Lubricant support motor having electrical conductors as outer race

Abstract

An electric motor includes a stator presenting a first surface. A rotor is rotatable relative to the stator. The rotor presents a rotor raceway disposed in spaced relation to the first surface of the stator. The first surface of the stator defines a plurality of slots in spaced relation to one another to define a plurality of spaced teeth between the plurality of slots. At least one electrical conductor is disposed in each of the plurality of slots and is configured to selectively generate a moving magnetic field to act on the rotor to provide rotational motion of the rotor. A portion of the at least one electrical conductor extends substantially in radial alignment with the first surface of the stator or extends beyond the first surface of the stator to at least partially define a stator raceway of the stator for engaging the rotor raceway of the rotor during relative radial motion between the rotor and the stator.

Description

[0001] Cross-citation of related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 036,167, filed June 8, 2020, the entire disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure generally relates to a lubricant-supported electric motor. More specifically, this disclosure relates to a lubricant-supported electric motor having a raceway of a stator defined by a plurality of electrical conductors. Background Technology

[0004] This section provides a general overview of the background information, and the various comments and examples provided in this section are not necessarily prior art of this disclosure.

[0005] Various powertrain systems in automobiles, trucks, and certain off-highway applications derive power from a central prime mover, such as an internal combustion engine (ICE), and distribute that power to multiple wheels using multiple mechanical devices, such as multiple transmissions, multiple driveshafts, multiple propeller shafts, and multiple drive shafts. However, increasing attention is turning to alternative arrangements of multiple prime movers that offer improved environmental performance, eliminate multiple mechanical powertrain components, and produce multiple lighter vehicles, providing more space for multiple passengers and payloads.

[0006] "On-wheel," "in-wheel," or "near-wheel" motor configurations are alternative arrangements of multiple conventional ICE prime movers that distribute the prime mover's functionality to each or some of the multiple wheels via one or more motors located on, within, or near the multiple wheels. For example, in one case, a traction motor supporting the rotor via a central shaft and bearings for rolling multiple elements can be used as an "on-wheel," "in-wheel," or "near-wheel" motor configuration. In another case, a lubricant-supported motor, such as that described in U.S. Application No. 16 / 144,002, can be used as an "on-wheel," "in-wheel," or "near-wheel" motor configuration. While each of these motor configurations results in a smaller size and lighter weight arrangement compared to multiple prime movers based on multiple ICEs, there is still room for further improvement.

[0007] For example, using multiple traction motors as the “on-wheel,” “in-wheel,” or “near-wheel” configuration still results in a relatively heavy number of motors, which are often insufficient to withstand shock loads and cannot be optimized for a variety of wheel-end applications. In other words, current multiple traction motors consist of multiple large and heavy structures supported by bearings with multiple rolling elements, which are relatively heavy for a variety of practical wheel-end applications. In an automotive or land vehicle application, multiple lubricated support motors as the “on-wheel,” “in-wheel,” or “near-wheel” motors are a lightweight alternative to multiple traction motors. Such lubricated support motors include a lubricant disposed in a gap between a rotor and a stator, which supports the rotor within the stator and provides continuous contact between these components. The lubricant can thus act as a bearing (e.g., a suspension) between the rotor and stator, thereby minimizing or preventing contact between them. It is known to place a bearing sleeve made of a high resistivity material, such as Hastelloy or Delrin, between the rotor and stator to accommodate rotational contact between the rotor and stator. One problem with these types of bearing sleeves is that they induce multiple eddy current losses in the stator, leading to performance degradation. A non-conductive polymer bearing sleeve is also known to be used between the rotor and stator, but these sleeves have several relatively poor mechanical properties. Furthermore, both options require additional manufacturing and assembly steps. Therefore, while the known lubricated motors offer a lightweight alternative to several traction motors, further improvements are still needed. Summary of the Invention

[0008] An electric motor includes a stator having a first surface. A rotor extends about an axis and is rotatable relative to the stator. The stator has a rotor raceway spaced apart from the first surface of the stator to define a gap therebetween for receiving a lubricant. The first surface of the stator defines a plurality of slots spaced apart from each other to define a plurality of spaced teeth between the slots. At least one electrical conductor is disposed in each of the slots and configured to selectively generate a moving magnetic field to act on the rotor to provide rotational motion of the rotor in response to a current applied to the at least one electrical conductor. A portion of the at least one electrical conductor in each of the slots extends substantially radially aligned with or beyond the first surface of the stator to at least partially define a stator raceway of the stator for engaging the rotor raceway during relative radial movement between the rotor and the stator, serving as a bearing while also generating the moving magnetic field.

[0009] Using one or more electrical conductors, such as windings (and optionally the stator core), to define the outer raceway allows the multiple electrical conductors to not only provide current conduction to drive the rotor, but also to mechanically support the stator. This eliminates the need for a separate stator bearing sleeve to mechanically support the stator, thus providing a simpler and more compact assembly and simplifying the manufacture and assembly of the motor. Attached Figure Description

[0010] Several other aspects of this disclosure will be readily understood because they can be better understood by referring to the following detailed description when considered in conjunction with the aforementioned figures, wherein:

[0011] Figure 1 This is a schematic diagram of a lubricant supporting an electric motor;

[0012] Figure 2 This is a perspective sectional view of the stator of the lubricant-supported motor, showing an inner diameter of the stator, which consists of multiple electrical conductors and multiple teeth of the stator;

[0013] Figure 3 This is a perspective view of a rotor of the electric motor supported by the lubricant.

[0014] Figure 4 This is a partial front cross-sectional view of a stator and a rotor of the lubricant-supported electric motor, showing multiple electrical conductors in a slot of the stator that serves as an inner raceway;

[0015] Figure 4A This is a partial front cross-sectional view of a stator of the lubricant-supported motor, showing an alternative arrangement of multiple electrical conductors in a slot. Detailed Implementation

[0016] Several exemplary embodiments of a lubricant-supported electric motor having at least one electrical conductor serving as an outer raceway of a stator, according to this disclosure, will now be described more fully. Each of these exemplary embodiments is provided so that this disclosure is thorough and fully conveys to those skilled in the art the scope of the various concepts, features, and advantages of the invention. To this end, numerous specific details, such as numerous examples of specific components, devices, and mechanisms associated with the lubricant-supported electric motor, are set forth to provide a thorough understanding of each of the various embodiments associated with this disclosure. However, it will be apparent to those skilled in the art that not all the specific details described herein are necessary, and the various exemplary embodiments may be embodied in many different forms and should therefore not be construed as limiting the scope of this disclosure. The following exemplary embodiments describe a radial flux motor 10 having a rotor 14 rotatably located within a stator 12. Without departing from the scope of this subject matter disclosure, the various teachings herein can also be applied to a reverse radial flux motor, multiple axial flux motors, and multiple axial / radial flux motors having a rotor rotatably positioned around a stator.

[0017] Figures 1 to 4A A lubricant-supported electric motor 10 is shown according to one aspect of this disclosure. For example... Figure 1 As best shown, the lubricant-supported motor 10 includes a stator 12 and a rotor 14, the rotor 14 extending along an axis A and rotatably disposed within the stator 12 to define a gap 16 therebetween. A lubricant 18 is disposed in the gap 16 to support the rotor 14 within the stator 12 and to provide continuous contact between these components. The lubricant 18 can thus act as a buffer (e.g., suspension) between the rotor 14 and the stator 12 to minimize or prevent contact between them. In other words, the lubricant 18 minimizes direct contact between the stator 12 and the rotor 14 and provides an electrically powered, lubricant-supported motor 10 that can withstand shock and vibration loads due to the presence of the lubricant 18. Alternatively or additionally, a substantially incompressible lubricant 18 can be used to minimize the gap between the stator 12 and the rotor 14.

[0018] like Figure 1As further shown, the stator 12 defines one or more channels 20 in fluid communication with the gap 16 for introducing the lubricant 18. Without departing from the disclosure of this subject matter, the channels 20 may also be provided on any other component of the lubricant-supported motor 10. According to one aspect, the lubricant 18 may be circulated or pumped through the channels 20 and into the gap 16 in various ways. For example, a high-pressure source 21 of the lubricant 18 (e.g., a pump, schematically shown) may be fluidly coupled to a low-pressure source 23 of the lubricant 18 (e.g., an oil sump, schematically shown), and the lubricant may move from the high-pressure source to the low-pressure source 23, through the channels 20, and into the gap 16. Furthermore, the rotation of the rotor 14 relative to the stator 12 may serve as a self-pump to drive the lubricant 18 through the channels 20 and into the gap 16.

[0019] like Figure 1 As further shown, the rotor 14 is coupled to a drive assembly 22 for coupling the lubricant-supported motor 10 to one of the plurality of wheels of the vehicle. For example, in one case, the drive assembly 22 may include a planetary gear system. Alternatively, the drive assembly 22 may include one or more parallel-axis gears. The stator 12 and rotor 14 are configured to apply an electromagnetic force between them to convert electrical energy into mechanical energy, move the rotor 14, and ultimately drive the wheel coupled to the lubricant-supported motor 10 via the drive assembly 22. The plurality of drive assemblies 20 may provide one or more reduction ratios between the lubricant-supported motor 10 and the wheel in response to the movement of the rotor 14.

[0020] refer to Figure 1 , 2 4 and 4A, the stator 12 includes a core 23, which is composed of a plurality of axially compressed laminations 25 of a steel material. Figure 1(Schematic illustration). The core 23 presents a machined radially inner (first) surface 26 and a radially outer (second) surface 24. The radially inner surface 26 defines a plurality of radially outwardly extending slots 28, which are circumferentially spaced from each other and define a plurality of teeth 30 therebetween. One or more electrical conductors 31 are received in each of the plurality of slots 28 and are collectively configured to selectively generate a moving magnetic field acting on the rotor 14 to provide rotation of the rotor 14 in response to a current applied thereto. As shown in the example embodiment, the plurality of electrical conductors 31 may consist of one or more axially extending conductive rods 31. Alternatively, the plurality of electrical conductors 31 may consist of a plurality of windings wound or otherwise coupled to the plurality of teeth 30. At least a portion of one or more of the plurality of electrical conductors 31 in each of the plurality of slots 28 extends radially inward from the slot 28, substantially radially aligned with or through the inner surface 26 of the stator 12, such that the electrical conductor 31 at least partially defines an outer stator raceway 32. The plurality of electrical conductors 31 can thus individually define the outer stator raceway 32, or in combination with the inner surface 26 of the stator 12. In the arrangement where the outer stator raceway 32 is defined by the plurality of electrical conductors 31 and the inner surface 26 of the stator 12, the outer raceway 32 can be defined by a plurality of circumferentially alternating segments of the plurality of electrical conductors 31 and the inner surface 26 of the stator 12. Using the plurality of electrical conductors 31 to define the outer raceway 32 allows the plurality of electrical conductors 31 to not only provide current conduction to drive the rotor 14, but also to mechanically support the stator 12. This eliminates the need for a separate stator bearing sleeve to mechanically support the stator 12, thereby providing a simpler and more compact assembly and simplifying the manufacture and assembly of the motor 10. Figure 4 The rightmost slot 28 shows an arrangement in which the plurality of electrical conductors 31 extend radially inward from the stator 12, while Figure 4 The other plurality of slots 28 show various arrangements, wherein the plurality of electrical conductors 31 are substantially aligned with the stator 12. They can be used... Figure 4A Any combination of the plurality of electrical conductors 31 / plungers 28 shown.

[0021] refer to Figure 1 , 3 And 4, the rotor 14 consists of a rotor core 33 and a plurality of magnets 35, the plurality of magnets 35 being positioned around an outer surface of the rotor core 33. For example Figure 3As shown, the plurality of magnets 35 may each extend generally axially and may be arranged circumferentially spaced from each other. A radial outer perimeter 34 of the rotor 14 (along the plurality of magnets 35) defines an inner rotor raceway 36. If the inner raceway 32 and the outer raceway 36 come into contact with each other in response to radial movement between the rotor 10 and the stator 12, the outer raceway 32 and the inner raceway 36 are configured to act as a bearing by accommodating relative rotational movement between the stator 12 and the rotor 14. As will be discussed in further detail below, because the plurality of electrical conductors 31 partially define the outer raceway 32, they are configured not only to conduct a current to provide rotation of the rotor 14, but also to mechanically support the stator 12.

[0022] like Figure 4 and 4A As best shown, the plurality of electrical conductors 31 may consist of two or more layers 38, 40, 42 of the plurality of electrical conductors 31, which are stacked on top of each other in the radial direction. According to the example embodiment, the stacked layers 38, 40, 42 of the plurality of electrical conductors 31 include a top layer 38, an intermediate layer 40, and a bottom layer 42; however, more or fewer layers 38, 40, 42 may be used without departing from the scope of the subject matter disclosure. The stacked layers 38, 40, 42 of the plurality of electrical conductors 31 are assembled using any of a variety of techniques to provide a tight fit in the groove 28, such as interference compression fitting, thermal shrinkage fitting, and displacement / deformation rolling processes. Figure 4 As shown, each layer 38, 40, 42 of the plurality of electrical conductors 31 can be composed of multiple conductive rods; however, as Figure 4A As shown, each layer 38, 40, and 42 can also consist of a single conductive rod.

[0023] The top layer 38 defining the portion of the outer raceway 32 is composed of a material (e.g., copper-iron (CuFePCoSn) or copper-zinc (CuZn5)) with lower conductivity than the layers 40, 42 below it, to provide minimum resistance for the overall plurality of electrical conductors 31, while also providing a harder surface for the outer raceway 32. On the other hand, the intermediate and bottom layers 40, 42 are composed of a material (e.g., oxygen-carrying copper (Cu-ETP) or oxygen-free high conductivity copper (Cu-OF)) with higher conductivity than the top layer 38, to provide a sufficient magnetic field. Multiple copper alloys with very high conductivity are typically mechanically soft and not optimal for multiple bearing surfaces. Conversely, harder copper alloys more suitable for multiple bearing surfaces typically have lower conductivity, which would be detrimental to motor efficiency if used in a layer below the top layer. By using multiple high-conductivity / soft materials and multiple low-conductivity / hard materials at the multiple correct radial locations of the plurality of electrical conductors 31, a hard bearing surface and sufficient conductivity are provided. Figure 4 and 4A As shown, the structure of the stacked layers 38, 40, 42 of the plurality of electrical conductors 31 achieves mechanical rigidity by arranging the layers 38, 40, 42 of the plurality of electrical conductors 31 with a plurality of flat surfaces 45, the plurality of flat surfaces 45 being stacked on top of each other and having a minimum insulating layer between them. More specifically, each of the plurality of layers of electrical conductors 38, 40, 42 includes at least one substantially flat bottom and / or top surface 45, wherein the plurality of substantially flat surfaces 45 overlap and engage with each other in the groove 28.

[0024] like Figure 4 As further shown, according to one embodiment, the outer raceway 32 may present a substantially smooth surface in the circumferential direction. This may be provided individually by the plurality of electrical conductors 31 or in combination with the plurality of teeth 30. As part of this arrangement, a polymer coating 47 may extend on the first surface of the plurality of electrical conductors 31 in each of the plurality of grooves 28 and the stator 12 to define the substantially smooth surface. The smooth surface may be provided around a portion or the entire circumference of the outer raceway 32.

[0025] like Figure 4 As further shown, one or more of the plurality of electrical conductors 31 may define a cooling channel 43, which may receive coolant from the high-voltage source 21 or the low-voltage source 24 to cool the plurality of electrical conductors 31. Any number of plurality of cooling channels 43 may be provided on any number of plurality of electrical conductors 31.

[0026] The plurality of stator laminations 25 are assembled and held with sufficient multiple compression forces and seals to prevent lubricating oil from seeping into the plurality of laminations 25. Various technologies / features providing such compression forces and seals include:

[0027] • The overall multiple structures of the plurality of laminations 25 of the core 23 of the stator 12 are compressed. For example, a housing can be retracted to fit on an outer diameter of the stator 12 and may include a plurality of end plates held together by a plurality of bolts or other fasteners.

[0028] This secures the plurality of stacked pieces 25 in place.

[0029] • The surfaces of the plurality of laminations 25 of the core 23 of the stator 12 are welded / joined. For example, the outer diameter and / or inner diameter of the stator 12 can be welded to ensure the integrity of the plurality of stacked laminations 25 of the stator 12. Alternatively, an outer or inner diameter of the stator 12 can be joined with a structural adhesive or molding polymer layer to ensure the integrity of the stator 12 and seal the stator 12 to prevent oil ingress.

[0030] • Insulation of the plurality of laminations 25 of the stator 12 having sealing / joining characteristics. More specifically, the plurality of laminations 25 of the stator 12 may be electrically insulated from each other using a material such as varnish.

[0031] During assembly, after the stacked layers 38, 40, 42 of the plurality of electrical conductors 31 are positioned within the plurality of grooves 28, the outer raceway 32 may optionally be machined or finished to produce a smooth polish suitable for the application of interest. The inner raceway 36 and outer raceway 32 may include multiple features (e.g., close-tolerance area, pocket area, etc.) that improve and retain the film of lubricant 18. This may include multiple bearing structures, such as those known for combining multiple journal bearings. Furthermore, the multiple assembly structures of the stator 12 may also be used to form multiple bearing surface features along the outer raceway 36, for example:

[0032] • Multiple bearing hydrodynamic, tight clearance regions (see, for example) Figure 4 (37) of the densely packed void region.

[0033] • Multiple bearing hydrostatic cavitation areas:

[0034] One or more of the plurality of electrical conductors 31 may be located slightly radially outward of the plurality of teeth 30 (i.e., the plurality of electrical conductors 31 may be slightly shallower than the plurality of teeth 30).

[0035] The multiple edges of the multiple slots 28 may be formed by multiple laminations or multiple copper windings, which extend radially inward over a greater extent than the multiple teeth 30 of the stator 12.

[0036] See, for example Figure 4 The perimeter of the plurality of copper laminations 39 shown.

[0037] olike Figure 2 As shown, a plurality of drainage channels 41 may be formed along an inner diameter of the stator 12, and a plurality of hydrodynamic recesses 43 may be formed along an inner diameter of the plurality of electrical conductors 31.

[0038] • Multiple bearing hydrodynamic zones conforming to specifications can provide tight clearance release under various high-speed, high-dynamic-pressure conditions; and

[0039] • Multiple bearing hydrodynamic regions conforming to specifications provide load sharing under multiple impact loads and high acceleration conditions (creating multiple conditions favorable for the extrusion of multiple films). More specifically, the multiple closely spaced bearing hydrodynamic regions where the stiffness of the multiple stator laminations and / or multiple copper conductors 31 can be reduced or "compliant" allow the stator 12 to deform slightly under multiple heavy impact loads where the rotor presses heavily on the stator 12, thereby increasing the contact between the rotor 10 and the stator 12 in the aforementioned regions.

[0040] In view of the foregoing, the stacked layers 38, 40, 42 of the plurality of electrical conductors 31 arranged circumferentially between the plurality of teeth 30 of the stator 12 are arranged in such a manner as follows:

[0041] • Provides rigid, compressible mechanical support to compensate for multiple loads applied to the outer raceway 26.

[0042] • The plurality of teeth 30 provide circumferential electrical insulation between the plurality of electrical conductors 31.

[0043] • Provides heat conduction to the core 23 of the stator 12 for cooling purposes.

[0044] Provide mechanical support for the plurality of electrical conductors 31 when they are subjected to multiple magnetic forces and multiple mechanical vibrations.

[0045] • Multiple cooling channels 43 can be installed in the tank 28 as needed (e.g., Figure 4 (As shown).

[0046] The stator 12 provides mechanical support for the core 23 and the plurality of electrical conductors 31 under various conditions of different thermal expansion of the plurality of laminations of the core 23 and electrical conductors 31 structure. For example, the tapered shape of the plurality of slots 28 presses the plurality of electrical conductors 31 downward toward the radial outer surface 24 of the core 23, which maintains a certain diameter of the outer raceway 32.

[0047] • Various different materials are provided in the lower layers 40, 42, which are mainly used to provide electrical conductivity, while the top layer 38 of the multiple electrical conductors 31 mainly serves as part of the inner raceway 36.

[0048] The structure of the stator 12 may also include multiple features supporting other aspects of motor operation, such as:

[0049] • Multiple bearing lubricant supply channels 20.

[0050] • Multiple bearing lubricant supply channels 20 have multiple capillary orifice areas to restrict lubricant flow.

[0051] • The bearing area is cooled by oil that reaches the stator 12 through the supply channel 20.

[0052] • Proximity sensing of rotor 14 / stator 12 with multiple capacitance bridge measurements.

[0053] • Proximity sensing of rotor 14 / stator 12 with variable reluctance or Hall effect magnetic force sensing.

[0054] Obviously, based on the foregoing teachings, many modifications and variations of the invention are possible, and it can be practiced in ways different from those specifically described within the scope of the appended claims. These preceding statements should be construed as covering any combination of novel elements that exercise the utility of the invention.

Claims

1. An electric motor, characterized in that: The electric motor includes: An annular stator extending about an axis and presenting a first radial surface; A rotor extending about the axis and rotatable relative to the stator, and presenting a second radial surface defining a rotor raceway, the rotor raceway being spaced apart from the first radial surface of the stator to define a gap therebetween for accommodating a lubricant. The first radial surface of the stator defines a plurality of slots spaced apart from each other to define a plurality of spaced teeth between the plurality of slots; At least one electrical conductor, disposed in each of the plurality of slots and configured to selectively generate a moving magnetic field to act on the rotor to provide rotational motion of the rotor in response to a current applied to the at least one electrical conductor; and A portion of at least one electrical conductor in each of the plurality of slots substantially extends radially aligned with or beyond the first radial surface of the stator to at least partially define a stator raceway of the stator for engaging the rotor raceway of the rotor during relative movement between the rotor and the stator, serving as a bearing while also generating the moving magnetic field. The at least one electrical conductor in each of the plurality of slots includes a plurality of electrical conductors in each of the plurality of slots, and wherein the plurality of electrical conductors in each of the plurality of slots includes at least one first electrical conductor, the first electrical conductor being radially stacked on a second electrical conductor, and wherein the first electrical conductor is made of a material that is harder and less conductive than the second electrical conductor.

2. The electric motor as described in claim 1, characterized in that: The first electrical conductor is composed of one of copper-iron and copper-zinc materials, and the second electrical conductor is composed of one of oxygen-containing copper and oxygen-free high-conductivity copper.

3. The electric motor as described in claim 1, characterized in that: Each of the plurality of slots further includes a third electrical conductor radially below the second electrical conductor, and wherein the first electrical conductor is made of a material that is harder and less conductive than the third electrical conductor.

4. The electric motor as described in claim 1, characterized in that: The first and second electrical conductors in each of the plurality of slots are assembled in the slot using at least one of an interference compression fit, a thermal shrinkage fit, and a displacement / deformation rolling process to provide a tight fit between the first and second electrical conductors in the slot.

5. The electric motor as described in claim 1, characterized in that: Each of the first and second electrical conductors in each of the plurality of slots defines at least one substantially flat surface, and wherein the plurality of substantially flat surfaces of the first and second electrical conductors overlap and engage with each other in the slots to provide mechanical stiffness and minimize insulation between the first and second electrical conductors.

6. The electric motor as described in claim 1, characterized in that: At least one electrical conductor in each of the plurality of slots is an axially extending conductive rod.

7. The electric motor as described in claim 1, characterized in that: The at least one electrical conductor in each of the plurality of slots is composed of a plurality of windings.

8. The electric motor as described in claim 1, characterized in that: At least one electrical conductor in each of the plurality of slots extends radially inward through the first radial surface of the stator.

9. The electric motor as described in claim 1, characterized in that: At least one electrical conductor in each of the plurality of slots extends to be radially aligned with the first radial surface of the stator, such that the stator raceway is defined by a plurality of circumferentially alternating segments of the plurality of electrical conductors and the first radial surface of the stator.

10. The electric motor as claimed in claim 1, characterized in that: The stator raceway presents a substantially smooth surface in a circumferential direction.

11. The electric motor as claimed in claim 10, characterized in that: A polymer coating extends on the first radial surface of the stator and the at least one electrical conductor in each of the plurality of grooves to define the substantially smooth surface of the stator raceway.

12. The electric motor as claimed in claim 1, characterized in that: The stator defines at least one channel in fluid communication with the gap for delivering a lubricant into the gap.

13. The electric motor as claimed in claim 1, characterized in that: A bearing sleeve is located radially within the gap between the stator and the rotor.

14. An electric motor, characterized in that: The electric motor includes: An annular stator extending about an axis and presenting a first radial surface; A rotor extending about the axis and rotatable relative to the stator, and presenting a second radial surface defining a rotor raceway, the rotor raceway being spaced apart from the first radial surface of the stator to define a gap therebetween for accommodating a lubricant. The first radial surface of the stator defines a plurality of slots spaced apart from each other to define a plurality of spaced teeth between the plurality of slots; At least one electrical conductor, disposed in each of the plurality of slots and configured to selectively generate a moving magnetic field to act on the rotor to provide rotational motion of the rotor in response to a current applied to the at least one electrical conductor; and A portion of at least one electrical conductor in each of the plurality of slots substantially extends radially aligned with or beyond the first radial surface of the stator to at least partially define a stator raceway of the stator for engaging the rotor raceway of the rotor during relative movement between the rotor and the stator, serving as a bearing while also generating the moving magnetic field. The at least one electrical conductor in each of the plurality of slots includes a plurality of electrical conductors in each of the plurality of slots, and wherein the plurality of electrical conductors in each of the plurality of slots includes at least one first electrical conductor, the first electrical conductor being radially stacked on a second electrical conductor; Each of the first and second electrical conductors in each of the plurality of slots defines at least one substantially flat surface, and wherein the plurality of substantially flat surfaces of the first and second electrical conductors overlap and engage with each other in the slots to provide mechanical stiffness and minimize insulation of the first and second electrical conductors.

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