CROSS-REFERENCE TO RELATED APPLICATIONS

[0001 J This PCT International Patent Application claims the benefit of and priority to U.S. Provisional Patent Application Serial No. 63/353,318, filed June 17, 2022, titled “Jet Cooling For Electric Motors,” the entire disclosure of which is hereby incorporated by reference.

FIELD

|0002| The present disclosure relates generally to cooling electric machines, such as electric motors.

BACKGROUND

[0003] High temperatures in stator and rotor windings of electric machines such as electric motors or motor/generators may cause degradation in electric motor performance. For wound field synchronous machines, the rotor windings in particular can be challenging to cool due to demand for a higher slot fill (total copper area/slot area). Higher slot fill translates to higher flux production and torque density, however copper losses increase due to the induced current in the copper. Insulation material of copper wiring can be damaged if winding temperatures exceed optimal ranges. Rotor active windings may also prove challenging to cool as direct cooling within the core of the machine is not possible through conventional cooling methods. A cooling solution that allows direct cooling of the rotor windings is crucial. However, direct rotor cooling can cause cooling fluid to enter the airgap between the rotor and stator, causing significant drag losses.

[0004] Several different techniques may be used for cooling electric machines. For example, direct jet impingement may be used to directly cool stator end windings. The cooling system is capable of removing large heat loads from the stator windings by the formation of a very thin boundary layer along the windings due to the jet impingement. Integrating this cooling system towards cooling rotor windings may be problematic at high rotational speeds as the impinging jet can bend and deviate from the intended target as it enters a rotating frame. Furthermore, maintaining temperature uniformity throughout the stator windings is only possible with a large number of jets. A large number of jets can also create problems, since jet velocity can decrease with an increase in number of jets, which can lead to reduced heat transfer performance.

(0005] Another technique for cooling electric machines includes shaft cooling, with a cooling system integrated in a motor shaft. Shaft cooling may enable compact packaging, wherein centrifugal forces push coolant through a hollow shaft. However, it is difficult to cool components sufficiently far from the shaft such stator lamination and windings with just shaft cooling. Transferring the cooling fluid from a stationary part to the rotating shaft can also be problematic in terms of cost and manufacturing.

[0006] Another technique for cooling electric machines includes fin or channel cooling, in which an array of fins or cooling air passages surround the stator. Offset plates may be used to disrupt cooling air flow to reduce boundary layer formation which aids in heat transfer performance. Fin or channel cooling can have some disadvantages, such as relatively large system pressure drop due to flow disturbance caused by the offset plates. Furthermore, incorporating channels and fluid flow to directly cool the rotor is complex.

SUMMARY

[0007] The present disclosure provides an electric machine. The electric machine includes a stator, a rotor configured to rotate about an axis, and a housing surrounding the rotor and the stator. The housing includes a jacket having a tubular shape disposed circumferentially around the stator. The jacket defines a central passage extending circumferentially around at least a portion of the stator. The central passage is configured to convey a cooling fluid therethrough. The jacket extends axially beyond the stator and defines an end passage extending circumferentially through at least a portion thereof. The housing further defines an inlet port providing fluid communication for coolant flow into the central passage, and a transfer passage spaced apart from the inlet port by a first rotational separation around the tubular shape of the jacket. The transfer passage provides fluid communication for coolant flow from the central passage to the end passage. The housing further includes an end cap at an axial end of the electric machine. The housing encloses an end space between the rotor and the end cap. The electric machine also includes a nozzle configured to discharge the cooling fluid from the end passage and into the end space.

(0008] The present disclosure also provides an electric machine. The electric machine includes a stator, a rotor configured to rotate about an axis, and a housing surrounding the rotor and the stator. The housing includes a jacket having a tubular shape disposed circumferentially around the stator. The jacket defines a central passage extending circumferentially around at least a portion of the stator. The central passage is configured to convey a cooling fluid therethrough in a first cooling loop. The housing further includes an end cap at an axial end of the electric machine. The housing encloses an end space between the rotor and the end cap. The electric machine also includes a nozzle a nozzle fluidly coupled to a second cooling loop that is fluidly isolated from the first cooling loop. The nozzle is configured to discharge the second cooling fluid into the end space.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Further details, features and advantages of designs of the invention result from the following description of embodiment examples in reference to the associated drawings.

(0010] FIG. 1A shows a fragmentary perspective view including a cross-section of a first electric machine in accordance with an aspect of the present disclosure. [0011] FIG. IB shows a fragmentary side view including a cross-section of the first electric machine shown in FIG. 1A.

[00.12] FIG. 2A shows a fragmentary perspective view including a cross-section of a second electric machine in accordance with an aspect of the present disclosure.

[0013] FIG. 2B shows a fragmentary side view including a cross-section of the second electric machine shown in FIG. 2A.

[0014] FIG. 3 shows a fragmentary side view including a cross-section of a third electric machine in accordance with an aspect of the present disclosure.

[0015] FIG. 4A shows an end view of a rotor of the third electric machine of FIG. 3.

[0016] FIG. 4B shows an enlarged portion of the end view of the rotor of FIG. 4A, including details of one rotor slot.

[0017] FIG. 5 shows a first inter-slot blocker for the third electric machine of FIG. 3.

[0018| FIG. 6 shows a second inter-slot blocker for the third electric machine of FIG. 3.

[0019] FIG. 7 shows a third inter-slot blocker for the third electric machine of FIG. 3.

[0020] FIG. 8A shows a fragmentary perspective view including a cross-section of a fourth electric machine in accordance with an aspect of the present disclosure.

[0021] FIG. 8B shows a fragmentary side view including a cross-section of the fourth electric machine shown in FIG. 8A.

[0022] FIG. 9 shows an end view of a rotor of the fourth electric machine of FIG. 8.

[0023] FIG. 10A shows a fragmentary perspective view including a cross-section of a fifth electric machine in accordance with an aspect of the present disclosure.

[0024] FIG. 10B shows a fragmentary side view including a cross-section of the fifth electric machine shown in FIG. 10A. DETAILED DESCRIPTION

[0025] Referring to the drawings, the present invention will be described in detail in view of following embodiments. The present disclosure provides for an electric machine, such as a motor or a motor/generator cooled by a liquid coolant. The apparatus of the present disclosure may address and solve several different problems with conventional cooling of electric machines.

(0026] The electric machines and cooling solutions therefore presented in the present disclosure may improve cooling through a direct approach where a cooling fluid, such as oil, directly wets stator and rotor components. Furthermore, the electric machines and cooling solutions therefore presented in the present disclosure may also simultaneously reduce drag losses, especially drag losses that can result from cooling fluid in an air gap between the stator and rotor components of the electric machine.

[0027] The apparatus of the present disclosure functions to cool stator and rotor windings to optimal and safe operating temperatures while maintaining low system pressure drop, temperature uniformity over entire winding structure, and low drag losses.

[0028] FIGS. 1A - IB show a cross-sectional views of a first electric machine 20 of the present disclosure. The first electric machine 20 may function, for example, as a motor or a motor/generator and may be used for a variety of different applications such as, for example, as a traction motor of an electrified vehicle. The first electric machine 20 includes a stator 22, 23 and a rotor 24, 25 that is configured to rotate about an axis A. The stator 22, 23, includes a stator core 22 and stator windings 23 that extend through slots in the stator core 22. The stator core 22 may also be called a stator lamination. The rotor 24, 25 includes a rotor core 24 and rotor windings (not shown) that extend through rotor slots 25 in the rotor core 24, and which protrude out of the rotor core 24 as rotor winding ends 70, 71. In some embodiments the rotor 24, 25 may have another configuration that may not include the rotor windings. The first electric machine 20 also includes a shaft (not shown) that is coupled to the rotor 24 to rotate therewith.

[0029] The first electric machine 20 also includes a first housing 30 surrounding the rotor 24, 25 and the stator 22, 23. The first housing 30 includes a first cooling jacket 32 which has a tubular shape disposed circumferentially around the stator 22, 23. The first cooling jacket 32 defines a first central passage 34 which extends circumferentially around at least a portion of the stator 22, 23 and is configured to convey a cooling fluid therethrough. In some embodiments, and as shown in FIGS. 1A-1B, the first central passage 34 is formed as a circumferential trough in an inner surface of the first cooling jacket 32 and is bounded on a radially-inner surface by stator core 22. However, the central passage 34 may have another configuration and may be bounded on one or more sides by one or more different structures.

[0030] The first cooling jacket 32 also defines an inlet port 36 that provides fluid communication for coolant flow into the first central passage 34. The inlet port 36 is shown in FIGS. 1A-1B, being centrally located and on a top surface of the first electric machine 20. However, the inlet port 36 may have a different location, such as a side. Furthermore, the first electric machine 20 may include two or more inlet ports 36 to provide for coolant flow into the first central passage 34.

[0031] The first cooling jacket 32 extends axially beyond the stator core 22 in a first direction, which may also be called a front. The first cooling jacket 32 defines a first end passage 37 extending circumferentially through at least a portion thereof and axially spaced apart from the stator core 22 in the first direction. The first cooling jacket 32 also extends axially beyond the stator core 22 in a second direction opposite the first directly, which may also be called a rear of the first electric machine 20. The first cooling j acket 32 defines a second end passage 38 extending circumferentially through at least a portion thereof and axially spaced apart from the stator core

22 in the second direction.

[0032] The first housing 30 of the first electric machine 20 also includes two transfer passages 39, with each of the transfer passages 39 providing fluid communication for coolant flow from the first central passage 34 to a corresponding one of the end passages 37, 38. The transfer passages 39 are spaced apart from the inlet port 36 by a first rotational separation around the tubular shape of the first cooling jacket 32. This first rotational separation provides pathway for the cooling fluid through the first central passage 34, between the inlet port 36 and the transfer passages 39, and which extends around at least a portion of the stator core 22 for the cooling fluid to remove heat therefrom. The first rotational separation may be 180-degrees, as shown in FIGS. 1A - IB. However, in some embodiments, the first rotational separation may be less than 180- degrees. In some embodiments, the first rotational separation may be greater than 180-degrees.

|0033| The first housing 30 of the first electric machine 20 also includes a first end cap 40 located at a first axial end of the first electric machine 20. The first housing 30 thus encloses a first end space 42 between the stator core 22 and the rotor 24, 25 and the first end cap 40. The first housing 30 also includes a second end cap 44 located at a second axial end of the first electric machine 20, opposite from the first end cap 40. The first housing 30 thus encloses a second end space 46 that extends between the stator core 22 and the rotor 24, 25 and the second end cap 44. [0034] The first electric machine 20 also includes a first nozzle 50 configured to discharge the cooling fluid from the first end passage 37 and into the first end space 42. The first electric machine 20 also includes a second nozzle 52 configured to discharge the cooling fluid from the second end passage 38 and into the second end space 46. Either or both of the nozzles 50, 52 may be formed as a hole that extends through the first cooling jacket 32. Alternatively or additionally, either or both of the nozzles 50, 52 may include additional components to direct and/or form the coolant flow in one or more particular directions and/or in a particular spray pattern.

[0035] In some embodiments, either or both of the nozzles 50, 52 may be configured to discharge the cooling fluid in a direction tangential to the rotation of the rotor. In some embodiments, either or both of the nozzles 50, 52 may be configured to discharge the cooling fluid in a direction parallel to the axis A. For example, either or both of the nozzles 50, 52 may be configured to discharge the cooling fluid in a stream that is parallel to the axis A and directly toward the stator windings 23 and/or the windings of the rotor 24,25.

(0036] In some embodiments, and as shown in FIGS. 1 A-1B, either or both of the nozzles 50, 52 may be spaced apart from the transfer passage 39 by a second rotational separation around the tubular shape of the first cooling jacket 32. This second rotational separation may provide for an annular flow path of the cooling fluid through the end passages 37, 38. In some embodiments, the second rotational separation is at least about 180-degrees. However, in some embodiments, the second rotational separation may be less than 180-degrees. In some embodiments, the second rotational separation may be greater than 180-degrees. In some embodiments, the second rotational separation is equal to the first rotational separation between the transfer passages 39 and the inlet port 36.

[0037] The first electric machine 20 also includes a first outlet port 60 disposed in a bottom surface of the first cooling jacket 32 to provide fluid communication from the first end space 42 for the cooling fluid to drain from the first housing 30. A coolant tank 62 may be provided in fluid communication with the first outlet port via a first outlet conduit 64 to collect the cooling fluid that drains from the first electric machine. The cooling fluid may then be recirculated out of the coolant tank 62 via a shared outlet port 63 and back through the inlet port 36 and/or to other systems. The first electric machine 20 also includes a second outlet port 66 disposed in a bottom surface of the first cooling jacket 32 to provide fluid communication from the second end space 46 for the cooling fluid to drain from the first housing 30. A second outlet conduit 68 may fluidly couple the second outlet port 66 to the coolant tank 62 to provide fluid communication therebetween.

[0038] The first electric machine 20 of FIGS. 1A-1B is cooled by cooling fluid, such as oil, that enters the inlet port 36 of the first cooling jacket 32. The first cooling jacket 32 consists of three loops. Cooling fluid first enters the top half of the first central passage 34 and flows to the bottom half of the first central passage 34 to uniformly cool the active region of the stator 22, 23. Since cooling fluid enters form the top of the first housing 30, cooling fluid flows from top to bottom with the aid of gravity which will help reduce pressure losses. Through the central loop, cooling fluid is in direct contact with the stator core 22, allowing for improved heat transfer compared to more conventional cooling jackets where additional conductive thermal resistances exist between the cooling fluid and the stator core 22. Cooling fluid then flows through channels into the bottom half of the first end passage 37 and the second end passage 38. After cooling the bottom half of the end portions of the stator 22, 23, cooling fluid flows upwards to the top half of the first end passage 37 and the second end passage 38. Next, cooling fluid enters a first nozzle 50 located on the first end cap 40, and a second nozzle 52 located on the second end cap 44. Cooling fluid is expelled from the first nozzle 50 into the first end space 42 and from the second nozzle 52 into the second end space 46 to aid in cooling the ends of the stator windings 23 within corresponding ones of the end spaces 42, 46. Cooling fluid will also wet the rotor winding ends 70, 71. Due to the high rotational speed of the shaft, there may be induced splashing and mixing of the cooling fluid that wets the rotor winding ends 70, 71. Induced mixing of the cooling fluid will improve convective heat transfer rates from the rotor core 24, the rotor winding ends 70, 71, the stator core 22, and the ends of the stator windings 23 in the end spaces 42, 46. Due to cooler stator and rotor end windings, the active stator windings (i.e., the portions of the stator windings 23 extending through the stator core 22) and the active rotor windings (i.e. the portions of the rotor windings that extend through the rotor slots 25 in the rotor core 24) will indirectly be cooled as there is a greater temperature differential between active winding regions and end winding regions to drive conductive heat transfer. Cooling fluid will drain from the first outlet port 60 and the second outlet port 66 and collect into the coolant tank 62 before draining from a shared outlet port 63.

(0039] FIGS. 2A - 2B show a cross-sectional views of a second electric machine 120 of the present disclosure. The second electric machine 120 may be similar or identical to the first electric machine 20, except for a few differences described herein. The second electric machine 120 includes a second housing 130 in place of the first housing 30 of the first electric machine 20. The second housing 130 includes a second cooling jacket 132 that is similar to the first cooling jacket 30, but without the end passages 37, 38 or the transfer passages 39. Instead, cooling fluid circulates a first cooling loop through the first central passage 34 from the inlet port 36 to a jacket discharge port 139.

(0040] The second electric machine 120 also includes one or more third nozzles 150 configured to discharge cooling fluid into the first end space 42. The second electric machine 120 also includes one or more fourth nozzles 152 configured to discharge cooling fluid into the second end space 46. One or more of the third nozzles 150 and/or the fourth nozzles 152 may be formed tubular protrusions that extend from a corresponding one of the first end cap 40 or the second end cap 44. Alternatively or additionally, one or more of the third nozzles 150 and/or the fourth nozzles 152 may include additional components to direct and/or form the coolant flow in one or more particular directions and/or in a particular spray pattern. Each of the third nozzles 150 and/or the fourth nozzles 152 may be coupled to a second cooling loop that is fluidly isolated from the first cooling loop. The first and second cooling loops may include different types of cooling fluid. For example, the first cooling loop may use water or a glycol mix as a cooling fluid, and the second cooling loop may use an oil-based cooling fluid.

(0041] In some embodiments, one or more of the third nozzles 150 and/or the fourth nozzles 152 may be configured to discharge the cooling fluid in a direction tangential to the rotation of the rotor. In some embodiments, one or more of the third nozzles 150 and/or the fourth nozzles 152 may be configured to discharge the cooling fluid in a direction parallel to the axis A. For example, one or more of the third nozzles 150 and/or the fourth nozzles 152 may be configured to discharge the cooling fluid in a stream that is parallel to the axis /I and directly toward the stator windings 23 and/or the windings of the rotor 24, 25.

[0042] The first cooling loop of the second electric machine 120 may be primarily dedicated to cooling the stator 22, 23. The second cooling loop of the second electric machine 120 may be primarily dedicated to cooling the rotor 24, 25. Cooling fluid, such as water or oil first enters the top half of the first central passage 34 and flows to the bottom half thereof to uniformly cool the active region of the stator. Cooling fluid in the first cooling loop may be in direct contact with the stator core 22, allowing for enhanced convective heat transfer from the stator core 22 and active parts of the stator windings 23. When the cooling fluid flows towards the bottom half of the second cooling jacket 132, it will soon exit the stator cooling circuit through the jacket discharge port 139.

(0043] For the second cooling circuit, cooling fluid, such as oil, enters jet inlets on the end caps 40, 44 coupled to the third and fourth nozzles 150, 152, which may also be called jet nozzles. Cooling fluid is expelled from the third and fourth nozzles 150, 152 into the corresponding one of the end spaces 42, 46. The cooling fluid can be expelled axially (parallel to the shaft/axis of rotation) or tangentially (perpendicular to the shaft/axis of rotation). Cooling fluid within the end spaces 42, 46 will swirl around the shaft. At higher rotational speeds there will be enhanced mixing of oil around the rotor winding ends 70, 71 which will improve convective heat transfer. Consequently, lower rotor end winding temperatures will aid in cooling the rotor active windings (i.e., the portions of the rotor windings within the rotor slots 25). As the rotor core 24 is also in direct contact with the oil, heat can also be removed directly from the rotor lamination when wetted with the oil. Like the first electric machine 20, cooling fluid will drain from a first outlet port 60 and a second outlet port 66 and will collect into a coolant tank 62 before draining from a shared outlet port 63.

[0044] FIG. 3 shows a fragmentary side view including a cross-section of a third electric machine 220 in accordance with an aspect of the present disclosure. The third electric machine 220 may be similar or identical to one or both of the first electric machine 20 and/or the second electric machine 120 except for differences described herein. The third electric machine 220 includes a third housing 230 in place of the first housing 30 of the first electric machine 20 or the second housing 130 of the second electric machine 120. The third housing 230 includes a third cooling jacket 232 that is similar to the first cooling jacket 30, but with one or more third central passages 234 from instead of a single first central passage 34. The third central passages 234 may include one or more helical shaped passages extending through the third cooling jacket 232.

[0045] The third electric machine 220 also includes one or more third and fourth nozzles

150, 152 that may be similar or identical to those in the second electric machine 120. (0046] Referring to Fig. 3, cooling fluid, such as oil, enters the third electric machine 220 through jet inlets on the end caps 40, 44 coupled to the third and fourth nozzles 150, 152, which may also be called jet nozzles. Cooling fluid is expelled from the third and fourth nozzles 150, 152 into the corresponding one of the end spaces 42, 46. As the cooling fluid is expelled axially from the third and fourth nozzles 150, 152, a jet is formed with an enhanced velocity due to the prevailing rotational motion of fluid (such as air and liquid spray) within the corresponding end spaces 42, 46. The magnitude of the enhanced velocity depends on the rotational speed of the shaft and on a radial distance between the shaft and the corresponding one of the third and fourth nozzles 150, 152. The cooling fluid begins to swirl around the shaft and then wets the rotor winding ends 70, 71 at a high velocity.

[0047] FIG. 4A shows an end view of a rotor of the third electric machine 220, and FIG. 4B shows an enlarged portion of the end view of the rotor of FIG. 4A, including details of one of the rotor slots 25.

[0048] Through splashing, cooling fluid will enter cavities 74 in the rotor slots 25 located between consecutive ones of the active rotor windings 76. The cavities 74 are highlighted in FIGS. 4A-4B 4. Cooling fluid within the cavities 74 will aid in cooling of the active rotor windings 76. However, cooling fluid could flow radially outwards due to centrifugal forces. To prevent the radial flow from entering an air gap between the rotor 24, 25 and the stator 22, 23, an inter-slot blocker 320, 322, 324 may be positioned between the consecutive ones of the rotor windings 76 within each of the cavities 74. Examples of the inter-slot blockers 320, 322, 324 are shown in FIGS. 5-8.

[0049] Each of the inter-slot blockers 320, 322, 324 includes a top confinement wall 330 which prevents radial flow from entering the air gap. A front support 332 and rear support 334 allow for the mounting of the inter-slot blocker 320, 322, 324, and they can be modified to control the amount of cooling fluid that flows through the rotor slots 25. The side supports 336 may allow for the simple mounting of the inter-slot blockers 320, 322, 324. The side supports 336 may have a size and/or shape that varies from the illustrated example.

[0050] FIG. 5 shows a first inter-slot blocker 320, which includes a top confinement wall 330 that covers a radially-outer edge of the corresponding one of the axial slots, and wherein the inter-slot blocker does not extend beyond the top confinement wall 330 for a substantial portion of the axial length thereof. In other words, the first inter-slot blocker 320 includes only the top confinement wall 330 for substantially all of its axial length. The first inter-slot blocker 320 may include one or more other portions, such as the front support 332 and rear support 334 adjacent to axial ends thereof. The front support 332 and rear support 334 may function to prevent the first inter-slot blocker 320 from sliding out of the cavities 74 during high-speed rotational operations. The top confinement wall 330 blocks cooling fluid from migrating out of corresponding ones of the rotor slots 25 and into the airgap between the rotor 24, 25 and the stator 22, 23. With open sides, the first inter-slot blocker 320 allows cooling fluid to directly cool the active rotor windings 76. Since the cooling fluid may be in direct or close contact with the active rotor windings 76, thermal conducting properties of the first inter-slot blocker 320 are not critical.

[0051] FIG. 6 shows a second inter-slot blocker 322 which has a generally tubular shape including a top confinement wall 330 that covers a radially-outer edge of the corresponding one of the rotor slots 25 and with closed-shape cross-section that remains constant along an axial length thereof. The second inter-slot blocker 322 may be made of a material with a high thermal conductivity. [0052] FIG. 7 shows a third inter-slot blocker 324, which has a solid cross-section that remains constant along an axial length thereof. The solid cross-section of the third inter-slot blocker 324 may be configured to match a shape of a corresponding one of the cavities 74 within a corresponding one of the rotor slots 25 and between two or more sets of the active rotor windings 76 extending therethrough.

[0053] The third inter-slot blocker 324 may be completely filled with thermal conducting material, and which defines solid end faces 338 at either axial end thereof. One or more jets of cooling fluid may wet the rotor winding ends 70, 71. Simultaneously, the jets will wet the solid end faces 338 of the third inter-slot blocker 324, which may be completely closed/filled with thermal conducting material. The thermal conducting material of the third inter-slot blocker 324 will enhance conductive heat transfer from the active rotor windings 76 to the rotor winding ends 70, 71. With the third inter-slot blocker 324, cooling fluid oil cannot enter the cavities 74. Therefore, the cooling fluid will not flood the airgap between the rotor 24, 25 and the stator 22, 23, thereby reducing reduces overall drag.

[0054] The inter-slot blockers 320, 322, 324 can be inserted after the rotor 24, 25 is wound through manufacturing processes, such as transfer molding. The side supports 336 of the second inter-slot blocker 322 and/or the solid body of the third inter-slot blocker 324 may fdl the gaps between the active rotor windings 76, allowing for improved conduction within the active rotor windings 76. The front support 332 and rear support 334 of the first inter-slot blocker 320 are open allowing for cooling fluid splashed from the rotor core 24, and/or either or both of the rotor winding ends 70, 71 to flow into the cavities 74 between consecutive ones of the rotor windings 76. The cooling fluid will then cool the sides of the inter-slot blocker through convection, effectively cooling the rotor windings overall. (0055] As shown in FIG. 4B, the top confinement wall 330 of the second inter-slot blocker 322 is supported by pole tips 340, 342 of the rotor slots 25 to improve structural integrity particularly during high-speed operation of the rotor 24, 25. The shape of the top confinement wall 330 can be adjusted to match the shape of the rotor 24, 25. A similar configuration may be used with any of the inter-slot blockers 320, 322, 324 of the present disclosure.

(0056] FIGS. 8A - 8B show cross-sectional views of a fourth electric machine 420 of the present disclosure. The fourth electric machine 420 may be similar to one or more of the first electric machine 20, the second electric machine 120, and/or the third electric machine 220 except for differences described herein. The fourth electric machine 420 includes a second rotor core 442 that defines second rotor slots 440 and which may include a stack of laminations. Rotor winding ends 441 protrude from each axial end of the second rotor core 442. The fourth electric machine 420 also includes a fourth inter-slot blocker 443 located in each of the second rotor slots 440, and coil carriers 444 located around the rotor windings to increase structural integrity at different rotor speeds. The fourth electric machine 420 also includes a second stator core 445, and second stator end windings 446, 447 at the front and the rear sides, respectively.

10057] The fourth electric machine 420 includes a fourth housing 430 in place of the third housing 230 of the third electric machine 220. The fourth housing 430 includes a fourth cooling jacket 434 that is similar or identical to the third cooling jacket 232 of the third housing 230, except for locations of the inlet pipe 449 and the outlet. The fourth housing 430 also includes a coolant passage 450 at each axial end, with two coolant inlets 451 and two coolant outlets 452.

|0058| The fourth electric machine 420 also includes one or more fifth nozzles 453 and sixth nozzles 454, each having a higher inlet to outlet area ratio to reduce a pressure drop thereacross. (0059] Referring to FIGS. 8A - 8B, cooling fluid, such as oil, enters the fourth electric machine 420 through the coolant inlets 451 and through the coolant passage 450. The cooling fluid is transmitted cooling passage and to the fifth and sixth nozzles 453, 454, which may also be called rotor jet nozzles. Cooling fluid is expelled from the fifth and sixth nozzles 453, 454 into the corresponding one of the end spaces 455, 456. The cooling fluid begins to impinge directly and then wets the rotor winding ends 441 at a low velocity and/or or swirl around the shaft and then wets the rotor winding ends 441 at a high velocity.

10060] FIG. 9 shows an end view of a rotor 442, 458 for the fourth electric machine 420. Through splashing, cooling fluid will enter cavities 457 in the second rotor slots 440 located between consecutive ones of the rotor windings 458. Cooling fluid within the cavities 457 will aid in cooling of active regions of the rotor windings 458. However, cooling fluid could flow radially outwards due to centrifugal forces. To prevent the radial flow from entering an air gap between the rotor 442, 458 and the second stator core 445, a fourth inter-slot blocker 443 may be positioned between adjacent ones of the rotor windings 458 within each of the cavities 457. The fourth interslot blocker 443 may be secured in place with potting material around the rotor windings 458.

|0061] FIGS. 10A - 10B show cross-sectional views of a fifth electric machine 460 of the present disclosure. The fifth electric machine 460 may be similar or identical to the fourth electric machine 420, except for differences described herein. The fifth electric machine 460 includes a fifth housing 470 in place of the fourth housing 430 of the fourth electric machine 420. The fifth housing 470 includes a fifth cooling jacket 471 that is similar or identical to the first cooling jacket 30 of the first electric machine 20, except that cooling fluid, such as oil, enters fifth cooling j acket 471 from a fluid inlet 472 at the bottom and then it comes up and fills a main passage 474 at the center and then it enters front and rear passages 476, 478 at opposite axial ends of the main passage 474. The cooling fluid flows through the front and rear passages 476, 478 and is directed outwardly therefrom through corresponding ones of the stator jets 480, 482. The stator jets 480, 482 may direct the cooling fluid to impinge onto the stator end windings 446, 447. Another difference is that there is a thin wall between the main passage 474 of the fifth cooling jacket 471 and the second stator core 445, which isolates the cooling fluid from contacting the second stator core 445.

(0062] Still referring to FIGS. 10A - 10B, oil can also enter the fifth electric machine 460 through the coolant inlets 451 and be conveyed through the coolant passage 450 to the fifth and sixth nozzles 453, 454 and into contact with the rotor windings 458, directly and/or with assistance from swirling fluid in the end spaces. Finally, fluid that comes in from both the center of the machine and from the coolant inlets 451 leaves the fifth electric machine 460 thought the coolant outlets 452.

[0063] The foregoing description is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.