Cooling of rotor assemblies in motors

Abstract

A rotor assembly for a motor assembly includes a rotor coupled to the rotor shaft and having a plurality of rotor teeth and at least two bobbins attached to the rotor on axial ends of the rotor. Each bobbin has at least one bobbin tooth. The rotor and the at least two bobbins rotate about the axis in response to the rotation of the shaft. The rotor assembly includes a plurality of windings, a first coolant channel running through the rotor to conduct the coolant through thereof, and a first heat dissipation element to dissipate heat generated from a winding of the plurality of windings The first heat dissipation element includes at least one fin in contact with and to divide the winding of the plurality of winding into a plurality of sections and a plate contiguous with the at least one fin and in contact with the first coolant channel.

Description

COOLING OF ROTOR ASSEMBLIES IN MOTORSTECHNICAL FIELD

[0001] The present subject matter relates, in general, to motors, and in particular, to cooling of rotor assemblies in motors.BACKGROUND

[0002] Motors, particularly, Electrically Excited Synchronous Motors (EESM) are used in applications that require high torque density and current density. For instance, EESM are used in vehicles, such as hybrid vehicles and electric vehicles, to propel the vehicles using electrical energy stored in one or more rechargeable batteries of the vehicles. The EESM may include a stator and a rotor. The rotor has a plurality of windings wound thereof. The plurality of windings may generate a magnetic field. Particularly, when an electric current passes through the plurality of windings, a magnetic field is generated. The generated magnetic field interacts with magnetic field of the stator. The interaction of the magnetic field generated in the rotor and the magnetic field of the stator causes the rotor to rotate. The rotation generates mechanical motion, which is used to drive various applications.BRIEF DESCRIPTION OF DRAWINGS

[0003] The features, aspects, and advantages of the present subject matter will be better understood with regard to the following description, and accompanying figures. The use of the same reference number in different figures indicates similar or identical features and components.

[0004] Fig. 1 illustrates a perspective view of a rotor assembly of an EESM, in accordance with an implementation of the present subject matter;

[0005] Fig. 2 illustrates a perspective view of a rotor and bobbins of a rotor assembly of an EESM, in accordance with an implementation of the present subject matter;

[0006] Fig. 3 illustrates a cross-sectional of a rotor assembly of an EESM, in accordance with an implementation of the present subject matter;

[0007] Fig. 4 illustrates an exploded view depicting a rotor and bobbins of an EESM, in accordance with an implementation of the present subject matter;

[0008] Fig. 5 illustrates a rotor shaft and a bobbin of a rotor assembly of an EESM, in accordance with an implementation of the present subject matter;

[0009] Fig. 6 illustrates a bobbin of a rotor assembly of an EESM, in accordance with an implementation of the present subject matter;

[0010] Fig. 7 illustrates a sectional front view of a rotor assembly of an EESM, in accordance with an implementation of the present subject matter;

[0011] Fig. 8a illustrates a cross-sectional view of a rotor assembly of an EESM, in accordance with an implementation of the present subject matter; and

[0012] Fig. 8b illustrates a perspective view of a heat dissipation element of a rotor assembly of an EESM, in accordance with an implementation of the present subject matter.DETAILED DESCRIPTION

[0013] Electrically Excited Synchronous Motors (EESM) are used in high current density and high torque applications, such as in vehicles, as traction motors owing to their high performance. However, when electric current flows through the plurality of windings, made of copper, the electric current encounters electrical resistance. Due to joule effect, the energy of an electric current may be dissipated as heat as the electric current encounters resistance. The process of dissipation of energy due to electrical resistance encountered when electric current flows through the plurality of windings of the rotor is referred to as copper loss. In some scenarios, this may lead to overheating of the EESM and thereby, leading to hampering performance, operation, and efficiency of the EESM. The effect on the performance, operation, and efficiency of the EESM may affect the application in which the EESM is used. For instance, reliability, efficiency, and performance of a vehicle may also be affected when the EESM is used in the vehicle.

[0014] Accordingly, to prevent impact on the operation of the EESM and to enhance the performance and efficiency of the EESM, the generated heat will have to be minimized or heat dissipation capabilities will have to be enhanced. For instance, to minimize generation of heat, copper losses are minimized by using high-quality conductive materials and optimizing windings designs. To enhance heat dissipation capabilities, cooling mechanisms will have to be implemented.

[0015] Conventionally, to increase the heat dissipation, a coolant is circulated through a rotor shaft of the EESM. The circulation of the coolant through the rotor shaft, however, does not substantially reduce the temperature of the plurality of windings of the rotor. This is because heat generated through the rotor windings have to travers several layers of thermal resistance, including winding enamel coating, slot insulation, and rotor core before reaching the coolant in the rotor shaft.

[0016] In another conventional technique, the temperature of the rotor winding is reduced by spraying a coolant onto the rotor, as the rotor spins. However, such a technique is not efficient to dissipate the heat generated by the plurality of windings of the rotor. Further, if the sprayed coolant is contaminated, the spraying of the same on the rotor causes issues during operation of the rotor. Furthermore, spraying of the coolant may cause electrical shorting issues. Therefore, the conventional techniques do not provide sufficient rotor cooling for applications that require high torque and high current density.

[0017] The present subject matter relates to cooling of rotor assemblies in motors, such as an Electrically Excited Synchronous Motors (EESM). With the implementation of the present subject matter, rotor assemblies of EESM can be cooled efficiently and effectively. Accordingly, the present subject matter ensures optimal performance of the EESM and the applications where the EESM is used, such as in vehicles.

[0018] In an implementation of the present subject matter, a rotor assembly may be used in a motor assembly, such as an Electrically Excited Synchronous Motor (EESM) Assembly. The motor assembly may be usedin vehicles, such as hybrid vehicles and / or electric vehicles, as a traction motor for powering the vehicles.

[0019] The motor assembly may include a stator. The rotor assembly may rotate relative to the stator. Further, the rotor assembly may include a rotor shaft, a rotor, at least two bobbins, and a plurality of windings.

[0020] The rotor shaft may rotate about an axis. For instance, the rotor shaft may rotate about an axis passing through a centre of the rotor shaft. The rotor may be coupled to the rotor shaft and may have a plurality of rotor teeth. The rotor may be attached to one bobbin at a first axial end thereof and another bobbin at a second axial end thereof. Each bobbin has a plurality of bobbin teeth. The rotor and the bobbins rotate about the axis in response to the rotation of the rotor shaft.

[0021] Each winding of the plurality of windings wound over a tooth of the plurality of rotor teeth. The winding may be, for example, made of copper. When electric current passes through the plurality of windings, heat may be generated. To dissipate the generated heat, the rotor assembly may include a first coolant channel running through the rotor to conduct coolant through thereof. In an example, the first coolant channel may extend through a rotor tooth of the plurality of rotor teeth along an axial direction through an axial length of the rotor.

[0022] Further, the rotor assembly may include a first heat dissipation element to dissipate heat generated from a winding of the plurality of windings. In an example, the first heat dissipation element may extend along an axial direction in a rotor tooth of the plurality of rotor teeth.

[0023] The first heat dissipation element may include at least one fin and a plate. The at least one fin may be in contact with and to divide the winding of the plurality of winding into a plurality of sections. The at least one fin extends along an axial direction through an axial length of the rotor. Further, in an example, the at least one fin comprises a first fin and a second fin separated from each other along a radial direction.

[0024] The plate may be contiguous with the at least one fin and in contact with the first coolant channel. The plate extends along an axial direction through an axial length of the rotor.

[0025] In addition to the first coolant channel, the rotor assembly may include a second coolant channel running through the rotor to conduct the coolant through thereof. The second coolant channel may extend through the rotor tooth of the plurality of rotor teeth along the axial direction and may be separated at a distance along a circumferential direction from the first coolant channel. In other words, one rotor tooth may have two coolant channels. In an example, each of the plurality of the rotor teeth may have two coolant channels.

[0026] In addition to the first heat dissipation element, a second heat dissipation element to dissipate heat generated from the winding of the plurality of windings. The second heat dissipation element may extend along the axial direction in the rotor tooth of the plurality of rotor teeth and may be separated at a distance from the first heat dissipation element along a circumferential direction. Similar to the first heat dissipation element, the second heat dissipation element may include at least one fin and a plate. The at least one fin of the second heat dissipation element may be in contact with and to divide the winding of the plurality of windings into a plurality of sections. Further, the plate may be contiguous with the at least one fin and may be in contact with the second coolant channel. The at least one fin of the second heat dissipation element may extend along an axial direction through an axial length of the rotor. Further, in an example, the at least one fin of the second heat dissipation element may include a third fin and a fourth fin separated from each other along a radial direction. The plate may be contiguous with the at least one fin and in contact with the first coolant channel. The plate extends along an axial direction through an axial length of the rotor.

[0027] In an implementation, the plate of the first heat dissipation element and the plate of the second heat dissipation element may include a plurality of protrusions in contact with the first coolant channel to enhance dissipation of heat from the winding of the plurality of windings. The first heat dissipation element and the second heat dissipation element may be made of a thermally conductive element.

[0028] In an example, to accommodate the first heat dissipation element, the rotor assembly may include a first groove extending along an axial direction. Accordingly, shape of the first groove corresponds to a shape of the first heat dissipation element. Similarly, to accommodate the second heat dissipation element, the rotor assembly may include a second groove extending along an axial direction. In this regard, shape of the groove corresponds to a shape of the first heat dissipation element.

[0029] The coolant may be conducted through the at least two bobbins, the rotor, and the rotor channel. In this regard, each of the at least two bobbins may include a bobbin coolant channel aligned with the first coolant channel and the second coolant channel to conduct the coolant. Further, the rotor shaft may be hollow, and may include a first inlet opening and a first outlet opening. The first inlet opening may provide the coolant to the bobbin coolant channel of a bobbin at the first axial end of the rotor. The first outlet opening may receive the coolant from the bobbin coolant channel of a bobbin at the second axial end of the rotor. The coolant may be received into the first outlet opening is conducted through the rotor shaft.

[0030] With the implementation of the present subject matter, rotor assemblies of EESM can be cooled efficiently and effectively. In the present subject matter, the coolant channels are provided in the rotor assembly. In addition, in the present subject matter, the heat dissipation elements, which are made of thermally-conductive materials, are in contact with the windings of the rotor and with the coolant channels. Therefore, heat is dissipated from the windings of the rotor assembly through the heat dissipation elements and the coolant channels. Therefore, despite having thermally resistant layers of the EESM, including the winding enamel coating, slot insulation, and the rotor core, the present subject matter effectively dissipates the heat.

[0031] Further, since the heat dissipation elements run through an axial length of the rotor, the present subject matter provides increased surface area for heat dissipation and therefore, better cooling of the windings of the rotor. Furthermore, due to the arrangement of the heat dissipation elements and the coolant channels, the present subject matter prevents spraying a coolant onto the rotor assembly as the rotor assemblyspins to cool the rotor assembly. Therefore, the present subject matter prevents issues caused due to coolant contamination and electrical shorting issues. Since the present subject matter ensures efficient cooling of the EESM, the present subject matter enables usage of wound field copper windings instead of magnets. Therefore, the present subject matter enables using the EESM in high torque density and high current density applications. Accordingly, the present subject matter ensures optimal performance of the EESM and the applications where the EESM is used, such as in vehicles.

[0032] Further, the present subject matter is simple, is easy to manufacture and implementation of the coolant channels and the heat dissipation elements. The present subject matter also provides a leak-proof circulation of the coolant and therefore, prevents any electrical shorting issues that may occur due to leakage of the coolant. In addition, in the present subject matter, coolant is isolated from the rotor-stator air gap.

[0033] The above and other features, aspects, and advantages of the subject matter will be better explained with regard to the following description, and accompanying figures. It should be noted that the description and figures merely illustrate the principles of the present subject matter along with examples described herein and, should not be construed as a limitation to the present subject matter. It is thus understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and examples thereof, are intended to encompass equivalents thereof. Further, for the sake of simplicity, and without limitation, the same numbers are used throughout the drawings to reference like features and components.

[0034] Fig. 1 illustrates a perspective view of a rotor assembly 100 of an Electrically Excited Synchronous Motor (EESM), in accordance with an implementation of the present subject matter. Fig. 2 illustrates a perspective view of a rotor 102 and bobbins 105, 106 of the rotor assembly of the EESM, in accordance with an implementation of the present subject matter. For the sake of brevity, Figs. 1 -2 are explained in conjunction with each other.

[0035] The motor assembly may be, for example, an Electrically Excited motor (EESM) assembly. The motor assembly may be used in vehicles, such as hybrid vehicles and / or electric vehicles, as a traction motor for powering the vehicles. Hereinafter, the motor assembly will be explained with reference to EESM and being used in the vehicles.

[0036] The motor assembly may include a stator (not shown in Figs. 1 - 2) and the rotor assembly 100. The rotor assembly 100 may rotate relative to the stator. Further, the rotor assembly 100 may include a rotor shaft 108, the rotor 102, at least two bobbins 105, 106, and a plurality of windings.

[0037] The rotor shaft 108 may be hollow. Further, the rotor shaft 108 may rotate about an axis B-B. The axis B-B may be passing through a centre of the rotor shaft 108. The rotor 102 may be coupled to the rotor shaft 108 and may have a plurality of rotor teeth 112, 1 14, 116, 1 18, 202, 204. The rotor 102 may include a first axial end 120 and a second axial end 122. The first axial end 120 and the second axial end 122 may be separated at a distance from each other along the axial direction 'A’. The rotation of the rotor shaft 108 may cause the rotation of the rotor assembly 100.

[0038] In an example, as is depicted herein, the rotor 102 may include six rotor teeth 112, 1 14, 1 16, 1 18, 202, 204. However, the rotor 102 may include any number of rotor teeth 1 12, 114, 1 16, 1 18, 202, 204. In other examples. Hereinafter, the rotor 102 may be explained with reference to having six teeth, such as a first rotor tooth 1 12, a second rotor tooth 1 14, a third rotor tooth 1 16, a fourth rotor tooth 202, a fifth rotor tooth 204, and a sixth rotor tooth 1 18.

[0039] A bobbin 105 (hereinafter referred to as “first bobbin”) may be attached to the rotor 102 at the first axial end 120 and another bobbin 106 (hereinafter referred to as “first bobbin”) at the second axial end 122.

[0040] Each bobbin 105,106 has a plurality of bobbin teeth, as will be explained with reference to Figs. 4 and 5. The rotor 102 and the bobbins 105, 106 rotate about the axis B-B in response to the rotation of the rotor shaft 108. In other words, the rotor 102, the first bobbin 105, and the second bobbin 106 may rotate about the axis B-B.

[0041] Each winding of the plurality of windings wound over a tooth of the plurality of rotor teeth 112, 1 14, 1 16, 1 18, 202, 204. For instance, the plurality of windings may include a first winding, a second winding, a third winding, a fourth winding, a fifth winding, and a sixth winding. The first winding may be wound over the first rotor tooth 1 12, the second winding may be wound over the second rotor tooth 114, and the third winding may be wound over the third rotor tooth 1 16. The fourth winding may be wound over the fourth rotor tooth 202, the fifth winding may be wound over the fifth rotor tooth 204, and the sixth winding may be wound over the sixth rotor tooth 118. Each of the plurality of windings may be, for example, made of copper. When electric current passes through the plurality of windings, heat may be generated. To dissipate the generated heat, the rotor assembly may include coolant channels and heat dissipation elements, as will be explained with reference to Fig. 3.

[0042] Fig. 3 illustrates a cross-sectional view of the rotor assembly 100 of the EESM, in accordance with an implementation of the present subject matter. The heat generated during the operation of the EESM may have to be dissipated. In this regard, a coolant is circulated through the rotor assembly. The coolant may be, for example, oil or water. Accordingly, the rotor assembly 100 may include various coolant channels.

[0043] The rotor assembly 100 may include a first coolant channel 302 running through the rotor 102 to conduct coolant through thereof. In an example, the first coolant channel 302 may extend through the first rotor tooth 1 12 along the axial direction ‘A’ through an axial length of the rotor 102. Further, the rotor assembly 100 may include a second coolant channel 304 running through the rotor 102 to conduct the coolant through thereof. The second coolant channel 304 may extend through the first rotor tooth 1 12 along the axial direction ‘A’ and may be separated at a distance along a circumferential direction ‘C’ from the first coolant channel 302. In other words, the first rotor tooth 1 12 may include the first coolant channel 302 and the second coolant channel 304 to conduct the coolant.

[0044] In an example, each of the plurality of the rotor teeth 1 12, 1 14, 1 16, 202, 204, 1 18 may have two coolant channels. Similar to the firstcoolant channel 302 and the second coolant channel 304, the rotor assembly 100 may have a third coolant channel 306 and a fourth coolant channel 308, a fifth coolant channel 310 and a sixth coolant channel 312, a seventh coolant channel 314 and an eighth coolant channel 316, a ninth coolant channel 318 and a tenth coolant channel 320, and an eleventh coolant channel 322 and a twelfth coolant channel 324. The third coolant channel 306 and the fourth coolant channel 308 may extend through the second rotor tooth 114 and may be separated at a distance along the circumferential direction ‘C’. The fifth coolant channel 310 and the sixth coolant channel 312 may extend through the third rotor tooth 116 and may be separated at a distance along the circumferential direction ‘C’. The seventh coolant channel 314 and the eighth coolant channel 316 may extend through the fourth rotor tooth 202 and may be separated at a distance along the circumferential direction ‘C’. The ninth coolant channel 318 and the tenth coolant channel 320 may extend through the fifth rotor tooth 204 and may be separated at a distance along the circumferential direction ‘C’. The eleventh coolant channel 322 and the twelfth coolant channel 324 may extend through the sixth rotor tooth 118 and may be separated at a distance along the circumferential direction ‘C’.

[0045] While there are coolant channels provided, there may be layers of thermal resistance for the heat to be dissipated from the plurality of windings to the coolant channels, such as winding enamel coating, slot insulation, and the rotor core before reaching the coolant in the rotor shaft. In this regard, to enable effective heat dissipation from the plurality of windings, such as the first winding 330, the second winding 332, the third winding 334, the fourth winding 336, the fifth winding 338, and the sixth winding 340, to the coolant channels, the rotor assembly 100 may include heat dissipation elements. Particularly, the rotor assembly 100 may include a first heat dissipation element 350 and a second heat dissipation element 352. The first heat dissipation element 350 and the second heat dissipation element 352 may be, for example, made of thermally-conductive material, such as Aluminium, or the like. The first heat dissipation element 350 may dissipate heat generated from the first winding 330. The second heatdissipation element 352 may dissipate heat generated from the second winding 332. In an example, the first heat dissipation element 350 may extend along the axial direction ‘A’ in the first rotor tooth 1 12. Similarly, the second heat dissipation element 352 may extend along the axial direction ‘A’ in the first rotor tooth 1 12.

[0046] Each of the first heat dissipation element 350 and the second heat dissipation element 352 may include a plate 354 and at least one fin 356-1 , 356-2. The at least one fin 356-1 , 356-2 may extend along the axial direction ‘A’ through the axial length of the rotor 102. The at least one fin 356-1 , 356-2 may be in contact with and to divide the first winding 330 into a plurality of sections. Further, in an example, the at least one fin 356-1 , 356-2 may include a first fin 356-1 and a second fin 356-2 separated from each other along the radial direction ‘R’. Accordingly, the first winding 330 may be divided into three sections through the first fin 356-1 and the second fin 356-2 of each of the first heat dissipation element 350 and the second heat dissipation element 352. Since the first winding 330 runs through the axial length of the rotor 102 and the first fin 356-1 and the second fin 356-2 also run through the axial length of the rotor 102, there is an increased contact area with the first winding 330. This enables higher heat dissipation from the first winding 330. The first fin 356-1 and the second fin 356-2 may be, for example, of rectangular cross-section.

[0047] Further, the plate 354 may be contiguous with the at least one fin 356-1 , 356-2 and in contact with the corresponding coolant channel. For instance, the plate 354 of the first heat dissipation element 350 may be in contact with the first coolant channel 302 and the plate of the second heat dissipation element 352 may be in contact with the second coolant channel 304. In other words, the plate 354 may be contiguous with the first fin 356-1 and the second fin 356-2. Furthermore, the plate 354 may extend along the axial direction ‘A’ through the axial length of the rotor 102. The plate 354 may, for example, have a rectangular cross-section.

[0048] In an example, the plate 354 and the at least one fin 356-1 , 356-2 may extend in perpendicular directions. For instance, the plate 354 may extend along the radial direction ‘R’ and the at least one fin (the first fin 356-1 and the second fin 356-2 may extend along the circumferential direction ‘C’.

[0049] As will be understood, the first fin 356-1 and the second fin 356-2 of the first heat dissipation element 350 and the second heat dissipation element 352 may transfer the heat from the first winding 330 to the plate 354 of the first heat dissipation element 350 and the second heat dissipation element 352 respectively. From the plate 354 of the heat dissipation elements 350, 352, heat may be transferred to the coolant in the first coolant channel 302 and the second coolant channel 304. Therefore, the rotor assembly 100 ensures effective and efficient heat dissipation and cooling of the rotor assembly 100.

[0050] In an example, similar to the first heat dissipation element 350 and the second heat dissipation element 352, each of the plurality of rotor teeth 1 12, 1 14, 1 16, 202, 204, 118 may have heat dissipation elements. For instance, the second rotor tooth 114 may include a third heat dissipation element 358 and a fourth heat dissipation element 360. The third rotor tooth 1 16 may include a fifth heat dissipation element 362 and a sixth heat dissipation element 364. The fourth rotor tooth 202 may include a seventh heat dissipation element 366 and an eighth heat dissipation element 368. The fifth rotor tooth 204 may include a ninth heat dissipation element 370 and a tenth heat dissipation element 372. The sixth rotor tooth 1 18 may include an eleventh heat dissipation element 374 and a twelfth heat dissipation element 376. Similar to the first heat dissipation element 350 and the second heat dissipation element 352, each of the heat dissipation elements 358-376 may include at least one fin, such as a first fin 356-1 and a second fin 356-2, and a plate 354.

[0051] In an example, to accommodate the first heat dissipation element 350, the rotor assembly 100 may include a first groove (not shown in Fig. 3) extending along the axial direction ‘A’. Accordingly, shape of the first groove corresponds to a shape of the first heat dissipation element 350. In other words, the first groove may include a plate groove to accommodate the plate 354 of the first heat dissipation element 350 and a fin groove to accommodate the at least one fin 356-1 , 356-2. The plate groove may havea shape corresponding to shape of the plate 354 of the first heat dissipation element 350. The fin groove may have a shape corresponding to the at least one fin, such as the first fin 356-1 and the second fin 356-2, to accommodate the first fin 356-1 and the second fin 356-2. Similarly, to accommodate the second heat dissipation element 352, the rotor assembly may include a second groove (not shown in Fig. 3) extending along the axial direction ‘A’. In this regard, shape of the second groove corresponds to a shape of the second heat dissipation element 352. Similar to the first groove, the second groove may also include a plate groove to accommodate the plate 354 of the second heat dissipation element 352 and a fin groove to accommodate the at least one fin 356-1 , 356-2 of the second heat dissipation element 352.

[0052] In an example, similar to the first groove and the second groove, the rotor assembly may include a third groove (not shown in Fig. 3), a fourth groove (not shown in Fig. 3), a fifth groove (not shown in Fig. 3), a sixth groove (not shown in Fig. 3), a seventh groove (not shown in Fig. 3), an eighth groove (not shown in Fig. 3), a ninth groove (not shown in Fig. 3), a tenth groove (not shown in Fig. 3), an eleventh groove (not shown in Fig. 3), and a twelfth groove (not shown in Fig. 3). The third groove and the fourth groove may accommodate the third heat dissipation element 358 and the fourth heat dissipation element 360 respectively. The fifth groove and the sixth groove may accommodate the fifth heat dissipation element 362 and the sixth heat dissipation element 364 respectively. The seventh groove and the eighth groove may accommodate the seventh heat dissipation element 366 and the eighth heat dissipation element 368 respectively. The ninth groove and the tenth groove may accommodate the ninth heat dissipation element 370 and the tenth heat dissipation element 372 respectively. The eleventh groove and the twelfth groove may accommodate the eleventh heat dissipation element 374 and the twelfth heat dissipation element 376 respectively. The shape of the groove may correspond to the shape of the heat dissipation element that is to be accommodate in the groove.

[0053] Fig. 4 illustrates an exploded view depicting the rotor 102 and the bobbins 105, 106 of the EESM, in accordance with an implementation of the present subject matter. Fig. 5 illustrates the rotor shaft 108 and thesecond bobbin 106 of the rotor assembly 100 of an EESM, in accordance with an implementation of the present subject matter. For the sake of brevity, Figs. 4 and 5 are explained in conjunction with each other.

[0054] In the example depicted herein, each bobbin 105, 106 may have six bobbin teeth. For instance, the first bobbin 105 may include a first bobbin tooth 402, a second bobbin tooth 404, a third bobbin tooth 406, a fourth bobbin tooth 408, a fifth bobbin tooth 410, and a sixth bobbin tooth 412. The second bobbin 106 may include a seventh bobbin tooth 502, an eighth bobbin tooth 504, a ninth bobbin tooth 506, a tenth bobbin tooth 508, a eleventh bobbin tooth 510, and a twelfth bobbin tooth 512.

[0055] In an example, the coolant may be received by the rotor 102 from the first bobbin 105. In this regard, the first bobbin 105 may have coolant channels. In particular, the first bobbin 105 may include a first bobbin inlet coolant channel 414, a second bobbin inlet coolant channel 416, a third bobbin inlet coolant channel 418, a fourth bobbin inlet coolant channel 420, a fifth bobbin inlet coolant channel 422, a sixth bobbin inlet coolant channel 424, a seventh bobbin inlet coolant channel 426, an eighth bobbin inlet coolant channel 428, a ninth bobbin inlet coolant channel 430, a tenth bobbin inlet coolant channel 432, an eleventh bobbin inlet coolant channel 434, and a twelfth bobbin inlet coolant channel 436. Each coolant channel of the first bobbin 105 may be aligned with a coolant channel of the rotor 102. For instance, the first coolant channel 302 and the second coolant channel 304 may be aligned with the first bobbin inlet coolant channel 414 and the second bobbin inlet coolant channel 416 respectively. The third coolant channel 306 and the fourth coolant channel 308 may be aligned with the third bobbin inlet coolant channel 418 and the fourth bobbin inlet coolant channel 420 respectively. The fifth coolant channel 310 and the sixth coolant channel 412 may be aligned with the fifth bobbin inlet coolant channel 422 and the sixth bobbin inlet coolant channel 424 respectively. The seventh coolant channel 314 and the eighth coolant channel 316 may be aligned with the seventh bobbin inlet coolant channel 426 and the eighth bobbin inlet coolant channel 428 respectively. The ninth coolant channel 318 and the tenth coolant channel 320 may be aligned with the ninth bobbininlet coolant channel 430 and the tenth bobbin inlet coolant channel 432 respectively. The eleventh coolant channel 322 and the twelfth coolant channel 324 may be aligned with the eleventh bobbin inlet coolant channel 434 and the twelfth bobbin inlet coolant channel 436 respectively. Accordingly, when the coolant enters the first bobbin 105 through a coolant channel of the first bobbin 105, the coolant may enter the corresponding coolant channel of the rotor 102 aligned with coolant channel of the first bobbin 105. In other words, the coolant entering the first bobbin inlet coolant channel 414 may be received into the first coolant channel 302 of the rotor and so on.

[0056] Further, the coolant upon being circulated through the rotor 102 may exit from thereof through the second bobbin 106. In this regard, the second bobbin 106 may include a first bobbin outlet coolant channel 514, a second bobbin outlet coolant channel 516, a third bobbin outlet coolant channel 518, a fourth bobbin outlet coolant channel 520, a fifth bobbin outlet coolant channel 522, a sixth bobbin outlet coolant channel 524, a seventh bobbin outlet coolant channel 526, an eighth bobbin outlet coolant channel 528, a ninth bobbin outlet coolant channel (not shown in Figs. 4-5), a tenth bobbin outlet coolant channel 532, an eleventh bobbin outlet coolant channel 534, a twelfth bobbin outlet coolant channel 536. Each coolant channel of the second bobbin 106 may be aligned with a coolant channel of the rotor 102. For instance, the first coolant channel 302 and the second coolant channel 304 may be aligned with the first bobbin outlet coolant channel 514 and the second bobbin outlet coolant channel 516 respectively. The third coolant channel 306 and the fourth coolant channel 308 may be aligned with the third bobbin outlet coolant channel 518 and the fourth bobbin outlet coolant channel 520 respectively. The fifth coolant channel 310 and the sixth coolant channel 312 may be aligned with the fifth bobbin outlet coolant channel 522 and the sixth bobbin outlet coolant channel 524 respectively. The seventh coolant channel 314 and the eighth coolant channel 316 may be aligned with the seventh bobbin outlet coolant channel 526 and the eighth bobbin outlet coolant channel 528 respectively. The ninth coolant channel 318 and the tenth coolant channel 320 may be aligned withthe ninth bobbin outlet coolant channel and the tenth bobbin outlet coolant channel 532 respectively. The eleventh coolant channel 322 and the twelfth coolant channel 324 may be aligned with the eleventh bobbin outlet coolant channel 534 and the twelfth bobbin outlet coolant channel 536 respectively. Accordingly, when the coolant exits the rotor 102, the coolant may be received into a coolant channel of the second bobbin 106 from the corresponding coolant channel of the rotor 102 aligned with coolant channel of the second bobbin 106. In other words, the coolant exiting the rotor 102 from the first coolant channel 302 may be received in the first bobbin outlet coolant channel 514 and so on.

[0057] Fig. 6 illustrates the bobbin 105 of the rotor assembly 100 of the EESM, in accordance with an implementation of the present subject matter. Herein, the first bobbin 105 and the rotor shaft 108 are depicted. As mentioned earlier, the rotor shaft 108 may be hollow and may enable conducting the coolant through the rotor assembly 100. In this regard, the rotor shaft 108 may conduct the coolant which may be received into the first bobbin 105 for circulation from the first bobbin 105. In an example, the rotor shaft 108 may include a plurality of inlet openings, such as a first inlet opening 602, a second inlet opening 604, a third inlet opening 606, a fourth inlet opening 608, a fifth inlet opening 610, and a sixth inlet opening 612. Each coolant channel of the first bobbin 105 may receive the coolant from an inlet opening of the rotor shaft 108. In other words, the coolant conducted through a hollow portion of the rotor shaft 108 may be received into a coolant channel of the first bobbin 105 through an opening of the rotor shaft 108. For instance, the first bobbin inlet coolant channel 414 and the second bobbin inlet coolant channel 416 may receive the coolant from the first inlet opening 602. The third bobbin inlet coolant channel 418 and the fourth bobbin inlet coolant channel 420 may receive the coolant from the second inlet opening 604. The fifth bobbin inlet coolant channel 422 and the sixth bobbin inlet coolant channel 424 may receive the coolant from the third inlet opening 606. The seventh bobbin inlet coolant channel 426 and the eighth bobbin inlet coolant channel 428 may receive the coolant from the fourth inlet opening 608. The ninth bobbin inlet coolant channel 430 and the tenthbobbin inlet coolant channel 432 may receive the coolant from the fifth inlet opening 610. The eleventh bobbin inlet coolant channel 434 and the twelfth bobbin inlet coolant channel 436 may receive the coolant from the sixth inlet opening 612.

[0058] In an example, two bobbin inlet coolant channels of the first bobbin 105 may be connected together to be aligned with an inlet opening of the rotor shaft 108 for receiving the coolant from the inlet opening of the rotor shaft 108. For example, the first bobbin inlet coolant channel 414 and the second bobbin inlet coolant channel 416 may be connected together and a connection portion thereof may be aligned with the first inlet opening 602. The third bobbin inlet coolant channel 418 and the fourth bobbin inlet coolant channel 420 may be connected together and a connection portion thereof may be aligned with the second inlet opening 604.

[0059] The fifth bobbin inlet coolant channel 422 and the sixth bobbin inlet coolant channel 424 may be connected together and a connection portion thereof may be aligned with the third inlet opening 606. The seventh bobbin inlet coolant channel 426 and the eighth bobbin inlet coolant channel 428 may be connected together and a connection portion thereof may be aligned with the fourth inlet opening 608.

[0060] The ninth bobbin inlet coolant channel 430 and the tenth bobbin inlet coolant channel 432 may be connected together and a connection portion thereof may be aligned with the fifth inlet opening 610. The eleventh bobbin inlet coolant channel 434 and the twelfth bobbin inlet coolant channel 436 may be connected together and a connection portion thereof may be aligned with the sixth inlet opening 612.

[0061] The coolant upon being conducted by the rotor 102 may be received into the second bobbin 106 (not shown in Fig. 6). Further, the coolant may exit the second bobbin 106 into the rotor shaft 108. Accordingly, in an example, the rotor shaft 108 may include a plurality of outlet openings, such as a first outlet opening (not shown in Fig. 6), a second outlet opening (not shown in Fig. 6), a third outlet opening (not shown in Fig. 6), a fourth outlet opening (not shown in Fig. 7), a fifth outlet opening (not shown in Fig. 6), and a sixth outlet opening (not shown in Fig. 6). Eachcoolant channel of the second bobbin 106 may receive the coolant from an outlet opening of the rotor shaft 108. In other words, the coolant conducted by the second bobbin 106 may be received into the hollow portion of the rotor shaft 108 through an outlet opening of the rotor shaft 108. For instance, the first outlet opening may receive the coolant from the first bobbin outlet coolant channel 514 (not shown in Fig. 6) and the second bobbin outlet coolant channel 516 (not shown in Fig. 6). The second outlet opening may receive the coolant from the third bobbin outlet coolant channel 518 (not shown in Fig. 6) and the fourth bobbin outlet coolant channel 520 (not shown in Fig. 6). The third outlet opening may receive the coolant from the fifth bobbin outlet coolant channel 522 (not shown in Fig. 6) and the sixth bobbin outlet coolant channel 524 (not shown in Fig. 6). The fourth outlet opening may receive the coolant from the seventh bobbin outlet coolant channel 526 (not shown in Fig. 6) and the eighth bobbin outlet coolant channel 528 (not shown in Fig. 6). The fifth outlet opening may receive the coolant from the ninth bobbin outlet coolant channel (not shown in Fig. 6) and the tenth bobbin outlet coolant channel 532 (not shown in Fig. 6). The sixth outlet opening may receive the coolant from the eleventh bobbin outlet coolant channel 534 (not shown in Fig. 6) and the twelfth bobbin outlet coolant channel 536 (not shown in Fig. 6).

[0062] In an example, two bobbin outlet coolant channels may be connected together to be aligned with an outlet opening of the rotor shaft 108 to supply the coolant to the outlet opening of the rotor shaft 108. For example, the first bobbin outlet coolant channel 514 and the second bobbin outlet coolant channel 516 may be connected together and a connection portion thereof may be aligned with the first outlet opening. The third bobbin outlet coolant channel 518 and the fourth bobbin outlet coolant channel 520 may be connected together and a connection portion thereof may be aligned with the second outlet opening.

[0063] The fifth bobbin outlet coolant channel 522 and the sixth bobbin outlet coolant channel 524 may be connected together and a connection portion thereof may be aligned with the third outlet opening. The seventh bobbin outlet coolant channel 526 and the eighth bobbin outlet coolantchannel 528 may be connected together and a connection portion thereof may be aligned with the fourth outlet opening.

[0064] The ninth bobbin outlet coolant channel and the tenth bobbin outlet coolant channel 532 may be connected together and a connection portion thereof may be aligned with the fifth outlet opening. The eleventh bobbin outlet coolant channel 534 and the twelfth bobbin outlet coolant channel 536 may be connected together and a connection portion thereof may be aligned with the sixth outlet opening.

[0065] Fig. 7 illustrates a sectional front view of the rotor assembly 100 of the EESM, in accordance with an implementation of the present subject matter. Herein, the flow path 702 of the coolant in the rotor assembly 100 is depicted. In an example, the coolant may be entering into the rotor shaft 108, particularly, the hollow portion of the rotor shaft 108. Subsequently, from the rotor shaft 108, the coolant may be received into the first bobbin 105. Particularly, the coolant may be received into corresponding inlet coolant channels of the first bobbin 105 through an inlet opening of the rotor shaft 108 aligned with the inlet coolant channels of the first bobbin 105, as explained with reference to Fig. 6.

[0066] Further, from the first bobbin 105, the coolant may be received into the rotor 102 through a corresponding coolant channel of the rotor 102 aligned with the inlet coolant channel of the first bobbin 105, as explained with reference to Figs. 4 and 5. Upon being conducted through the rotor 102, the coolant may be received into the second bobbin 106. As will be understood, the coolant may be received into an outlet coolant channel of the second bobbin 106 that is aligned with a corresponding coolant channel of the rotor 102, as explained with reference to Figs. 4 and 5.

[0067] From the second bobbin 106, the coolant may be received into the hollow portion of the rotor shaft 108 through an outlet opening of the rotor shaft 108 that is aligned with the corresponding outlet coolant channels of the second bobbin 106, as explained with reference to Fig. 6.

[0068] While the coolant is being circulated through the coolant channels, the heat dissipation elements 350, 352, 358, 360, 362, 364, 366, 368, 370, 372, 374, 376 (not shown in Fig. 7) may dissipate the heat fromthe plurality of windings 330, 332, 334, 336, 338, 340 (not shown in Fig. 7) to the coolant channels (not shown in Fig. 7). Therefore, in the rotor assembly 100, the heat generated during the operation of the EESM is effectively dissipated and the EESM is adequately cooled.

[0069] Fig. 8a illustrates a cross-sectional view of the rotor assembly 100 of the EESM, in accordance with an implementation of the present subject matter. Fig. 8b illustrates a perspective view of a heat dissipation element of the rotor assembly 100 of the EESM, in accordance with an implementation of the present subject matter.

[0070] In an example, to enhance the heat dissipation from the plurality of windings 330, 332, 334, 336, 338, 340 further, each of the heat dissipation elements 350, 352, 358, 360, 362, 364, 366, 368, 370, 372, 374, 376 may include a plurality of protrusions 802. Particularly, the plate 354 of the each of heat dissipation elements 350, 352, 358, 360, 362, 364, 366, 368, 370, 372, 374, 376 may include the plurality of protrusions 802. The plurality of protrusions 802 may be in contact with the corresponding coolant channel to enhance dissipation of heat from the plurality of windings 330, 332, 334, 336, 338, 340. For instance, the plurality of protrusions 802 of the first heat dissipation element 350 may be in contact with the first coolant channel 302 and so on.

[0071] Referring to Fig. 8b, the heat dissipation element will be explained with reference to first heat dissipation element 350. For instance, the plurality of protrusions 802 of the first heat dissipation element 350 may extend in a direction opposite to the first fin 356-1 and the second fin 356-2 of the first heat dissipation element 350. The provision of the plurality of protrusions 802 may cause turbulence in flow of heat energy from the first heat dissipation element 350 to the first coolant channel 302 and thereby, causing an enhanced heat transfer. While Fig. 8b was explained with reference to the first heat dissipation element 350, it will be understood that the heat dissipation element may also correspond to other heat dissipation elements, such as heat dissipation element 352, 358, 360, 362, 364, 366, 368, 370, 372, 374, 376.

[0072] With the implementation of the present subject matter, rotors of EESM can be cooled efficiently and effectively. In the present subject matter, the coolant channels are provided in the rotor assembly. In addition, in the present subject matter, the heat dissipation elements, which are made of thermally-conductive materials, are in contact with the windings of the rotor and with the coolant channels. Therefore, heat is dissipated from the windings of the rotor assembly through the heat dissipation elements and the coolant channels. Therefore, despite having thermally resistant layers of the motor, including the winding enamel coating, slot insulation, and the rotor core, the present subject matter effectively dissipates the heat. Further, since the heat dissipation elements run through an axial length of the rotor, the present subject matter provides increased surface area for heat dissipation and therefore, better cooling of the windings of the rotor. Furthermore, due to the arrangement of the heat dissipation elements and the coolant channels, the present subject matter prevents spraying a coolant onto the rotor as the rotor spins to cool the rotor and the windings of the rotor. Therefore, the present subject matter prevents issues caused due to coolant contamination and electrical shorting issues. Since the present subject matter ensures efficient cooling of the EESM, the present subject matter enables usage of wound field copper windings instead of magnets. Therefore, the present subject matter enables using the EESM in high torque density and high current density applications. Accordingly, the present subject matter ensures optimal performance of the EESM and the applications where the EESM is used, such as in vehicles. Further, the present subject matter is simple, enables easy manufacturing and implementation of the coolant channels and the heat dissipation elements. The present subject matter also provides a leak-proof circulation of the coolant and therefore, prevents any electrical shorting issues that may occur due to leakage of the coolant. In addition, in the present subject matter, coolant is isolated from the rotor-stator air gap.

[0073] Although the present subject matter has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosedembodiments, 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.

Claims

I / We Claim:

1. A rotor assembly for a motor assembly, the rotor assembly comprising: a rotor shaft to rotate about an axis; a rotor coupled to the rotor shaft and having a plurality of rotor teeth; at least two bobbins attached to the rotor on axial ends of the rotor, wherein each bobbin has at least one bobbin tooth, wherein the rotor and the at least two bobbins rotate about the axis in response to the rotation of the shaft; a plurality of windings, each winding of the plurality of windings wound over a tooth of the plurality of rotor teeth; a first coolant channel running through the rotor to conduct coolant through thereof; a first heat dissipation element to dissipate heat generated from a winding of the plurality of windings, wherein the first heat dissipation element: at least one fin in contact with and to divide the winding of the plurality of winding into a plurality of sections; and a plate contiguous with the at least one fin and in contact with the first coolant channel.

2. The rotor assembly as claimed in claim 1 , wherein the at least one fin comprises a first fin and a second fin separated from each other along a radial direction.

3. The rotor assembly as claimed in claim 1 , wherein the at least one fin extends along an axial direction through an axial length of the rotor.

4. The rotor assembly as claimed in claim 1 , wherein the plate extends along an axial direction through an axial length of the rotor.

5. The rotor assembly as claimed in claim 1 , wherein the first heat dissipation element extends along an axial direction in a rotor tooth of the plurality of rotor teeth.

6. The rotor assembly as claimed in claim 1 , wherein the rotor comprises a first groove extending along an axial direction to accommodatethe first heat dissipation element therein, and wherein shape of the first groove corresponds to a shape of the first heat dissipation element.

7. The rotor assembly as claimed in claim 1 , the first coolant channel extends through a rotor tooth of the plurality of rotor teeth along an axial direction through an axial length of the rotor, and wherein the rotor assembly comprises: a second coolant channel running through the rotor to conduct the coolant through thereof, wherein the second coolant channel is separated at a distance along a circumferential direction from the first coolant channel, and wherein the second coolant channel extends through the rotor tooth of the plurality of rotor teeth along the axial direction.

8. The rotor assembly as claimed in claim 7, comprising: a second heat dissipation element to dissipate heat generated from the winding of the plurality of windings, wherein the second heat dissipation element is separated at a distance from the first heat dissipation element along a circumferential direction, wherein the second heat dissipation element comprises: at least one fin in contact with and to divide the winding of the plurality of windings into a plurality of sections; and a plate contiguous with the at least one fin and in contact with the second coolant channel.

9. The rotor assembly as claimed in claim 8, wherein the second heat dissipation element extends along the axial direction on a rotor tooth of the plurality of rotor teeth.

10. The rotor assembly as claimed in claim 8, wherein the rotor comprises a second groove extending along the axial direction to accommodate the second heat dissipation element therein, and wherein shape of the second groove corresponds to a shape of the first heat dissipation element.1 1 . The rotor assembly as claimed in claim 1 , the first coolant channel extends through a rotor tooth of the plurality of rotor teeth along an axialdirection through an axial length of the rotor, and wherein the rotor assembly comprises: a second coolant channel running through the rotor to conduct the coolant through thereof, wherein the second coolant channel is separated at a distance along a circumferential direction from the first coolant channel, and wherein the second coolant channel extends through the rotor tooth of the plurality of rotor teeth along the axial direction; and wherein each of the at least two bobbins comprises: a bobbin coolant channel aligned with the first coolant channel and the second coolant channel to conduct the coolant.

12. The rotor assembly as claimed in claim 1 1 , wherein the rotor shaft is hollow, and wherein the rotor shaft comprises: a first inlet opening to provide the coolant to the bobbin coolant channel of a bobbin of the at least two bobbins at a first axial end of the rotor; and a first outlet opening to receive the coolant from the bobbin coolant channel of a bobbin of the at least two bobbins at a second axial end of the rotor, wherein the coolant received into the first outlet opening is conducted through the rotor, and wherein the first axial end of the rotor is separated at a distance along the axial direction from the second axial end.

13. The rotor assembly as claimed in claim 1 , wherein the plate of the first heat dissipation element comprises a plurality of protrusions in contact with the first coolant channel to enhance dissipation of heat from the winding of the plurality of windings.

14. The rotor assembly as claimed in claim 1 , wherein the first heat dissipation element is made of a thermally conductive element.

15. A motor assembly comprising: a stator; a rotor assembly to rotate in relation to the stator, wherein the rotor assembly comprises: a rotor shaft to rotate about an axis; a rotor coupled to the rotor shaft and having a plurality of rotor teeth;at least two bobbins attached to the rotor on axial ends of the rotor, wherein each bobbin has at least one bobbin tooth, wherein the rotor and the at least two bobbins rotate about the axis in response to the rotation of the shaft; a plurality of windings, each winding of the plurality of windings wound over a tooth of the plurality of rotor teeth; a first coolant channel running through the rotor to conduct the coolant through thereof; a first heat dissipation element to dissipate heat generated from a winding of the plurality of windings, wherein the first heat dissipation element: at least one fin in contact with and to divide the winding of the plurality of winding into a plurality of sections; and a plate contiguous with the at least one fin and in contact with the first coolant channel.

16. The motor assembly as claimed in claim 15, wherein the at least one fin comprises a first fin and a second fin separated from each other along a radial direction.

17. The motor assembly as claimed in claim 15, wherein the at least one fin extends along an axial direction through an axial length of the rotor.

18. The motor assembly as claimed in claim 15, wherein the plate extends along an axial direction through an axial length of the rotor.

19. The motor assembly as claimed in claim 15, wherein the first heat dissipation element extends along an axial direction in a rotor tooth of the plurality of rotor teeth.

20. The motor assembly as claimed in claim 15, wherein the rotor comprises a first groove extending along an axial direction to accommodate the first heat dissipation element therein, and wherein shape of the first groove corresponds to a shape of the first heat dissipation element.21 . The motor assembly as claimed in claim 15, the first coolant channel extends through a rotor tooth of the plurality of rotor teeth along an axial direction through an axial length of the rotor, and wherein the rotor assembly comprises:a second coolant channel running through the rotor to conduct the coolant through thereof, wherein the second coolant channel is separated at a distance along a circumferential direction from the first coolant channel, and wherein the second coolant channel extends through the rotor tooth of the plurality of rotor teeth along the axial direction.

22. The motor assembly as claimed in claim 21 , comprising: a second heat dissipation element to dissipate heat generated from the winding of the plurality of windings, wherein the second heat dissipation element is separated at a distance from the first heat dissipation element along a circumferential direction, wherein the second heat dissipation element comprises: at least one fin in contact with and to divide the winding of the plurality of windings into a plurality of sections; and a plate contiguous with the at least one fin and in contact with the second coolant channel.

23. The motor assembly as claimed in claim 22, wherein the second heat dissipation element extends along the axial direction on a rotor tooth of the plurality of rotor teeth.

24. The motor assembly as claimed in claim 22, wherein the rotor comprises a second groove extending along the axial direction to accommodate the second heat dissipation element therein, and wherein shape of the second groove corresponds to a shape of the first heat dissipation element.

25. The motor assembly as claimed in claim 15, the first coolant channel extends through a rotor tooth of the plurality of rotor teeth along an axial direction through an axial length of the rotor, and wherein the rotor assembly comprises: a second coolant channel running through the rotor to conduct the coolant through thereof, wherein the second coolant channel is separated at a distance along a circumferential direction from the first coolant channel, and wherein the second coolant channel extends through the rotor tooth of the plurality of rotor teeth along the axial direction; andwherein each of the at least two bobbins comprises: a bobbin coolant channel aligned with the first coolant channel and the second coolant channel to conduct the coolant.

26. The motor assembly as claimed in claim 25, wherein the rotor shaft is hollow, and wherein the rotor shaft comprises: a first inlet opening to provide the coolant to the bobbin coolant channel of a bobbin of the at least two bobbins at a first axial end of the rotor; and a first outlet opening to receive the coolant from the bobbin coolant channel of a bobbin of the at least two bobbins at a second axial end of the rotor, wherein the coolant received into the outlet opening is conducted through the rotor, and wherein the first axial end of the rotor is separated at a distance along the axial direction from the second axial end.

27. The motor assembly as claimed in claim 15, wherein the plate of the first heat dissipation element comprises a plurality of protrusions in contact with the first coolant channel to enhance dissipation of heat from the winding of the plurality of windings.

28. The motor assembly as claimed in claim 15, wherein the motor assembly is an Electrically Excited Synchronous Motor (EESM) Assembly.

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