Selective permeability rotor sleeve for built-in permanent magnet motor

Abstract

A radial flux electric motor includes a stator having a radially inner stator surface and a stator winding disposed on the radially inner stator surface. The motor also includes a rotor mounted inside the stator and configured to rotate relative to the stator about an axis. The rotor has a rotor core defined by a rotor outer surface and includes a magnetic pole configured to generate a magnetic flux and define a magnetic flux leakage region. The motor additionally includes a selective permeability sleeve disposed circumferentially on the rotor and secured to an outer surface of the rotor such that an air gap is established between the sleeve and the stator. The sleeve provides reinforcement for the rotor core and magnetic poles and includes regions of relatively high permeability and regions of relatively low permeability alternating around the rotor exterior surface. A region of relatively low permeability is disposed radially outward and opposite the magnetic flux leakage region to control magnetic flux distribution in the motor.

Description

Technical Field

[0001] introduction

[0002] The present disclosure relates to a selective permeability sleeve for a rotor of an interior permanent magnet electric machine. Background Art

[0003] An electric motor is an electrical machine that converts electrical energy into mechanical energy. Electric motors can be configured as either alternating current (AC) or direct current (DC) types. The operation of an electric motor is based on the electromagnetic interaction between permanent magnets and the magnetic field generated by the selectively energized coils of the motor. Based on the direction of the magnetic field, electric motors are generally divided into two categories - axial flux motors and radial flux motors.

[0004] An interior permanent magnet (IPM) electric motor is an AC synchronous brushless motor in which permanent magnets are encased in the rotor core. IPM motors are typically characterized by a favorable ratio of output torque relative to the physical size of the motor, and reduced input voltage. Electric motor torque is typically generated by the flux linkage between the field of the rotor permanent magnets and the electromagnetic field of the stator. IPM motors can augment such permanent magnet torque with reluctance torque that allows the use of thinner rotor magnets. Summary of the invention

[0005] A radial flux electric motor includes a stator having a radially inner stator surface and a stator winding disposed on the radially inner stator surface. The electric motor also includes a rotor mounted inside the stator and configured to rotate relative to the stator about a rotation axis. The rotor has a rotor core defined by a rotor outer surface and includes magnetic poles configured to generate magnetic flux and define magnetic flux leakage zones. The electric motor additionally includes a selective permeability sleeve circumferentially disposed on the rotor and fixed to the rotor outer surface, thereby establishing an air gap between the sleeve and the stator. The selective permeability sleeve provides reinforcement for the rotor core and the magnetic poles and includes relatively high permeability regions and relatively low permeability regions alternating around the rotor outer surface. The relatively low permeability regions are disposed radially outward and across from the flux leakage zones to control the magnetic flux distribution in the electric motor.

[0006] Each region of relatively high magnetic permeability may be comprised of a ferromagnetic material and each region of relatively low magnetic permeability comprised of a paramagnetic material.

[0007] The ferromagnetic material may be ferrous steel, and the paramagnetic material may be austenitic steel.

[0008] The radial flux electric motor may additionally include a dielectric layer. In such embodiments, each relatively high permeability region may be electrically insulated from each relatively low permeability region by the dielectric layer.

[0009] Each of the regions of relatively low magnetic permeability may have a relative magnetic permeability of less than ten.

[0010] The selective permeability sleeve may have a yield strength equal to or greater than 300 MPa and a Young's modulus equal to or greater than 150 GPa.

[0011] Each magnetic pole may include at least one rotor pocket having at least one permanent magnet enclosed or disposed in the rotor pocket and configured to generate magnetic flux. In such embodiments, each rotor pocket may have at least a portion thereof disposed adjacent to an outer surface of the rotor and define a corresponding magnetic flux leakage region.

[0012] The rotor core may include a structural bridge extending from at least one of the rotor pockets to the rotor outer surface. In such embodiments, one of the regions of relatively low magnetic permeability may be arranged radially outwardly and opposite the structural bridge.

[0013] Each magnetic pole may include adjacent permanent magnets arranged in corresponding adjacent rotor pockets. The rotor core may also include a structural web positioned between adjacent rotor pockets. In such embodiments, one of the regions of relatively low magnetic permeability may be arranged radially outward and opposite the structural web.

[0014] Each relatively high permeability region may be configured to facilitate magnetic flux from at least one magnetic pole through the air gap to the stator windings.

[0015] Each region of relatively low magnetic permeability may span an arc having a length at least twice the length of the air gap.

[0016] The number of regions of relatively low magnetic permeability may be at least equal to the number of magnetic poles.

[0017] Radial flux electric motors can be either interior permanent magnet (IPM) or surface mounted permanent magnet (SPM) synchronous motors.

[0018] A motor vehicle having a radial flux electric motor of the type described above is also disclosed.

[0019] The present invention also discloses the following technical solutions:

[0020] 1. A radial flux electric motor comprising:

[0021] a stator having a radially inner stator surface and a stator winding disposed on the radially inner stator surface;

[0022] a rotor mounted inside the stator and configured to rotate relative to the stator about a rotation axis, wherein the rotor has a rotor core defined by a rotor exterior surface and includes magnetic poles configured to generate magnetic flux and define magnetic flux leakage regions; and

[0023] A selective permeability sleeve is circumferentially disposed on the rotor and secured to the rotor outer surface to establish an air gap between the sleeve and the stator, wherein the sleeve provides reinforcement for the rotor core and the magnetic poles and includes relatively high permeability regions and relatively low permeability regions alternating around the rotor outer surface such that the relatively low permeability regions are disposed radially outwardly and opposite the flux leakage regions to control magnetic flux distribution in the electric motor.

[0024] 2. A radial flux electric motor according to technical solution 1, wherein each relatively high magnetic permeability region is composed of ferromagnetic material, and each relatively low magnetic permeability region is composed of paramagnetic material.

[0025] 3. A radial flux electric motor according to technical solution 2, wherein the ferromagnetic material is ferrous steel and the paramagnetic material is austenitic steel.

[0026] 4. A radial flux electric motor according to technical solution 1, wherein each relatively low permeability region has a relative permeability less than 10.

[0027] 5. The radial flux electric motor according to technical solution 1 further includes a dielectric layer, wherein each relatively high magnetic permeability region is electrically insulated from each relatively low magnetic permeability region by the dielectric layer.

[0028] 6. A radial flux electric motor according to technical solution 1, wherein each magnetic pole includes at least one rotor pocket, the rotor pocket having at least one permanent magnet, the permanent magnet being loaded into the rotor pocket and configured to generate magnetic flux, and wherein each rotor pocket has at least a portion thereof arranged near the outer surface of the rotor and defines a corresponding magnetic flux leakage area.

[0029] 7. A radial flux electric motor according to Technical Solution 6, wherein the rotor core includes a structural bridge extending from at least one of the rotor recesses to the outer surface of the rotor, and one of the relatively low magnetic permeability regions is arranged radially outside and opposite the structural bridge.

[0030] 8. The radial flux electric motor according to claim 6, wherein:

[0031] The at least one permanent magnet includes adjacent permanent magnets disposed in respective adjacent rotor pockets;

[0032] The rotor core includes a structural web positioned between adjacent rotor pockets; and

[0033] One of the regions of relatively low magnetic permeability is arranged radially outwardly and opposite the structural web.

[0034] 9. A radial flux electric motor according to technical solution 1, wherein each relatively high permeability region is configured to facilitate magnetic flux from at least one magnetic pole to pass through the air gap to reach the stator winding.

[0035] 10. A radial flux electric motor according to technical solution 1, wherein each relatively low permeability region spans an arc having a length at least twice the length of the air gap.

[0036] 11. A motor vehicle comprising:

[0037] A radial flux electric motor configured to generate torque for propelling the motor vehicle, the radial flux electric motor comprising:

[0038] a stator having a radially inner stator surface and a stator winding disposed on the radially inner stator surface;

[0039] a rotor mounted inside the stator and configured to rotate relative to the stator about a rotation axis, wherein the rotor has a rotor core defined by a rotor exterior surface and includes magnetic poles configured to generate magnetic flux and define magnetic flux leakage regions; and

[0040] A selective permeability sleeve is circumferentially disposed on the rotor and secured to the rotor outer surface to establish an air gap between the sleeve and the stator, wherein the sleeve provides reinforcement for the rotor core and the magnetic poles and includes relatively high permeability regions and relatively low permeability regions alternating around the rotor outer surface such that the relatively low permeability regions are disposed radially outwardly and opposite the flux leakage regions to control magnetic flux distribution in the electric motor.

[0041] 12. A motor vehicle according to technical solution 11, wherein each region of relatively high magnetic permeability is composed of ferromagnetic material, and each region of relatively low magnetic permeability is composed of paramagnetic material.

[0042] 13. A motor vehicle according to technical solution 12, wherein the ferromagnetic material is ferrous steel and the paramagnetic material is austenitic steel.

[0043] 14. A motor vehicle according to technical solution 11, wherein each relatively low magnetic permeability area has a relative magnetic permeability of less than 10.

[0044] 15. A motor vehicle according to technical solution 1, wherein the radial flux electric motor additionally includes a dielectric layer, wherein each relatively high magnetic permeability region is electrically insulated from each relatively low magnetic permeability region by the dielectric layer.

[0045] 16. A motor vehicle according to technical solution 11, wherein each magnetic pole includes at least one rotor pocket, the rotor pocket having at least one permanent magnet, the permanent magnet being loaded into the rotor pocket and configured to generate magnetic flux, and wherein each rotor pocket has at least a portion thereof arranged near the outer surface of the rotor and defines a corresponding magnetic flux leakage area.

[0046] 17. A motor vehicle according to technical solution 16, wherein the rotor core includes a structural bridge extending from at least one of the rotor recesses to the outer surface of the rotor, and one of the relatively low magnetic permeability regions is arranged radially outside and opposite to the structural bridge.

[0047] 18. The motor vehicle according to claim 16, wherein:

[0048] The at least one permanent magnet includes adjacent permanent magnets disposed in respective adjacent rotor pockets;

[0049] The rotor core includes a structural web positioned between adjacent rotor pockets; and

[0050] One of the regions of relatively low magnetic permeability is arranged radially outwardly and opposite the structural web.

[0051] 19. A motor vehicle according to technical solution 11, wherein each area of ​​relatively high magnetic permeability is configured to facilitate magnetic flux from at least one magnetic pole to pass through the air gap to reach the stator winding.

[0052] 20. A radial flux electric motor comprising:

[0053] a stator having a radially inner stator surface and a stator winding disposed on the radially inner stator surface;

[0054] a rotor mounted inside the stator and configured to rotate relative to the stator about a rotation axis, wherein the rotor has a rotor core defined by a rotor exterior surface and includes magnetic poles configured to generate magnetic flux and define magnetic flux leakage regions; and

[0055] a selective permeability sleeve disposed circumferentially on the rotor and secured to the rotor exterior surface so as to establish an air gap between the sleeve and the stator, wherein:

[0056] The sleeve provides reinforcement for the rotor core and the magnetic poles and includes relatively high permeability regions and relatively low permeability regions alternating around the outer surface of the rotor such that the relatively low permeability regions are arranged radially outwardly and opposite the magnetic flux leakage regions to control magnetic flux distribution in the electric motor; and

[0057] Each region of relatively high magnetic permeability is composed of a ferromagnetic material, and each region of relatively low magnetic permeability is composed of a paramagnetic material.

[0058] The above features and advantages and other features and advantages of the present disclosure will become apparent from the following detailed description of the embodiment(s) and best mode(s) for carrying out the described disclosure when taken in conjunction with the accompanying drawings and the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 is a schematic illustration of a motor vehicle having a powertrain that employs a radial flux motor-generator for propulsion.

[0060] Figure 2 According to the present disclosure Figure 1 A schematic close-up, partially cut-away perspective view of a radial flux dynamoelectric machine shown in , depicting a selective permeability sleeve comprising a plurality of adjacent rings mounted on a rotor.

[0061] Figure 3 According to the embodiment of the present disclosure Figure 2 Schematic front view of an embodiment of a rotor and selective permeability sleeve shown in FIG.

[0062] Figure 4 According to the embodiment of the present disclosure Figure 2 A schematic front view of another embodiment of a rotor and selective permeability sleeve is shown in FIG.

[0063] Figure 5 According to the embodiment of the present disclosure Figure 2 A schematic front view of another embodiment of a rotor and selective permeability sleeve is shown in FIG.

[0064] Figure 6 According to the embodiment of the present disclosure Figure 2 A schematic front view of another embodiment of a rotor and selective permeability sleeve is shown in FIG. DETAILED DESCRIPTION

[0065] The embodiments of the present disclosure described herein are intended to be examples. Other embodiments may take various and alternative forms. In addition, the drawings are generally schematic and are not necessarily drawn to scale. Some features may be enlarged or reduced to show the details of specific components. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but only as a representative basis for teaching those skilled in the art to use the present disclosure in a variety of ways.

[0066] Certain terms may be used in the following description for reference purposes only and are therefore not intended to be limiting. For example, terms such as "above" and "below" refer to directions in the drawings to which reference is made. Terms such as "front," "rear," "front," "rear," "left," "right," "rear," "side," "upward," "downward," "top," and "bottom" describe the orientation and / or position of parts of a component or element in a consistent but arbitrary reference system, which becomes clear by reference to the text and related drawings describing the component or element in question.

[0067] In addition, terms such as "first", "second", "third", etc. may be used to describe individual components. Such terms may include the words specifically mentioned above, their derivatives and words of similar meanings, and are used descriptively for the purposes of the drawings and do not represent limitations on the scope of the present disclosure as defined by the appended claims. In addition, the present teachings may be described herein in terms of functional and / or logical block components and / or various processing steps. It should be recognized that such block components may include multiple hardware, software, and / or firmware components configured to perform the specified functions.

[0068] refer to Figure 1 , depicting a motor vehicle 10 having a powertrain 12. The motor vehicle 10 may include, but is not limited to, a commercial vehicle, an industrial vehicle, a passenger vehicle, an aircraft, a watercraft, a train, etc. It is also contemplated that the motor vehicle 10 may be a mobile platform, such as an airplane, an all-terrain vehicle (ATV), a boat, a personal mobility device, a robot, etc., for purposes of the present disclosure. The powertrain 12 includes a first power source 14, which is depicted as an electric generator and is configured to generate a first power source torque T1 (e.g., Figure 1 ), for propelling the motor vehicle 10 relative to a road surface via driven wheels 16. The motor generator 14 may be configured as a radial flux electric motor, in which the magnetic flux is generated perpendicular to the motor's axis of rotation, and the air gap between the rotor and stator of the motor is arranged concentrically with the axis of rotation.

[0069] like Figure 1As shown in , the powertrain 12 may also include a second power source 20, such as an internal combustion engine configured to produce a second power source torque T2. The power sources 14 and 20 may work together to provide power to the motor vehicle 10 and may be operably connected to a transmission assembly 22. The transmission assembly 22 may be configured to transmit the first and / or second power source torques T1, T2 to a final drive unit 24, which in turn may be connected to the driven wheels 16. The first power source 14 (which will be referred to as an electric generator or electric motor in the remainder of this disclosure) may be mounted to the second power source 20, to (or coupled to) the transmission assembly 22, to the final drive unit 24, or may be a separate component mounted to the structure of the vehicle 10, for example. As shown, the motor vehicle 10 additionally includes: a programmable electronic controller 26, which is configured to communicate via a high voltage bus 27 and control the powertrain 12 to produce a predetermined amount of power source torque (the sum of T1 and T2); and various other vehicle systems. Motor vehicle 10 additionally includes an energy storage system 28 , such as one or more batteries, that is configured to generate and store electrical energy to power power sources 14 and 20 .

[0070] Figure 2 The radial flux dynamoelectric machine 14 is shown in general cross-section. As shown, the dynamoelectric machine 14 includes a rotationally fixed stator 30 having a generally cylindrical core 32 and winding slots 34. For example, Figure 2 , the stator core 32 also has a radially inner stator core surface 32A. The motor generator 14 also includes a rotor 36 that defines an axis of rotation X and is mounted for rotation within the stator 30. The stator 30 may include a multi-phase AC winding 34A disposed within the winding slots 34, wherein the winding receives multi-phase AC from a power inverter to establish a rotating magnetic field that exerts a torque on the rotor 36. The stator winding 34A is generally contained within the winding slots 34, wherein the end turns of the winding extend beyond the confines of the cylindrical core 32 at axially opposite stator ends (first end 32-1 and second end 32-2).

[0071] The rotor 36 has a ferromagnetic rotor core 38. The rotor core 38 has axially opposite rotor core ends, a first end 38-1 and a second end 38-2, and is defined by a radially outer rotor surface 38A. The rotor core 38 may be constructed of a relatively soft magnetic material, such as laminated silicon steel. The rotor 36 also includes a plurality of magnetic poles 40, each of which is configured to generate a magnetic flux 42 and define a magnetic flux leakage region 44. Specifically, the stacked rotor laminations may include gaps forming internal pockets 46, wherein permanent magnets 48 are disposed or encased in the internal pockets 46, together defining the magnetic poles 40. As shown in FIG. Figure 2As shown in , each rotor pocket 46 may have at least a portion 46A disposed adjacent the rotor exterior surface 38A, defining a corresponding flux leakage region 44. As will be appreciated by those skilled in the art, the radial flux electric motor 14 may be an interior permanent magnet (IPM) or surface mounted permanent magnet (SPM) synchronous machine.

[0072] like Figures 2 to 6 As shown in , the motor generator 14 also includes a selective magnetic permeability sleeve 50 that is circumferentially arranged on the rotor 36 and fixed to the rotor outer surface 38A (such as pressed onto the rotor outer surface 38A). Therefore, the selective magnetic permeability sleeve 50 is directly opposite the radially inner stator core surface 32A and thereby establishes an air gap 52 between the rotor 36 and the stator 32. The sleeve 50 is configured to provide mechanical reinforcement to the rotor core 38 and reinforcement / retention of the magnetic poles 40. As shown in FIG. Figures 2 to 6 As shown in , the sleeve 50 specifically includes regions of relatively high magnetic permeability 50 - 1 and regions of relatively low magnetic permeability 50 - 2 that are spaced along and alternate around the rotor exterior surface 38A.

[0073] The sleeve 50 is mounted on the rotor core 38 so that each relatively high permeability region 50-1 allows the magnetic flux 42 from the corresponding (multiple) magnetic poles 40 to pass through the air gap 52 to the stator winding 34A. On the other hand, the relatively low permeability region 50-2 is arranged radially outside and opposite the magnetic flux leakage region 44 to control the magnetic flux distribution in the electric motor 14. The number of relatively low permeability regions 50-2 may be at least equal to the number of magnetic poles 40. A specific relatively low permeability region 50-2 may be arranged radially outside and opposite the rotor recess portion 46A located closest to the rotor outer surface 38A. Figure 2 As shown in , each region of relatively low magnetic permeability 50 - 2 may span an arc 54 having a length at least twice the length of the air gap 52 .

[0074] Each of the relatively low permeability regions 50-2 may have a relative permeability of less than 10 and further less than 1.2. Each relatively high permeability region 50-1 may be composed of a ferromagnetic material, and each relatively low permeability region 50-2 may be composed of a paramagnetic material. The ferromagnetic material may be, for example, ferrous steel, and the paramagnetic material may be austenitic steel. The difference between the relative permeability of the ferromagnetic material and the permeability of the paramagnetic material may be at least 10, and may be equal to or greater than 100,000. The resulting selective permeability sleeve 50 structure may have a yield strength of at least 300 MPa and further equal to or greater than 1500 MPa and a Young's modulus equal to or greater than 150 GPa to withstand the hoop stress generated by the spinning rotor 36 and provide sufficient reinforcement for the rotor core 38.

[0075] like Figure 3 and Figure 6 As shown in , the rotor core 38 may include a structural bridge 56 extending from an individual rotor pocket 46 to the rotor outer surface 38A. One of the relatively low permeability regions 50-2 may be arranged radially outward and opposite a particular structural bridge 56. The individual magnetic poles 40 may include adjacent permanent magnets 48 arranged in respective adjacent rotor pockets 46, wherein the rotor core includes a structural connecting plate 58 positioned between adjacent rotor pockets. A particular arrangement of the permanent magnets 48 may have a generally "V" shape, wherein the structural connecting plate 58 is positioned at the tip of the "V", as shown in FIG. Figure 6 As shown in . The corresponding relatively low permeability region 50 - 2 may be arranged radially outwardly and opposite the structural connection plate 58 .

[0076] An alternative construction of the rotor 36 may be characterized by the absence of a structural bridge extending from the individual rotor pockets 46 to the rotor outer surface 38A such that the permanent magnets 48 are not constrained by the outer rotor surface 38A. Furthermore, the rotor core 38 may be characterized by the absence of a structural connecting plate such that the permanent magnets 48 that make up the individual poles do not have separate structures therebetween. In such a rotor 36 construction, the sleeve 50 may be configured (i.e., designed and constructed) to withstand greater forces to retain the permanent magnets 48 within the corresponding rotor pockets 46 during operation of the electric motor 14.

[0077] Continue to refer Figure 2, the radial flux electric motor 14 may additionally include a plurality of dielectric separators or layers 59 radially arranged relative to the rotation axis X. Specifically, a corresponding dielectric layer 59 may be used to electrically insulate each relatively high permeability region 50-1 from an adjacent relatively low permeability region 50-2. Each dielectric layer 59 may be a coating applied to the relatively high permeability region 50-1 or to the relatively low permeability region 50-2, or may be configured as a thin strip of material disposed therebetween. For example, each dielectric layer 59 may be configured as an organic coating (such as epoxy resin or varnish), or may be composed of an inorganic material (such as ceramic or glass).

[0078] like Figure 2 As shown in , the selective permeability sleeve 50 may include a plurality of adjacent rings 60, each ring 60 having alternating relatively high permeability regions 50-1 and relatively low permeability regions 50-2. The adjacent rings 60 may be constrained or fixed together by an interference fit with the rotor core 38 or by being pressed together via rotor end plates (not shown) positioned at opposite rotor core ends 38, 38-2. In general, the alternating relatively high permeability regions 50-1 and relatively low permeability regions 50-2 of the selective permeability sleeve 50 are arranged radially outwardly and opposite the rotor flux leakage region 44 to control the magnetic flux distribution in the electric motor 14. In addition, the selective permeability sleeve 50 provides mechanical reinforcement for the rotor core and provides retention of the rotor permanent magnets.

[0079] The detailed description and the accompanying drawings or figures are used to support and describe the present disclosure, but the scope of the present disclosure is limited only by the claims. Although some best modes and other embodiments for implementing the claimed disclosure have been described in detail, there are various alternative designs and embodiments for practicing the disclosure defined in the appended claims. In addition, the embodiments shown in the drawings or the features of the various embodiments mentioned in this specification do not have to be understood as embodiments independent of each other. On the contrary, it is possible that each of the features described in one of the examples of the embodiments can be combined with one or more other desired features from other embodiments, thereby producing other embodiments that are not described in words or with reference to the drawings. Therefore, such other embodiments fall within the framework of the scope of the appended claims.

Claims

1. A radial flux electric motor comprising: a stator having a radially inner stator surface and a stator winding disposed on the radially inner stator surface; a rotor mounted inside the stator and configured to rotate relative to the stator about a rotation axis, wherein the rotor has a rotor core defined by a rotor exterior surface and includes magnetic poles configured to generate magnetic flux and define magnetic flux leakage regions; and A selective permeability sleeve is circumferentially disposed on the rotor and secured to the rotor outer surface to establish an air gap between the sleeve and the stator, wherein the sleeve provides reinforcement for the rotor core and the magnetic poles and includes relatively high permeability regions and relatively low permeability regions alternating around the rotor outer surface such that the relatively low permeability regions are disposed radially outwardly and opposite the flux leakage regions to control magnetic flux distribution in the electric motor.

2. The radial flux electric motor according to claim 1, wherein: Each region of relatively high magnetic permeability is composed of a ferromagnetic material, and each region of relatively low magnetic permeability is composed of a paramagnetic material.

3. The radial flux electric motor according to claim 2, wherein: The ferromagnetic material is ferrous steel and the paramagnetic material is austenitic steel.

4. The radial flux electric motor according to claim 1, wherein: Each relatively low permeability region has a relative permeability of less than ten.

5. The radial flux electric motor of claim 1 further comprising a dielectric layer, wherein: Each relatively high magnetic permeability region is electrically insulated from each relatively low magnetic permeability region by the dielectric layer.

6. The radial flux electric motor of claim 1, wherein: Each magnetic pole includes at least one rotor pocket having at least one permanent magnet housed therein and configured to generate magnetic flux, and wherein each rotor pocket has at least a portion thereof disposed adjacent to an outer surface of the rotor and defines a corresponding magnetic flux leakage region.

7. The radial flux electric motor according to claim 6, wherein: The rotor core includes a structural bridge extending from at least one of the rotor pockets to the rotor outer surface, and one of the regions of relatively low magnetic permeability is disposed radially outwardly and opposite the structural bridge.

8. The radial flux electric motor of claim 6, wherein: The at least one permanent magnet includes adjacent permanent magnets disposed in respective adjacent rotor pockets; The rotor core includes a structural web positioned between adjacent rotor pockets; and One of the regions of relatively low magnetic permeability is arranged radially outwardly and opposite the structural web.

9. The radial flux electric motor of claim 1, wherein: Each relatively high permeability region is configured to facilitate magnetic flux from at least one magnetic pole through the air gap to the stator winding.

10. The radial flux electric motor of claim 1, wherein: Each region of relatively low magnetic permeability spans an arc having a length at least twice the length of the air gap.

Images