Stator for an electric machine and electric machine thereof

FIELD OF THE INVENTION

[001] The present invention generally relates to an electric machine, more particularly, to an electric motor or an electric generator mounted with one or more cooling tubes for dissipating heat therein during operation. BACKGROUND OF THE INVENTION

[002] In recent past, due to rise in demand for electric vehicles, use of electric machines such as electric motors and generators have been paramount particularly in automobile industry. The electric vehicles generally include an energy source such as a battery pack, coupled to the electric machine for actuation. The electric machine, upon receiving electric current from the battery pack, axially rotates a rotor mounted on a stator due to electro magnetic interaction therebetween. The rotor is mechanically coupled to wheels of the electric vehicle for vehicle movement.

[003] One of the issues currently encountered in the electric vehicles is lower range or the distance travelled by the vehicle in a single charge of the battery pack. Typically, such an issue may arise due to heat generated power losses in the electric machine during its operation.

[004] Advent of modern technology has paved way for mitigating the aforesaid limitations by providing a thermal management system for the electric machine. The thermal management system is adapted to dissipate heat generated within the electric machine during operation, thereby ensuring operation of the electric machine under optimal thermal capacity. As such, performance of the electric machine may improve, inherently enhancing the power density of the electric machine and performance of the electric vehicle.

[005] One such thermal management system is an air-cooling system mounted onto the electric machine. The air-cooling system is provided with fins on the outer surface of the electric machine. The fins increase the surface area available for ambient air contact for the electric machine and enable heat transfer therefrom to the surroundings. As such, contact of the ambient air onto the fins dissipates the heat generated therein, thereby cooling the electric machine. However, the rate of cooling or heat dissipation of the air- cooling system is low due to lower co-efficient of heat transfer of the ambient air. Moreover, the air-cooling systems are typically bulky, which is undesirable.

[006] To overcome the limitations in air-cooled system, liquid cooling systems are employed. In the liquid cooling systems, structure of casing of the electric machine are modified, such that inner side of the casing is configured with channels required for flow of cooling fluid therein. The flow of cooling fluid within the channels dissipates the heat generated in the electric machine during operation. Due to higher co-efficient of heat transfer of the cooling fluid, the heat is dissipated at a faster rate in the liquid cooling system than that of the air-cooling system. However, the liquid cooling systems are associated with complex construction, due to requirement of inclusion of cooling channels within the electric machine. Such complexity increases manufacturing and maintenance costs, which is undesirable.

[007] To overcome aforesaid limitations in the air-cooling and liquid cooling systems, several efforts have been made for converting the air-cooling system into liquid cooling systems. However, such efforts require incorporation of coolant channels within the inner casing for liquid cooling, which results in complex construction. As such, existing techniques do not provide a possibility of efficiently converting the air-cooled electric machine into the liquid cooled electric machine nor a system which is a combination of the air and liquid cooling system. [008] In view of the above, there is a need for an electric machine which can overcome one or more limitations stated above in addition to provide additional technical advantages.

SUMMARY OF THE INVENTION

[009] In one aspect, the present invention is directed to a stator for an electric machine. The stator includes a hollow cylindrical member adapted to receive a rotor of the electric machine and having a longitudinal axis, front face, a rear face, an inner surface and an outer surface. The inner surface is defined with a plurality of teeth along its periphery for receiving windings of the electric machine. Further, one or more cooling tubes are mounted onto the outer surface of the hollow cylindrical member. The cooling tubes are adapted to receive and circulate a cooling fluid therein for dissipating heat from the hollow cylindrical member and the windings during operation.

[010] In an embodiment of the invention, the one or more cooling tubes include one or more ports fluidly coupled to a coolant reservoir for receiving the cooling fluid.

[011] In an embodiment of the invention, the one or more cooling tubes include a first annular cooling tube, a second annular cooling tube and at least one connector tube. The first annular cooling tube is aligned coaxially to the longitudinal axis and mounted proximal to the front face of the hollow cylindrical member, wherein the first annular cooling tube is adapted to surround the outer surface of the hollow cylindrical member. The second annular cooling tube is also aligned coaxially to the longitudinal axis and mounted proximal to the rear face of the hollow cylindrical member. The second annular cooling tube is adapted to surround the outer surface of the hollow cylindrical member. Further, at least one connector tube extends along the longitudinal axis and engages with the outer surface, wherein the at least one connector tube is fluidly coupled to the first annular cooling tube and the second annular cooling tube for enabling flow of the cooling fluid therebetween. [012] In an embodiment of the invention, the one or more cooling tubes include at least one third annular cooling tube disposed between the first annular cooling tube and the second annular cooling tube. The third annular cooling tube is fluidly connected to the first annular cooling tube and the second annular cooling tube via the connector tube.

[013] In an embodiment of the invention, the hollow cylindrical member includes one or more grooves defined on the outer surface and extending from the front face to the rear face. Each groove is adapted to engage with a projection defined on the cooling tubes for slidably receiving the cooling tubes onto the hollow cylindrical member. [014] In an embodiment of the invention, the stator has a first end cap mounted onto the front face and a second end cap mounted onto the rear face, wherein the first end cap and the second end cap are configured to secure the rotor and the cooling tubes on the stator. The stator also has a portion of the outer surface uncovered by the one or more cooling tubes. The portion is exposed to the air to enable heat dissipation in the stator by air cooling and liquid cooling.

[015] In an embodiment of the invention, the stator has a cover member defined with plurality of fin members along its peripheral surface and adapted to envelop the stator. The fin members are configured to dissipate heat generated in the stator and the windings during operation by air cooling.

[016] In an embodiment of the invention, an electric machine is disclosed. The electric machine includes the rotor and the stator. The stator having a hollow cylindrical member adapted to receive the rotor and having the longitudinal axis, the front face, the rear face, the inner surface and the outer surface. The inner surface is defined with the plurality of teeth along its periphery for receiving windings of the electric machine, wherein supply of electric current to the windings induces electromechanical force onto the rotor for operation. One or more cooling tubes are mounted onto the outer surface of the hollow cylindrical member. The cooling tubes are adapted to receive and circulate a cooling fluid therein for dissipating heat from the hollow cylindrical member, the rotor and the windings during operation.

BRIEF DESCRIPTION OF THE DRAWINGS [017] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments. Figure 1 is a perspective view of a stator of an electric machine assembled with one or more cooling tubes, in accordance with an embodiment of the present invention.

Figure 2 is another perspective of the stator, in accordance with an embodiment of the present invention. Figure 3 is a schematic perspective view of the stator of the electric machine, in accordance with an embodiment of the present invention.

Figure 4 is a schematic view of cooling tubes of the electric machine fluidly coupled to a coolant reservoir, in accordance with an embodiment of the present invention. Figure 5 is an exploded view of the stator, in accordance with an embodiment of the present invention.

Figure 6 is an exploded view of the electric machine, in accordance with an embodiment of the present invention.

Figure 7 is a sectional view of the electric machine assembled with the cooling tubes, in accordance with an embodiment of the present invention.

Figure 8 is an exploded view of the electric machine, in accordance with another embodiment of the present invention.

Figure 9 is an exploded view of the electric machine, in accordance with another embodiment of the present invention. Figure 10 is an assembled view of the electric machine, in accordance with another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[018] Various features and embodiments of the present invention here will be discernible from the following further description thereof, set out hereunder.

[019] The present invention relates to a stator for an electric machine. The stator includes a hollow cylindrical member adapted to receive a rotor. A plurality of teeth are defined along an inner surface of the stator for receiving windings of the electric machine. One or more cooling tubes are fluidly coupled to a coolant reservoir and mounted onto an outer surface of the hollow cylindrical member. Each of the cooling tubes are aligned coaxially to a longitudinal axis of the stator and are adapted to surround the outer surface. The cooling tubes are secured onto the stator via mounting of a first end cap onto a front face and a second end cap onto a rear face of the stator.

[020] During operation of the stator, the cooling tubes circulate the cooling fluid received from the coolant reservoir for dissipating the heat generated in the stator, by liquid cooling. Additionally, a portion of the outer surface of the hollow cylindrical member which is uncovered by the cooling tubes is exposed to surrounding air for air cooling of the stator. In an embodiment, a cover member defined with a plurality of fin members are also mounted onto the stator for enhancing air cooling.

[021] Further, the present invention also discloses the electric machine including the rotor and the stator mounted with the one or more cooling tubes. The stator with the cooling tubes dissipates heat generated during operation of the electric machine to the surroundings by liquid cooling as well as air cooling. In other words, the construction on the stator provides a thermal management system which enables heat dissipation to the surroundings by air-cooling and liquid-cooling. The construction also enables modification of conventional air-cooling system into the air-liquid cooling system by making modifications in the construction of the stator in a simple manner. As such, the electric machine is operated under optimal thermal conditions, and thus provides an increased power out. Consequently, improving the power density, while improving life of the electric machine. [022] Figures 1 and 2 in one exemplary embodiment of the present invention disclose perspective views of a stator 100 of an electric machine 200. The stator 100 or the resulting electric machine 200 is adapted to dissipate heat generated therein during operation, to the surroundings via liquid cooling as well as air cooling. Moreover, the construction of the stator 100 or the machine 200 may be altered selectively for ensuring air cooling and/or liquid cooling in a simple manner.

[023] The stator 100 includes a hollow cylindrical member 104 adapted to receive a rotor 106 of the electric machine 200. In an embodiment, the hollow cylindrical member 104 includes a longitudinal slot 102 axially aligned to a longitudinal axis X-X’ for receiving the rotor 106. In the present embodiment, the hollow cylindrical member 104 and the rotor 106 are made of electromagnetic materials for ease of interaction therebetween during operation. The hollow cylindrical member 104 also includes a plurality of teeth 116 defined along periphery of its inner surface 112 [also shown in Figure 3], for receiving windings 118. The plurality of teeth 116 extend from the inner surface 112 towards the longitudinal axis X-X’ of the hollow cylindrical member 104 upto a required length, for looping the windings 118 on each tooth. Alternatively, a casing 144 including the windings 118 is assembled onto the plurality of teeth 116 [for e.g. as shown in Figures 6 and 8] The number of turns of the windings 118 are selected as per power transmission or generation requirement of the machine 200. The windings 118 are coupled to an electric supply (not shown in Figures) for receiving electric current to enable operation of the stator 100. In an embodiment, the windings 118 are coupled to a three-phase power supply for receiving a three-phase alternating current. Alternatively, the windings 118 are coupled to a Direct Current (DC) power supply for receiving a direct current. The stator 100 is adapted to generate a rotating magnetic field onto the rotor 106, upon receiving electric current from the power supply, for axially rotating the rotor 106.

[024] Referring to Figure 2 in conjunction with Figure 1 , the stator 100 further includes one or more cooling tubes 120 mounted onto an outer surface 114 of the hollow cylindrical member 104. The cooling tubes 120 upon operation are adapted to dissipate the heat generated during operation of the stator 100 and/or the electric machine 200 by liquid cooling, which will be described in description pertaining to Figures 4 and 5.

[025] The hollow cylindrical member 104 is defined with one or more grooves 132 on its outer surface 114 [more clearly depicted in Figure 3] Correspondingly, the cooling tubes 120 are also configured with a projection 134 [more clearly depicted in Figures 4 and 5] for engagement with each of the grooves 132. Upon engagement of the grooves 132 with the projection 134, the cooling tubes 120 are slidably received by the hollow cylindrical member 104 [for e.g. as shown in Figure 5] The groove 132 is a trough defined on the outer surface 114 while the projection 134 is pin like protrusion extending from the inner surface 120a of the cooling tubes 120, for engagement with the groove 132. Further, the number of grooves 132 and the corresponding projections 134 are selected as per design feasibility and requirement of assembly between the hollow cylindrical member 104 and the cooling tubes 120.

[026] Referring to Figure 3, the grooves 132 extend from a front face 108 upto a rear face 110 of the hollow cylindrical member 104. That is, the grooves 132 extend along the length of the hollow cylindrical member 104, so that the cooling tubes 120 are positioned at any location on the outer surface 114 as per requirement. The dimensions of the grooves 132 are defined for facilitating engagement with the cooling tubes 120, without affecting the structural integrity of the hollow cylindrical member 104, i.e. the stator 100.

[027] In an embodiment, the one or more grooves 132 are four in number that are positioned at equal intervals along the outer surface 114 of the hollow cylindrical member 104. Accordingly, four projections 134 are provided at corresponding locations on an inner surface 120a of the cooling tubes 120 for facilitating engagement with the hollow cylindrical member 104. Alternatively, the grooves 132 and the projection 134 are provided interchangeably between the hollow cylindrical member 104 and the inner surface 120a of the cooling tube 120 to facilitate engagement therebetween. In other words, the grooves 132 are configured on the cooling tubes 120, while the projection 134 is configured on the outer surface 114 of the hollow cylindrical member 104 for engagement therebetween.

[028] In another embodiment, the grooves 132 are selectively provided on the outer surface 114, instead of extending along the entire length of the hollow cylindrical member 104. [029] Referring now to Figure 4, an exemplary construction of the one or more cooling tubes 120 fluidly coupled to a coolant reservoir 122 is depicted. Each of the cooling tube 120 is tubular in construction adapted to be mounted onto the outer surface 114 of the hollow cylindrical member 104. The construction of the cooling tubes 104 is selected suitably for ensuring optimal thermal contact with the hollow cylindrical member 104, for facilitating heat dissipation in the stator 100.

[030] The cooling tubes 120 are fluidly coupled to a coolant reservoir 122 for receiving the cooling fluid. The cooling fluid is circulated within the cooling tubes 120 for heat dissipation in the stator 100. The flow of cooling fluid within the cooling tubes 120 is represented via arrow heads in Figure 4. The cooling fluid is a liquid refrigerant such as chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), ammonia and the like, which are adapted to ensure heat dissipation from the stator 100 upon contact therewith. Additionally, the coolant reservoir 122 is located within the stator 100 or externally to the stator 100, and fluidly coupled to the cooling tubes 120 via ports 124. The ports 124 allow transfer or exchange of the cooling fluid between the cooling tubes 120 and the coolant reservoir 122, which ensures optimum dissipation of heat generated in the stator 100 during operation.

[031] In an embodiment, the cooling tubes 120 are directly mounted onto the stator 100 of an air-cooled electric machine, so that the stator 100 dissipates heat generated therein by air cooling as well as liquid cooling. As such, the air-cooled electric machine is modified into a liquid and air-cooled electric machine 200 by merely mounting the cooling tubes 120 thereon, without the need for complex and cumbersome modifications.

[032] In an embodiment, the cooling tubes 120 are made of a metallic material or a composite material which establishes thermal contact with the stator for dissipating heat therefrom during operation. Also, suitable pressure applying devices such as a pump [not shown in Figures] are employed for regulating flow of the cooling fluid between the coolant reservoir 122 and the cooling tubes 120. The pressure applying devices are selected as per flow rate requirements of the cooling fluid in the cooling tubes 120. [033] Further, as shown in Figure 4, the one or more cooling tubes 120 include a first annular cooling tube 126, a second annular cooling tube 128 and at least one connector tube 130, in an exemplary embodiment of the present invention. The first annular cooling tube 126 is aligned coaxially to the longitudinal axis X-X’ and mounted proximal to the front face 108 of the hollow cylindrical member 104 [for e.g. as shown in Figures 1 , 2, 6, 8 and 9] The first annular cooling tube is mounted such that it contacts and surrounds the outer surface of the hollow cylindrical member, thereby establishing thermal contact with the stator 100. The first annular cooling tube 126 includes the projection 134 which is aligned and mounted onto the groove 132 on the outer surface 114 for engagement with the stator 100. Also, the first annular cooling tube 126 is fluidly connected to the coolant reservoir 122 via a port 124a of the port 124. The first annular cooling tube 126 is connected to the coolant reservoir 122 via a conduit [not shown in Figures] for ensuring fluid flow therebetween. The port 124a is adapted to regulate flow of cooling fluid between the first annular cooling tube 126 and the coolant reservoir 122.

[034] Further, the second annular cooling tube 128 is aligned co-axially to the longitudinal axis X-X’ and mounted proximal to the rear face 110 of the hollow cylindrical member 104 [for e.g. as shown in Figures 1 , 2, 6, 8 and 9] The second annular cooling tube 128 also contacts and surrounds the outer surface 114 of the hollow cylindrical member 104. As such, the second annular cooling tube 128 also establishes thermal contact with the stator 100. The second annular cooling tube 128 includes the projection 134 which is aligned and mounted onto the groove 132 on the outer surface 114. Also, the second annular cooling tube 128 is fluidly connected to the coolant reservoir via a port 124b of the port 124. The second annular cooling tube 128 is connected to the coolant reservoir 122 via a conduit [not shown in Figures] for ensuring fluid flow therebetween. The port 124b is adapted to regulate flow of cooling fluid between the second annular cooling tube 128 and the coolant reservoir 122. [035] Further, the first and the second annular cooling tubes 126, 128 are fluidly coupled to one another via the at least one connector tube 130 for enabling flow of the cooling fluid therebetween. As such, the connector tube 130 acts as an intermediary tube for ensuring connection between the first and the second annular cooling tubes 126, 128, which enhances the cooling efficiency of the cooling tubes 120. The connector tube 130 extends along the longitudinal axis X-X’ and engages the outer surface 114 while connecting the first and the second annular cooling tubes 126, 128. In an embodiment, the first annular cooling tube 126, the second annular cooling tube 128 and the connector tube 130 are connected to form a singular unit, and thereafter assembled directly onto the outer surface 114 [for e.g. as shown in Figure 5] for ease of assembly. In another embodiment, each of the first annular cooling tube 126, the second annular cooling tube 128 and the connector tube 130 are made of a monolithic member or are formed by linking plurality of tubular members [not shown in Figures]

[036] Further, at least one third annular cooling tube 146 [for e.g. as shown in Figure 10] is mounted between the first and the second annular cooling tubes 126, 128. The third annular cooling tube 146 is coupled to the coolant reservoir 122 via the port 124. Additionally, the third annular cooling tube 146 is coupled to the first and the second annular cooling tubes 126, 128, via the connecting tube 130 for ensuring flow of cooling fluid therebetween. The third annular cooling tube 146 further enhances the heat dissipation characteristics in the stator 100 by liquid cooling, due to increase in volume of the cooling fluid flowing thereon.

[037] In an embodiment, the dimensions and configuration of each of the first annular cooling tube 126, the second annular cooling tube 128 and the connecting tube 130 are selected as per heat dissipation requirements of the stator 100. In other words, when the heat generated within the stator 100 is high, correspondingly the cooling tubes 120 of larger dimensions are assembled thereon, for ensuring operation of the stator 100 in optimal thermal conditions. Alternatively, when the heat generated within the stator 100 is low, correspondingly the cooling tubes 120 of smaller dimensions are assembled thereon. Typically, the dimensions of the cooling tubes are considered corresponding to size of the stator 100 and/or the machine 200. Additionally, the amount of cooling fluid stored within the coolant reservoir 122 is selected as per cooling requirements necessary for the stator 100. Accordingly, the flow rate of the cooling fluid flowing within the cooling tubes 120 is also selected and/or adjusted as per cooling requirements. The adjustments in flow rate are made by controlling rate of opening and closing of the ports 124.

[038] Further, a first end cap 136 is mounted onto the front face 108 and a second end cap 138 is mounted onto the rear face 110 of the hollow cylindrical member 104 [shown in Figure 6] The first and the second end caps 136, 138 are mounted onto the front face 108 and the rear face 110 respectively, by conventional mounting techniques such as snap fitting, fastening, bonding and the like. The first and the second end caps 136, 138 are adapted to secure the rotor 106 and the cooling tubes 120 onto the stator 100 [as shown in Figure 7] In an embodiment, the grooves 132 include stoppers [not shown Figures] configured within, for directly securing the cooling tubes 120 thereon. [039] Further, the outer surface 114 of the hollow cylindrical member 104 includes a portion 114a, which is uncovered by the cooling tubes 120. As an example, the portion 114a is a central portion of the hollow cylindrical member 104, with the end portions being surrounded by the cooling tubes 120. As another example, the portion 114a is the end portions [not shown in Figures] of the hollow cylindrical member 104 while the central portion is surrounded by the cooling tubes 120. The portion 114a is adapted to be exposed to ambient air and thus is subjected to air cooling. As such, the stator 100 is subjected to air-cooling due to contact of ambient air on the portion 114a and liquid cooling due to the cooling tubes 120 during operation. Additionally, in an embodiment, a cover member 140 [for e.g. as shown in Figure 9] envelops the stator 100. The cover member 140 is defined with a plurality of fin members 142 defined along its peripheral surface for enhancing area of contact with the ambient air. As such, contact of ambient air onto the fins 142 improves air-cooling of the stator 100. The cover member 140 is configured to enclose the stator 100 and the rotor 106. The cover member 140 is a two-part unit having a front portion 140a adapted to be mounted onto the front face 108 and a rear portion 140b adapted to be mounted onto the rear face 110 of the hollow cylindrical member 104. The front and the rear portions 140a, 140b are coupled to one another for enclosing the stator 100. The coupling of the front and the rear portions 140a, 140b is carried out by conventional coupling techniques such as snap fitting, fastening and the like.

[040] Figure 6 in one exemplary embodiment of the present invention, is an exploded view of the electric machine 200. The electric machine 200 is an induction machine operated via an AC power supply or a DC machine operated via a DC power supply. As such, the electric machine 200 is an induction motor, an induction generator, a DC motor or a DC generator. The electric machine 200 includes the stator 100 described here insofar in the present description. Hence, the construction and embodiments of the stator 100 described herein so far corresponds to the stator of the electric machine 200, as well. A rotor such as the rotor 106 is also mounted onto the stator 100. The rotor 106 is mounted onto the stator 100 via the casing 144 including the windings [for e.g. as shown in Figure 8] Further, the cooling tubes 120 as already described in description pertaining to Figure 4 is mounted onto the stator 100. Thereafter, the first and the second end caps, such as the caps 136, 138 are mounted on the front face 108 and the rear face 110 respectively, for securing the cooling tubes 120 on the stator 100 [as shown in Figure 7] In an embodiment, based on the type of electric machine 200, the construction of the stator 100 and the rotor 106 are selected as per requirement.

[041] Referring to Figure 9 in conjunction to Figures 6-8, the cover member 140 is provided in place of the first and the second end caps 136, 138. The cover member 140 is adapted to envelop the stator 100. In an embodiment, the cover member 140 includes an internal projection [not shown in figures] which engages on the outer surface 114 of the stator 100. The internal projection is adapted to secure the cooling tubes 120 onto the stator 100 upon engagement. The cover member 140 includes plurality of fin members 142 for increasing the surface area available for ambient air to flow thereon. Thus, the construction of the cooling tubes 120 and the cover member 140 enables liquid-cooling as well as air-cooling to the electric machine 200, thereby reducing the heat related losses therein. Particularly, cooling of the stator 100 of the machine 200 inherently prevents overheating of the windings 118, thereby mitigating losses arising due to demagnetization. Consequently, the performance and the power density of the electric machine 200 is increased. Additionally, the cooling tubes 120 are mounted directly onto the air-cooled electric machine, thereby effortlessly modifying the air-cooled electric machine into the liquid and air-cooled electric machine 200. As such, requirement for complex modifications for converting the air-cooled electric machine into the liquid and air-cooled electric machine 200 is mitigated.

[042] In an operational embodiment, the electric machine 200 receives a three-phase alternating current from an AC supply to the windings. Upon receiving the AC current, the stator 100 and the rotor 106 interact electromagnetically, resulting in rotation of the rotor 106 which generates heat. At this scenario, the cooling fluid in the cooling tubes 120 flow along the outer surface 114 and absorb the heat generated in the machine 200 via the stator 100, thereby dissipating the heat. Additionally, the portion 114a of the stator 100 is exposed to the ambient air for facilitating air cooling. Also, in the embodiment, where the stator 100 is provided with the cover member 140 and the fins 142, air cooling of the electric machine 200 is enhanced in addition to the liquid cooling, while the cover member 140 protects exposed surface of the stator 100 and the cooling tubes 120. Thus, the heat generated in the electric machine 200 is dissipated by both liquid cooling as well as air cooling, thereby reducing heat associated losses. This consequently improves the power density of the electric machine 200. Additionally, due to the simple construction of the cooling tubes 120 and the stator 100, the air-cooled electric machine is effortlessly modified into the liquid and air-cooled electric machine 200, without the need for complex or substantial modifications to the stator 100. Consequently, reducing the costs associated with manufacturing and maintenance of the electric machine 200. [043] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims. List of reference numerals:

100- Stator

102- Longitudinal slot

104 - Hollow cylindrical member

106- Rotor

108 - Front face of hollow cylindrical member

110 - Rear face of hollow cylindrical member

112- Inner surface of hollow cylindrical member

114- Outer surface of hollow cylindrical member

114a- Portion of hollow cylindrical member

116- Plurality of teeth

118- Windings

120- Cooling tubes

122- Coolant reservoir

124- Ports

126- First annular cooling tube

128 - Second annular cooling tube

130- Connector tube

132 - Groove

134- Projection

136- First end cap

138- Second end cap

140- Cover member

140a - Front portion of cover member

140b - Rear portion cover member

142 - Fin members

144- Casing

146 - Third annular cooling tube 200 - Electric machine

X-X’ - Longitudinal axis