Electric motor with unvarnished end windings for the stator

Abstract

The electric motor comprises: a rotor; a stator having a stack of laminations, wherein the stator windings include wires with individual insulation, the wires forming slot windings disposed within slots of the stator, the wires further forming end windings disposed outside the slots at each end of the stator; varnish within the slots of the stator, the varnish contacting the laminations and the slot windings, wherein the varnish does not contact the end winding at least one of the ends of the stator; and a cooling system for applying liquid coolant to at least the end windings, wherein the liquid coolant passes between the wires of the end windings.

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims priority to U.S. Provisional Patent Application No. 63 / 373,837, filed August 29, 2022, entitled "ELECTRIC MOTOR WITH UNVARNISHED END WINDING FOR STATOR," the entire disclosure of which is incorporated herein by reference.

[0002] This document relates to an electric motor with at least one unvarnished end winding. [Background technology]

[0003] A typical stator for an electric motor consists of windings wound around an iron core to create the stator. The portions of the windings that are outside the iron core on either side are called end windings. The stator windings are impregnated with a liquid resin or varnish that provides a layer of resin in the slots and also covering and passing through the end windings. Such varnish typically penetrates deep into all layers of wire and the stator slots and is sometimes referred to as secondary insulation.

[0004] Secondary insulation has been used to serve several purposes. First, it improves the mechanical structure of the windings by bonding them to each other and to the body of the stator. Second, it can improve the electrical insulation of the wires. Third, the varnish increases the thermal mass of the stator. Summary of the Invention

[0005] In a first aspect, an electric motor includes a rotor; a stator having a stack of laminations, wherein the stator windings include wires with individual insulation, the wires forming slot windings disposed within slots of the stator, the wires further forming end windings disposed outside the slots at each end of the stator; varnish within the slots of the stator, the varnish contacting the laminations and the slot windings, wherein the varnish does not contact the end winding at least one of the ends of the stator; and a cooling system for applying liquid coolant to at least the end windings, wherein the liquid coolant passes between the wires of the end windings.

[0006] The implementation may include any or all of the following features: The varnish does not contact any of the end windings; The wires have a rectangular cross-sectional profile; The wires have a circular cross-sectional profile; The end windings form a continuous wave pattern with respect to the slots of the stator; The end windings are hairpin windings; The individual insulators include at least a first layer covering each of the wires and a second layer covering the first layer; The first layer includes enamel; The second layer includes resin; and The varnish includes resin.

[0007] In a second aspect, an electric motor includes a rotor; a stator having a stack of laminations, wherein the stator windings include wires with individual insulation, the wires forming slot windings disposed within slots of the stator, the wires further forming end windings disposed outside the slots at each end of the stator; varnish within the slots of the stator, the varnish contacting the laminations and the slot windings; and means for applying liquid coolant to at least the end windings such that the liquid coolant passes between the wires of the end windings. [Brief explanation of the drawings]

[0008] [Figure 1] 1 shows a cross section of an example electric motor.

[0009] [Figure 2] 1 shows a cross section of an example of one-sixth of an electric motor.

[0010] [Figure 3A] 1 illustrates a cross-sectional view of an example stator slot in a stator lamination.

[0011] [Figure 3B] 1 illustrates a cross-sectional view of an example end winding in a stator.

[0012] [Figure 4] 1 shows an example of applying varnish only to the slots in the stator and not to the end windings.

[0013] [Figure 5] 1 is a diagram with an example of a graph showing torque over time for an electric motor.

[0014] [Figure 6] 1 is a diagram with an example graph showing stator slot temperature over time for an electric motor.

[0015] Like reference numbers in the various drawings indicate like elements. DETAILED DESCRIPTION OF THE INVENTION

[0016] This document describes example systems and techniques for providing electric motors with unvarnished end windings. In some implementations, resin is omitted from the end windings, allowing the individually insulated wires to directly contact a coolant, such as motor oil (e.g., automatic transmission fluid). This can improve thermal management of the end windings, resulting in better heat extraction, higher thermal performance, and the ability of the motor to sustain higher peak torque at each time interval or to maintain a given peak torque for a longer time interval. For example, the amount of exposed winding area in the end windings can be increased, reducing the thermal resistance of the heat path from the wire to the coolant. This allows the windings, and thereby the stator as a whole, to cool significantly faster; higher sustained torque can be achieved; and / or performance criteria (e.g., 0-60 mph (26.82 m / s) time or quarter-mile (402.34 meter) race time or speed) can be significantly improved.

[0017] The examples described herein refer to vehicles. A vehicle is a machine that transports passengers, cargo, or both. A vehicle can have one or more motors that use at least one type of fuel or other energy source (e.g., electricity). Examples of vehicles include, but are not limited to, cars, trucks, and buses. The number of wheels can vary between vehicle types, and one or more (e.g., all) of the wheels can be used to propel the vehicle. A vehicle can include a passenger compartment that accommodates one or more people.

[0018] The examples described herein refer to electric motors. An electric motor as used herein can be any type of electric motor, including but not limited to a permanent magnet motor, an induction motor, a synchronous motor, or a reluctance motor.

[0019] Examples described herein may refer to above, below, in front, or behind. These and similar expressions identify things or aspects in a relative manner based on an explicit or arbitrary concept of perspective. That is, these terms are merely examples used for illustrative purposes and do not necessarily indicate the only possible positions, orientations, etc.

[0020] Generally, an electric motor may comprise a stator and a rotor, where the interaction of magnetic fields generated by each of these components with appropriate current results in torque at the rotor. The torque generated by an electric motor is directly related to the amount of current that can be passed through the windings. The magnet wire used to form the windings has a specified temperature rating (temperature index). Short-duty torque generation is defined by the amount of time that current can be applied while maintaining the windings below the specified temperature rating. In high-power-density motors, extracting heat from the windings is difficult. Effectively removing such heat increases the time at peak torque and / or the peak torque. Liquid cooling of the motor is one such effective mechanism for extracting heat from the windings to improve the motor's short-duty torque rating. For traction motors used in electric vehicles, this directly impacts vehicle performance metrics such as 0-60 and quarter-mile times.

[0021] Varnishing is the process of applying a varnish (e.g., resin) that covers the stator windings, filling the air pockets in the end windings and between the slot windings and the stator stack. The resin used in varnishing has high dielectric strength, adhesive properties, and relatively better thermal conductivity than air. This improves electrical insulation in the slots and heat conduction from the wires to the stack. It also helps adhere the windings to the stack, protecting them from vibration and potential damage caused by high-frequency electromagnetic and mechanical forces acting against them during motor operation.

[0022] Commonly used methods of applying varnish include dip-and-bake, vacuum pressure impregnation (VPI), and trickle coating processes. For example, the entire stator can be preheated and then submerged in liquid varnish. These processes are typically designed to cover air pockets in the slots and end windings, and some offer more control over coverage than others.

[0023] In some implementations, a tailored varnishing process is used that varnishes the slot windings while leaving the end windings free of varnish. For example, a resin dispensing nozzle can be precisely repositioned to the target area, or the end windings can be masked (e.g., in the case of a dip-and-bake or VPI process). Advantages of the present subject matter can include, but are not limited to: increased exposed winding area in the end windings or reduced thermal resistance of the thermal path. This can improve the efficiency of heat extraction from the end windings, which are cooled by forced distribution of fluid.

[0024] In terms of architecture, a motor consists of a stationary and rotating portion called the stator and rotor, with an air gap between them. The stator can be made from laminated steel sheets with slots, and the laminations are stacked to the required length. Round or rod-shaped copper conductors are inserted into the slots, resulting in a portion of the winding extending out of the stack at each end of the stator. The slot conductors are connected to the conductors in other slots through end windings. The stator assembly then undergoes a varnishing process to improve the winding's dielectric strength and thermal conductivity. Furthermore, the end windings allow motor designers to establish different winding connections, such as series / parallel or star / delta.

[0025] In operation, the process of electrical-to-mechanical energy conversion begins by injecting an appropriate current into the stator to establish a stator magnetic field. Depending on the motor topology, the rotor can have permanent magnets or windings or other conductors, any of which produce the rotor magnetic field. As a result of the interaction between these two magnetic fields from the stator and rotor, torque is generated in the rotor, which can be used to perform any mechanical work in applications such as electric vehicle powertrains, fans, and pumps. The torque generated is proportional to the strength of the magnetic field established, which in turn is directly proportional to the current injected into the stator. In other words, higher torque demands mean that more current must pass through the stator windings. The increased current, in turn, results in greater heat generation in the stator windings.

[0026] The majority of losses in the process of converting electrical energy into mechanical energy are resistive losses (i 2 R). The heat generated in the stator slots is conducted to the stack of stator laminations, which can be effectively removed by different methods such as water jackets, oil cooling, or forced air, to name just a few. Because the end windings are surrounded by air, which is typically a poor conductor of heat, and because the winding insulation has a specific temperature rating, the stator current density is typically around 20 amperes per square millimeter (A / mm 2 ), is limited to a prescribed level. In traction applications, high torque at low speeds may be desirable to achieve desirable high performance metrics, such as acceleration from 0 to 60 mph (26.82 m / s) or shorter times for completing a quarter-mile (402.34 meter) race. High current density may be desirable to achieve higher torque, but current density is currently limited by thermal bottlenecks in the end windings.

[0027] Extracting heat from the stator can be challenging, especially in high-power-density motor implementations. Therefore, successfully and effectively removing heat from the end windings can provide significant benefits in meeting high traction power demands and increasing drive unit power density. Current density in the windings is often limited due to the temperature rating of the winding insulation. The temperature rating corresponds to a temperature index and can reflect the maximum temperature the wire can handle before its electromechanical properties deteriorate. Thus, effectively removing heat can increase the amount of time the motor can operate at peak torque and / or increase the level of peak torque, both of which are very important performance features.

[0028] Attempts to cool the end windings have previously been made by placing some kind of coolant, such as oil, in contact with the windings. In previous motors, the end windings were varnished so that the coolant would remove the thermal energy by extracting heat from the end windings when they were heated. The coolant could eventually be discharged into the motor plant sump. This allowed the stator to draw a maximum of about 30 A / mm 2 This may enable the thermal resistance to current densities up to 1000 .mu.m.

[0029] In the present subject matter, end winding cooling can be further enhanced with the aid of a tailored varnishing technique that varnishes the slot winding while leaving the end winding unvarnished. This can be accomplished either by precisely repositioning the resin dispensing nozzle to the target area or by masking the end winding in the case of dip-and-bake or VPI processes. As a result, the winding area exposed to the coolant (e.g., oil) can be significantly increased. The thermal resistance between the coolant and the wire material (e.g., copper) can also be significantly reduced compared to varnished end windings, where a composite of copper, insulation, and varnish can exist between the winding and the oil. The efficiency of heat extraction from forced-fluid-cooled end windings has been approximately 60 A / mm in some cases. 2It may be acceptable to use a derating strategy that allows for a current density greater than

[0030] The subject inventors have discovered that the mechanical, insulating, and thermal benefits associated with varnishing end windings do not preclude the use of a different approach in motor manufacturing, in which the end windings remain unvarnished. The thermal mass of the varnish previously applied to the end windings provides a slight improvement in thermal performance because it allows heat to be transferred from the end windings to the varnish. However, this benefit may only be realized at transient load levels, such as when the motor operates at or near its full capacity, and even then, the varnish may become saturated with thermal energy after the initial transient. Also, applying varnishing to the end windings has the effect of significantly reducing the surface area of ​​the end windings that is available for thermal isolation. For example, rather than using the cumulative surface area of ​​all the individual wires in the end winding for heat transfer, the varnished end winding may use only the outer varnish surface, which may have a significantly smaller total area than the wires.

[0031] FIG. 1 provides a cross-sectional view of the major elements of a motor and integrated cooling system 100. The motor and integrated cooling system 100 may be a coolant injection system that can inject coolant directly into the motor enclosure. In at least one embodiment, the motor housing is a multi-piece housing comprised of a cylindrical motor casing 101 that is mechanically coupled to forward and aft end caps 103 and 105, respectively. The motor core assembly, supported at each end by bearing assemblies 107 and 109, includes a rotor 111 and a rotor shaft 113. A center portion 115 of the rotor shaft 113 may be hollow. Also visible in this view is a stator 117.

[0032] At one end of the rotor shaft 113 is a drive gear 119. Although not shown in this view, the drive gear 119 may be housed in a gearbox (i.e., gear housing). The gearbox may be separate from the motor; alternatively, the gearbox, or at least one wall of the gearbox, may be integral with the forward end cap 103.

[0033] The coolant intake 121 is integrated into one of the end caps of the motor assembly, for example, the forward end cap 103 as shown. The coolant is non-gaseous and can have thermal and mechanical properties suitable for a liquid motor coolant, such as a high heat capacity, a high decomposition temperature, and a relatively low viscosity. Furthermore, because the coolant flows between the rotor and stator and small portions of the rotor shaft and the end cap, the coolant can also be a good lubricant and can be electrically non-conductive. Thus, in at least one embodiment, oil (e.g., automatic transmission fluid) is used as the coolant.

[0034] In the embodiment shown in FIG. 1 , coolant passing into the inlet 121 can be pressurized through a coolant inlet tube 125 via a coolant pump 123. In this embodiment, the coolant pump 123 is an external pump, e.g., an electric pump, although other types of pumps, such as a mechanical pump powered by the rotor shaft 113, can also be used. The coolant inlet 121 is coupled to a coolant passage 127. The passage 127 connects the inlet 121 to one or more injection nozzles 129 and from there into a region 131 of the motor enclosure. The injection nozzles 129 can be located at either end of the stator 117 and at or near the top of the motor casing 101. As a result of this nozzle location, the coolant flowing from the injection nozzles 129 can pass over the stator 117 and the stator end windings 133. For example, the stator end windings 133 can be said to be splashed with coolant during operation. The stator end windings 133 are now free of any varnish, resin, or other bulk material. Rather, the stator winding wires have individual insulation, and no secondary insulation is applied to the wires in the stator end windings 133. As a result, coolant flowing from the injection nozzles 129 can pass between the wires in the stator end windings 133. The stator 117 may be formed from stacked laminations that form slots for the stator winding wires. Within these slots, in contrast, varnish may be applied so that it contacts both the laminations and the winding wires within the slots. This approach can improve the thermal performance of the motor and the integrated cooling system 100.

[0035] At least some of the coolant flowing through injection nozzles 129 may be dispersed throughout the motor enclosure by the spinning rotor 111 and rotor end rings. The coolant may eventually pass through one or more casing output openings 135 located at or near the bottom of the casing and collect in a reservoir 137. Reservoir 137 is coupled to coolant pump 123. The heat absorbed by the coolant may then be transferred to the ambient environment or to another thermal system (e.g., a refrigeration system) using any of a variety of known techniques.

[0036] 2 shows a cross-sectional view of one sixth of an example electric motor 200. Here, only one sixth is shown, with the remainder of electric motor 200 omitted for clarity. As such, the below-described components of electric motor 200 may additionally include other features and / or portions not visible here. Electric motor 200 can be used with one or more other examples described elsewhere herein.

[0037] Electric motor 200 includes rotor 202. Rotor 202 is shown here as having an outer periphery 202A (sometimes referred to as the outer diameter) and an inner periphery 202B (sometimes referred to as the inner diameter). Rotor 202 is configured to be driven by a rotating magnetic field to rotate about a central axis (not shown). For example, rotor 202 may have a so-called active core where a differential (not shown) is fully or partially integrated within the interior of the rotor shaft.

[0038] The rotor 202 can be designed according to any of several operating principles. In some implementations, the rotor 202 is formed from laminations 204 stacked essentially perpendicular to the axis of rotation. For example, the laminations 204 can be made from a metal, including but not limited to a steel material.

[0039] The rotor 202 can be designed with multiple poles that encourage the rotor 202 to be driven by a rotating magnetic field during operation of the electric motor 200. The poles of the rotor 202 can be generated in different ways. In some implementations, the rotor 202 can include permanent magnets. Other approaches can be used.

[0040] The electric motor 200 includes a stator 206 that surrounds the rotor 202. The stator 206 is formed from a stack of laminations and includes a plurality of slots 208. Each of the slots 208 is configured to hold a wire 210 that forms a stator winding of the stator 206. The stator 206 can have a plurality of wires 210 in each of the slots 208 to form a slot winding. The wires 210 can have any suitable shape. In some implementations, the wires 210 have a rectangular cross-sectional profile (e.g., as shown). In some implementations, the wires 210 have a circular cross-sectional profile. The wires 210 can be arranged within the slots 208 in one or more ways. In some implementations, each of the slots 208 is configured to hold a plurality of wires 210 in a linear arrangement between a rear portion 208A of the slot 208 and a front portion 208B of the slot 208. A front portion 208B of the slot 208 may be positioned adjacent to the air gap between the stator 206 and the rotor 202, the air gap being formed in a stator bore of the stator 206 that houses the rotor 202.

[0041] Each of the slots 208 has a varnish 212 disposed within the slot 208 such that the varnish 212 contacts the laminations of the stator 206 and the wires 210 within the slot 208. The varnish 212 does not extend beyond the front 208B of the slot 208. Also, the varnish 212 does not cover any of the end windings (not shown) of the stator 206.

[0042] FIG. 3A shows a cross-sectional view of an example stator slot 300 in a stator lamination 302. For simplicity, only one instance of the stator slot 300 and the portion of the stator lamination 302 closest to the stator slot 300 are shown. This example can be used with one or more other examples described elsewhere herein. Each of the stator slots 300 has a varnish 304. The varnish 304 is disposed within each of the slots 300 to contact the stator laminations and the wires 306 within the stator slot 300. The stator can have multiple wires 306 in each of the stator slots 300 to form slot windings. The wires 306 can have any suitable shape. In some implementations, the wires 306 have a circular cross-section (e.g., as shown). In some implementations, the wires 306 have a rectangular cross-section. The varnish 304 does not extend beyond the front of the stator slot 300. Also, the varnish 304 does not cover any of the stator end windings (not shown).

[0043] Enlarged view 308 shows a partial cross-section of the interface between wire 306 and varnish 304. This example illustrates that wire 306 can have individual insulation. In some implementations, material 310 of wire 306 is electrically conductive (e.g., material 310 is a metal such as copper). Layer 312 can cover the outer surface of material 310. In some implementations, layer 312 can include enamel. Layer 314 can cover the outer surface of layer 312. In some implementations, layer 314 can include a resin. For example, a semi-crystalline thermoplastic material can be used for layer 314. Layers 312 and / or 314 can provide electrical insulation for wire 306. Varnish 304 can also contact at least some of the outer surface of layer 314.

[0044] 3B shows a cross-sectional view of one example of an end winding 316 in a stator. The end winding 316 can be used with one or more other examples described elsewhere herein. This figure shows a cross-section of an individual instance of wire 306. The end winding 316 can have any of several configurations, including, but not limited to, a hairpin winding or a continuous wave pattern. The individual shapes of the cross-sections through each wire 306 can vary and need not all be identical as shown here for simplicity.

[0045] The wires 306 have individual insulation (see, e.g., FIG. 3A ). The end windings 316 are not varnished. For example, the varnish 304 ( FIG. 3A ) that contacts the slot windings does not contact the end windings 316. Thus, there may be gaps between the wires 306 of the end windings 316. This may allow coolant (e.g., oil) to pass between the wires 306 of the end windings 316. Here, path 318 illustrates one possible path that the coolant may take through the end windings 316. Along path 318, the coolant passes by a greater number of wires 306 and / or contacts a larger surface area of ​​the wires 306 than if the end windings 316 were varnished. Thus, having the varnish-free end windings 316 may improve the thermal performance of the electric motor.

[0046] FIG. 4 illustrates an example 400 of applying varnish only to slots in a stator, but not to the end windings. Example 400 can be used with one or more other examples described elsewhere herein. Example 400 illustrates a portion of a stator 402 to which varnish is currently being applied. The stator 402 has laminations 404 forming slots 406 that are currently covered by a protective layer 408. For example, the protective layer 408 can include insulating paper with dielectric strength. The stator 402 has end windings 410. For example, the end windings 410 can be hairpin windings or continuous wave pattern windings. A nozzle 412 currently dispenses varnish 414 in liquid form, which impinges on a wire 410′ extending from the end winding 410. The varnish 414 can impinge on the wire 410′ at the point where the wire 410′ enters one of the slots 406. In some implementations, the stator 402 can be preheated prior to the varnishing process. The varnish 414 enters one of the slots 406 into which the wire 410' extends (this slot may contain multiple wires), filling some or all of the gaps that may extend between the laminations 404 and the slot winding in that slot. The varnish 414 does not impinge on the end windings 410. Thus, the individually insulated wires of the end windings 410 are free of the varnish 414. For example, heating the stator 402 for the varnishing process can cause the varnish 414 to flow toward the center of the stator 402, which may have a relatively higher temperature, rather than toward the end windings 410, which may have a relatively lower temperature.

[0047] 5 is a diagram 500 with an example graph showing torque over time for an electric motor. Diagram 500 may illustrate one or more example features described elsewhere herein. Diagram 500 shows torque on the vertical axis as a function of time, shown on the horizontal axis. Portions of diagram 500 have been omitted for simplicity.

[0048] Graphs 502 and 504 reflect the torque for an electric motor with varnished end windings. Graph 502 may be referred to as the baseline torque demand, and graph 504 may be referred to as the baseline torque supply. For example, at time T1, graph 504 may deviate downward from graph 502 due to derating applied by the control algorithm.

[0049] Graphs 506 and 508 reflect torque for an electric motor with unvarnished end windings. Graph 506 may be referred to as unvarnished torque demand, and graph 508 may be referred to as unvarnished torque supply. Here, graph 506 shows that the drive unit is required to produce its maximum torque at all speeds. At time T2, graph 508 may deviate downward from graph 506 due to field weakening. Graph 508 has greater torque than graph 504 essentially everywhere in diagram 500. Thus, the unvarnished end windings associated with graph 508 enhance the performance of the electric motor.

[0050] 6 is a diagram 600 with an example graph showing stator slot temperature over time for an electric motor. Diagram 600 may illustrate one or more example features described elsewhere herein. Diagram 600 shows temperature on the vertical axis as a function of time, shown on the horizontal axis. Portions of diagram 600 have been omitted for simplicity.

[0051] Graph 602 reflects temperatures for an electric motor with varnished end windings. Graph 602 may be referred to as the baseline slot temperature. Graph 604 reflects temperatures for an electric motor with unvarnished end windings. Graph 604 may be referred to as the unvarnished slot temperature. From time T3 to at least time T4, graph 604 deviates downward from graph 602, indicating a lower slot temperature in the electric motor with unvarnished end windings. Thus, the unvarnished end windings associated with graph 604 enhance the performance of the electric motor. The fact that graph 602 exhibits a lower temperature than graph 604 just before time T3 may be due to the varnish in the electric motor of graph 602 acting as a thermal mass to mask heating of the wires. Therefore, the wires of the electric motor of graph 602 may reach a temperature equal to that of the wires of the electric motor of graph 604 in the region just before time T3.

[0052] As used throughout this specification, the terms "substantially" and "about" are used to describe and report small variations, such as those due to processing variations. For example, they can refer to less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%. Also, as used herein, indefinite articles such as "a" or "an" mean "at least one."

[0053] It should be understood that all combinations of the foregoing concepts, and additional concepts discussed in more detail below, (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein.

[0054] Although several implementations have been described, it will be understood that various modifications may be made without departing from the spirit and scope of the specification.

[0055] Additionally, the logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. Furthermore, other processes may be provided in or deleted from the described flows, and other components may be added or removed from the described systems. Accordingly, other implementations are within the scope of the following claims.

[0056] While certain features of the described implementations have been shown as described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and variations that fall within the scope of the implementations. They have been presented by way of example only, and not limitation, and it should be understood that various changes in form and detail may be made. Any portions of the apparatus and / or methods described herein may be combined in any combination, except in mutually exclusive combinations. The implementations described herein may include various combinations and / or subcombinations of the functions, components, and / or features of the various implementations described. (Other possible items) (Item 1) rotor; a stator having a stack of laminations, wherein the windings of the stator include wires with individual insulation, the wires forming slot windings disposed within slots of the stator, the wires further forming end windings disposed outside the slots at each end of the stator; a varnish in the slots of the stator, the varnish contacting the laminations and the slot windings, wherein the varnish does not contact the end winding of at least one of the ends of the stator; and a cooling system for applying a liquid coolant to at least the end windings, wherein the liquid coolant passes between the wires of the end windings; An electric motor comprising: (Item 2) Item 1. The electric motor of item 1, wherein the varnish does not contact any of the end windings. (Item 3) 3. The electric motor according to item 1 or 2, wherein the cross-sectional profile of the wire is rectangular. (Item 4) 3. The electric motor according to item 1 or 2, wherein the cross-sectional profile of the wire is circular. (Item 5) 5. The electric motor of any one of claims 1 to 4, wherein the end windings form a continuous wave pattern with respect to the slots of the stator. (Item 6) 6. The electric motor of any one of claims 1 to 5, wherein the end windings are hairpin windings. (Item 7) 7. The electric motor of any one of items 1 to 6, wherein the individual insulation includes at least a first layer covering each of the wires and a second layer covering the first layer. (Item 8) 8. The electric motor of claim 7, wherein the first layer comprises enamel. (Item 9) Item 9. The electric motor of item 8, wherein the second layer comprises a resin. (Item 10) 10. The electric motor according to any one of the preceding claims, wherein the varnish comprises a resin. (Item 11) rotor; a stator having a stack of laminations, wherein the windings of the stator include wires with individual insulation, the wires forming slot windings disposed within slots of the stator, the wires further forming end windings disposed outside the slots at each end of the stator; a varnish in the slots of the stator, the varnish contacting the laminations and the slot windings; and means for applying liquid coolant to at least the end windings such that the liquid coolant passes between the wires of the end windings; An electric motor comprising:

Claims

1. rotor; a stator having a stack of laminations, wherein the windings of the stator include wires with individual insulation, the wires forming slot windings disposed within slots of the stator, and the wires further forming end windings disposed outside the slots at each end of the stator; a varnish in the slots of the stator, the varnish contacting the laminations and the slot windings, wherein the varnish does not contact the end winding of at least one of the ends of the stator; and a cooling system for applying a liquid coolant to at least the end windings, wherein the liquid coolant passes between the wires of the end windings; An electric motor comprising:

2. 10. The electric motor of claim 1, wherein the varnish does not contact any of the end windings.

3. The electric motor of claim 1 , wherein the cross-sectional profile of the wire is rectangular.

4. The electric motor of claim 1 , wherein the cross-sectional profile of the wire is circular.

5. 10. The electric motor of claim 1, wherein the end windings form a continuous wave pattern with respect to the slots of the stator.

6. The electric motor of claim 1 , wherein the end windings are hairpin windings.

7. The electric motor of claim 1 , wherein the individual insulation includes at least a first layer covering each of the wires and a second layer covering the first layer.

8. The electric motor of claim 7 , wherein the first layer comprises enamel.

9. The electric motor of claim 8 , wherein the second layer comprises a resin.

10. 10. An electric motor according to claim 1, wherein the varnish comprises a resin.

11. rotor; a stator having a stack of laminations, wherein the windings of the stator include wires with individual insulation, the wires forming slot windings disposed within slots of the stator, and the wires further forming end windings disposed outside the slots at each end of the stator; a varnish in the slots of the stator, the varnish contacting the laminations and the slot windings; and means for applying liquid coolant to at least the end windings such that the liquid coolant passes between the wires of the end windings; An electric motor comprising:

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