor windings 122, which may include copper or aluminum coils. The rotor windings 122 are connected to a power source 124 via electrical connections 126. The power source 124 may include an inverter or DC-DC converter for exciting the rotor windings, which may be electrically coupled to the energy storage device 110 and / or another suitable energy storage device. Furthermore, due to the use of separately excited rotor windings in the electric machine, no permanent magnets may be included in the rotor.

[0013] The electric drive 100 may be coupled to downstream components 128. In the example of the electric vehicle, the downstream components 128 may include one or more axle assemblies, drive wheels, a transmission (e.g., a manual transmission), and the like.

[0014] The electric machine 102 further comprises a cooling system 150 configured to dissipate heat from the rotor 114. The cooling system 150 is shown schematically in Fig. 1. However, it is understood that the cooling system has a greater complexity, which is explained here using the Fig. The example cooling systems shown in Figures 2-10 are explained in more detail.

[0015] In the illustrated example, the cooling system 150 includes a heat exchanger 152 and a pump 154. The heat exchanger 152 and the pump 154 ​​are shown external to the electric machine 102 in the illustrated example. However, in other embodiments, the heat exchanger and / or the pump may be integrated into the electric machine.

[0016] In one example, the outlet of the heat exchanger 152 may be in fluidic communication with an inlet 156 of a rotor shaft cooling channel, and the inlet of the pump may be in fluidic communication with a sump 158 or in direct fluidic communication with rotor end winding enclosures that immersively cool the windings. In another example, the outlet of the pump may be in fluidic communication with rotor shaft cooling channels, and the inlet of the heat exchanger may be in fluidic communication with a sump or in direct fluidic communication with rotor end winding enclosures that immersively cool the windings. In other embodiments, the pump and heat exchanger may be in fluidic communication with a portion of the rotor cooling system that cools the rotor end windings either through coolant spray or through immersion cooling.In such an example, the rotor cooling system may include heat pipes integrated into the rotor, and the heat pipes may be sprayed with coolant that is also directed toward the rotor's end windings or extend into the immersive cooling enclosures around the end windings. Various architectures of exemplary rotor cooling systems are described in the . Fig. 2-10 and are explained in more detail here.

[0017] The cooling system 150 comprises a cooling device 162 which is Fig. 1. However, it should be understood that in practice the cooling device has a greater complexity, which is explained in more detail here. The cooling device 162 may include cooling tubes, heat pipes, and / or coolant channels arranged in gaps between winding wires. More specifically, the rotor 114 includes metal wire bundles for each pole with gaps between the wires. The gaps, which are explained in more detail herein, may be formed in the rotor for manufacturing reasons. By way of illustration, one method for winding the copper coils of the rotor may include a needle winding process in which the round copper wire is guided around the iron poles by a comparatively small needle. For reasons of mechanical strength, these needles may have a minimum diameter that is larger than the diameter of the copper wire.In addition, the needle can be kept at a sufficient distance from the adjacent coil to avoid unwanted contact that could damage the insulation. Other coil winding methods can also be used, which also require a minimum distance between the coils for similar reasons. The wire bundles can be made of a suitable metal such as copper, aluminum, combinations thereof, and the like.

[0018] The coolant in the cooling system 150, which is in Fig. 1, as well as in the other cooling systems described herein, may be oil. Bearings 160 are coupled to rotor shaft 118 in the illustrated example. In one example, the rotor shaft cooling passage may direct oil through the bearings to lubricate them and reduce bearing wear.

[0019] The electric drive 100 may further comprise a control system 190 with a control unit 192, as shown in Fig. 1. The control unit 192 may include a microcomputer with components such as a processor 193 (e.g., a microprocessor unit), input / output interfaces, an electronic storage medium 194 for executable programs and calibration values ​​(e.g., a read-only memory chip, random access memory, keep-alive memory, a data bus, and the like). The storage medium may be programmed with computer-readable data representing instructions executable by a processor to perform the methods and control techniques described herein, as well as other variations expected but not specifically listed. Control techniques, methods, and the like discussed herein may be stored as instructions in non-volatile memory.

[0020] The control unit 192 may receive various signals from sensors 195 associated with various areas of the electric drive 100. For example, the sensors 195 may include a rotor current sensor, an electric machine speed sensor, a stator current sensor, an electric machine temperature sensor, an auxiliary contact sensor, a battery charge level sensor, an inverter current sensor, and the like. The speed of the electric machine may be determined based on the power supplied by the inverter 108 to the electric machine 104. An input device 198 (e.g., accelerator pedal, brake pedal, drive mode selector, gear selector, combinations thereof, and the like, in the example of an electric vehicle) may also provide input signals indicating an operator's intent regarding the control of the electric drive.

[0021] Although in Fig. 1, the electric drive and the system in which it is incorporated, such as a vehicle, may include multiple control units. In the EV example, for example, a vehicle control unit (VCU) may be integrated into the control system 190. Additionally, a motor control unit (MCU) may be integrated into the control system. In such an example, the VCU and the MCU may be separate control units with independent hardware and formed in separate housings that are spaced apart from each other. However, in other examples, the VCU and the MCU may be arranged side by side. In both cases, the VCU and the MCU are in electronic communication with each other.

[0022] After receiving the signals from the various sensors 195 of Fig. 1, the control unit 192 processes the received signals and deploys various actuators 196 of the electric drive components to adjust the components based on the received signals and the instructions stored in the memory of the control unit 192. For example, the control unit 192 may receive a signal indicating an operator request for increased power from the electric machine. The control unit 192 may then command the operation of the inverter 108 to adjust the mechanical power of the electric machine and increase the power delivered by the separately excited electric machine 104 to the downstream components 128. The other controllable components in the electric drive may function similarly with respect to sensor inputs and command outputs.

[0023] An axis system is in Fig. 1 and in Fig. 2-10 for reference. In one example, the z-axis may be a vertical axis (e.g., parallel to a gravitational axis), the x-axis may be a lateral axis (e.g., a horizontal axis), and the y-axis may be a longitudinal axis. In other examples, the axes may have other orientations. Also, in Fig. 1 a rotational axis 180 of the electric machine 104 is provided as a reference.

[0024] The Fig. 2-10 show examples of cooling devices for cooling systems used in the Fig. 1 shown separately excited electrical machine 104 or other suitable separately excited electrical machines. For clarification, the Fig. 2 to 4 and 9 show cross-sectional views of exemplary rotor cooling devices in which the cutting plane is perpendicular to the rotational axis of the electric machine, and the Fig. 5 to 8 and 10 show cross-sectional views of exemplary rotor cooling devices in which the cutting plane is a radial plane passing through the axis of rotation of the electric machine.

[0025] Fig. Figure 2 specifically shows an example of a cooling system 200 in a rotor 208 of a separately excited electric machine. The separately excited electric machine described herein and the other electric machines may, in particular, be synchronously separately excited electric machines in which the rotation of the shaft is synchronized with the frequency of the supply current.

[0026] The rotor windings 204 extend through a rotor body 206 within the rotor 208. The rotor windings 204 are formed from metal wires 210 (e.g., copper wires, aluminum wires, combinations thereof, and the like). A cooling tube 212 is included in the cooling system 200. The cooling tube 212 is positioned in a gap 214 between the wires 210. For clarity, in the illustrated example, the cooling tube 212 includes sections 216 configured as passageways to guide the tube through the rotor 208 in a circuitous manner. It is understood that other windings in the rotor with a gap therein may include a similar cooling tube. In such an example, the cooling tubes in the gaps may be fluidly connected in parallel, which has the advantage of limiting the impact of cooling fluid heating on the rotor cooling performance.In other examples, each gap in the various rotor winding sections may include multiple cooling tubes through which coolant is directed in parallel. Fig. 8-9 show another example of a cooling system 800 in a rotor 802, including a plurality of cooling tubes 804 through which coolant is directed in parallel through a gap 806 in the rotor windings 808. The rotor cooling system 800 also includes coolant collectors 810 on both axial sides. The coolant collectors 810 may include a coolant outlet 812 and a coolant inlet 814, or vice versa, allowing coolant to be directed to a pump and / or other suitable cooling system components. The end windings 816 may be disposed within the coolant collectors 810.

[0027] The central axes 218 of the sections 216 may be parallel to the rotational axis of the electric machine. Additionally, in one embodiment, each axial side of the electric machine may have a cooling tube with a similar arrangement. In such an example, the cooling tubes may receive coolant from a channel that traverses the rotor shaft. The rotor shaft cooling channel is described here with reference to the Fig. 5-7 explained in more detail.

[0028] Continuing the example of the cooling device with cooling pipes made of Fig. 3, the cooling tube outlets can either direct coolant for immersion cooling into the space around the rotor end windings or direct coolant to nozzles that spray coolant onto the end windings. The rotor shaft coolant channel can receive coolant from a pump and a heat exchanger.

[0029] In the illustrated example, a thermosetting material 220 is located around the cooling tube 212 and between the winding wires 210. The thermosetting material 220 comprises an epoxy and / or a thermoplastic. A thermosetting material may be provided around at least a portion of the other cooling devices described herein, which are disposed in the space between the rotor winding wires. Using a thermosetting material in the cooling system may increase the structural strength of the cooling assembly, thereby extending the service life of the cooling system.

[0030] Fig. Figure 3 shows another example of a cooling system 300 in a rotor 301 of a separately excited electric machine with a coolant channel 302 formed in a gap 304 between end winding wires 306. One end of the gap may be blocked to retain the coolant in the gaps. For clarity, it should be noted that, as in Fig. 10, a groove 1000 may be provided in an end plate 1002 to direct coolant back to the coolant channel 302 in the rotor 301. More specifically, the groove 1000 is formed as a radial, inwardly directed channel integrated into the end plate 1002 to direct fluid back to the rotor shaft.

[0031] Fig. Figure 4 shows another example of a cooling system 400 in a rotor 402 of a separately excited electric machine. The cooling system 400 includes heat pipes 404 arranged in a gap 405 between wires 407. The heat pipes 404 each include a vapor cavity 408 surrounded by a wick portion 410. Both the vapor cavity 408 and the wick portion 410 are enclosed by a housing 412 to form a sealed enclosure.

[0032] Fig. 5 shows a cross-section of a cooling system 500 in a rotor 502 of a separately excited electric machine, wherein the cooling system comprises cooling tubes 504. In the illustrated example, the cooling tubes 504 are guided through the gap such that they form several longitudinal passages. Thus, each cooling tube 504 comprises several sections 506 that run parallel to one another, as well as curved sections 508 that fluidically connect the parallel sections of the tubes. However, other cooling tube contours are also possible.

[0033] In addition, a rotor shaft cooling channel 510 supplies the cooling tubes 504 with coolant. For explanation, the rotor shaft cooling channel 510 extends axially through the rotor shaft 512 over an axial portion 514 and additionally includes a radially extending portion 516, which, in the illustrated example, is located centrally along the rotor shaft. The rotor shaft cooling channel 510 receives coolant from a pump and can direct coolant through one or more bearings coupled to the rotor shaft 512.

[0034] The outlet openings 518 of the cooling tubes 504 are in fluid communication (e.g., direct fluid communication) with the nozzles 520. The nozzles 520 spray coolant onto the rotor end windings 522 to improve rotor cooling.

[0035] Fig. 6 shows a cross-section of a cooling system 600 in a rotor 602 of a separately excited electrical machine, wherein the cooling system 600 comprises cooling tubes 604 in fluid communication with a rotor shaft cooling channel 606, similar to that shown in Fig. 5. For clarity, a redundant description of the overlapping features of the cooling systems is omitted. However, the outlet openings 608 of the cooling tubes 604 are in fluid communication with rotor end winding enclosures 610, which surround the rotor end windings 612 and thus immersively cool the end windings. The enclosures 610 include outlet openings 614, which, in the illustrated example, are in fluid communication with a coolant sump.

[0036] Fig. Figure 7 shows another example of a cooling system 700 with a coolant channel 702 formed in a gap 703 between the end winding wires. In the illustrated example, the coolant channel 702 is in fluid communication with a rotor shaft cooling channel 704. One end of the gap may be blocked to retain the coolant in the gaps.

[0037] The Fig. 1 to 7 illustrate a method of operating a separately excited cooling system for electric machines. The method may be implemented by any of the cooling systems for electric machines described herein or by combinations of the cooling systems. In other examples, the method may be implemented by other suitable cooling systems. Furthermore, the method may be implemented by a control unit including memory containing instructions for implementing the method steps that may be performed by a processor, as previously indicated. The method includes introducing coolant from a pump into a rotor shaft cooling channel. Next, the method includes directing coolant from the rotor shaft cooling channel to a cooling device from the rotor shaft cooling channels. More specifically, the method includes introducing coolant into a cooling device disposed in the plurality of gaps.The method further includes, for example, introducing coolant from the cooling device into the submerged rotor end windings, in one embodiment. In another example, the method may further include spraying coolant onto the rotor end windings via nozzles that are in direct fluid communication with the cooling device.

[0038] The technical effect of the operating methods described here for cooling systems for separately excited electrical machines is to effectively cool the rotor windings by conducting coolant through gaps between the winding wires and thereby increase the efficiency of the electrical machine.

[0039] The Fig.1-10 show example configurations with relative positioning of the various components. When these elements are in direct contact with each other or are directly coupled, they may be referred to as being in direct contact or directly coupled, respectively, at least in one example. Similarly, elements shown next to or adjacent to each other may be adjacent to or adjacent to each other, at least in one example. For example, components that are in surface-to-surface contact with each other may be referred to as being in surface-to-surface contact. As another example, in at least one instance, elements that are separated from each other with only a gap between them and that do not have any other components may be referred to as such.In yet another example, elements depicted above / below, on opposite sides, or to the left / right of each other may be referred to as such, relative to each other. Further, in at least one example, as depicted in the figures, a topmost element or point of an element may be referred to as a "top" of the component, and a bottommost element or point of the element may be referred to as a "bottom" of the component. As used herein, the terms top / bottom, upper / lower, above / below may refer to a vertical axis of the figures and may be used to describe the positioning of elements of the figures relative to each other. Thus, in one example, elements displayed above other elements are arranged vertically above the other elements.As another example, the shapes of the elements depicted in the figures may be referred to as such (e.g., circular, straight, flat, curved, rounded, beveled, angled, and the like). Furthermore, in one example, elements that are coaxial with each other may be referred to as such. Further, in at least one example, the depicted elements that intersect each other may be referred to as intersecting elements or as intersecting elements. Furthermore, an element depicted inside another element or outside another element may be referred to as such. In other examples, elements that are offset from each other may also be referred to as such.

[0040] The invention is further described in the following paragraphs. In one embodiment, a cooling system for a separately excited electric machine is provided, comprising rotor windings arranged radially outwardly of a rotor shaft and having a plurality of gaps between metal wire bundles, and a cooling device arranged in a plurality of gaps and configured to directly cool the rotor windings. In one example, the cooling device may comprise a plurality of cooling tubes. In another example, the plurality of cooling tubes may be embedded in a thermally thermosetting material. In another example, the thermosetting material may include one or more of the following materials: epoxy and thermoplastic. In another example, the plurality of cooling tubes may be in fluid communication with a rotor shaft cooling channel.In another example, the rotor shaft cooling channel may be in fluid communication with a rotor shaft bearing. In another example, the plurality of cooling tubes may be in fluid communication with the rotor end winding enclosures. In another example, the cooling device may include a plurality of heat pipes. In another example, the plurality of heat pipes may be cooled via a spray nozzle at the rotor end or via submerged rotor end winding enclosures. In another example, a working fluid in the electric machine cooling system may be oil.

[0041] In another aspect, a method of operating a separately excited cooling system for a separately excited electric machine is provided, comprising introducing a coolant into a cooling device disposed in the plurality of gaps, the separately excited cooling system for electric machines comprising rotor windings disposed radially outward of a rotor shaft and comprising a plurality of gaps between metal wire bundles, and a cooling device disposed in the plurality of gaps and configured to directly cool the rotor windings. In one example, the method may further comprise introducing coolant from the cooling device into submerged rotor end winding enclosures. In one example, the method may further comprise spraying coolant onto the rotor end windings via nozzles in direct fluid communication with the cooling device.In one example, introducing the coolant into the cooling device may include introducing the coolant from a rotor shaft cooling channel into the cooling device. In one example, the cooling system may include a plurality of cooling tubes embedded in epoxy or a thermoplastic material.

[0042] In another embodiment, a cooling system for a separately excited synchronous electric machine comprises: rotor windings arranged radially outwardly of a rotor shaft and having a plurality of gaps between metal wire bundles; and a plurality of cooling tubes arranged in the plurality of gaps and configured to directly cool the rotor windings; and a rotor shaft cooling channel in direct fluidic communication with the plurality of cooling tubes. In another example, the outlet openings of the plurality of cooling tubes may be configured to direct coolant to a plurality of nozzles that spray coolant toward the rotor windings; or to direct coolant to submerged rotor end windings. In another example, the plurality of cooling tubes may be in fluidic communication with a rotor shaft cooling channel.In another example, the plurality of cooling tubes may be embedded in an epoxy or thermally thermosetting material. In another example, the separately excited synchronous electric machine may be a traction motor included in an electric drive.

[0043] Although various embodiments have been described above, it should be understood that these are only examples and not limitations. Those skilled in the art will appreciate that the disclosed subject matter may be embodied in other specific forms without departing from the spirit of the subject matter. The embodiments described above are, therefore, to be considered in all respects as illustrative and not restrictive. Thus, the configurations and routines disclosed herein are exemplary in nature, and the specific examples are not to be considered limiting, as numerous variations are possible. For example, the above technology may be applied to a variety of systems including electric drives with various powertrain types, including internal combustion engines, such as in a hybrid vehicle.The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, as well as other features, functions and / or properties disclosed herein.

[0044] It should be noted that the example control and estimation routines contained herein can be used with various electric drive and / or system configurations. The control methods and routines disclosed herein may be stored as executable instructions in non-transitory memory and may be executed by the control system, including the controller, in combination with the various sensors, actuators, and other electric drive and / or system hardware in combination with the electronic controller. Therefore, the described actions, operations, and / or functions may graphically represent code to be programmed into the non-transitory memory of the computer-readable storage medium in the electric drive and / or system.The various actions, operations, and / or functions illustrated may be performed in the order shown, in parallel, or in some cases omitted. Accordingly, the order of processing is not required to achieve the features and advantages of the examples described herein, but is provided for convenience only. One or more of the actions, operations, and / or functions illustrated may be performed repeatedly depending on the specific strategy employed. One or more of the process steps described herein may be omitted if desired.

[0045] The following claims particularly point out certain combinations and subcombinations that are considered novel and non-obvious. These claims may refer to "a" element or "a first" element, or the equivalent thereof. Such claims are to be construed as including the inclusion of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed by amending the present claims or by filing new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope than the original claims, are also to be considered included within the subject matter of the present disclosure. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 8,022,582 B2

[0003]

Claims

[1] Cooling system for a separately excited electrical machine, comprising: Rotor windings arranged radially around a rotor shaft and having a plurality of gaps between bundles of metal wires; and a cooling device arranged in the plurality of gaps and configured to directly cool the rotor windings. [2] A cooling system for a separately excited electric machine according to claim 1, wherein the cooling device comprises a plurality of cooling tubes. [3] A cooling system for a separately excited electric machine according to claim 2, wherein the plurality of cooling tubes are embedded in a thermoplastic material. [4] A cooling system for a separately excited electric machine according to claim 2, wherein the plurality of cooling tubes are embedded in an epoxy. [5] Cooling system for a separately excited electric machine according to one of claims 2 to 4, wherein the plurality of cooling tubes are in fluid communication with a rotor shaft cooling channel. [6] Cooling system for a separately excited electrical machine according to claim 5, wherein the rotor shaft cooling channel is in fluid communication with a rotor shaft bearing. [7] A cooling system for a separately excited electric machine according to any one of claims 2 to 6, wherein the plurality of cooling tubes are in fluid communication with a rotor end winding enclosure. [8] Cooling system for a separately excited electrical machine according to one of the preceding claims, wherein the cooling device comprises a plurality of heat pipes. [9] A cooling system for a separately excited electric machine according to claim 8, wherein the plurality of heat pipes are cooled via a rotor end winding spray nozzle or via immersed rotor end winding enclosures. [10] Cooling system for a separately excited electrical machine according to one of the preceding claims, wherein: a working fluid in the cooling system of the separately excited electrical machine is oil; and / or the separately excited electric machine is a traction motor contained in an electric drive.

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