Cooling of end windings in a stator assembly

Abstract

The present subject matter relates to a rotary machine (100) that includes a shell (102), a stator assembly (104), and a rotor assembly. The shell includes two axial ends (124), at least one of the two axial ends (124) being closed by an end plate (118). The end plate (118) includes an inner face (122) wherein a curvature (120) is formed. The hollow shaft (110) includes a first set of ducts (114) arranged circumferentially. An inlet of each of the first set of ducts (114) is open to a hollow region (112) in the hollow shaft (110) and an outlet of each of the first set of ducts (114) is open to a cavity (126) in the shell (102). The outlet is directed towards the curvature (120) of the end plate (118).

Description

COOLING OF END WINDINGS IN A STATOR ASSEMBLYFIELD OF INVENTION

[0001] The present subject matter relates in general to cooling of a rotary machine, and particularly, to cooling of end windings in a stator assembly of the rotary machine.BACKGROUND

[0002] Rotary machines are widely used in automotive applications and very much so as traction motor. Rotary machines typically include a stator and a rotor that are arranged coaxial to each other, the rotor being configured to rotate about a rotational axis. The stator and the rotor are disposed to face each other along the rotational axis in a housing. The rotor is mounted on a rotor shaft that extends out of the housing to mechanically interact with a pulley or a gear so that a transfer of torque is facilitated. In a known arrangement, the stator is supported by a bracket provided in the housing. In such an arrangement, the rotor is disposed within a cavity of the stator. Further, a gap is maintained between the outer periphery of the stator and the inner periphery of the bracket. Such a gap is particularly required in liquid cooled rotary electrical machine where a cooling medium is made to circulate through said gap. This gap functions as a channel to permit distribution of a cooling medium, such as oil, to cool the stator, specifically, to permit flow of the cooling medium to end windings of the stator.

[0003] In the conventional rotary machines, having the abovedescribed configuration, the cooling medium is made to flow in the channel and made to flow out, or sprayed, to the end windings at both ends of the stator. Such a configuration does not provide an even distribution of the cooling medium to the end windings. The end windings are not cooled inan efficient manner. Rotary machines of such configuration therefore tends to perform poorly and in an inefficient manner.

[0004] Therefore, the technical problem to be solved by the present subject matter is how to provide improved cooling of end windings of a stator assembly in a rotary machine.SUMMARY OF THE INVENTION

[0005] The present subject matter seeks to solve the above- mentioned technical problem in conventional rotary machines. The present subject matter relates to a rotary machine comprising: a shell comprising two axial ends, at least one of the two axial ends being closed by an end plate, wherein the end plate comprises an inner face facing inside the shell wherein a curvature is formed in the inner face, said curvature comprising two distinct ends and a smooth transitioning curved profile between said two distinct ends; a stator assembly, disposed in the shell, comprising a stator core and a stator windings provided with end windings; and a rotor assembly arranged on an inner side of the stator core and rotatable about a central axis common to the stator assembly, the rotor assembly comprising a rotor mounted on a hollow shaft through which a cooling medium flows, the hollow shaft comprising a first set of ducts arranged circumferentially in said hollow shaft, and wherein an inlet of each of the first set of ducts is open to a hollow region in the hollow shaft and an outlet of each of the first set of ducts is open to a cavity in the shell and directed towards the curvature of the end plate. Accordingly, during operation of the rotary machine, the cooling medium is directed from the hollow region in the hollow shaft, through the first set of ducts. The configuration of the two distinct ends of the curvature facilitates the cooling medium to follow the path along said curvature and towards an inner wall of the shell from which the cooling medium is splashed to an outer diametric side of the end windings. Therefore, by virtue of the first set of ducts and the curvature, thecooling medium reaches the outer diametric side, said outer diametric side referring to an outermost end of the end windings in a radial direction from the central axis. Accordingly, an efficient cooling of the end windings is achieved by cooling medium from the hollow shaft. Moreover, by virtue of the improved efficiency in cooling the end windings, the performance of the rotary machine is improved.

[0006] According to an aspect of the present subject matter, the first set of ducts is in a first angle to a first reference line parallel to the central axis. By virtue of a centrifugal force from the rotation of the hollow shaft during operation, the cooling medium enters the first set of ducts through the inlet. The inclination of the first set of ducts in the first angle permits flow of cooling medium in the path along the curvature.

[0007] According to an aspect of the present subject matter, the first end, of the two distinct ends in the curvature, is inclined in a second angle to the first reference line, said second angle being equal in value to the first angle. The first set of ducts and the first end of the curvature are therefore in line to facilitate flow of cooling medium in the path that is optimum for cooling the outer diametric side of the end windings. By virtue of the first and the second angle, the cooling medium from the first set of ducts is precisely directed to the curvature. Accordingly, the cooling medium is evenly spread to the outer diametric side of the end windings.

[0008] According to an example of the present subject matter, the curvature is formed in a convex shape curving in an axial direction away from the inside of the shell, said axial direction being parallel to the central axis.

[0009] According to an example of the present subject matter, the curvature is an arc shaped groove formed on the inner face of the end plate, said arc shaped groove formed circumferentially about the central axis.

[0010] According to an aspect of the present subject matter, a second end, of the two distinct ends in the curvature, is included in a third angle to a second reference line parallel to the central axis, said second reference line being coincident to an inner wall of the shell. Accordingly, an optimum incidence of the cooling medium to the inner wall is achieved, and optimum amount of cooling medium is facilitated to splash to the outer diametric side from said inner wall.

[0011]

[0012] According to an example of the present subject matter, the hollow shaft comprises a second set of ducts, each of said second set of ducts being open at a second inlet to the hollow region of the hollow shaft and open at another end by a second outlet directed towards an inner diametric side of the end windings, said inner diametric side referring to an innermost end of the end windings in the radial direction from the central axis. The second set of ducts therefore facilitate the cooling medium to reach an inner diametric side of the end windings, whilst the first set of ducts and the curvature facilitate the cooling medium to reach the outer diametric side of the end windings. The outer diametric side and the inner diametric side of the end windings is therefore cooled by cooling medium from the hollow region in the hollow shaft.

[0013] According to an example of the present subject matter, the inlet of the first set of ducts and the second inlet of the second set of ducts is a single inlet opening. Accordingly, cooling medium from the hollow shaft flows into the single inlet opening and bifurcates to the first set of ducts and second set of ducts to effectively cool the outer diametric side and inner diametric side respectively.

[0014] According to an example of the present subject matter, the outlet of the first set of ducts has an oblong shape, or a circular shape, ora rectangular shape. A suitable shape may be selected to optimize flow of cooling medium from the oulet.

[0015] According to an example of the present subject matter, the stator core comprise channels extending parallel to the central axis, said channels being open towards an outer diametric side of the end windings. Accordingly, cooling medium is facilitated to reach the end windings from the hollow shaft and from the channels provided in the stator core. An improved cooling may therefore be achieved.

[0016] The present subject matter relates also to a method to cool end windings of a stator assembly in a rotary machine, configured in accordance with the present subject matter, the method comprising: detecting a rotational speed of the hollow shaft; detecting a temperature of the end windings; communicating a speed signal and a temperature signal to a control unit, the speed signal being pertaining to the rotational speed detected, and the temperature signal pertaining to the temperature detected from the end windings; determining an adjusted rate of flow of the cooling medium, by the control unit, based on the temperature and rotational speed; and dispersal of cooling medium into the hollow shaft and facilitate a flow of cooling medium through the first set of ducts in the path along the curvature of the end plate. Accordingly, at every instant, the rate of flow is adjusted to meet optimum cooling requirements of the end windings. Particularly, depending the temperature and the rotational speed, an optimum amount of cooling medium is dispersed, at the adjusted rate of flow, to the hollow region of the hollow shaft; and an optimum amount of cooling medium is passed through to the first set of ducts that facilitate said cooling medium to reach the outer diametric side of the end windings.BRIEF DESCRIPTION OF DRAWINGS

[0017] The features, aspects, and advantages of the present invention will be better understood with regard to the following descriptionand accompanying figures. The description refers to the annexed drawings, wherein:

[0018] FIG. 1 A illustrates a schematic cross-sectional view of a rotary machine, configured in accordance with an aspect of the present subject matter; and

[0019] FIG. 1 B illustrates a focused view of the rotary machine shown in FIG. 1 A, configured in accordance with the present subject matter;

[0020] FIG. 2A illustrates the rotary machine at A, configured in accordance with an aspect present subject matter;

[0021] FIG. 2B illustrates another perspective rotary machine at A, with stator assembly removed from the rotary machine, configured in accordance with an aspect present subject matter;

[0022] FIG. 2C illustrates a focused view of the aspect shown in FIG. 2B, showing closely a first set of ducts and a second set of ducts, configured in accordance with the present subject matter;

[0023] FIG. 3 illustrates an isometric view of an end plate of the rotary machine, configured in accordance with an example of the present subject matter;

[0024] FIG. 4 illustrates a hollow shaft of the rotary machine, configured in accordance with an example of the present subject matter;

[0025] FIG. 5 illustrates an exploded view of the rotary machine, configured in accordance with the present subject matter; and

[0026] FIG. 6 illustrates a method for cooling end windings of a stator assembly in the rotary machine, configured in accordance with an aspect of the present subject matter;

[0027] The figures are not necessarily to scale, and the size of some parts may be exaggerated to more clearly illustrate the example shown. Moreover, the drawings provide examples and / or examples consistent with the description, however, the description is not limited to the examples and / or examples provide in the drawings.DETAILED DESCRIPTION

[0028] In the description that follows, reference is made to accompanying drawings, which form part thereof, and in which is shown by way of illustration specific implementations in which the invention maybe practiced. These implementations are described in sufficient detail to enable that skilling in the art to practice the invention, and it is to be understood that the implementations may be combined, or that other implementations may be utilized, and that structural and logical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.

[0029] FIG. 1 A is a schematic cross-sectional view of a rotary machine 100, configured in accordance with the present subject matter. FIG. 1 B is a focused view of the rotary machine 100 shown in Fig. 1 A.

[0030] The rotary machine 100 includes a shell 102, a stator assembly 104, and a rotor assembly. The shell 102 has two axial ends 124, at least one of said two axial ends 124 being closed by an end plate 1 18. The end plate 1 18 includes an inner face 122 on which a curvature 120 is formed. The curvature 120 includes two distinct ends and a smooth transitioning curved profile between said two distinct ends. The stator assembly 104 is disposed in the shell 102. The stator assembly 104 includes a stator core 106 and stator windings provided with end windings 108. The rotor assembly (shown in another figure) is arranged on an innerside of the stator core 106. The rotor assembly is rotatable about a central axis 126 that is common to the stator assembly 104. The rotor assembly includes a rotor mounted on a hollow shaft 1 10 through which a cooling medium (or, ‘cooling means’) flows. The hollow shaft 1 10 includes a first set of ducts 1 14 arranged circumferentially. An inlet of each of the first set of ducts 1 14 opens to a hollow region 1 12 in the hollow shaft 1 10. An outlet of each of the first set of ducts 1 14 is open to a cavity 126 in the shell 102. Further, the outlet is directed towards the curvature 120 of the end plate 118.

[0031] Within the meaning of the present subject matter:

[0032] “axially” or “axial direction” refers to “a direction parallel to the central axis 126 that is common to the stator assembly 104 and the rotor assembly.” The rotor assembly is configured to rotate about the central axis 126.

[0033] “radial” or “radially” means “in a direction perpendicular to the central axis 126 and along a straight line intersecting this central axis 126”,

[0034] The two axial ends 124 of the shell include a drive end 124 at one end of the rotary machine 100 and a non drive end (not shown in FIGs. 1 A and 1 B) at another end of the rotary machine 100. FIG. 1 A shows the drive end 124 closed by the end plate 1 1 . The hollow shaft 1 10 is passed through the end plate 1 18, attached to the shell 102 at the drive end 124, to permit a distal end of the hollow shaft 1 10 to engage with a pinion or pulley for a transfer of torque during operation of the rotary machine 100.

[0035] The stator core 106, disposed in the shell 102, extends in length along the axial direction. One end of the stator core 106, along the axial direction, is mounted (hence, supported) to the shell 102 by fasteners 134. According to an example of the present subject matter, the stator core 106 is a laminated stator core 106 that includes a plurality of stackedlaminations (not shown), although it is permissible for the stator core 106 to be non-laminated. The stator core 106, in said example, includes a ferromagnetic material such as steel, although use of any one or more electrically conductive materials is permissible without departing from the scope of the present subject matter. Preferably, the stator core 106 includes a plurality of arcuately spaced apart, generally radially extending teeth. More particularly, each of the teeth includes a generally circumferentially extending yoke, a generally radial arm extending from the yoke, and a crown extending generally circumferentially from the arm. The stator windings is electrically conductive wiring wound multiple times about each tooth to form a plurality of turns or loops. The electrically conductive wiring is preferably formed of copper or aluminum, although any one or more of a variety of electrical conductive materials or a combination thereof may be used within the ambit of the present subject matter. Further, the wiring may be coated or uncoated. The wiring is wound around the teeth in a particular manner according to the configuration and desired performance characteristics of the rotary machine 100. Alternatively, the stator windings may be formed from isolated copper rods (or aluminum, or a combination thereof) in the form of what are referred to as pins, or U-pins, or hairpin.

[0036] The end plate 1 18 is attached to the shell 102 in a manner to close the drive end 124 of the shell 102. The end plate 118 is attached and mounted to the shell 102 in a manner that the inner face 122 is facing, or exposed, towards the cavity 126 of the shell 102. In other words, the inner face 122 is facing the stator core 106 and the end windings 108. Therefore, the curvature 120 is also exposed to the cavity 126 of the shell 102. The curvature 120 is formed in a convex shape, meaning curved away from the inside of the shell 102.

[0037] According to an aspect of the present subject matter, the first set of ducts 1 14 is directed towards a first end of the curvature 120, the first end being one of the two distinct ends of the curvature 120 formed on theinner face 122 of the end plate 1 18. During operation, cooling medium from the hollow region 1 12, in the hollow shaft 1 10, is made to flow into the first set of ducts 1 14. The cooling medium then takes a path 130 along the curvature 120 from the first end to a second end. At the second end, cooling medium comes in contact with the inner wall 128 of the shell 102. From the inner wall 128, the cooling medium is dispersed to the end windings 108. More specifically, the dispersal of the cooling medium is towards an outer diametric side of the end windings 108, said outer diametric side referring to an outermost end of the end windings 108 in the radial direction from the central axis 126.

[0038] FIG. 2A illustrate an aspect of the rotary machine 100, configured in accordance with the present subject matter, shown at region A of FIG. 1 B. FIG. 2B illustrate region A with the end windings 108 and the stator core 106 removed from view. FIG. 2C illustrates a focused, or zoomed in, view of the hollow shaft 1 10 where the first set of ducts 114 are formed, configured in accordance with the present subject matter.

[0039] In FIGs. 2A and 2B, two distinct ends 200, 202 of the curvature 120 is shown. The two distinct ends 200, 202 include a first end 200 and a second end 202. Further, the smooth transitioning curved profile is provided between the first end 200 and the second end 202. The curvature 120 is arranged so that the first end 200 is closer in distance radially from the central axis 126 in comparison to the distance radially of the second end 202 from the central axis 126. Each of the first set of ducts 1 14 include an inlet 204 open to the hollow region 1 12 of the hollow shaft 1 10. Each of the first set of ducts 1 14 further include an outlet 206 open towards the cavity 126 in the shell 102. The arrangement of the first set of ducts 1 14 permits flow of cooling medium in the path 130 that passes through the first set of ducts 1 14, and along the curvature 120, and contacting the inner wall 128, and finally dispersing to the end windings 108 by way of a splash 204 towards the outer diametric side of the end windings 108.

[0040] According to an aspect of the present subject matter, the first set of ducts 1 14 is inclined to facilitate flow of cooling medium in the path 130 along the curvature 120. The first set of ducts 1 14, in said example, is inclined in a first angle 91 to a first reference line Y1 shown in FIG. 2B. The first reference line Y1 is a line parallel to the central axis 126. Accordingly, the first end 200 of the curvature 120 is formed to be inclined in a second angle 62 to the first reference line Y1. In a non limiting manner, the first angle 61 and the second angle 92 have equal value in degrees. The first set of ducts 114 and the first end 200 of the curvature 120 are therefore in line to facilitate flow of cooling medium in the path 130. Accordingly by virtue of a centrifugal force from the rotation of the hollow shaft 1 10 during operation, said cooling medium enters through the first set of ducts 1 14 through the inlets 204. The inclination of the first set of ducts 114 in the first angle 91 permits flow of cooling medium in the path 130. The path 130 through the first set of ducts 1 14 is therefore a straight path inclined at the first angle 91. The cooling medium reaches the first end 200 of the curvature 120 following the straight path aforementioned. The first end 200 is inclined at the second angle 92, the second angle 92 being equal in value to the first angle 91 , thereby ensuring the path 130 of the cooling medium, upon reaching the first end 200, does not diverge from the straight path followed whilst flowing through the first set of ducts 114. Such a configuration allows for the cooling medium to reach the curvature 120 from the first set of ducts 1 14 in a non-turbulent manner. From the first end 200, the coolant continues to flow the path 130 along the smooth transitioning curved profile of the curvature 120 and reach the second end 202.

[0041] According to an aspect of the present subject matter, the second end 202 of the curvature 120 is inclined in a third angle 93 to a second reference line Y2. The second reference line Y2 is a line parallel to the central axis 126, hence, also parallel to the first reference line Y1 also. Further, the second reference line Y2 is coincident to the inner wall wherethe cooling medium is dispersed in a splash 204. According to an example of the present subject matter, the curvature 120 is formed such that the third angle 03 is equal in value (in degrees) to the second angle 02. The third angle 03 may alternatively be different in value to the second angle 02. A suitable value of the third angle 03 is chosen to facilitate optimum incidence of cooling medium to the inner wall 128 so that a splash 204 is formed for even dispersal of cooling medium to the outer diametric side of the end windings 108.

[0042] FIG. 3 the end plate 1 18 of the rotary machine 100, configured in accordance with an aspect of the present subject matter. The end plate 118 includes a through hole 300 through which the hollow shaft 1 10 is passed through. The end plate 1 18 further include fastening provisions, formed for instance as lugs, that permit fasteners 134 (shown in FIG. 1 B) to pass through and facilitate an attachment and mounting to the shell 102. The curvature 120 is formed on the inner face 122 of the end plate 1 18. The inner face 122 is formed facing inside the shell 102. The curvature 120 is therefore formed in a convex shape curving in an axial direction away from the inside of the shell 102. According to the example shown in FIG. 3, the curvature 120 is an arc shaped groove formed circumferentially about the central axis 126.

[0043] FIG. 4 illustrates the hollow shaft 110, in accordance with an example of the present subject matter. According to said example, the hollow shaft 1 10 includes the first set of ducts 1 14 and a second set of ducts 1 16 (also visible in FIGs, 1 A, 1 B, 2A, 2B and 2C). The second set of ducts 1 16 is arranged circumferentially around the hollow shaft 110. Each of the second set of ducts 1 16 is open at a second inlet 208 (shown in FIG. 2C) to the hollow region 112. Further, each of the second set of ducts 1 16 is open at a second outlet 210 (shown in FIG. 2C), formed for instance in a circular shape, and directed towards an inner diametric side of the end windings 108, said inner diametric side referring to an innermost end of theend windings 108 in the radial direction from the central axis 126. During operation, cooling medium is made to pass through the second set of ducts 116 by virtue of a centrifugal force due to the hollow shaft 1 10 rotation. The cooling medium, enters the second set of ducts 1 16 through the second inlet 208 and is dispersed to the inner diametric side of the end windings 108 via the second outlet 210. Accordingly, cooling medium is dispersed to the inner diametric side by virtue of the second set of ducts 1 16, and to the outer diametric side by virtue of the first set of ducts 1 14 and curvature 120 of the end plate 1 18.

[0044] In an example of the present subject matter, the inlet 204 of the first set of ducts 1 16 and the second inlet 208 of the second set of ducts 1 16 is a single inlet opening (not shown). Therefore, during operation when the hollow shaft 1 10 is in rotation, cooling medium flows into the single inlet opening where said cooling medium is diverged to the first set of ducts 1 16 and the second set of ducts 1 14.

[0045] According to the example shown in FIG. 4, the outlet 206 of the first set of ducts 114 is formed in an oblong shape. Alternatively, the outlet 206 has a circular shape, or a rectangular shape, or any other shape suitable for optimum flow of cooling medium through the said outlet 206 to follow the path 130 along the curvature 120 of the end plate 1 18.

[0046] FIG. 5 illustrates an exploded view of the rotary machine 100 configured in accordance with the present subject matter. The rotary machine 100 includes the shell 102, the stator assembly 104 and a rotor assembly disposable in an inner side 504 of the stator core 106. The rotor assembly includes a rotor 500 and the hollow shaft 1 10, configured in accordance with the present subject matter, on which the rotor 500 is mounted. The shell 102 is closed at either one or both of two axial ends 124, 502. The two axial ends 124, 502 are the drive end 124 and a non drive end 502. In the examples shown in FIGs. 1 A through 5, the end plate118 is shown to be attached to the drive end 124 for the sake of simplicity in description. Another end plate, configured in the same manner as the end plate 1 18, may be attached to the shell 102 at the non drive end 502.

[0047] The rotary machine 100 is suitably applicable for propulsion of a motor vehicle. The rotary machine 100 may operate in a motor mode in which an electrical current passes across the stator windings, and allows the creation of a magnetic field that causes a rotation of the rotor 500. When the rotary machine 100 is operating in a generator mode, the rotational movement of the rotor 500 allows the creation of a magnetic field into the stator core 106, such magnetic field being turned into electrical current which passes across the stator windings of the stator assembly 104 to ensure the power supply of various equipment in the motor vehicle.

[0048] In both examples of motor mode and generator mode, the first set of ducts 1 14 and the second set of ducts 1 16 facilitate flow of cooling medium to reach the outer diametric side and the inner diametric side respectively, of the end windings 108. According to another example, the stator core 106 include channels 132 (shown in FIG. 1 A) that extend parallel to the central axis 126. These channels 132 are open towards the outer diametric side of the end windings 108, and permit a flow of cooling medium to the outer diametric side of the end windings 108. The outer diametric side of the end windings 108 therefore receives more cooling medium in addition to the cooling medium from the hollow shaft 1 10.

[0049] FIG. 6 illustrates a flowchart depicting a method 600 to cool the end windings 108 of the stator assembly 104 in the rotary machine 100 configured in accordance with the present subject matter. The method 600 includes a step of detecting 602 a rotational speed of the hollow shaft 1 10. The rotational speed may be detected by means of a position sensor mounted on a distal end of the hollow shaft 1 10. For instance, the sensor is an encoder mounted on the non drive end 502 to detect the rotationalspeed whilst the hollow shaft 1 10 is in rotation. The method 600 further includes a step of detecting 604 a temperature of the end windings 108. The aforementioned step of detecting 604 may be achieved by a temperature sensor directed towards the end windings 108. The method 606 further includes a step of communicating 606 a speed signal and a temperature signal to a control unit (not shown). The speed signal pertains to the rotational speed is detected in the step of detecting 602 rotational speed of the hollow shaft 1 10. Further, the temperature signal pertains to the temperature detected in the step of detecting 604 the temperature of the end windings 108. The method 600 further includes a step of determining 608 an adjusted rate of flow of the cooling medium based on the temperature and rotational speed. Said step of determining 608 is performed by the control unit. The adjusted rate of flow is then communicated to a dispersal device (not shown), for instance a pump. Further, the method 600 includes a step of dispersal 610 of cooling medium at the adjusted rate of flow into the hollow shaft 110 and facilitated to flow through the first set of ducts 1 14, in the path 130 along the curvature 120. The cooling medium follows the path 130 to reach the inner wall 128 and disperses to the outer diametric side of the end windings 108.

[0050] Various modifications of the disclosed embodiments, as well as alternate embodiments of the subject matter, will become apparent to persons skilled in the art upon reference to the description of the subject matter. It is therefore contemplated that such modifications can be made without departing from the scope of the present subject matter is defined.

Claims

Claims1 . A rotary machine (100) comprising: a shell (102) comprising two axial ends (124; 502), at least one of the two axial ends (124; 502) being closed by an end plate (118), wherein the end plate (1 18) comprises an inner face (122) facing inside the shell (102), wherein a curvature (120) is formed in the inner face (122), said curvature (120) comprising two distinct ends (200; 202) and a smooth transitioning curved profile between said two distinct ends (200; 202); a stator assembly (104), disposed in the shell (102), comprising a stator core (106) and stator windings provided with end windings (108); and a rotor assembly arranged on an inner side (504) of the stator core (106) and rotatable about a central axis (126) common to the stator assembly (104), the rotor assembly comprising a rotor (500) mounted on a hollow shaft (1 10) through which a cooling medium flows, the hollow shaft (1 10) comprising a first set of ducts (1 14) arranged circumferentially in said hollow shaft (1 10), and wherein an inlet (204) of each of the first set of ducts (1 14) is open to a hollow region (1 12) in the hollow shaft (1 10) and an outlet (206) of each the first set of ducts (1 14) is open to a cavity (126) in the shell (102) and directed towards the curvature (120) of the end plate (1 18).

2. The rotary machine (100), as claimed claim 1 , wherein the first set of ducts (1 14) is inclined in a first angle (61 ) to a first reference line (Y1 ) parallel to the central axis (126).

3. The rotary machine (100), as claimed in any of the preceding claims, wherein a first end (200), of the two distinct ends (200; 202) in the curvature (120), is inclined in a second angle (62) to the first reference line (Y1 ), said second angle (62) being equal in value to the first angle (61 ).

4. The rotary machine (100), as claimed in any one of the preceding claims, wherein the curvature (120) is an arc shaped groove formed on the inner face (122) of the end plate (118), said arc shaped groove formed circumferentially about the central axis (126).

5. The rotary machine (100), as claimed in any one of the preceding claims, wherein a second end (202), of the two distinct ends (200; 202) in the curvature (120), is inclined in a third angle (03) to a second reference line (Y2) parallel to the central axis (126), said second reference line (Y2) being coincident to an inner wall (128) of the shell (102) .

6. The rotary machine (100), as claimed in the preceding claim, wherein the hollow shaft (110) comprises a second set of ducts (116), each of said second set of ducts (116) being open at a second inlet (208) to the hollow region (112) of the hollow shaft (110) and open at another end by a second outlet (210) directed towards an inner diametric side of the end windings (108).

7. The rotary machine, as claimed in the preceding claim, wherein the inlet (204) of the first set of ducts (116) and the second inlet (208) of the second set of ducts (116) is a single inlet opening.

8. The rotary machine (100), as claimed in any one of the preceding claims, wherein the outlet (206) of the first set of ducts (114) has an oblong shape, or a circular shape, or a rectangular shape.Accordingly, the inlet 114 of the first set of ducts 114 is configured to have a shape at least substantially similar to the shape of the outlet 206.

9. The rotary machine (100), as claimed in any one of the preceding claims, wherein the stator core (106) comprise channels (132) extendingparallel to the central axis (126), said channels (132) being open towards an outer diametric side of the end windings (108).

10. A method (600) to cool end windings (108) of a stator assembly (104) in a rotary machine (100) configured in accordance with any one of the preceding claims, the method (600) comprising: detecting a rotational speed of the hollow shaft (110); detecting a temperature of the end windings (108); communicating a speed signal and a temperature signal to a control unit, the speed signal pertaining to the rotational speed and the temperature signal pertaining to the temperature from the end windings; determining an adjusted rate of flow of the cooling medium, by the control unit, based on the temperature and rotational speed; and dispersal of cooling medium into the hollow shaft (110) and facilitate a flow of cooling medium through the first set of ducts (114) in a path (130) along the curvature (120) of the end plate (118).

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