Direct cooling of an electric motor

Abstract

The present subject matter relates to an electric motor comprising a stator 102 and a rotor, the stator 102 comprises a plurality of stator stacks each having a stator yoke 102-1 with stator teeth 102-2 securely mounted on the stator yoke 102-1. Each of the stator teeth 102-2 has stator windings 104, wherein each of the stator yoke 102-1 is provided with a plurality of through holes 102-3 along a circumference of the respective stator yoke 102-1. A transition lamination 102'' interleaving adjacent stator stacks in the plurality of stator stacks 102' comprises a plurality of radial grooves 610. The plurality of the radial grooves 610 of the transition lamination 102'' align with the plurality of through holes 102-3 of the stator yoke 102-1 in the adjacent stator stacks to direct a coolant to an active portion 104-1 of the stator windings in each of stator teeth. Further, the coolant is directed from the active portion 104-1 of the stator windings to winding-end portion 104-2 of the stator windings 104 in each of stator teeth 102-2.

Description

DIRECT COOLING OF AN ELECTRIC MOTORTECHNICAL FIELD

[0001] The present subject matter relates, in general, to electric motors, and particularly but not exclusively, to direct cooling of electric motors of automobiles.BACKGROUND

[0002] Automobiles such as electric vehicles include components that generate heat. Excessive heat build-up can cause performance degradation or damage to the components.

[0003] In conventional vehicles, thermal management is required to cool down their internal combustion engine, thermostat, coolant, and radiator system etc. Removal of heat from the internal combustion engine is done to avoid the excessive buildup of heat that can adversely affect the optimum performance of the vehicle. Similarly, electric vehicles need optimal temperatures (neither warm nor cold) to run efficiently and thus for a high level of efficiency in electric vehicles, optimal temperature maintenance is essential. The optimal temperature is regulated by a cooling system of the electric vehicle. Usually, the cooling system regulates the electric vehicle temperature, which includes the battery pack temperature, power electronic-based drive temperature, and electric motor temperature. Generally, in the cooling system a coolant is circulated using an electric pump to cool the batteries, electronics, motor, and related systems.

[0004] Since electric motors are one of the most important components in electric vehicles, efficient cooling of the electric motors is essential to dissipate heat generated during motor operation, as excessive heat can lead to reduced efficiency, increased wear, and premature failure.

[0005] As efficient cooling is a necessity for electric motors, various cooling strategies have been proposed to cool the motors with different requirements.BRIEF DESCRIPTION OF DRAWINGS

[0006] The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference features and components.

[0007] Figure 1 represents a cross-sectional view of an electric motor housing to house an electric motor and depicts a coolant distribution pattern within the electric motor housing, in accordance with an implementation of the present subject matter.

[0008] Fig. 2 illustrates a perspective view of the housing 100 of an electric motor for depicting the movement of the coolant to the stator yoke, active portion, and winding-end portion of the stator windings, in accordance with an implementation of the present subject matter.

[0009] Fig. 3 represents a schematic diagram showing the configuration of the stator yoke with stator teeth mounted on the stator yoke, and the placement of through holes on the stator yoke, in an implementation of the present subject matter.

[0010] Fig. 4 shows a top view of the stator that depicts the placement of through holes on the stator yoke and the windings mounted across the stator teeth in accordance with an implementation of the present subject matter.

[0011] Figure 5 shows an exploded view of the stator showing the position and shape of a transition lamination in accordance with an implementation of the present subject matter.

[0012] Figure 6 shows a transition lamination comprising a plurality of radial grooves along a circumference of circular ring, each of the radial grooves comprising a first end located towards the outer periphery of the circular ring while the second end is along the inner periphery of the circular ring, in accordance with an implementation of the present subject matter.

[0013] Figure 7 depicts a perspective view illustrating the placement of transition lamination and winding configured within the stator teeth of the stator stack in accordance with an implementation of the present subject matter.

[0014] Figure 8 depicts a perspective view of the stator showing second end of the radial grooves of the transition lamination aligned with the location of stator windings that are placed in the gap between adjacent stator teeth in accordance with an implementation of the present subject matter.

[0015] Figure 9 depicts an additional perspective view of the stator showing the active portion of the stator windings and the end portion (turn-up portion) of the stator windings and depicts a direction of flow of the coolant therebetween in accordance with an implementation of the present subject matter.

[0016] Figure 10 depicts a stator tooth assembly, wherein the stator tooth assembly includes a plurality of stator teeth being arranged in a formation that corresponds to the shape of the yoke to which the teeth are secure, in accordance with an implementation of the present subject matter.

[0017] Figure 11 depicts a perspective view of a stator tooth without insulator and Figure 12 shows a perspective view of the stator tooth with insulator comprising coolant channels, in accordance with an implementation of the present subject matter.

[0018] Figure 13 depicts a pattern of movement of the coolant where the coolant moves from the active portion of the windings towards an end portion of the stator windings in accordance with an implementation of the present subject matter.

[0019] Figure 14 depicts the placement of the coolant channel located between the active portion of the stator windings and an insulator placed in each of the stator teeth, in accordance with an implementation of the present subject matter.DETAILED DESCRIPTION

[0020] The present subject matter relates to aspects relating to the direct cooling of an electric motor.

[0021] As mentioned above, as electric motors operate, they generate heat that needs to be efficiently dissipated to prevent overheating and potential damage to the motor components. For example, heat is generated due to losses within the stator slot-windings, stator end-windings, stator laminations, rotor laminations, and rotor magnets or conductors. The cooling of electric motors is a critical aspect for ensuring optimal performance and longevity of electric motors. Accordingly, for a high level of efficiency in electric vehicles, optimal temperature maintenance is essential. For regulating the optimal temperature of the electric vehicle, various cooling strategies have been proposed to cool the electric motors with differentrequirements. In some conventional techniques, coolants, such as oil is commonly used within the electric motor to directly cool rotor or stator windings of the electric motor.

[0022] Various other thermal management techniques exist to address the cooling of electric motors with different heat requirements. Several types of cooling systems are available for electric motors, including air cooling, liquid cooling, heat pipes cooling, and hybrid cooling with heat pipes and liquid. The heat generated by the electric motor is distributed throughout multiple components within the electric motor.

[0023] Traditional cooling methodologies, however, often face limitations in effectively removing heat from specific areas within the electric motor especially in hard-to-reach areas such as the stator active winding and end windings, in turn leading to the hotspots, or, in other words, points of localized high heat accumulation that experience higher temperatures than others, in an electric motor.

[0024] Also, with the increasing demand for high torque density motors, wherein due to high torque density, high heat generation increases the temperature of the motor, may damage the motor in severe cases, there is a persistent need for an even more efficient cooling system to address the intensified heat dissipation challenges. Without proper cooling, electric motors can quickly overheat, leading to reduced performance, increased wear and tear, and even premature motor failure.

[0025] To overcome the issues related to the overheating of electric motors, several methods are used for cooling electric motors in electric vehicles. For instance, in the method of air cooling, the motor is cooled by air flowing over the motor housing. This is achieved by natural convention, where a fan or blower is used to circulate air over the motor where the motor is exposed to ambient air or forced convection. Air cooling is, however, not sufficient for high-power or high- temperature applications. Some liquid cooling methods involve circulating a coolant, such as water or a mixture of water and glycol, through channels or passages in the motor to absorb and transfer heat. Liquid cooling is more effective than air cooling in removing heat from the motor, and it allows for precisetemperature control. However, it requires additional components such as a radiator, pump, and hoses, which can increase the complexity and cost of the motor system.

[0026] The choice of cooling method depends on various factors, such as the power and temperature requirements of the motor, the operating environment, and the cost consideration. Some indirect cooling methods, and direct cooling methods wherein a separate heat exchanger, that is external to the motor is used to absorb the heat from the motor via the heat exchanger, however, since the components of the electric motor do not come into the direct contact with the coolant, it creates an additional thermal resistance between the coolant and the electric motor components thereby impacting the cooling efficiency. Further, since the coolant is in direct contact with motor windings or other heat-generating components, thus direct cooling methods are effective in removing heat from critical components of the electric motor. In some conventional techniques that use direct cooling, the coolant is brought in direct contact with a stator yoke of the electric motor to cool the stator yoke, however, certain areas of the electric motor, such as hard-to-reach areas like stator active winding portions and turn up portions of the windings still do not come into direct contact with the oil, creating an additional thermal resistance between the oil and the windings, thereby impacting cooling efficiency. This further leads to localized heat buildup and potential damage to motor components.

[0027] In some other conventional cooling techniques, cooling channels are placed within the stator tooth, which enables cooling of the thermal hotspot areas of the electric motor such as stator windings. Additionally, some conventional methods allow spraying of oil directly onto the tum-up (end) portion of the windings for cooling the end portion of the windings, they are however ineffective in providing optimal cooling efficiency as the oil is directly sprayed onto the end portion of the windings without circulating it through the active portion of the windings. The active portion of the windings which are crucial for efficient heat dissipation during motor operation do not come into direct contact with the coolant and are therefore not effectively cooled thereby leading to an uneven distribution of coolant within the electric motor housing further degrading the performance of the electric motor.

[0028] The traditional cooling methods are hence not effective in terms of providing optimized heat dissipation from hard-to-reach areas, such as the stator active winding portion and end windings portion and do not provide an optimized even distribution of coolant throughout the electric motor housing. Accordingly, it is desirable to provide an efficient and even distribution of coolant within all the crucial components of the electric motor, such as the hard-to-reach areas of the electric motors or thermal hotspots, like the stator yoke, stator active winding and end windings to improve the performance of the electric motor.

[0029] Accordingly, to solve the above-mentioned problems of the conventional methods of cooling electric motors, in accordance with an embodiment of the present subject matter, an electric motor comprising a stator and a rotor is provided. The electric motor comprises a housing to house the stator and the rotor, wherein the stator comprises a plurality of stator stacks each having a stator yoke with stator teeth securely mounted on the stator yoke. Each of the stator teeth have stator windings, wherein each of the stator yoke is provided with a plurality of through holes along a circumference of the respective stator yoke. The through holes allow a coolant accumulated external to the stator to flow through the respective stator yoke in an axial direction, wherein the axial direction is parallel to an axis of rotation of the electric motor. The stator further includes a transition lamination interleaving adjacent stator stacks in the plurality of stator stacks. The transition lamination comprises lamination sheets stacked together and have a shape of a circular ring. The transition lamination comprises a plurality of radial grooves along a circumference of the circular ring, wherein each of the radial groove comprises a first end and a second end. The plurality of the radial grooves of the transition lamination aligns with the plurality of through holes of the stator yoke in the adjacent stator stacks. The alignment of transition lamination aligns with the plurality of through holes such that the first end of each of the plurality of radial grooves is to receive coolant incoming through the plurality of through holes in the axial direction and direct the coolant in a radial direction perpendicular to the axial direction, such that the coolant is directed to the active portion of the stator windings in each of stator teeth. The stator further comprises each of the stator teethcomprising a coolant channel to direct the coolant from the active portion of the stator windings in each of the stator teeth to the winding-end portion of the stator windings in each of the stator teeth, wherein the coolant channel is located between the active portion of the stator windings and an insulator placed in each of the stator teeth.

[0030] As will be understood, the electric motor of the present invention enables an even distribution of the coolant owing to the movement of the coolant from the stator yoke to the active portion of the stator windings and then to the winding-end portion of the stator windings. This provides efficient cooling by circulating the coolant such that the coolant is in direct contact with three significant areas of heat generation of the electric motor, i.e., the stator yoke, active winding portion, and end winding portion. The efficient cooling of these components provides optimal circulation of coolant and addresses heat dissipation in a comprehensive manner, thereby optimizing heat dissipation. Since the coolant can be in contact with the stator yoke (stator core) and the windings at the same time, the contact area is large, the heat dissipation capacity of the stator core, and the winding is improved significantly. Also, the service life of the motor is prolonged as a consequence of better thermal management. The uniformity of temperature distribution of the stator core and the winding improves the heat dissipation capability and thus the performance efficiency of the electric motor.

[0031] The above and other features, aspects, and advantages of the subject matter will be better explained with regard to the following description and accompanying figures. It should be noted that the description and figures merely illustrate the principles of the present subject matter along with examples described herein and should not be construed as a limitation to the present subject matter. It is thus understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and examples thereof, are intended to encompass equivalents thereof. Further, for the sake of simplicity, and without limitation, the same numbers are used throughout the drawings to reference like features and components.

[0032] Figure 1 represents a cross-sectional view of an electric motor housing 100 to house an electric motor and depicts a coolant distribution pattern within the electric motor housing 100, in accordance with an implementation of the present subject matter. As is understood, the electric motor comprises, inter alia, two mechanical parts: a rotor, which moves, and a stator, which does not. As shown in Figure 1, stator 102 of the electric motor is the stationary component and it consists of a laminated stator core (yoke) and coils of insulated wire known as the stator windings 104. The housing 100 illustrated in Figure 1 that houses the stator 102 and rotor may be any exterior case or enclosure that is used to protect the internal components of the electric motor such as stator 102, windings, rotor, etc. The housing 100 may also have integrated fittings or brackets to keep internal components in place. The stator 102 of the electric motor comprises a plurality of stator stacks 102’ (visibly shown in Figure 6), wherein the plurality of stator stacks 102’ each have a stator yoke 102-1 with stator teeth 102-2 securely mounted on the stator yoke 102-1, and each of the stator teeth 102-2 have stator windings.

[0033] In accordance with an embodiment of the present invention, each of the stator yoke 102-1 is provided with a plurality of through holes 102-3 along a circumference of the respective stator yoke 102-1, wherein the through holes 102- 3 allow a coolant accumulated external to the stator, in the electric motor housing 100, to flow through the respective stator yoke 102-1 in an axial direction. The axial direction may be understood as a direction that is parallel to an axis of rotation the rotor of the electric motor. The coolant enters within the electric motor housing 100 via an opening 108 that directs the flow of coolant towards the stator yoke 102-1 and then directs the flow of coolant to the active portion 104-1 of the windings and finally towards the end portion 104-2 of the stator windings. After circulating the coolant through the stator yoke 102-1 and windings, the coolant is then directed to outlet 110 from where the coolant is removed from the electric motor housing. The path of circulation of the coolant through the stator yoke 102-1 and windings is elaborated subsequently.

[0034] The cooling path configuration as described herein, wherein the coolant flows from the opening 108 towards a stator yoke 102-1 and then from the statoryoke 102-1 towards an active portion of the windings and finally to the end portion of the windings allows for targeted and efficient cooling of both the yoke and the windings, and particularly of end portion of the windings where it is generally difficult for coolant to be delivered to. This provides efficient cooling by circulating the coolant such that the coolant is in direct contact with three significant areas of heat generation of the electric motor, i.e., the stator yoke, active winding portion, and end winding portion.

[0035] Further, reference is made to Figure 2 which provides a perspective view of the housing 100 of an electric motor for depicting the movement of the coolant to the stator yoke, active portion, and winding-end portion of the stator windings as illustrated with reference to Figure 1.

[0036] As shown in Figures 1 and 2, the housing 100 of the electric motor comprises at least one opening 108. The at least one opening 108, shown as a pair of openings 108-1 and 108-2 in Figure 2, allows the coolant to enter in a radial direction into a concealed space formed on either side of the plurality of stator stacks 102’. The concealed space is created by flow separators 112-1, and 112-2 positioned within the housing 100 which are ring-like structures placed between the housing wall and the stator 102. (The ring-like structure of the flow separators 112- 1, and 112-2 is shown in Figure 5 subsequently.)

[0037] The pair of flow separators 112, shown as flow separators 112-1 and 112-2 in Figure 2, are positioned on either side of the plurality of stator stacks. Each of the flow separators 112-1 and 112-2 is configured to conceal a space between a part of the housing 100 corresponding to the respective openings 108-1 and 108-2 and the stator stack 102’ that is most proximate to the respective openings 108-1 and 108-2, to form the concealed space which acts as a coolant sump to hold the coolant.

[0038] The part of the stator stack 102’ being concealed by the respective flow separators 112 comprises the plurality of through holes 102-3 (shown in Figure 3) along the circumference of the respective stator 102. The flow separators 112-1, 112-2 isolate the least one opening 108-1, 108-2, respectively, in the radial direction such the coolant incoming from the least one opening 108-1, 108-2 is preventedfrom being directed towards the end portion of the stator windings 104. To ensure even distribution of the coolant supplied from the opening 108 on the stator yoke 102-1, the flow separators 112-1, and 112-2 are strategically positioned on either side of the stator stacks 102’. The flow separator 112 serves the dual purpose of preventing direct contact of the coolant with the end portion of the windings, while effectively directing the oil towards the designated through holes 102-3 on the stator yoke 102-1.

[0039] Reference is made to Figure 3 which provides a schematic diagram showing the configuration of the stator yoke 102-1 with stator teeth 102-2 mounted on the stator yoke 102-1, and the placement of through holes 102-3 on the stator yoke 102-1. The stator 102 (shown in Figures 1 and 2) comprises a plurality of stator stacks 102’ each having a stator yoke 102-1 with stator teeth 102-2 securely mounted on the stator yoke 102-1. The stator teeth 102-2 are securely mounted in the stator yoke 102-1 using a variety of techniques, such as a dovetail connection, where a shoulder of the dovetail firmly fits into the stator yoke 102-1 for enhancing the flow of coolant within the active portion of the windings. Such connection techniques being generally known to a person skilled in the art, are not elaborated herein for the sake of brevity.

[0040] Stator windings 104 (shown in Figure 4) are wound on each of the stator teeth 102-2. Each of the stator yoke 102-1 is provided with a plurality of through holes 102-3 along a circumference of the respective stator yoke 102-1, wherein the through holes 102-3 allow the coolant accumulated external to the stator 102 to flow through the respective stator yoke 102-1 in an axial direction, the axial direction being parallel to an axis of rotation the electric motor. As explained earlier, the coolant is accumulated in the coolant sump formed by the flow separators 112-1, and 112-2.

[0041] Figure 4 shows a top view of the stator 102 that depicts the placement of through holes 102-3 on the stator yoke 102-1 and the windings 104 mounted across the stator teeth 102-2 in accordance with an implementation of the present subject matter. The through holes 102-3 on the stator yoke 102-1 allow the coolant from the coolant sump to flow through the stator yoke 102-1 in the axial direction,through the body of the stator yoke 102-1. Similarly, the other stator yokes in the stator stack of the stator 102 that are not depicted in the figure also include through holes 102-3 along their respective circumference. The coolant is then directed from the stator yoke 102-1 towards an active portion of the stator windings 104 by means of a transition lamination (not shown in Figure 4) that is elaborated with reference to Figures 5 and 6.

[0042] Figure 5 illustrates an exploded view of the stator 102 showing the position and shape of a transition lamination 102” in accordance with an implementation of the present subject matter. As mentioned above with reference to Figures 1 and 2, the stator 102 comprises a plurality of stator stacks 102’, each having a stator yoke 102-1 with stator teeth 102-2 securely mounted on the stator yoke 102-1. The stator 102 further includes a transition lamination 102” interleaving adjacent stator stacks 102’ in the plurality of stator stacks 102’. In the embodiment depicted in Figure 5, two stators in the plurality of stator stacks are shown along with one transition lamination interposed between the two stators. In another embodiment, if there are three stators, two transition lamination may be interposed between the plurality of stator stacks. For instance, one transition lamination will be provided between the first stator and the second stator, and another transition lamination will be provided between the second stator and the third stator respectively.

[0043] The transition lamination 102”comprises lamination sheets stacked together and having the shape of a circular ring having a width (depicted as ‘W’ in Figure 6) that is dimensioned in accordance with that of the stator yoke 102-1 the transition lamination 102” interleaves.

[0044] As shown in Figure 6, in accordance with an implementation of the present subject matter, the transition lamination 102’ ’ comprises a plurality of radial grooves 610 along the circumference of the circular ring, each of the radial grooves 610 comprising a first end 102”-l and a second end 102” -2 wherein the first end 102”- 1 is located towards the outer periphery of the circular ring while the second end 102” -2 is along the inner periphery of the circular ring. The length of a radialgroove 610 is less than the width ‘W’ such that a small distance exists between the first end 102” - 1 and the outer periphery of the circular ring.

[0045] The plurality of the radial grooves 610 of the transition lamination 102” align with the plurality of through holes 102-3 (as depicted via an arrow 620 in Figure 6) of the stator yoke in the adjacent stator stacks such that the first end 102”- 1 of each of the plurality of radial grooves 610 is to receive coolant incoming through the plurality of through holes 102-3 in the axial direction and direct the coolant in a radial direction perpendicular to the axial direction, such that the coolant is directed to active portion 104 of the stator windings in each of stator teeth 102-2.

[0046] Referring now to Figures 7 and 8, Figure 7 depicts a perspective view illustrating the placement of transition lamination 102” and winding 104 configured within the stator teeth 102-2 of the stator stack in accordance with an implementation of the present subject matter. As already explained above, the plurality of the radial grooves 610 of the transition lamination 102” align with the plurality of through holes 102-3 of the stator yoke 102- 1 in the adjacent stator stacks 102’ such that the first end 102” - 1 of each of the plurality of radial grooves 610 receives the coolant incoming through the plurality of through holes 102-3 in the axial direction. The coolant received at the first end 102”-l of a radial groove 610 of the transition lamination is directed towards the second end 102” -2 of the radial groove 610. The coolant is thus directed in the radial direction perpendicular to the axial direction, such that the coolant is directed to active portion 104-1 of the stator windings 104 in the corresponding stator tooth 102-2.

[0047] As depicted in Figure 8, the second end 102” -2 of the radial grooves 610 of the transition lamination 102” align with the location of stator windings that are placed in the plurality of stator teeth 102-2, i.e., the gap between adjacent stator teeth. The second end 102” -2 of the radial grooves 610 being open, allows the coolant to drip on the active portion of the stator windings. From the active portion 104-1 of the stator windings, the coolant is directed towards the end portion 104-2 of the windings. As will be understood, the end portion 104-2 of the windings is the portion of the stator winding that extends beyond the stator yoke at each end or thatcan be seen as bulging out at the turn-up position of the stator yoke is also clearly visible from Figure 7. Similarly, the active portion 104-1 of the stator windings is the part of the windings that reside within the length of the stator teeth 102-2.

[0048] Further, each of the stator teeth 102-2 comprises a coolant channel (not shown in Figure 7) to direct the coolant from the active portion 104-1 of the stator windings in each of stator teeth 102-2 to winding-end portion 104-2 of the stator windings in each of stator teeth 102-2. The coolant channel of the stator teeth 102- 2 is described in detail below. The coolant is then removed from electric motor housing 100 via outlet 110 after cooling the winding-end portion 104-2 of the stator winding 104.

[0049] Figure 9 depicts an additional perspective view of the stator 102 showing the active portion 104-1 of the stator windings 104 and the end portion 104-2 (turn-up portion) of the stator windings 104 and depicts a direction of flow of the coolant there between in accordance with an implementation of the present subject matter. The direction of flow of the coolant from active portion 104-1 of the stator windings 104 to the tum-up portion 104-2 is depicted using arrows 900-1 and 900-2. As shown, the location of the transition lamination 102” corresponds to center of active portion 104-1 of the stator windings in the respective teeth. The coolant flows from the center of the active portion 104-1 of the stator windings to the tum-up portion on either side. The direction of flow of the coolant from the center of the active portion 104-1 of the stator windings to the turn-up portion 104- 2 is depicted using arrows 900-1 and 900-2.

[0050] Further, reference is made to Figure 10 which depicts a stator tooth assembly, wherein the stator tooth assembly includes a plurality of stator teeth being arranged in a formation that corresponds to the shape of the yoke to which the teeth are secured. Gaps exist between the stator teeth where windings are inserted. The arrangement of stator teeth in the yoke and winding of stator windings around the plurality of stator teeth within the gaps is generally known in the art and thus not elaborated herein for the sake of brevity. Figure 10 which also depicts the central portion 1002 plurality of stator teeth, midway between the length of the stator teeth, which is aligned with the position of the transition lamination upon assembly.Absence of insulator from the central portion 1002 of plurality of stator teeth, as will be elaborated later, provides for accumulation of the coolant in this region of the stator teeth and their subsequent channelization to the turn-up portion of the winding beyond the edges of the stator teeth.

[0051] Figure 11 depicts a perspective view of a stator tooth 1100 without insulator and Figure 12 shows a perspective view of the stator tooth 1100 with insulator 1202 comprising coolant channels 1210, in accordance with an implementation of the present subject matter. As mentioned above, the coolant channels 1210 have a configuration that enables to specifically direct the flow of coolant from the active portion 104-1 of the stator windings 104 in the stator tooth 1100 to winding-end portion 104-2 of the stator windings 104 of the tooth.

[0052] In an example embodiment, the coolant channel 1210 in the stator tooth 1100 is formed by a set of ribs 1204 formed in the insulator 1202 of the tooth. The set of ribs 1204 in the insulator material channelises the coolant to move from a centre of the active portion 104 of a stator winding in the stator tooth towards a winding-end portion of the stator winding on either side of the centre. The coolant channel 1210 is located between the active portion 104 of the stator windings and the insulator 1202 placed in each of the stator teeth 102-2.

[0053] The coolant channels 1210 can also be created by way of a set of grooves formed in the insulator of the respective teeth, in another example embodiment.

[0054] The absence of insulator material from the central portion 1002 of the plurality of stator teeth allows to create a space for accumulating the coolant therein. Thus, the coolant is accumulated in the central portion 1002 and then moves up and down in a zig-zag manner through the coolant channels 1210 as shown in Figure 13. As can be seen the set of grooves in the stator tooth are positioned parallel to each other to circulate the coolant along the active portion 104-1 of the stator winding 104 in the stator teeth and guide a flow of coolant from the centre 1002 of the active portion 104-1 throughout the dimension of the active portion and gradually towards an aperture 1220 at a periphery of the stator teeth 102-2’, 102- 2”, the aperture 1220 coinciding with a location of exit of the active portion 104 of the stator winding from the stator teeth 120-2’, 120-2”.

[0055] The aperture 1220 has a constricted opening, wherein the coolant exiting from the active portion 104-1 of the stator winding is ejected through the aperture 1220 creating a jet effect (as can be seen from Figure 13) to impinge onto the winding-end portion 104-2 of the stator winding.

[0056] Thus, the pattern of movement of the coolant where the coolant moves from the active portion 104-1 of the windings towards an end portion 104-2 of the stator windings can be clearly understood with reference to Figure 13.

[0057] Further, reference is made to Figure 14 which depicts the placement of the coolant channel 1210 located between the active portion 104-1 of the stator windings and an insulator 1202 placed in each of the stator teeth 102-2, in accordance with an implementation of the present subject matter. As can be seen from Figure 14, each of the stator teeth 102-2 comprises a coolant channel 1210 to direct the coolant from the active portion 104-1 of the stator windings in each of stator teeth to winding-end portion 104-2 of the stator windings in each of stator teeth 102-2. The coolant channel 1210 is located between the active portion 104-1 of the stator windings and an insulator 1202 is placed in each of the stator teeth 102- 2. The coolant channels 1210 in the stator teeth 102-2 comprise a set of grooves formed in the insulator 1202 of the respective teeth, wherein the set of grooves in a stator tooth 102-2 channelises the coolant to move from a centre of the active portion 104-1 of the stator winding 104 in the stator tooth 102-2 towards a windingend portion 104-2 of the stator winding 104 on either side of the centre. The set of grooves in the stator tooth 102-2 are positioned parallel to each other to circulate the coolant along the active portion 104-1 of the stator winding in the stator teeth 102-2 and guide a flow of coolant from the centre of the active portion 104-1 towards an aperture 1220 at a periphery of the stator teeth, the aperture 1220 coinciding with a location of exit of the active portion 104-1 of the stator winding from the stator teeth 102-2. The aperture 1220 has a constricted opening, wherein the coolant exiting from the active portion 104-1 of the stator winding is ejected through the aperture creating a jet effect to impinge onto the winding-end portion 104-2 of the stator winding.

[0058] Thus, with the configuration of the stator illustrated above that provides a designated cooling path and provides an even distribution of the coolant owing to the movement of the coolant from the stator yoke to the active portion of the stator windings and then to the winding-end portion of the stator windings enables improving the heat dissipation capability and thus the performance efficiency of the electric motor. As the radial grooves 610 on the transition lamination 102” are aligned with gaps between the stator teeth where active portions 104-1 of stator windings are placed, the coolant is delivered from the radial grooves 610 of the transition lamination 102” to the active portion 104-1 of the stator windings 104 for effectively cooling the active portion 104-1 of the stator windings 104. Upon reaching the active portion 104-1 of the windings the coolant is then directed towards an end portion 104-2 of the stator windings 104 by means of dedicated coolant channels 1210 provided on the stator teeth 102-2 having a configuration that enables the coolant to specifically move towards the end winding 104-2 portion and thus provides an even distribution of the coolant throughout the active portion 104-1 of the stator windings 104. To facilitate coolant flow and provide structural support for the stator windings, injection molding technology has been employed on each individual tooth to create dedicated coolant flow channels. The injection molding technique is generally known in the art and therefore it is not reproduced herein for the sake of brevity. Accordingly, the present invention enables efficient heat dissipation and optimum cooling thereby enhancing the performance of the electric motor.

[0059] Although implementations for the electric motor that provides efficient cooling with even distribution of coolant in hard to reach areas of the electric motor are described, it is to be understood that the present subject matter is not necessarily limited to the specific features of the methods and systems described herein. Rather, the specific features are disclosed as implementations for the electric motor that facilitates efficient cooling.

Claims

I / We Claim:

1. An electric motor comprising a stator (102) and a rotor, wherein the electric motor comprises a housing (100) to house the stator (102) and the rotor, the stator (102) comprising: a plurality of stator stacks (102’) each having a stator yoke (102-1) with stator teeth (102-2) securely mounted on the stator yoke (102-1), each of the stator teeth (102-2) having stator windings (104), wherein each of the stator yoke (102-1) is provided with a plurality of through holes (102-3) along a circumference of the respective stator yoke (102-1), wherein the through holes (102-3) allow a coolant accumulated external to the stator (102) to flow through the respective stator yoke in an axial direction, the axial direction being parallel to an axis of rotation the electric motor; a transition lamination (102”) interleaving adjacent stator stacks (102’) in the plurality of stator stacks, the transition lamination (102”) comprising lamination sheets stacked together and having a shape of a circular ring, the transition lamination (102”) comprising a plurality of radial grooves (610) along a circumference of the circular ring, each of the radial groove (610) comprising a first end (102”-l, 102” -2) and a second end, wherein the plurality of the radial grooves (610) of the transition lamination (102”) align with the plurality of through holes (102-3) of the stator yoke (102-1) in the adjacent stator stacks such that the first end (102” 1) of each of the plurality of radial grooves (610) is to receive coolant incoming through the plurality of through holes (102-3) in the axial direction and direct the coolant in a radial direction perpendicular to the axial direction, such that the coolant is directed to active portion (104-1) of the stator windings in each of stator teeth (102-2), each of the stator teeth (102-2) comprising a coolant channel (1210) to direct the coolant from the active portion (104-1) of the stator windingsin each of stator teeth (102-2) to winding-end portion (104-2) of the stator windings in each of stator teeth (102-2), wherein the coolant channel (1210) is located between the active portion (104-1) of the stator windings and an insulator (1020) placed in each of the stator teeth (102-2).

2. The electric motor as claimed in claim 1, wherein a pair of flow separators (112-1, 112-2) are positioned on either side of the plurality of stator stacks, each of flow separators (112-1, 112-2) being configured to conceal a space between the housing (100) and at least a part of a stator stack, from amongst the plurality of stator stacks, that is most proximate to the housing (100), to form a coolant sump to hold the coolant.

3. The electric motor as claimed in claim 2, wherein the part of the stator stack being concealed by the respective flow separators (112-1, 112- 2) comprises the plurality of through holes (102-3) along the circumference of the respective stator yoke (102-1).

4. The electric motor as claimed in claim 1, wherein the coolant channels (1210) in the stator teeth (102-2) comprise a set of grooves formed in the insulator (1202) of the respective teeth, wherein the set of grooves in a stator tooth channelises the coolant to move from a centre (1002) of the active portion (104-1) of a stator winding in the stator tooth towards a winding-end portion (104-2) of the stator winding on either side of the centre.

5. The electric motor as claimed in claim 4, wherein the set of grooves in the stator tooth (102-2) are positioned parallel to each other to circulate the coolant along the active portion (104-1) of the stator winding in the stator teeth and guide a flow of coolant from the centre (1002) of the active portion (104-1) towards an aperture (1220) at a periphery of the stator teeth (102- 2), the aperture (1220) coinciding with a location of exit of the active portion (104-1) of the stator winding from the stator teeth (102-2).

6. The electric motor as claimed in claim 5, wherein the aperture (1220) has a constricted opening, wherein the coolant exiting from the active portion (104-1) of the stator winding is ejected through the aperture (1220) creating a jet effect to impinge onto the winding-end portion (104-2) of the stator winding.

7. The electric motor as claimed in claim 2, wherein the housing (100) of the electric motor comprises at least one opening (108-1, 108-2) to allow the coolant to enter in the radial direction into the concealed space between the housing (100) and the corresponding stator stack formed by the flow separators (112-1, 112-2) positioned on either side of the plurality of stator stacks (102’).

8. The electric motor as claimed in claim 2, wherein the flow separators (112-1, 112-2) isolate the least one opening (108-1, 108-2) in the radial direction such the coolant incoming from the least one opening (108-1, 108- 2) is prevented from being directed towards end portion (104-2) of the stator windings (104).

9. The electric motor as claimed in claim 1, wherein the housing (100) of the electric motor comprises an outlet (110) to remove the coolant from electric motor housing (100) after cooling the winding-end portion (104-2) of the stator windings.

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