Variable cross-section conductor to reduce axial flux, radial flux, and alternating current loss of skewed motors

Abstract

The invention relates to a variable cross-section conductor for reducing axial flux, radial flux and alternating current loss of skewed motors. A vehicle electric motor system includes an electric motor having a rotor. A plurality of windings are respectively mounted on the rotor and have coil conductors including a plurality of conductor elements. The continuous conductor elements have different widths.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to electric motors and electrical conductors for electric motors. BACKGROUND

[0002] For axial flux motors (AFM) including electric motors used in vehicles, copper conductor losses can be artificially split between a direct current (DC) portion related to the size of the copper conductor and an alternating current (AC) portion due to non-uniformity of current density distribution. The AC portion is produced by the time-varying magnetic field that passes through the copper conductor and is produced by two sources. The first source defines the magnetic field produced by the skin effect of the conductor itself. The second source defines the magnetic field produced by other sources of magnetic field including proximity effect. In electric motors, these effects add up together producing a strong variable magnetic field that passes through the motor conductor close to the air gap, thus producing AC production losses.

[0003] Therefore, while the current systems and methods for reducing AC losses in electric motors achieve their intended purpose, there is still a need for a new and improved system and method for reducing AC losses in electric motors. SUMMARY

[0004] According to several aspects, a vehicle electric motor system includes an electric motor having a rotor. A plurality of windings mounted on the rotor respectively have a coil conductor including a plurality of conductor elements. A width of each conductor element of the plurality of conductor elements is different.

[0005] In another aspect of the present disclosure, the electric motor defines an axial flux motor having a centrally located stator.

[0006] In another aspect of the present disclosure, the conductor elements include a first conductor element having a first width, a second conductor element having a second width greater than the first width, a third conductor element having a third width greater than the second width, a fourth conductor element having a fourth width substantially equal to the third width, a fifth conductor element having a fifth width substantially equal to the second width, and a sixth conductor element having a sixth width substantially equal to the first width.

[0007] In another aspect of the disclosure, the conductor elements include: a first conductor element having a first width; a second conductor element having a second width greater than the first width; a third conductor element having a third width substantially equal to the second width; a fourth conductor element having a fourth width substantially equal to the second width and the third width; a fifth conductor element having a fifth width substantially equal to the second width, the third width, and the fourth width; and a sixth conductor element having a sixth width substantially equal to the first width.

[0008] In another aspect of the disclosure, the rotor defines a first rotor having an axial skew and a second rotor having an axial skew, where the first rotor is positioned proximate a d-axis of the electric motor and the second rotor is positioned proximate a q-axis of the electric motor.

[0009] In another aspect of the disclosure, the conductor elements include: a first conductor element having a first width; a second conductor element having a second width greater than the first width; a third conductor element having a third width substantially equal to the second width; a fourth conductor element having a fourth width substantially equal to the second width; a fifth conductor element having a fifth width substantially equal to the second width; and a sixth conductor element having a sixth width less than the first width.

[0010] In another aspect of the disclosure, the plurality of conductor elements includes: a first conductor element having a first width; a second conductor element having a second width greater than the first width; a third conductor element having a third width greater than the second width; a fourth conductor element having a fourth width less than the third width and greater than the second width; a fifth conductor element having a fifth width less than the second width and greater than the first width; and a sixth conductor element having a sixth width less than the first width.

[0011] In another aspect of the disclosure, the electric motor defines a radial flux electric motor having an axial rotor skew.

[0012] In another aspect of the disclosure, the electric motor defines a radial flux electric motor and the rotor defines a dual rotor.

[0013] In another aspect of the disclosure, the electric motor defines a radial flux electric motor having a stator defining a dual stator.

[0014] According to several aspects, a vehicle electric motor system includes an electric motor having at least one rotor and at least one stator. A plurality of permanent magnets are located on the at least one stator. A plurality of windings are respectively mounted on the at least one rotor, the plurality of windings having a coil conductor comprising a plurality of conductor elements, each of the plurality of conductor elements having a different width. The rotor includes an axial rotor skew.

[0015] In another aspect of the disclosure, the electric motor defines a radial flux electric motor.

[0016] In another aspect of the disclosure, the at least one rotor defines a first rotor and a second rotor; and wherein the at least one stator defines a first stator and a second stator.

[0017] In another aspect of the disclosure, a first air gap is located between the first rotor and the first stator, a second air gap is located between the second rotor and the second stator, the first air gap and the second air gap together defining a dual air gap.

[0018] In another aspect of the disclosure, at least one of the plurality of conductor elements is positioned proximate to the first rotor and the second rotor and skews the load toward a d-axis of the radial flux electric motor and has a cross-sectional variation in an axial direction; at least one of the plurality of conductor elements is shaped to have a smaller cross-section compared to each of the plurality of conductor elements positioned proximate to a q-axis and skews the load toward a q-axis of the radial flux electric motor. At least one of the plurality of conductor elements includes a minimum cross-sectional area having a first thickness approximately at a midpoint of the at least one of the plurality of conductor elements and opposing ends respectively positioned opposite the minimum cross-sectional area having a conductor element second thickness greater than the first thickness.

[0019] In another aspect of the disclosure, at least one of the plurality of conductor elements positioned proximate to the first rotor and the second rotor and skewed to a d-axis of the radial flux electric motor has a cross-sectional variation in an axial direction of the electric motor. At least one of the plurality of conductor elements includes a continuous tapered body in the axial direction.

[0020] In another aspect of the disclosure, the electric motor defines an axial flux electric motor having an axial rotor skew.

[0021] According to several aspects, a method for reducing AC losses of a vehicle electric motor, comprising: producing an electric motor, including mounting a plurality of windings on a first stator and an opposing second stator defining a dual stator; positioning the first stator and the second stator between a first rotor and a second rotor defining a dual rotor; positioning a first air gap between the first rotor and the first stator and a second air gap between the second rotor and the second stator, the first air gap and the second air gap together defining a dual air gap; positioning a plurality of permanent magnets on the first stator and the second stator; mounting a plurality of windings on the first rotor and the second rotor; configuring individual coil conductors for each winding of the plurality of windings having a plurality of conductor elements; and varying a width of each conductor element of the plurality of conductor elements.

[0022] In another aspect of the disclosure, the method further includes configuring the electric motor as an axial flux electric motor, wherein the first rotor and the second rotor have an axial skew.

[0023] In another aspect of the disclosure, the method further includes configuring the electric motor as a radial flux electric motor, wherein the first rotor and the second rotor have an axial skew.

[0024] Further areas of application will become apparent from the description provided herein. It should be understood that these descriptions and specific examples are intended to be illustrative only and are not intended to limit the scope of the disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0025] The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the disclosure in any way.

[0026] Figure 1 is a left perspective view of a vehicle having a vehicle electric motor system according to exemplary aspects.

[0027] Figure 2 is a cross-sectional side elevational view of an axial flux electric motor of the vehicle electric motor system of Figure 1

[0028] Figure 3 is a cross-sectional side elevational view of an axial flux electric motor of the vehicle electric motor system of Figure 1

[0029] Figure 4 is a cross-sectional front elevational view taken along section 4 of Figure 3

[0030] Figure 5 is a cross-sectional front elevational view taken along section 5 of Figure 2

[0031] Figure 6 is a cross-sectional front elevational view taken along section 5 of Figure 4 ​​​​a cross-sectional side elevation view of a modified axial flux motor having a six-turn winding with a gradually asymmetric cross-section;

[0032] Figure 7 is based on Figure 4 a cross-sectional side elevation view of a modified axial flux motor having a six-turn winding with an incrementally asymmetric cross-section;

[0033] Figure 8 is a front elevation view of an interior permanent magnet motor with skewed radial flux having a vehicle motor system according to an exemplary aspect;

[0034] Figure 9 It is along Figure 8 a cross-sectional side elevation view of the conductor taken at section 9;

[0035] Figure 10 is a front elevation view of a radial flux induction motor with skew having a vehicle motor system according to an exemplary aspect;

[0036] Figure 11 It is along Figure 10 A cross-sectional side elevation view of a conductor taken at section 11;

[0037] Figure 12 It is skewed Figure 11 a top view of a rotor portion of an axial flux motor of a vehicle motor system; and

[0038] Figure 13 yes Figure 12 A top view of the multiple conductors of the windings of an axial flux motor. DETAILED DESCRIPTION

[0039] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

[0040] Reference Figure 1 , a vehicle motor system 10 is provided for a vehicle 12 powered by at least one axial flux electric motor 14. The axial flux electric motor 14 receives power from a battery pack 16 that provides power for propulsion and operation of multiple systems of the vehicle 12. The vehicle 12 may define a sedan, a sport utility vehicle, a van, a truck, or an autonomous vehicle that collectively define a battery electric vehicle. The battery pack 16 may include a plurality of battery cells 18 that each generate electrical power. The vehicle 12 may also include an additional power source including a gasoline engine or a hydrogen fuel cell to provide a portion of the battery charging current or a portion of the propulsion force to assist the battery pack 16 in powering the vehicle 12. According to several aspects, the battery cells 18 may include any configuration of battery cell geometries, including cylindrical battery cells and / or rectangular battery cells, with the cylindrical battery cell geometry shown for illustration only.

[0041] Referring to Figure 2 and referring again to Figure 1 , according to several aspects, a portion of the axial flux motor 20 can be provided with multiple windings including, for example, a first winding 22, a second winding 24, and a third winding 26, where the windings each include six turns of winding. The windings are mounted on a common first stator 28 and an opposing second stator 30 that define a dual stator between a first rotor 32 and a second rotor 34 that define a dual rotor. The first rotor 32 and the second rotor 34 have surface mounted permanent magnets and both rotate coaxially with respect to a longitudinal rotational axis 36. A first air gap 38 is located between the first rotor 32 and the first stator 28, and a second air gap 40 is located between the second rotor 34 and the second stator 30, the first air gap 38 and the second air gap 40 together defining a dual air gap. The use of a dual air gap in a disc motor can effectively eliminate unwanted axial forces between the stator and the rotor, which can enable higher power density of the motor.

[0042] Referring to Figure 3 and referring again to Figure 2 , the axial flux motor 42 is modified from the axial flux motor 20 to include multiple layers of wire 44 in each turn of the six turns of winding 46. The multiple layers of wire 44 reduce alternating current (AC) losses of the multiple windings.

[0043] Referring to Figure 4 and referring again to Figures 1 to 3, each winding (e.g., the illustrated first winding 22) can be provided with a coil conductor that includes different widths or cross-sections between different layers or portions of the conductor of the first winding 22. According to aspects, the first winding 22 can include conductor elements that all have a common height but vary in cross-section, including varying widths, such as a first conductor element 48 having a first width or narrowest width of the first winding conductor and a second conductor element 50 proximate the first conductor element 48 that has a width greater than the cross-section of the first conductor element 48. A third conductor element 52 positioned proximate the second conductor element 50 has a width greater than the width of the second conductor element 50 and substantially equal to a width of a fourth conductor element 54 positioned proximate the third conductor element 52. A fifth conductor element 56 positioned proximate the fourth conductor element 54 has a width substantially equal to the width of the second conductor element 50, and a sixth conductor element 58 positioned proximate the fifth conductor element 56 has a width substantially equal to the width of the first conductor element 48. Advantages provided by the first winding 22 include balancing AC and direct current (DC) loss effects by positioning those of the conductor elements having the smallest widths (e.g., the first conductor element 48 and the sixth conductor element 58) closest to the first air gap 38 and the second air gap 40, and positioning those having the greatest widths (e.g., the third conductor element 52 and the fourth conductor element 54) closest to the center of the grouping of conductor elements.

[0044] Referring to Figure 5 and again to Figure 4 , the winding 60 is modified from the first winding 22 to provide conductor elements (e.g., the first conductor element 62 and the sixth conductor element 72) that generally have the smallest width of the conductor elements at opposite ends of the winding 60. The second conductor element 64, the third conductor element 66, the fourth conductor element 68, and the fifth conductor element 70 each have a width equal to one another and greater than the widths of the first conductor element 62 and the sixth conductor element 72. Similar to the first winding 22, AC and direct current (DC) loss effects are balanced by positioning those of the conductor elements having the smallest widths (e.g., the first conductor element 62 and the sixth conductor element 72) closest to the first air gap 38 and the second air gap 40, and positioning those having the greatest widths (e.g., the second conductor element 64, the third conductor element 66, the fourth conductor element 68, and the fifth conductor element 70) closest to the center of the grouping of conductor elements.

[0045] Referring to Figure 6 and again to Figure 4 and Figure 5, the winding 74 is modified from the first winding 22 and the winding 60 to provide conductor elements having asymmetric widths or cross-sections, and conductor elements at opposite ends that define the minimum width of all the conductor elements. The conductor element asymmetric widths or cross-sections are provided with winding skew so that, in the event of a motor load, a portion of the load is skewed toward the motor d-axis and a portion is skewed toward the motor q-axis. According to aspects, the sixth conductor element 86 has a width that is less than the width of the first conductor element 76. The fifth conductor element 84 has a width that is greater than the width of the first conductor element 76 but less than the width of the second conductor element 78. The fourth conductor element 82 has a width that is greater than the width of the second conductor element 78, and thus greater than the width of the fifth conductor element 84, but less than the width of the third conductor element 80, which has the greatest width of the six conductor elements of the winding 74. The above references Figure 4 The air gap, AC and DC loss effects advantages described for the first winding 22 are likewise provided by the winding 74.

[0046] Referring to Figure 7 and again to Figures 4 to 6 , the winding 88 is modified from the first winding 22, the winding 60 and the winding 74 to provide conductor elements having asymmetric widths or cross-sections, and conductor elements at opposite ends that define the minimum width of all the conductor elements. As noted above with respect to Figure 6 , the conductor element asymmetric widths or cross-sections are provided with winding skew so that, in the event of a motor load, a portion of the load is skewed toward the motor d-axis and a portion is skewed toward the motor q-axis. According to aspects, the sixth conductor element 100 has a width that is less than the width of the first conductor element 90. The second conductor element 92, the third conductor element 94, the fourth conductor element 96 and the fifth conductor element 98 each have a width that is equal to one another and greater than the width of the first conductor element 90 and the sixth conductor element 100. The above references Figure 4 The air gap, AC and DC loss effects advantages described for the first winding 22 are likewise provided by the winding 88.

[0047] Referring to Figure 8 and again to Figures 1 to 7 , the interior permanent magnet radial flux motor 102 includes skew to maintain AC effects along the axial length of the radial flux motor 102. The first rotor 104 is axially skewed relative to the second rotor 106 to a similar extent, with the stator 108 located between the first rotor 104 and the second rotor 106. The motor rotor slots or stator slots can be skewed by a predetermined angle to provide alternating harmonics of the same polarity. Discontinuities on the rotor and stator surfaces break the motor's magnetic flux path as the rotor rotates. The flux path variations create harmonics that affect the motor performance. The difference between the number of stator slots and the number of rotor slots has a significant impact on the harmonics. One of the purposes of providing rotor skew is to reduce the magnetic noise.

[0048] Referring now to Figure 9 and referring again to Figure 8 , the exemplary conductor element 110, positioned proximate to the first rotor 104 and the second rotor 106 and tilted to the d-axis of the radial flux motor 102, has a cross-sectional variation in the axial direction 112. The conductor element 110 is shaped to have a smaller cross-section and to have a minimum cross-sectional area 114, with a thickness 116 approximately at the midpoint of the conductor element 110, as compared to conductor elements positioned closer to the q-axis of the conductor element 110. The opposite ends 118 and 120 have a conductor element maximum thickness 122 that is greater than the thickness 116. This cross-sectional thickness variation of the small cross-sectional area thickness 116 provides a variety of benefits, including locally increasing the axial slot fill factor in the conductor element 110, maintaining the slot fill factor in the remainder of the conductor element 110, while expanding one of the most deeply embedded conductor elements of the radial flux motor 102, which acts to reduce the DC losses of the radial flux motor 102, and providing a smaller slot area to increase the yoke size, while reducing the outer diameter of the conductor element 110.

[0049] Referring now to Figure 10 and referring again to Figure 8 and Figure 9 , the radial flux induction motor 124 is also provided with a skew to maintain the AC effect along the axial length of the induction motor 124. The rotor 126 is skewed over the entire length of the rotor.

[0050] Referring now to Figure 11 and referring again to Figure 10 , the exemplary conductor element 128 is modified from the conductor element 110 to provide a continuously tapered body along the axial direction 130. The conductor element 128 is narrowest at the first conductor end 132 and widest at the second conductor end 134. This cross-sectional thickness variation of the conductor element 128 provides the same benefits as the conductor element 110 described above with reference to Figure 9 .

[0051] Referring now to Figure 12 and referring again to Figure 8 and Figure 10 , skewing can also be incorporated into axial flux motors. Portions of the rotor assembly 136 are overlaid to show the position of the first conductor assembly 138 and the second conductor assembly 140, where the motor's conductor assembly positioned closest to the rotor portion tilted to the d-axis has a smaller cross-section as compared to the conductor assembly positioned closest to the rotor portion tilted to the motor's q-axis. As shown and described in greater detail with reference to Figure 13 , the cross-section of the conductor assembly varies from the inner diameter (ID) to the outer diameter (OD) to help reduce the AC effect or losses.

[0052] Referring now to Figure 13Referring again to Figure 12 The cross-section of the conductor assembly 142 varies from the inner diameter (ID) 144 to the outer diameter (OD) 146 in the radial direction 148. The first conductor element cross-section 150 has a first conductor element first end 152 proximate to a permanent magnet (PM) block 154 pointing in the d-axis and a first conductor element second end 156 proximate to a permanent magnet (PM) block 158. The second conductor element cross-section 160 has a second conductor element first end 162 proximate to the permanent magnet (PM) block 154 that is wider than the first conductor element first end 152 and a second conductor element second end 164 proximate to the permanent magnet (PM) block 158 that is substantially equal in width to the first conductor element second end 156. The third conductor element cross-section 166 has a substantially equal width across its length proximate to the PM block 154 and the PM block 158 that is wider than the second conductor element first end 162.

[0053] The fourth conductor element cross-section 170 is substantially equal in width dimension across its length proximate to the PM block 154 and the PM block 158 to the width of the third conductor element cross-section 166. The fifth conductor element cross-section 174 is substantially equal in dimension to the second conductor element cross-section 160. The sixth conductor element cross-section 180 is substantially equal in dimension to the first conductor element cross-section 150. Thus, in addition to varying from the inner diameter (ID) to the outer diameter (OD), the width of the various conductor element cross-sections varies with respect to the radial direction 148 and in an axial direction 186 that is parallel to the axis of the motor, which helps to reduce the AC effects or losses.

[0054] The vehicle motor system 10 of the present disclosure provides a number of advantages. These advantages include: improved high frequency motor efficiency; increased slot fill factor; conductor element cross-section asymmetry can be used to balance the asymmetry of the AC effects due to the introduction of motor skew; and the conductor element cross-section geometry can be optimized for uniformity at a predetermined operating point.

Claims

1. A vehicle electric motor system, comprising: an electric motor having a rotor; a plurality of windings mounted on the rotor, respectively, the plurality of windings having a coil conductor comprising a plurality of conductor elements; and a width of each of the plurality of conductor elements is different.

2. The vehicle electric motor system of claim 1, wherein the electric motor defines an axial flux electric motor having a centrally located stator.

3. The vehicle electric motor system of claim 2, wherein the conductor elements comprise: a first conductor element having a first width; a second conductor element having a second width greater than the first width; a third conductor element having a third width greater than the second width; a fourth conductor element having a fourth width substantially equal to the third width; a fifth conductor element having a fifth width substantially equal to the second width; and a sixth conductor element having a sixth width substantially equal to the first width. the conductor elements comprise:

4. The vehicle electric motor system of claim 2, wherein, a first conductor element having a first width; a second conductor element having a second width greater than the first width; a third conductor element having a third width substantially equal to the second width; a fourth conductor element having a fourth width substantially equal to the second and third widths; a fifth conductor element having a fifth width substantially equal to the second, third, and fourth widths; and a sixth conductor element having a sixth width substantially equal to the first width.

5. The vehicle electric motor system of claim 2, wherein the rotor defines a first rotor having an axial skew and a second rotor having an axial skew, the first rotor positioned proximate a d-axis of the electric motor and the second rotor positioned proximate a q-axis of the electric motor.

6. The vehicle electric motor system of claim 5, wherein the conductor elements comprise: a first conductor element having a first width; a second conductor element having a second width greater than the first width; a third conductor element having a third width substantially equal to the second width; a fourth conductor element having a fourth width substantially equal to the second width; a fifth conductor element having a fifth width substantially equal to the second width; and a sixth conductor element having a sixth width less than the first width.

7. The vehicle electric motor system of claim 5, wherein the conductor elements comprise: a first conductor element having a first width; a second conductor element having a second width greater than the first width; a third conductor element having a third width greater than the second width; a fourth conductor element having a fourth width substantially equal to the second and third widths; a fifth conductor element having a fifth width substantially equal to the second, third, and fourth widths; and a sixth conductor element having a sixth width substantially equal to the first width. a fourth conductor element having a fourth width that is less than the third width and greater than the second width; a fifth conductor element having a fifth width that is less than the second width and greater than the first width; and a sixth conductor element having a sixth width that is less than the first width.

8. The vehicle motor system of claim 1, wherein the motor defines a radial flux motor having axial rotor skew.

9. The vehicle motor system of claim 1, wherein the motor defines a radial flux motor and the rotor defines a dual rotor.

10. The vehicle motor system of claim 1, wherein the motor defines a radial flux motor having a stator that defines a dual stator. ​

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