System and method for direct winding heat exchanger in motor

Abstract

The invention relates to a system and method for a direct winding heat exchanger in a motor. A system includes: a rotor core; a rotor stack extending circumferentially from the rotor core, the rotor stack comprising: a first end; a second end opposite the first end; and a first slot in the rotor stack, the first slot extending from a first end to a second end; and a hairpin cooling tube in the first slot of the rotor stack.

Description

Technical Field

[0001] Various embodiments of the present disclosure relate generally to heat exchanger systems, and more particularly to systems and methods for direct-wound heat exchangers using porous layered tubes. Background Art

[0002] Thermal management is considered a key technical aspect of vehicle systems. Improving the thermal management of vehicle components, such as motors, can improve vehicle performance and reliability. An electric motor can refer to components such as the eMachine, stator, or rotor. Some systems can cool the motor at its outermost layer. However, the hottest areas of the motor may be located internally.

[0003] The present disclosure is directed to overcoming one or more of these challenges described above. Summary of the Invention

[0004] In some aspects, the technology described herein relates to a system comprising: a rotor core; a rotor stack extending circumferentially from the rotor core, the rotor stack comprising: a first end; a second end opposite the first end; and a first slot in the rotor stack, the first slot extending from the first end to the second end; and a hairpin cooling tube in the first slot of the rotor stack.

[0005] In some aspects, the technology described herein relates to a system wherein a hairpin cooling tube includes: a first elongated portion; a second elongated portion parallel to the first elongated portion; and a U-shaped connector connecting the first elongated portion to the second elongated portion.

[0006] In some aspects, the technology described herein relates to a system further comprising: a second slot extending from a first end of the rotor stack to a second end of the rotor stack; wherein the first slot of the rotor stack is configured to receive a first elongated portion of the hairpin cooling tube, and the second slot of the rotor stack is configured to receive a second elongated portion of the hairpin cooling tube.

[0007] In some aspects, the technology described herein relates to a system that also includes an inlet circuit extending circumferentially around a first end of a rotor stack and an outlet circuit extending circumferentially around the first end of the rotor stack.

[0008] In some aspects, the technology described herein relates to a system in which a first elongated section of a hairpin cooling tube is fluidly connected to an inlet circuit and a second elongated section of the hairpin cooling tube is fluidly connected to an outlet circuit.

[0009] In some aspects, the technology described herein relates to a system that also includes a pump, a filter, and a heat exchanger, wherein the pump, the filter, and the heat exchanger are fluidly connected to an inlet circuit of the rotor stack.

[0010] In some aspects, the technology described herein relates to a system further comprising: a sump, wherein the sump is fluidly connected to an outlet circuit of the rotor stack.

[0011] In some aspects, the technology described herein relates to a system wherein a rotor stack includes first and second laminations, first slots extend through the first and second laminations, and hairpin cooling tubes are disposed in the first slots in the first and second laminations.

[0012] In some aspects, the technology described herein relates to a system further comprising a stator, wherein the rotor core and the rotor stack are disposed within the stator, wherein the system is provided as a vehicle including the stator, the rotor core, and the rotor stack.

[0013] In some aspects, the technology described herein relates to a system comprising: a stator comprising: an outer barrel; a core positioned within the outer barrel, the core comprising a lamination stack, the lamination stack comprising: a first end; a second end opposite the first end; and a first slot in the lamination stack extending from the first end to the second end; and a hairpin cooling tube in the first slot of the lamination stack.

[0014] In some aspects, the technology described herein relates to a system wherein a hairpin cooling tube includes: a first elongated portion; a second elongated portion parallel to the first elongated portion; and a U-shaped connector connecting the first elongated portion to the second elongated portion.

[0015] In some aspects, the technology described herein relates to a system where the stator further comprises: a second slot extending from a first end of the lamination stack to a second end of the lamination stack; wherein the first slot of the lamination stack is configured to receive a first elongated portion of a hairpin cooling tube, and the second slot of the lamination stack is configured to receive a second elongated portion of the hairpin cooling tube.

[0016] In some aspects, the technology described herein relates to a system that also includes: an inlet circuit extending circumferentially around the stator; and an outlet circuit extending circumferentially around the stator.

[0017] In some aspects, the technology described herein relates to a system in which a first elongated section of a hairpin cooling tube is fluidly connected to an inlet circuit and a second elongated section of the hairpin cooling tube is fluidly connected to an outlet circuit.

[0018] In some aspects, the technology described herein relates to a system, wherein the system further comprises: a pump, a filter, and a heat exchanger, wherein the pump, the filter, and the heat exchanger are fluidly connected to the inlet circuit of the stator.

[0019] In some aspects, the technology described herein relates to a system, wherein the system further comprises: a reservoir, wherein the reservoir is fluidly connected to the outlet circuit of the stator.

[0020] In some aspects, the technology described herein relates to a system wherein a lamination stack includes first and second laminations, first slots extend through the first and second laminations, and hairpin cooling tubes are disposed in the first slots in the first and second laminations.

[0021] In some aspects, the technology described herein relates to a system that also includes a rotor, wherein the rotor is disposed within the stator.

[0022] In some aspects, the technology described herein relates to a method of assembling a cooling circuit, the method comprising: depositing an insulating layer on an outer surface of a tube; performing an induction process on an inner surface of the tube to form a deposit; reshaping the tube to have a rectangular cross-section; reshaping the tube into a hairpin shape as a hairpin tube; and assembling the hairpin tube into a slot in one or more of a rotor or a stator.

[0023] In some aspects, the technology described herein relates to a method wherein assembling a hairpin tube further comprises: inserting a first elongated portion of the hairpin tube into a first slot of a lamination stack; and inserting a second elongated portion of the hairpin tube into a second slot of the lamination stack, wherein the first elongated portion of the hairpin tube is parallel to the second elongated portion of the hairpin tube and is connected to the second elongated portion by a U-shaped connector.

[0024] Additional objects and advantages of the disclosed embodiments will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practicing the disclosed embodiments. The objects and advantages of the disclosed embodiments will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.

[0025] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosed embodiments, as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various exemplary embodiments and, together with the description, serve to explain the principles of the disclosed embodiments.

[0027] Figure 1 Depicted is an exemplary system infrastructure for a vehicle including an inverter, according to one or more embodiments.

[0028] Figure 2ADepicted is a cooling circuit including a stator including hairpin cooling tubes according to one or more embodiments.

[0029] Figure 2B Depicted is a cooling circuit including a rotor including hairpin cooling tubes according to one or more embodiments.

[0030] Figure 3 Depicted is a cross section of direct winding cooling utilizing hairpin cooling tubes according to one or more embodiments.

[0031] Figure 4 A flow chart is depicted of a process for manufacturing a motor having hairpin cooling tubes according to one or more embodiments.

[0032] Figure 5A Depicted are porous tubes for hairpin cooling tubes according to one or more embodiments.

[0033] Figure 5B Depicted is a porous tube having a rectangular cross-section according to one or more embodiments.

[0034] Figure 5C Hairpin cooling tubes are depicted according to one or more embodiments.

[0035] Figure 5D Depicted are stator slots with hairpin cooling tubes according to one or more embodiments. DETAILED DESCRIPTION

[0036] The foregoing summary description and the following detailed description are merely exemplary and illustrative and do not limit the claimed features. As used herein, the terms "comprises," "having," "comprising," or variations thereof are intended to encompass non-exclusive inclusions such that a process, method, article, or device comprising a series of elements includes not only those elements but may also include other elements that are not explicitly listed or that are inherent to such a process, method, article, or device. In this disclosure, unless otherwise stated, relative terms (e.g., "about," "substantially," and "approximately") are used to indicate a possible variation of ±10% in the value. In this disclosure, unless otherwise stated, any numerical value may include a possible variation of ±10% in the value.

[0037] The terms used below should be interpreted in their broadest reasonable manner, even when used in conjunction with the detailed description of certain specific examples of the present disclosure. In fact, certain terms may even be emphasized below; however, any term that is intended to be interpreted in any limited manner will be explicitly and specifically defined as such in this detailed description.

[0038] Various embodiments of the present disclosure relate generally to heat exchanger systems, and more particularly to systems and methods for direct-wound heat exchangers using porous layered tubes.

[0039] An electric vehicle (EV) or hybrid electric vehicle (HEV) may include an electric motor. An electric motor may be configured to convert electrical energy into mechanical energy. An electric motor may include components such as a stator and a rotor configured to rotate within the stator. The stator may generate a magnetic field that interacts with the rotor, causing the rotor to rotate. The rotational motion may then be used to drive a system. Exemplary electric motors include AC motors, DC motors, and stepper motors.

[0040] The motor assembly can have high operating temperatures when in use. The motor's performance, assembly process and time, and reliability can all depend on the built-in coolant structure. The motor's cooling structure can improve the vehicle's performance and reliability.

[0041] Some systems may include a cooling system (e.g., a jacket) located on the exterior surface of the motor. When in use, the motor may have its highest temperature internally, toward the center of the assembly. Therefore, an externally located cooling jacket may not effectively cool the motor because it contacts the least heated portion of the motor.

[0042] Some systems can use water-soluble thermoplastics (such as polyvinyl alcohol) to create direct windings for cooling motors. These direct windings can be placed inside the motor. Direct windings can be produced using 3D printers or through injection molding. However, water-soluble molded parts may have limited cooling performance.

[0043] Some systems can incorporate direct winding cooling by utilizing 3D-printed heat exchangers made of copper. These 3D-printed systems may include complex shapes for turbulent flow and for high heat exchange surfaces and can be difficult to produce. 3D-printed systems may also include issues such as assembly complexity, increased manufacturing costs, and reduced cooling performance of the motor.

[0044] One or more embodiments may include hairpin cooling tubes inserted into slots with the windings of the motor to dissipate heat from the motor's internal components (e.g., the stator or rotor). The windings may also include flat rectangular wire. The flat rectangular wire may increase the copper fill factor of the windings in the motor, while the hairpin cooling tubes may increase the cooling performance of the motor (and therefore increase continuous torque and power output).

[0045] One or more embodiments can be configured to improve cooling efficiency by providing a coolant device close to components that generate heat within the motor (i.e., in the motor's windings). For example, a heat exchanger (e.g., hairpin tubes) close to the heat-generating components (copper windings) can provide a high peak / continuous performance ratio for the motor.

[0046] One or more embodiments may include a hairpin tube within a slot of the motor. The hairpin tube may include a porous inner surface. The porous inner surface may increase the level of heat exchange performance by increasing the heat transfer coefficient due to turbulence generated within the hairpin tube.

[0047] One or more embodiments may include a large heat exchange area within the small tubes, enabling the system to be compact. This may result in a smaller motor outer diameter compared to some systems. The systems described herein may also include a low motor cycle temperature (at a given flow rate), which may provide better cycle efficiency (due to reduced copper losses). One or more embodiments may cool the stator and / or rotor. The slots within the motor may also include automatic transmission fluid (ATF) or water-ethylene glycol (WEG) configured to further cool the motor windings.

[0048] Figure 1 An exemplary system infrastructure for a vehicle including an inverter is depicted, according to one or more embodiments. An electric vehicle 100 may include an inverter 102, a connector 104, a drive motor 106, wheels 108, and a battery 110. The inverter 102 may include a power module 112. The connector 104 may connect the inverter 102 and the battery 110. The inverter 102 may include components that receive power from an external source and output power to charge the battery 110 of the electric vehicle 100. For example, the inverter 102 may convert DC power from the battery 110 in the electric vehicle 100 into AC power using the power module 112 to power the drive motor 106 and wheels 108 of the electric vehicle 100, but embodiments are not limited thereto. The inverter 102 may be bidirectional and may convert DC power to AC power, or vice versa, such as during regenerative braking. The inverter 102 may be a single-phase inverter or a multi-phase inverter, such as a three-phase inverter. The drive motor 106 may include Figure 2A and Figure 2B A stator cooling circuit 200a and / or a rotor cooling circuit 200b are shown.

[0049] Figure 2AA stator cooling circuit 200a is depicted, including a stator 208 and hairpin cooling tubes 215, according to one or more embodiments. The stator cooling circuit 200a may include a pump 202, a filter 204, a heat exchanger 206, the stator 208, and a reservoir 218. The pump 202 may be configured to transfer coolant through the stator cooling circuit 200a. The pump 202 may be in fluid communication with the filter 204. The filter 204 may be configured to filter the coolant flowing within the stator cooling circuit 200a.

[0050] The filter 204 can be in fluid communication with a heat exchanger 206. The heat exchanger 206 can transfer excess heat from the stator cooling circuit 200a. The heat exchanger 206 can be, for example, an engine coolant radiator, an oil cooler, or an intercooler. The heat exchanger 206 can be in fluid communication with the stator 208.

[0051] The stator 208 may be configured to generate a rotating magnetic field. The stator 208 may include an outer cylinder 229 and a core 211 within the outer cylinder 229. The stator 208 may include a first end 232 and a second end 234 opposite the first end 232. The stator 208 may include an opening 230 extending from the first end 232 to the second end 234. The opening 230 may be configured to receive a rotor (e.g., Figure 2B Rotor 209 shown).

[0052] The stator 208 may include a stack including a set of laminations (e.g., laminations 213a, 213b, etc.) that may include one or more slots (e.g., slot 219a and slot 219b) in the stack that are configured to receive the hairpin cooling tubes 215 (or Figure 5D hairpin tube 506) and insulated wire / winding (e.g., Figure 3 The stack (e.g., laminations 213a, 213b, etc.) may extend from the first end 232 of the stator 208 to the second end 234 of the stator 208. The slots (e.g., slots 219a and 219b) may extend from the first end 232 of the stator 208 to the second end 234 of the stator 208. The slots (e.g., slots 219a and 219b) may extend a portion of the axial length of the core 211.

[0053] The hairpin cooling tube 215 may include a first elongated portion 214, a second elongated portion 216 parallel to the first elongated portion 214, and a U-shaped connector 217 connecting a first end of the first elongated portion 214 to a first end of the second elongated portion 216. The slots may be parallel to each other. The slots may be configured to receive portions of the hairpin cooling tube 215. For example, the first elongated portion 214 and the second elongated portion 216 may each be input into a corresponding slot (e.g., slot 219a and slot 219b) of a stack (e.g., laminations 213a, 213b, etc.). The slots (e.g., slot 219a and slot 219b) may be Figure 5D Further described in.

[0054] The stator 208 can include an inlet circuit 210 and an outlet circuit 212. The inlet circuit 210 and the outlet circuit 212 can each extend circumferentially around the first end 232 of the stator 208. The inlet circuit 210 can be in fluid communication with the heat exchanger 206. The outlet circuit 212 can be in fluid communication with a reservoir 218, and the reservoir can be in fluid communication with the pump 202. The stack (e.g., laminations 213a, 213b, etc.) can include two slots (e.g., slot 219a and slot 219b). The first slot of the stack (e.g., slot 219a) can include a portion of the hairpin cooling tube 215 (e.g., first elongated portion 214) that can be in fluid communication with the inlet circuit 210. The second slot of the stack (e.g., slot 219b) can include a portion of the hairpin cooling tube 215 (e.g., second elongated portion 216) that can be in fluid communication with the outlet circuit 212.

[0055] Figure 2B Depicted is a rotor cooling circuit 200b including a rotor 209 and hairpin cooling tubes 215 according to one or more embodiments. Figure 2A The stator 208 may be configured to receive the rotor 209 within the opening 230 of the stator 208. The rotor cooling circuit 200b may include a pump 202, a filter 204, a heat exchanger 206, a rotor 209, and a reservoir 218, all in fluid communication.

[0056] The rotor 209 may include a rotor core 223 extending along a rotor axis 224 and a rotor stack 222 (e.g., one or more rotor laminations) extending circumferentially from the rotor core 223. The rotor 209 may include a first end 236 and a second end 238 opposite the first end. The one or more rotor laminations may be stacked from the first end 236 to the second end 238. The rotor stack 222 may include one or more slots (e.g., slots 219a and 219b) configured to receive the hairpin cooling tubes 215 and the flat copper wire 304, as shown. Figure 3As shown. The slots of the rotor stack 222 can be arranged and perform the same function as the slots of the stack of the stator 208. The rotor stack 222 can include a set of laminations arranged from a first end 236 of the rotor 209 to a second end 238 of the rotor 209. The slots (e.g., slots 219a and 219b) can extend from the first end 236 of the rotor 209 to the second end 238 of the rotor 209. The slots (e.g., slots 219a and 219b) can extend in a direction parallel to the rotor axis 224.

[0057] The rotor 209 may include an inlet circuit 210 and an outlet circuit 212. The inlet circuit 210 and the outlet circuit 212 may each extend circumferentially around the first end 236 of the rotor 209. The inlet circuit 210 may be in fluid communication with the heat exchanger 206. The outlet circuit 212 may be in fluid communication with a reservoir 218, and the reservoir may be in fluid communication with the pump 202. The rotor stack 222 may include two slots (e.g., slot 219a and slot 219b). The first slot (e.g., slot 219a) of the rotor stack 222 may include a portion (e.g., first elongated portion 214) of the hairpin cooling tube 215 that may be in fluid communication with the inlet circuit 210. The second slot (e.g., slot 219b) of the rotor stack 222 may include a portion (e.g., second elongated portion 216) of the hairpin cooling tube 215 that may be in fluid communication with the outlet circuit 212.

[0058] Figure 3 A cross section of direct winding cooling using hairpin cooling tubes is depicted in accordance with one or more embodiments. Direct winding cooling may be depicted within a stack 302 of a stator (e.g., stator 208). The cross section of stator 208 may include a cross section of outer barrel 229, stack 302 (e.g., laminations 213a, 213b, etc.), and slots 219a. Slots 219a may include flat copper wires 304 and cooling channels 306 (e.g., as shown in FIG. 2 ). Figure 3 The cooling channel 306 may be configured to receive an elongated portion of the hairpin cooling tube 215 or hairpin tube 506, as shown. Figure 4 As described in operation 412.

[0059] Flat copper wire 304 can increase the copper fill factor of the motor within a single tooth winding (eg, stack). Cooling channel 306 can include space for hairpin cooling tube 215 or hairpin tube 506 or can be configured to perform direct cooling of flat copper wire 304.

[0060] Figure 4A flowchart 400 is depicted of a manufacturing process for a motor having hairpin cooling tubes according to one or more embodiments. At operation 402, a tube may be received. The tube may be aluminum, copper, or steel. The tube may be a flat heat pipe. The tube may be flexible, ductile, and easily deformable. The tube may have various alternative shapes, such as a rectangular, square, circular, triangular, pentagonal, or hexagonal cross-section. The length of the tube may include, but is not limited to, 0.1 meters, 0.2 meters, 0.5 meters, 1.0 meters, 2.0 meters, etc. The tube may have a diameter of 1 mm, 5 mm, 10 mm, etc. The tube may be rectangular and have a width of approximately 3 mm, a height of approximately 2 mm, and a length of approximately 500 mm. The tube may be square and have a width of approximately 2 mm, a height of approximately 2 mm, and a length of approximately 500 mm.

[0061] The size of the tubes received may be based on a variety of factors, including, for example, one or more of the overall motor packaging requirements, heat exchange efficiency with respect to tube diameter and length, maximum authorized pressure drop per tube, tube material, or thickness of the inner layer.

[0062] At operation 404, an electrical insulation layer may be deposited on the outer surface of the tube from operation 402. The insulation layer may prevent the tube from leaking electricity when used in a motor (eg, within a stator or rotor).

[0063] At operation 406, a copper pore deposit may be applied to the inner surface of the tube from operation 404. This may allow the tube to be as Figure 5A The porous tube 500 is shown. The porous tube 500 may include a porous layer 502 on the inner surface (i.e., a portion of the inner surface) of the porous tube 500. The porous layer 502 may be formed by a sintering process and / or by an induction method. Operations 404 and 406 may increase the cooling capacity of the porous tube 500.

[0064] At operation 408, the porous tube 500 may be reshaped. For example, the porous tube 500 may be reshaped to have a rectangular cross-section, such as Figure 5B The porous tube 500 having a rectangular cross-section may be referred to as a rectangular cross-section tube 504 .

[0065] At operation 410, the rectangular cross-section tube 504 may be formed into a hairpin shape by bending and cutting the rectangular cross-section tube 504. After reshaping, the rectangular cross-section tube 504 may be referred to as a hairpin tube 506. Figure 5C5. Hairpin tubes 506 (e.g., a set of four hairpin tubes) are shown. Each hairpin tube 506 may include a first elongated portion 505, a second elongated portion 507 parallel to the first elongated portion 505, and a U-shaped connector 509 connecting a first end 514 of the first elongated portion 505 to a first end 516 of the second elongated portion 507. The second end 518 of the first elongated portion 505 and the second end 520 of the second elongated portion 507 may be configured to connect to an inlet and / or outlet circuit. Each hairpin tube 506 may be hollow, and the second end 518 of the first elongated portion 505 may be fluidically connected to the second end 520 of the second elongated portion 507.

[0066] At operation 412, the hairpin tube 506 can be inserted into the lamination stack of the motor. This can include inserting a particular elongated portion (e.g., the first elongated portion 505 or the second elongated portion 507) into an opening in the lamination stack. For example, the lamination stack can be lamination stack 508a, lamination stack 508b, lamination stack 508c, or lamination stack 508d, as shown in FIG. Figure 5D For example, each lamination stack (e.g., lamination stack 508a, lamination stack 508b, lamination stack 508c, or lamination stack 508d) can have a corresponding opening (e.g., opening 512a, opening 512b, opening 512c, opening 512d) configured to receive the elongated portion of the hairpin tube 506.

[0067] The lamination stack may include a liquid to assist in heat transfer from the stator to the hairpin tubes 506. The liquid may be ATF or WEG. The liquid may be located at the end of the stator closest to the opening (e.g., liquid 510a in lamination stack 508a or liquid 510c in lamination stack 508c). The liquid may also be located at the end of the stator farthest from the stator opening (e.g., liquid 510b in lamination stack 508b or liquid 510d in lamination stack 508d). Operation 412 may be performed during stator winding assembly.

[0068] At operation 414, respective ends (eg, second end 518 and second end 520) of the hairpin (eg, hairpin tube 506) may be connected to respective motors (eg, Figure 2A Stator 208 or Figure 2B For example, the second end 518 can be connected to the inlet circuit 210, and the second end 520 can be connected to the outlet circuit 212. These ends can be inserted and sealed into their respective circuits.

[0069] At operation 416, the corresponding motor (eg, Figure 2A Stator 208 or Figure 2B The cooling system of the rotor 209).

[0070] Hairpin cooling tubes can be configured to cool the stator windings directly from the inside. This direct internal cooling can provide improved stator cooling compared to external cooling systems. The method described herein can be a robust, reproducible, and rapid process. Compared to 3D-printed heat exchangers for motors, this method can be more efficient.

[0071] One or more embodiments may include hairpin cooling tubes inserted into slots with the windings of the motor to dissipate heat from the motor's internal components (e.g., the stator or rotor). The windings may also include flat rectangular wire. The flat rectangular wire may increase the copper fill factor of the windings in the motor, while the hairpin cooling tubes may increase the cooling performance of the motor (and therefore increase continuous torque and power output).

[0072] One or more embodiments can be configured to improve cooling efficiency by providing a coolant device close to components that generate heat within the motor (i.e., in the motor's windings). For example, a heat exchanger (e.g., hairpin tubes) close to the heat-generating components (copper windings) can provide a high peak / continuous performance ratio for the motor.

[0073] One or more embodiments may include a hairpin tube within a slot of the motor. The hairpin tube may include a porous inner surface. The porous inner surface may increase the level of heat exchange performance by increasing the heat transfer coefficient due to turbulence generated within the hairpin tube.

[0074] One or more embodiments may include a large heat exchange area within the small tube, enabling the system to be compact. This may result in a smaller motor outer diameter compared to some systems. The systems described herein may also include a low motor cycle temperature (at a given flow rate), which may provide better cycle efficiency (due to reduced copper losses). One or more embodiments may cool the stator and / or rotor. The slots within the motor may also include automatic transmission fluid (ATF) or water-ethylene glycol (WEG) configured to further cool the motor windings.

[0075] Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and embodiments be considered exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

Claims

1. A system, comprising: rotor core; A rotor stack extending circumferentially from the rotor core, the rotor stack comprising: First end; a second end opposite the first end; and a first slot in the rotor stack, the first slot extending from the first end to the second end; and Hairpin cooling tubes in the first slots of the rotor stack.

2. The system according to claim 1, wherein: The hairpin cooling tube comprises: a first elongated portion; a second elongated portion parallel to the first elongated portion; and A U-shaped connector connects the first elongated section to the second elongated section.

3. The system according to claim 2, further comprising: a second slot extending from the first end of the rotor stack to the second end of the rotor stack; Wherein, the first slot of the rotor stack is configured to receive the first elongated portion of the hairpin cooling tube, and the second slot of the rotor stack is configured to receive the second elongated portion of the hairpin cooling tube.

4. The system according to claim 2, further comprising: an inlet circuit extending circumferentially around the first end of the rotor stack; as well as An outlet circuit extends circumferentially around the first end of the rotor stack.

5. The system according to claim 4, wherein: The first elongated portion of the hairpin cooling tube is fluidly connected to the inlet circuit, and the second elongated portion of the hairpin cooling tube is fluidly connected to the outlet circuit.

6. The system according to claim 4, further comprising: pump, Filters; as well as A heat exchanger, wherein the pump, the filter and the heat exchanger are fluidly connected to the inlet circuit of the rotor stack.

7. The system according to claim 4, further comprising: A fluid reservoir, wherein the fluid reservoir is fluidly connected to the outlet circuit of the rotor stack.

8. The system according to claim 1, wherein: The rotor stack includes first and second laminations, the first slots extending through the first and second laminations, and the hairpin cooling tubes disposed in the first slots in the first and second laminations.

9. The system according to claim 1, further comprising: a stator, wherein the rotor core and the rotor stack are arranged inside the stator, Therein, the system is provided as a vehicle including the stator, the rotor core, and the rotor stack.

10. A system comprising a stator, the stator comprising: outer cylinder; The core in the outer cylinder comprises a lamination stack, wherein the lamination stack comprises: First end; a second end opposite the first end; and a first slot in the lamination stack, the first slot extending from the first end to the second end; and A hairpin cooling tube in the first slot of the lamination stack.

11. The system according to claim 10, wherein: The hairpin cooling tube comprises: a first elongated portion; a second elongated portion parallel to the first elongated portion; and A U-shaped connector connects the first elongated section to the second elongated section.

12. The system according to claim 11, wherein The stator further comprises: a second slot extending from the first end of the lamination stack to the second end of the lamination stack; Wherein, the first slot of the lamination stack is configured to receive the first elongated portion of the hairpin cooling tube, and the second slot of the lamination stack is configured to receive the second elongated portion of the hairpin cooling tube.

13. The system according to claim 11, further comprising: an inlet circuit extending circumferentially around the stator; as well as An outlet circuit extends circumferentially around the stator.

14. The system according to claim 13, wherein: The first elongated portion of the hairpin cooling tube is fluidly connected to the inlet circuit, and the second elongated portion of the hairpin cooling tube is fluidly connected to the outlet circuit.

15. The system of claim 13, further comprising: pump, Filters; as well as A heat exchanger, wherein the pump, the filter and the heat exchanger are fluidly connected to the inlet circuit of the stator.

16. The system of claim 13, further comprising: A fluid reservoir is provided, wherein the fluid reservoir is fluidly connected to the outlet circuit of the stator.

17. The system according to claim 10, wherein: The lamination stack includes a first lamination and a second lamination, the first slot extends through the first lamination and the second lamination, and the hairpin cooling tube is disposed in the first slot in the first lamination and the second lamination.

18. The system according to claim 10, further comprising: A rotor is provided inside the stator.

19. A method of assembling a cooling circuit, the method comprising: depositing an insulating layer on the outer surface of the tube; performing an induction method on the inner surface of the tube to form a deposit; reshaping the tube to have a rectangular cross-section; reshaping the tube into a hairpin shape as a hairpin tube; as well as The hairpin tubes are assembled into slots in one or more of the rotor or stator.

20. The method according to claim 19, wherein Assembling the hairpin tube further comprises: inserting the first elongated portion of the hairpin tube into the first slot of the lamination stack; and inserting the second elongated portion of the hairpin tube into the second slot of the lamination stack, Wherein, the first elongated portion of the hairpin-shaped tube is parallel to the second elongated portion of the hairpin-shaped tube and is connected to the second elongated portion via a U-shaped connector.

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