A COOLING SYSTEM AND METHOD FOR AN ELECTRIC MOTOR ARRANGEMENT
FIELD OF INVENTION
[001] The embodiments of the present invention relates generally to an electric motor and specifically to system and methods for cooling rotor assembly in an electric motor.
BACKGROUND TO THE INVENTION
[002] An electric motor can generate considerable heat due to the higher power generation. Therefore, the cooling of the electric motor becomes difficult. Especially, the traction motor which is being used in a vehicle with increased size and weight constraints need to undergo a method of cooling with higher efficiency. Further, the cooling system is provided with a pump to circulate a coolant inside the electrical motor through the passages provided to keep a rotor of the motor cool while the rotor is functioning.
[003] One type of an electric motor known in the art, includes a plurality of concentric shafts, wherein each end of the plurality of concentric shafts includes a seal. Further, the electric motor includes an inlet valve and an outlet valve which is coupled to each of the plurality of concentric shafts. A coolant is passed through the inlet valve and is collected at the outlet valve which makes the system complex and hence bulky. Moreover, the flow of the coolant has to be maintained even at a high rotation of the rotor which can be nearly 36000 rotations per minute. In such a case, if the system fails to maintain the flow of coolant, the system shall be at a high risk of getting damaged due to thermal issues. One such issue is melting of coils inside the motor.

[004] Another type of an electric motor discloses using a closed loop, liquid cooling circuit to try and achieve a temperature balance within the motor, the cooling circuit passing the coolant through both the stator and a rotor shaft. Within the rotor shaft is a stationary injection tube, the injection tube fixed to the stator flange. The coolant is pumped through the injection tube to the end of the rotor shaft where it is driven back between the injection tube and the rotor. The coolant then passes through a cylindrical cooling chamber extending over the length and periphery of the stator before cooling the stator structure and being returned to the injection tube.
[005] One type of rotor cooling system of an electric motor discloses using a cooling system, in which a feed tube is rigidly attached to the rotor shaft of the electric motor. Further, a coolant is pumped through the feed tube until it exits the end of the feed tube and flows against the inside surface of the closed end of the rotor shaft causing the coolant to change direction. The coolant then flows back through the coolant flow region, this region being defined as the space between the outer surface of the feed tube and the inner surface of the rotor shaft thus making the method of cooling more complex.
[006] Thus, in order to overcome at least some of the shortcomings in the cooling technology, the present invention provides an improved rotor cooling system of an electric motor in an electric vehicle system.
SUMMARY OF THE INVENTION
[007] In accordance with one embodiment of the disclosure, a cooling system for an electric motor arrangement is provided. The system includes a shaft operatively coupled to a rotor. Further, the shaft includes a central axis. The system also includes a concentric piping

arrangement which is rigidly coupled to the shaft and is enclosed within the shaft. The concentric piping arrangement is positioned in parallel along the central axis of the shaft. The concentric piping arrangement includes a first end and a second end. A coolant is circulated from the first end of the shaft to the second end by virtue of change in density due to change in temperature and the centrifugal force acting upon it, wherein the coolant absorbs the heat from rotor through the shaft and discharges the heat to a heat condensing region.
[008] In accordance with another embodiment of the disclosure, an electric vehicle system is disclosed. The electric vehicle system includes a chassis. The chassis is configured to provide a structure to the electric vehicle. The electric vehicle system also includes at least one controller operatively coupled within the chassis. The at least one controller is configured to control a plurality of electronic components within the electric vehicle. The electric vehicle system also includes an electric motor arrangement placed within the chassis and is operatively coupled to the at least one controller. The electric motor arrangement includes a rotor. The electric motor arrangement includes a shaft operatively coupled to a rotor. Further, the shaft includes a central axis. The system also includes a concentric piping arrangement which is rigidly coupled to the shaft and is enclosed within the shaft. The concentric piping arrangement is positioned in parallel along the central axis of the shaft. The concentric piping arrangement includes a first end and a second end. A coolant is circulated from the first end of the shaft to the second end by virtue of change in density due to change in temperature and the centrifugal force acting upon it, wherein the coolant absorbs the heat from rotor through the shaft and discharges the heat to a heat condensing region.
[009] To further clarify the advantages and features of the present disclosure, a more particular description of the disclosure will follow by reference to specific embodiments thereof, which

are illustrated in the appended figures. It is to be appreciated that these figures depict only typical embodiments of the disclosure and are therefore not to be considered limiting in scope. The disclosure will be described and explained with additional specificity and detail with the appended figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] The disclosure will be described and explained with additional specificity and detail with the accompanying figures in which:
[0011] FIG. 1 is a schematic cross-sectional view of the rotor cooling assembly with external liquid heat exchanger and a diaphragm in accordance with one embodiment of the present disclosure;
[0012] FIG. 2 is a schematic cross-sectional view of the concentric piping arrangement (140) enclosed in the cooling system of the electric motor of FIG. 1 in accordance with an embodiment of the present disclosure.
[0013] FIG.3 is a schematic cross-sectional view of the concentric piping arrangement (140) enclosed in the cooling system of the electric motor of FIG. 1 with a plurality of support members and a plurality of pair of concentric mounting rings.
[0014] FIG.4 is a schematic cross-sectional view of the concentric piping arrangement (140) enclosed in the cooling system of the electric motor of FIG. 1 with a plurality of support members and a plurality of internal fins.

[0015] FIG.5 is a schematic cross-sectional view of the concentric piping arrangement (140) enclosed in the cooling system of the electric motor of FIG. 1 with support member having plurality of slots.
[0016] FIG.5a is a schematic cross-sectional view of the concentric piping arrangement (140) enclosed in the cooling system of the electric motor of FIG. 1 with support member having plurality of oval slots.
[0017] FIG.5b is a schematic cross-sectional view of the concentric piping arrangement (140) enclosed in the cooling system of the electric motor of FIG. 1 with support member having plurality of rectangular slots.
[0018] FIG.5c is a schematic cross-sectional view of the concentric piping arrangement (140) enclosed in the cooling system of the electric motor of FIG. 1 with support member having plurality of circular slots.
[0019] FIG. 6 is a schematic cross-sectional view of the rotor cooling assembly having a cooling subsystem with an external air heat exchanger to extract heat enclosed in the electric motor of FIG. 1 in accordance with an embodiment of the present disclosure.
[0020] FIG.7 is a schematic cross-sectional view of the rotor cooling assembly with a concentric piping arrangement with a partially filled coolant enclosed in the shaft of a rotor of an electric motor instead of a diaphragm of FIG.1 in accordance with an embodiment of the present disclosure.

[0021] FIG.8 is a schematic cross-sectional view of the rotor cooling assembly having a spring-loaded piston replacing the diaphragm of electric motor of FIG. 6 in accordance with an embodiment of the present disclosure.
[0022] FIG.9 provides a perspective, partial cross-sectional view of a preferred embodiment of the invention.
[0023] Further, those skilled in the art will appreciate that elements in the figures are illustrated for simplicity and may not have necessarily been drawn to scale. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the figures by conventional symbols, and the figures may show only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the figures with details that will be readily apparent to those skilled in the art having the benefit of the description herein.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0024] For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiment illustrated in the figures and specific language will be used to describe them. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Such alterations and further modifications in the illustrated system, and such further applications of the principles of the disclosure as would normally occur to those skilled in the art are to be construed as being within the scope of the present disclosure.

[0025] The terms "comprise", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such a process or method. Similarly, one or more devices or sub-systems or elements or structures or components preceded by "comprises... a" does not, without more constraints, preclude the existence of other devices, sub-systems, elements, structures, components, additional devices, additional sub-systems, additional elements, additional structures or additional components. Appearances of the phrase "in an embodiment", "in another embodiment" and similar language throughout this specification may, but not necessarily do, all refer to the same embodiment.
[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this disclosure belongs. The system, methods, and examples provided herein are only illustrative and not intended to be limiting.
[0027] In the following specification and the claims, reference will be made to a number of terms, which shall be defined to have the following meanings. The singular forms “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise.
[0028] Embodiments of the present disclosure relate to a cooling system for an electric motor. The system includes a shaft operatively coupled to a rotor. Further, the shaft includes a central axis. The system also includes one concentric piping arrangement enclosed within the shaft. The one concentric piping arrangement is parallelly positioned along the central axis of the shaft. The one concentric piping arrangement includes a first end. The one concentric piping arrangement also includes a second end. The one concentric piping arrangement is configured

to cool the rotor by spreading a coolant within an inner surface of the concentric pipes from the first end to the second end.
[0029] FIG. 1 is a schematic cross-sectional view of the rotor cooling assembly with external liquid heat exchanger in accordance with one embodiment of the present disclosure. As used herein, the electric motor is defined as an electrical machine which converts electrical energy into mechanical energy. The system (100) includes a shaft (110) operatively coupled to a rotor (120). As used herein, a shaft (110) is a rotating machine element, usually circular in cross section, which is used to transmit power from one part to another, or from a machine which produces power to a machine which absorbs power. Also, the rotor (120) is a moving component of an electromagnetic system in the electric motor, electric generator, or alternator. Its rotation is due to the interaction between the windings and magnetic fields which produces a torque around the rotor's axis. Further, the shaft (110) includes a central axis (130). As used herein, the central axis (130) is defined as an imaginary line at the center of a body about which the body rotates. In one embodiment, the shaft (110) may be a hollow cylindrical shaft. In one specific embodiment, the shaft (110) may be locked to a lamination of the rotor (120).
[0030] The system (100) also includes one concentric piping arrangement (140). Furthermore, the concentric piping arrangement (140) is enclosed within the shaft (110) and is parallelly positioned along the central axis (130) of the shaft (110). In one embodiment, the concentric piping arrangement (140) may include a plurality of support members (not shown in FIG.1). Also, the system may include a diaphragm (170) fixed onto the second end (160) region of the concentric piping arrangement (140) in the shaft (110). As used herein, the diaphragm (170) is a sheet of a semi-flexible material anchored at its periphery and most often round in shape. It serves as a barrier between the coolant and gas chamber, moving slightly into one chamber or

down into the other depending on differences in pressure inside the chambers, allowing expansion or contraction of coolant inside the shaft (110).
[0031] The concentric piping arrangement (140) includes a first end (150). In one embodiment, the first end (150) act as a heat condensing region of the concentric piping arrangement (140). The concentric piping arrangement also includes a second end (160). In one embodiment, the second end (160) acts as a heat absorbing region of the concentric piping arrangement (140). Further, the concentric piping arrangement also includes a first concentric pipe (141) and a second concentric pipe (142). In one embodiment, the axes of the first concentric pipe (141) and the second concentric pipe (142) are collinear to the central axis (130) of the shaft (110). Also, the concentric piping arrangement (140) is said to be collinear with the central axis (130) of the shaft (110). Further, the concentric piping arrangement (140) is said to be filled fully with a coolant (180). Further, the concentric piping arrangement (140) is configured to cool the rotor (120) by spreading the coolant (180) within an inner surface of the concentric piping arrangement (140) from the first end (150) to the second end (160).
[0032] In one of the embodiments, the plurality of support members (not shown in FIG.1) of the concentric piping arrangement (140) is rigidly coupled to a pair of concentric mounting rings (not shown in FIG.1). In one of the embodiments, the support members (not shown in FIG.1) may include a plurality of oval slots (not shown in FIG.1). In one exemplary embodiment, the support members (not shown in FIG.1) may include a plurality of rectangular slots (not shown in FIG.1). In another exemplary embodiment, the support members (not shown in FIG.1) may include a plurality of circular slots (not shown in FIG.1).

[0033] In such embodiments, the heat absorbing region may be configured to absorb the heat from the rotor (120) by the coolant (180) through the shaft (110) and the heat condensing region may be configured to condense the heat from the rotor (120) by the coolant (180) through the shaft (110) within the concentric piping arrangement (140). In one embodiment, the coolant (180) comprises a liquid coolant, wherein the liquid coolant comprises at least one of water, acetone, methanol and ammonia. In one exemplary embodiment, the first end (150) of the concentric piping arrangement (140) may be extended along the shaft (110) and may be operatively coupled to a cooling subsystem (190) through a rotary bearing (not shown in FIG.1) and an oil seal. As used herein, the rotary bearings hold rotating components such as shafts or axles within mechanical systems, and transfer axial and radial loads from the source of the load to the structure supporting it. As used herein, the oil seal is a device which is fixed on to a shaft to prevent the coolant from the coolant subsystem entering the rotor assembly. The cooling subsystem (190) may be configured to cool the coolant (180) which is hot within the concentric piping arrangement (140). In such embodiment, the cooling subsystem (190) may be a liquid cooling subsystem.
[0034] In one specific embodiment, the concentric piping arrangement (140) may be configured to be filled with a coolant fully. Further, the concentric piping arrangement is configured to cool the rotor (120) as the coolant gets circulated from the first end (150) to the second end (160) due to the change in density of the coolant and centrifugal force acting upon it in the concentric piping arrangement (140). Further, the hot coolant may flow back to the first end (150) and may get condensed. The condensed coolant tends to flow back to the second end (160), thereby keeping the process continuous.

[0035] In operation, as the rotor (120) of the electric motor is in operation, the shaft (110) coupled to the rotor (120) also rotates. As the power produced by the motor is high, an enormous amount of heat is generated in the rotor (120). In order to transfer the heat generated in the rotor (120) away from the system (100), the concentric piping arrangement (140) is enclosed within the shaft (110) and is parallelly positioned along the central axis (130) of the shaft (110),wherein the concentric piping arrangement (140) is filled with the coolant such as water. Further, as the coolant (180) approaches the second end (160), the heat generated in the rotor (120) is absorbed by the coolant in external liquid heat exchanger. The coolant (180) in the shaft (110) tends to move from the first end (150) to the second end (160) due to the change in density of the coolant in the concentric piping arrangement (140) as the coolant at the first end (150) of the concentric piping arrangement (140) is colder than the coolant (180) at the second end (160) of the concentric piping arrangement (140). Henceforth the coolant at the first end (150) of the concentric piping arrangement (140) pushes the coolant (180) at the second end (160) of the concentric piping arrangement (140). Furthermore, due to the heat absorption at the second end (160), the coolant (180) absorbs the heat of the rotor (120) through the shaft (110).
[0036] Furthermore, the coolant (180) which is hot, tends to flow towards the first end (150) of the concentric piping arrangement (140). Further, as the coolant (180) which is hot approaches the first end (150), the concentric piping arrangement (140) along with the shaft (110) at the first end (150) is exposed to the cooling subsystem (190) which manages to cool the hot coolant (180), thereby the hot coolant tends to condense at the first end (150) of the concentric piping arrangement (140). Further, the condensed coolant tends to flow toward the second end (160) again due to the continuous rotation of the shaft (20) and hence due to the change in density of

the coolant in the concentric piping arrangement (140). Henceforth, the process is cyclic, thereby continuously removing the heat generated in the rotor (120). Further, the diaphragm (170) is fixed to the second end (160) of the shaft (110) allowing the coolant to expand inside the concentric piping arrangement (140).
[0037] FIG. 2 is a schematic cross-sectional view of the concentric piping arrangement (140) enclosed in the cooling system of the electric motor of FIG. 1 in accordance with an embodiment of the present disclosure. Further, the concentric piping arrangement (140) in the FIG.2 includes a plurality of support members (201, 202, 203, 204, 205, 206) rigidly coupled to the concentric piping arrangement (140). Further, the concentric piping arrangement also includes a first concentric pipe (141) and a second concentric pipe (142). In one embodiment, the axes of the first concentric pipe (141) and the second concentric pipe (142) are collinear to the central axis (130) of the shaft (110). Also, the concentric piping arrangement (140) is said to be collinear with the central axis (130) of the shaft (110). Further, the plurality of support members (201, 202, 203, 204, 205, 206) in FIG. 2 are slotted in nature.
[0038] FIG.3 is a schematic cross-sectional view of the concentric piping arrangement (140) enclosed in the cooling system of the electric motor of FIG. 1 with a plurality of support members and a plurality of pair of concentric mounting rings. Further, the concentric piping arrangement (140) in the FIG.3 includes a plurality of support members (201, 202, 203, 204, 205, 206) rigidly coupled to the concentric piping arrangement (140). The concentric piping arrangement (140) in the FIG.3 also includes a plurality of pair of concentric mounting rings (301, 302, 303, 304, 305, 306) rigidly coupled to the concentric piping arrangement (140). Further, the concentric piping arrangement also includes a first concentric pipe (141) and a second concentric pipe (142).

[0039] FIG.4 is a schematic cross-sectional view of the concentric piping arrangement (140) enclosed in the cooling system of the electric motor of FIG. 1 with a plurality of support members and a plurality of internal fins. The concentric piping arrangement (140) includes a first concentric pipe (141) and a second concentric pipe (142). The concentric piping arrangement (140) in the FIG.4 includes a plurality of support members (201, 202, 203, 204, 205, 206) rigidly coupled to the concentric piping arrangement (140). Further, the concentric piping arrangement (140) in the FIG.4 also includes a plurality of internal fins (401, 402, 403, 404, 405, 406) rigidly coupled to the concentric piping arrangement (140).
[0040] FIG.5 is a schematic cross-sectional view of the concentric piping arrangement (140) enclosed in the cooling system of the electric motor of FIG. 1 with support member rigidly coupled to the concentric piping arrangement (140). FIG.5a is a schematic cross-sectional view of the concentric piping arrangement (140) enclosed in the cooling system of the electric motor of FIG. 1 with a plurality of oval slots (501, 502, 503, 504, 505, 506, 507, 508). FIG.5b is a schematic cross-sectional view of the concentric piping arrangement (140) enclosed in the cooling system of the electric motor of FIG. 1 with a plurality of rectangular slots (511, 512, 513, 514, 515, 516, 517, 518). FIG.5c is a schematic cross-sectional view of the concentric piping arrangement (140) enclosed in the cooling system of the electric motor of FIG. 1 with a plurality of circular slots (521, 522, 523, 524, 525, 526, 527, 528).
[0041] FIG. 6 is a schematic cross-sectional view of the rotor cooling assembly having an external air cooling subsystem (601) comprising an air heat exchanger to extract heat enclosed in the electric motor of FIG. 1 in accordance with an embodiment of the present disclosure. The system (100) includes a shaft (110) operatively coupled to a rotor (120). Further, the shaft (110) includes a central axis (130). In one embodiment, the shaft (110) may be a hollow

cylindrical shaft. In one specific embodiment, the shaft (110) may be locked to a lamination of the rotor (120). In another embodiment the air-cooled external heat exchanger is coupled rigidly to the shaft (110).
[0042] The system (100) also includes one concentric piping arrangement (140). Furthermore, the concentric piping arrangement (140) is enclosed within the shaft (110) and is parallelly positioned along the central axis (130) of the shaft (110). In one embodiment, the concentric piping arrangement (140) may include a plurality of support members (not shown in FIG.6). Also, the system may include a diaphragm (170) fixed onto the second end (160) of the shaft (110). As used herein, the diaphragm (170) is a sheet of a semi-flexible material anchored at its periphery and most often round in shape. It serves either as a barrier between two chambers, moving slightly up into one chamber or down into the other depending on differences in pressure, or as a device that vibrates when certain frequencies are applied to it.
[0043] The concentric piping arrangement (140) includes a first end (150). In one embodiment, the first end (150) might act as a heat condensing region of the concentric piping arrangement (140). The concentric piping arrangement also includes a second end (160). In one embodiment, the second end (160) acts as a heat absorbing region of the concentric piping arrangement (140). Further, the concentric piping arrangement also includes a first concentric pipe (141) and a second concentric pipe (142). In one embodiment, the first concentric pipe (141) and the second concentric pipe (142) are collinear to the central axis (130) of the shaft (110). Also, the concentric piping arrangement (140) is said to be collinear with the central axis (130) of the shaft (110). Further, the concentric piping arrangement (140) is said to be fully filled with a coolant (180). Further, the concentric piping arrangement (140) is configured

to cool the rotor (120) by spreading the coolant (180) within an inner surface of the concentric piping arrangement (140) from the first end (150) to the second end (160).
[0044] In such embodiments, the heat absorbing region may be configured to absorb the heat from the shaft (110) by the coolant (180) and the heat condensing region may be configured to condense the heat from the shaft (110) by the coolant (180) within the concentric piping arrangement (140). In one embodiment, the coolant (180) may be at least one of water, acetone, methanol and ammonia. In one exemplary embodiment, the first end (150) of the concentric piping arrangement (140) may be extended along the shaft (110) and may be rigidly coupled to a cooling subsystem (601). The cooling subsystem (601) may be configured to condense the coolant (180) which is hot within the concentric piping arrangement (140). Further, the cooling subsystem (601) includes fins (611) and a fan (612). In one embodiment, the cooling subsystem (601) may be at least one of the air-cooling subsystems.
[0045] FIG.7 is a schematic cross-sectional view of the rotor cooling assembly with a concentric piping arrangement with a partially filled coolant (701) enclosed in the shaft of a rotor of an electric motor of FIG.1 in accordance with an embodiment of the present disclosure. The system (100) includes a shaft (110) operatively coupled to a rotor (120). Further, the shaft (110) includes a central axis (130). In one embodiment, the shaft (110) may be a hollow cylindrical shaft. In one specific embodiment, the shaft (110) may be locked to a lamination of the rotor (120).
[0046] The system (100) also includes one concentric piping arrangement (140). Furthermore, the concentric piping arrangement (140) is enclosed within the shaft (110) and is parallelly positioned along the central axis (130) of the shaft (110). In one embodiment, the concentric

piping arrangement (140) may include a plurality of support members (not shown in FIG.7). Also, the system may include a diaphragm (170) fixed onto the second end (160) of the shaft (110).
[0047] The concentric piping arrangement (140) includes a first end (150). In one embodiment, the first end (150) might act as a heat condensing region of the concentric piping arrangement (140). The concentric piping arrangement also includes a second end (160). In one embodiment, the second end (160) acts as a heat absorbing region of the concentric piping arrangement (140). Further, the concentric piping arrangement also includes a first concentric pipe (141) and a second concentric pipe (142). In one embodiment, the first concentric pipe (141) and the second concentric pipe (142) are collinear to the central axis (130) of the shaft (110). Also, the concentric piping arrangement (140) is said to be collinear with the central axis (130) of the shaft (110). Further, the concentric piping arrangement (140) includes a partially filled coolant (701). Further, the concentric piping arrangement (140) is configured to cool the rotor (120) by spreading the coolant (180) within an inner surface of the concentric piping arrangement (140) from the first end (150) to the second end (160).
[0048] In such embodiments, the heat absorbing region may be configured to absorb the heat from the shaft (110) by the coolant (180) and the heat condensing region may be configured to condense the heat from the shaft (110) by the coolant (180) within the concentric piping arrangement (140). In one embodiment, the coolant (180) may be at least one of water, acetone, methanol and ammonia. In one exemplary embodiment, the first end (150) of the concentric piping arrangement (140) may be extended along the shaft (110) and may be operatively coupled to a cooling subsystem (190) through a rotary bearing (not shown in FIG.7) and an oil seal. The cooling subsystem (190) may be configured to condense the coolant (180) which is

hot within the concentric piping arrangement (140). In one embodiment, the cooling subsystem (190) may be at least one of a liquid cooling subsystem.
[0049] FIG. 8 is a schematic cross-sectional view of the rotor cooling assembly having a spring-loaded piston (801) replacing the diaphragm (170) of electric motor of FIG. 6 in accordance with an embodiment of the present disclosure. The system (100) includes a shaft (110) operatively coupled to a rotor (120). Further, the shaft (110) includes a central axis (130). In one embodiment, the shaft (110) may be a hollow cylindrical shaft. In one specific embodiment, the shaft (110) may be locked to a lamination of the rotor (120).
[0050] The system (100) also includes one concentric piping arrangement (140). Furthermore, the concentric piping arrangement (140) is enclosed within the shaft (110) and is parallelly positioned along the central axis (130) of the shaft (110). In one embodiment, the concentric piping arrangement (140) may include a plurality of support members (not shown in FIG.8). Also, the system may include a spring-loaded piston (801) fixed onto the second end (160) of the shaft (110). As used herein, the spring-loaded piston (801) serves as a barrier between the coolant and gas chambers, allowing the expansion or contraction of coolant inside the shaft (110).
[0051] The concentric piping arrangement (140) includes a first end (150). In one embodiment, the first end (150) might act as a heat condensing region of the concentric piping arrangement (140). The concentric piping arrangement also includes a second end (160). In one embodiment, the second end (160) acts as a heat absorbing region of the concentric piping arrangement (140). Further, the concentric piping arrangement also includes a first concentric pipe (141) and a second concentric pipe (142). In one embodiment, the first concentric pipe

(141) and the second concentric pipe (142) are collinear to the central axis (130) of the shaft (110). Also, the concentric piping arrangement (140) is said to be collinear with the central axis (130) of the shaft (110). Further, the concentric piping arrangement (140) is said to be fully filled with a coolant (180). Further, the concentric piping arrangement (140) is configured to cool the rotor (120) by spreading the coolant (180) within an inner surface of the concentric piping arrangement (140) from the first end (150) to the second end (160).
[0052] In such embodiments, the heat absorbing region may be configured to absorb the heat from the shaft (110) by the coolant (180) and the heat condensing region may be configured to condense the heat from the shaft (110) by the coolant (180) within the concentric piping arrangement (140). In one embodiment, the coolant (180) may be at least one of water, acetone, methanol and ammonia. In one exemplary embodiment, the first end (150) of the concentric piping arrangement (140) may be extended along the shaft (110) and may be rigidly coupled to a cooling subsystem (601). The cooling subsystem (601) may be configured to condense the coolant (180) which is hot within the concentric piping arrangement (140). Further, the cooling subsystem (601) includes fins (611) and a fan (612). In one embodiment, the cooling subsystem (601) may be at least one of the air-cooling subsystems.
[0053] FIG. 9 provides a perspective, partial cross-sectional view of a preferred embodiment of the invention. In this embodiment the cooling system (100) is comprised of an air-cooling subsystem (901). Further, the first fin region (911) and the second fin region (912) of the air-cooling subsystem (901) are thermally coupled to the first end (150) of the concentric piping arrangement (140) rigidly coupled to a shaft (110) perform the function of the air-cooling subsystem (901). Furthermore, as the shaft (110) rotates during motor operation, the air flows from the first fin region (911) of the air-cooling subsystem (901) to the second fin region (912)

of the air-cooling subsystem (901), thereby promoting efficient heat withdrawal. It should be understood that the sub system used for the cooling of the rotor assembly may utilize any of a variety cooling subsystem including, but not limited to, air-cooling subsystem etc.
[0054] Various embodiments of the cooling system for an electric motor enables the system to maintain a constant flow of coolant within the concentric piping arrangement (140) even at high rotations per minute. Hence making the system highly efficient. Also, due to the change in density of the coolant (180) from the first end (150) to the second end (160) of the concentric piping arrangement, the cooling process of the rotor is enhanced. In addition, due to the use of the concentric mounting rings, the overall cost of the system is reduced.
[0055] While specific language has been used to describe the disclosure, any limitations arising on account of the same are not intended. As would be apparent to a person skilled in the art, various working modifications may be made to the method in order to implement the inventive concept as taught herein.
[0056] The figures and the foregoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, order of processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts need to be necessarily performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope

of embodiments is by no means limited by these specific examples.

WE CLAIM:
1. A cooling system (100) for an electric motor arrangement comprising:
a shaft (110) operatively coupled to a rotor (120) of the electric motor arrangement, the shaft (110) having a central axis (130);
a concentric piping arrangement (140) comprising at least one concentric pipe enclosed within the shaft (110), the axes of the concentric pipes being colinear with the central axis (130) of the shaft (110), the concentric pipes being coupled together with plurality of support members, such that, a coolant (180) absorbs heat produced in the rotor (120) through the shaft (110) and discharges the heat to a condensing region by circulation of it through the concentric piping arrangement (140) from a first end (150) to a second end (160) along the length of the shaft by virtue of change in density of it and centrifugal force acting upon it,
wherein, a recess is provided within the concentric piping arrangement (140) to allow change in volume of the coolant (180).
2. The cooling system (100) as claimed in claim 1, wherein the shaft (110) is a hollow cylindrical shaft.
3. The cooling system (100) as claimed in claim 1, wherein the concentric piping arrangement (140) comprise cylindrical pipes.
4. The cooling system (100) as claimed in claim 1, wherein at least one pipe of the concentric piping arrangement (140) is tapered on inner or outer side.

5. The cooling system (100) as claimed in claim 1, wherein the recess at the at least one end of the shaft (110) comprises a gas that expands or contracts to allow change in volume of the coolant.
6. The cooling system (100) as claimed in claim 1, wherein the recess at the at least one end of the shaft (110) comprises a diaphragm (170), the diaphragm (170) configured to allow change in volume of the coolant (180).
7. The cooling system (100) as claimed in claim 1, wherein the recess at the at least one end of the shaft (110) comprises a spring loaded piston (801), the spring loaded piston (801) configured to allow change in volume of the coolant (180).
8. The system (100) as claimed in claim 1, wherein the concentric piping arrangement (140) comprises a plurality of support members having oval or perforated or circular slots.
9. The system (100) as claimed in claim 1, wherein the first end (150) is configured as a heat condensing region of the concentric piping arrangement (140) and the second end (160) is configured as a heat absorbing region of the concentric piping arrangement (140).
10. The system (100) as claimed in claim 1, wherein the heat condensing region is cooled by an air or a liquid heat exchanger.
11. The system (100) as claimed in claim 1, wherein the coolant (180) comprises a liquid coolant, the liquid coolant being at least one of water, acetone, methanol and ammonia.