Cooling jacket with coolant mass balance for electric motors

Abstract

The present invention relates to a cooling jacket with a coolant mass balance for an electric motor. A permanent magnet electric motor includes a shaft extending along a longitudinal axis and a rotor mounted on the shaft. The rotor is rotatable about the longitudinal axis in conjunction with the shaft, and the rotor defines an innermost rotor edge. The innermost rotor edge is sized to receive the shaft. The permanent magnet electric motor also includes a stator. The shaft defines a jacket configured to receive a coolant. The jacket is disposed about the longitudinal axis. The jacket is elongated in a first direction. The first direction is parallel to the longitudinal axis. The rotor defines a plurality of longitudinal channels. Each of the plurality of longitudinal channels is elongated along the first direction, and each of the plurality of longitudinal channels is in fluid communication with the jacket to allow fluid flow between the jacket and the plurality of longitudinal channels.

Description

Technical Field

[0001] The present disclosure relates generally to electric motors, and more particularly to a cooling jacket with coolant mass balance for an electric motor. Background Art

[0002] High-speed electric motors may experience high temperatures in their rotors. Therefore, there is a need to cool the rotors of high-speed electric motors. Current cooling methods, such as injecting coolant onto the end rings of the electric motor, result in the coolant being blown away. As a result, the coolant is not effectively spread across the end rings of the electric motor, resulting in ineffective heat transfer between the coolant and the electric motor. Summary of the invention

[0003] Therefore, there is a need to develop a method to cool the rotor temperature while achieving a dynamic balance of coolant mass. The present disclosure describes a method for reducing the rotor temperature of an electric motor by allowing the coolant to flow into the shaft, into the rotor, and then back into the shaft. To this end, a diverter, a rotor jacket, and interconnecting channels are integrated into the electric motor to minimize the mass in the electric motor and minimize the heat in the rotor. The diverter is located in the shaft channel to direct the coolant from the shaft channel to the rotor jacket channel and then back to the shaft channel. In the present disclosure, the term "diverter" refers to a structure for dividing a flow into two or more parts and transferring the parts to different places. The rotor also defines interconnected channels to connect the rotor jacket channels to achieve a dynamic balance of coolant mass.

[0004] The present disclosure describes the optimal selection of parameters and structures for a cooling jacket enclosed in a rotor lamination by flowing coolant into the shaft, into the rotor, and then back into the shaft. These parameters and structures achieve an optimal dynamic balance of heat and mass for an electric motor by greatly increasing the convection surface area. As a result, the temperature of the permanent magnets is significantly reduced. In addition, the mass of the rotor is reduced due to the jacket of the rotor. The permanent magnet motor also includes a plurality of shunts located in the jacket of the shaft to direct coolant into the jacket of the shaft, into the longitudinal channels of the rotor, and then back to the jacket of the shaft.

[0005] In one aspect of the present disclosure, a permanent magnet electric motor includes a shaft extending along a longitudinal axis and a rotor mounted on the shaft. The rotor is rotatable about the longitudinal axis in conjunction with the shaft, and the rotor defines an innermost rotor edge. The innermost rotor edge is sized to receive the shaft. The permanent magnet electric motor also includes a stator electromagnetically coupled to the rotor, wherein the stator is disposed around the rotor and remains stationary relative to the rotor. The shaft defines a jacket configured to receive a coolant. The jacket is disposed about the longitudinal axis. The jacket is elongated in a first direction. The first direction is parallel to the longitudinal axis. The rotor defines a plurality of longitudinal channels. Each of the plurality of longitudinal channels is elongated along the first direction, and each of the plurality of longitudinal channels is in fluid communication with the jacket to allow fluid flow between the jacket and the plurality of longitudinal channels.

[0006] The rotor defines a plurality of interconnected channels, each of the plurality of interconnected channels directly interconnecting adjacent pairs of the plurality of longitudinal channels to direct coolant from one of the plurality of longitudinal channels to another of the plurality of longitudinal channels. The jacket is disposed entirely within the shaft. Each of the plurality of longitudinal channels is disposed entirely within the rotor, and each of the plurality of interconnected channels is disposed entirely within the rotor.

[0007] In one aspect of the present disclosure, the permanent magnet electric motor further comprises a first end ring and a second end ring opposite to the first end ring. The rotor comprises a first rotor end and a second rotor end opposite to the first rotor end. The first rotor end is spaced apart from the second rotor end along a first direction. The first end ring is attached to the rotor at the first rotor end. The second end ring is attached to the rotor at the second rotor end. The first end ring defines a first end channel. The second end ring defines a second end channel. The first end channel has an annular shape. The first end channel is in fluid communication with a plurality of longitudinal channels. The second end channel has an annular shape, and the second end channel is in fluid communication with a plurality of longitudinal channels.

[0008] In one aspect of the present disclosure, the permanent magnet electric motor further comprises a plurality of pole pieces. Each of the plurality of longitudinal channels has a first lateral end and a second lateral end opposite the first lateral end. Each of the plurality of longitudinal channels is shaped as an arc extending from the first lateral end to the second lateral end. Each of the plurality of longitudinal channels has a central angle. The central angle of each of the plurality of longitudinal channels is subtended by the arc extending from the first lateral end to the second lateral end. The central angle of each of the plurality of longitudinal channels is less than degrees, and M is the number of pole pieces.

[0009] In one aspect of the present disclosure, a rotor has a center, the rotor has an innermost rotor radius, the innermost rotor radius is defined from the center of the rotor to the innermost rotor edge, each of a plurality of longitudinal channels defines an innermost longitudinal channel end and an outermost longitudinal channel end opposite the innermost longitudinal channel end, the outermost longitudinal channel end of each of the plurality of longitudinal channels is farther from the center of the rotor than the innermost longitudinal channel end of each of the plurality of longitudinal channels, each of the plurality of longitudinal channels defines an innermost longitudinal channel radius and an outermost longitudinal channel radius, the innermost longitudinal channel radius is defined from the center of the rotor to the innermost longitudinal channel end. The innermost longitudinal channel radius is equal to or greater than: r + 5 millimeters, where r is the innermost rotor radius in millimeters.

[0010] In one aspect of the present disclosure, the rotor defines an outermost rotor edge, the outermost rotor edge is opposite the innermost rotor edge, the outermost rotor edge is farther away from the center of the rotor than the innermost rotor edge, the rotor has an outermost rotor radius, the outermost rotor radius is defined as from the center of the rotor to the outermost rotor edge of the rotor, each of the plurality of longitudinal channels defines an outermost longitudinal channel radius, the outermost longitudinal channel radius is defined as from the center of the rotor to the outermost longitudinal channel end of each of the plurality of longitudinal channels, and the outermost longitudinal channel radius is equal to or less than: R - 10 mm; and wherein R is the outermost rotor radius in millimeters.

[0011] In one aspect of the present disclosure, each of the plurality of longitudinal channels has a longitudinal channel midpoint between a first lateral end and a second lateral end, a first longitudinal channel distance from the first lateral end to the longitudinal channel midpoint is equal to a second longitudinal channel distance from the second lateral end to the longitudinal channel midpoint, each of the plurality of interconnecting channels has an interconnecting channel midpoint, each of the plurality of interconnecting channels includes a first side end and a second side end opposite the first side end, the first interconnecting channel distance from the first side end to the interconnecting channel midpoint is equal to the second interconnecting channel distance from the second side end to the interconnecting channel midpoint, each of the plurality of interconnecting channels is shaped as an arc extending from the first side end to the second side end, each of the plurality of interconnecting channels is angularly offset from an adjacent one of the plurality of longitudinal channels at an offset angle, the offset angle being defined as from the longitudinal channel midpoint of one of the plurality of longitudinal channels to the interconnecting channel midpoint of the adjacent one of the plurality of interconnecting channels, and the offset angle being equal to: , where M is the number of pole pieces.

[0012] In one aspect of the present disclosure, the rotor defines a plurality of permanent magnet slots, each of the plurality of permanent magnet slots being sized to receive a permanent magnet, each of the plurality of permanent magnet slots having an innermost slot point, the innermost slot point being disposed at a location of each of the permanent magnet slots closest to the center of the rotor, and a distance from an outermost longitudinal channel end to the innermost slot point being greater than 3 mm.

[0013] In one aspect of the present disclosure, each of the plurality of interconnected channels defines an innermost interconnected channel end and an outermost interconnected channel end opposite the innermost interconnected channel end, the outermost interconnected channel end of each of the plurality of interconnected channels being farther away from a center of the rotor than the innermost interconnected channel end of each of the plurality of interconnected channels, each of the plurality of interconnected channels defines an innermost interconnected channel radius and an outermost interconnected channel radius, the innermost interconnected channel radius being defined from the center of the rotor to the innermost interconnected channel end, the innermost interconnected channel radius being equal to or greater than: r + 5 mm, where r is the innermost rotor radius in millimeters.

[0014] In one aspect of the present disclosure, each of the plurality of interconnected channels defines an outermost interconnected channel radius, the outermost interconnected channel radius being defined as from the center of the rotor to the outermost interconnected channel end of each of the plurality of interconnected channels, and the outermost longitudinal channel radius is equal to or less than: R - 10 mm, where R is the outermost rotor radius in millimeters.

[0015] In one aspect of the present disclosure, each of the plurality of interconnected channels is shaped as an arc extending from a first side end to a second side end, each of the plurality of interconnected channels has a central angle, the central angle of each of the plurality of interconnected channels is subtended by the arc extending from the first side end to the second side end, and the central angle of each of the plurality of interconnected channels is less than degrees, and M is the number of pole pieces.

[0016] In one aspect of the present disclosure, a permanent magnet electric motor includes a plurality of inlets fluidly interconnecting a jacket of a shaft to a plurality of longitudinal channels of a rotor, a first end channel directly connected to all of the plurality of inlets, and at least one of the plurality of inlets directly connected to one of the plurality of longitudinal channels to allow coolant to flow from the first end channel to the plurality of longitudinal channels through the plurality of inlets.

[0017] In one aspect of the present disclosure, the plurality of inlets comprises between 4 and 12 inlets, and each of the plurality of inlets has an inlet diameter, and the inlet diameter is between 3 mm and 5 mm.

[0018] The permanent magnet electric motor also includes a plurality of outlets interconnecting the jacket fluid of the shaft to the plurality of longitudinal channels of the rotor. The plurality of outlets are spaced apart from the plurality of inlets along a first direction. The second end channel is directly connected to all of the plurality of outlets. At least one of the plurality of outlets is directly connected to one of the plurality of longitudinal channels to allow coolant to flow from the longitudinal channel to the second end channel through the plurality of outlets.

[0019] The present invention provides the following technical solutions.

[0020] Technical Solution 1. A permanent magnet electric motor, comprising:

[0021] a shaft extending along a longitudinal axis;

[0022] a rotor mounted on the shaft, wherein the rotor is rotatable concomitantly with the shaft about the longitudinal axis, the rotor defining an innermost rotor edge, and the innermost rotor edge is sized to receive the shaft;

[0023] a stator electromagnetically coupled to the rotor, wherein the stator is disposed about the rotor and remains stationary relative to the rotor;

[0024] wherein the shaft defines a jacket configured to receive a coolant, the jacket being disposed about the longitudinal axis, the jacket being elongated in a first direction, and the first direction being parallel to the longitudinal axis; and

[0025] The rotor defines a plurality of longitudinal channels, each of the plurality of longitudinal channels is elongated along the first direction, and each of the plurality of longitudinal channels is in fluid communication with the jacket to allow fluid flow between the jacket and the plurality of longitudinal channels.

[0026] Technical Solution 2. A permanent magnet electric motor according to Technical Solution 1, wherein the rotor defines a plurality of interconnected channels, each of the plurality of interconnected channels directly interconnects adjacent pairs of the plurality of longitudinal channels to guide the coolant from one of the plurality of longitudinal channels to another of the plurality of longitudinal channels, the jacket is completely disposed inside the shaft, each of the plurality of longitudinal channels is completely disposed inside the rotor, and each of the plurality of interconnected channels is completely disposed inside the rotor, and the permanent magnet motor also includes a plurality of flow dividers located in the jacket of the shaft to guide the coolant into the jacket of the shaft, into the longitudinal channels of the rotor, and then back to the jacket of the shaft.

[0027] Technical Solution 3. The permanent magnet electric motor according to Technical Solution 2 also includes a first end ring and a second end ring opposite to the first end ring, wherein the rotor includes a first rotor end and a second rotor end opposite to the first rotor end, the first rotor end is spaced apart from the second rotor end along the first direction, the first end ring is attached to the rotor at the first rotor end, the second end ring is attached to the rotor at the second rotor end, the first end ring defines a first end channel, the second end ring defines a second end channel, the first end channel has an annular shape, the first end channel is fluidically connected to the multiple longitudinal channels, the second end channel has an annular shape, and the second end channel is fluidically connected to the multiple longitudinal channels.

[0028] Technical Solution 4. The permanent magnet electric motor according to Technical Solution 3 further includes a plurality of pole pieces, each of the plurality of longitudinal channels having a first lateral end and a second lateral end opposite to the first lateral end, each of the plurality of longitudinal channels being formed as an arc extending from the first lateral end to the second lateral end, each of the plurality of longitudinal channels having a central angle, the central angle of each of the plurality of longitudinal channels being opposite to the arc extending from the first lateral end to the second lateral end, and the central angle of each of the plurality of longitudinal channels being less than degrees, and M is the number of pole pieces.

[0029] Technical Solution 5. A permanent magnet electric motor according to Technical Solution 4, wherein the rotor has a center, the rotor has an innermost rotor radius, the innermost rotor radius is defined as from the center of the rotor to the innermost rotor edge, each of the plurality of longitudinal channels defines an innermost longitudinal channel end and an outermost longitudinal channel end opposite to the innermost longitudinal channel end, the outermost longitudinal channel end of each of the plurality of longitudinal channels is farther away from the center of the rotor than the innermost longitudinal channel end of each of the plurality of longitudinal channels, each of the plurality of longitudinal channels defines an innermost longitudinal channel radius and an outermost longitudinal channel radius, the innermost longitudinal channel radius is defined as from the center of the rotor to the innermost longitudinal channel end, and the innermost longitudinal channel radius is equal to or greater than:

[0030] r + 5 mm; and

[0031] where r is the innermost rotor radius in millimeters.

[0032] Technical Solution 6. A permanent magnet electric motor according to Technical Solution 5, wherein the rotor defines an outermost rotor edge, the outermost rotor edge is opposite to the innermost rotor edge, the outermost rotor edge is farther away from the center of the rotor than the innermost rotor edge, the rotor has an outermost rotor radius, the outermost rotor radius is defined as from the center of the rotor to the outermost rotor edge of the rotor, each of the multiple longitudinal channels defines an outermost longitudinal channel radius, the outermost longitudinal channel radius is defined as from the center of the rotor to the outermost longitudinal channel end of each of the multiple longitudinal channels, and the outermost longitudinal channel radius is equal to or less than:

[0033] R - 10 mm; and

[0034] Where R is the outermost rotor radius in millimeters.

[0035] Technical Solution 7. A permanent magnet electric motor according to Technical Solution 6, wherein each of the plurality of longitudinal channels has a longitudinal channel midpoint between the first lateral end and the second lateral end, a first longitudinal channel distance from the first lateral end to the longitudinal channel midpoint is equal to a second longitudinal channel distance from the second lateral end to the longitudinal channel midpoint, each of the plurality of interconnected channels has an interconnected channel midpoint, each of the plurality of interconnected channels includes a first side end and a second side end opposite to the first side end, a first interconnected channel distance from the first side end to the interconnected channel midpoint is equal to a second interconnected channel distance from the second side end to the interconnected channel midpoint, each of the plurality of interconnected channels is shaped as an arc extending from the first side end to the second side end, each of the plurality of interconnected channels is angularly offset from an adjacent one of the plurality of longitudinal channels at an offset angle, the offset angle being defined as from the longitudinal channel midpoint of one of the plurality of longitudinal channels to the interconnected channel midpoint of an adjacent one of the plurality of interconnected channels, and the offset angle is equal to:

[0036]

[0037] Where M is the number of pole pieces.

[0038] Technical Solution 8. A permanent magnet electric motor according to Technical Solution 7, wherein the rotor defines a plurality of permanent magnet slots, each of the plurality of permanent magnet slots is sized to accommodate a permanent magnet, each of the plurality of permanent magnet slots has an innermost slot point, the innermost slot point is disposed at a position of each of the permanent magnet slots closest to the center of the rotor, and the distance from the outermost longitudinal channel end to the innermost slot point is greater than 3 mm.

[0039] Technical Solution 9. A permanent magnet electric motor according to Technical Solution 8, wherein each of the plurality of interconnected channels defines an innermost interconnected channel end and an outermost interconnected channel end opposite to the innermost interconnected channel end, the outermost interconnected channel end of each of the plurality of interconnected channels is farther away from the center of the rotor than the innermost interconnected channel end of each of the plurality of interconnected channels, each of the plurality of interconnected channels defines an innermost interconnected channel radius and an outermost interconnected channel radius, the innermost interconnected channel radius is defined as from the center of the rotor to the innermost interconnected channel end, and the innermost interconnected channel radius is equal to or greater than:

[0040] r + 5 mm; and

[0041] where r is the innermost rotor radius in millimeters.

[0042] Technical Solution 10. A permanent magnet electric motor according to Technical Solution 9, wherein each of the plurality of interconnected channels defines an outermost interconnected channel radius, the outermost interconnected channel radius being defined as from the center of the rotor to the outermost interconnected channel end of each of the plurality of interconnected channels, and the outermost longitudinal channel radius is equal to or less than:

[0043] R - 10 mm; and

[0044] Where R is the outermost rotor radius in millimeters.

[0045] Technical Solution 11. A permanent magnet electric motor according to Technical Solution 10, wherein each of the plurality of interconnected channels is shaped as an arc extending from the first side end to the second side end, each of the plurality of interconnected channels has a central angle, the central angle of each of the plurality of interconnected channels is subtended by the arc extending from the first side end to the second side end, and the central angle of each of the plurality of interconnected channels is less than degrees, and M is the number of pole pieces.

[0046] Technical Solution 12. The permanent magnet electric motor according to Technical Solution 11 also includes a plurality of inlets, which interconnect the jacket fluid of the shaft to the plurality of longitudinal channels of the rotor, the first end channel being directly connected to all of the plurality of inlets, and at least one of the plurality of inlets being directly connected to one of the plurality of longitudinal channels to allow the coolant to flow from the first end channel to the plurality of longitudinal channels through the plurality of inlets.

[0047] Technical Solution 13. A permanent magnet electric motor according to Technical Solution 12, wherein the plurality of inlets include between 4 and 12 inlets, and each of the plurality of inlets has an inlet diameter, and the inlet diameter is between 3 mm and 5 mm.

[0048] Technical Solution 14. The permanent magnet electric motor according to Technical Solution 13 also includes a plurality of outlets, which interconnect the jacket fluid of the shaft to the plurality of longitudinal channels of the rotor, the plurality of outlets are spaced apart from the plurality of inlets along the first direction, the second end channel is directly connected to all of the plurality of outlets, and at least one of the plurality of outlets is directly connected to one of the plurality of longitudinal channels to allow the coolant to flow from the longitudinal channel to the second end channel through the plurality of outlets.

[0049] Technical Solution 15. A permanent magnet electric motor, comprising:

[0050] a shaft extending along a longitudinal axis;

[0051] a rotor mounted on the shaft, wherein the rotor is rotatable concomitantly with the shaft about the longitudinal axis, the rotor defining an innermost rotor edge, and the innermost rotor edge is sized to receive the shaft;

[0052] a stator electromagnetically coupled to the rotor, wherein the stator is disposed about the rotor and remains stationary relative to the rotor;

[0053] wherein the shaft defines a jacket configured to receive a coolant, the jacket being disposed about the longitudinal axis, the jacket being elongated in a first direction, and the first direction being parallel to the longitudinal axis; and

[0054] wherein the rotor defines a plurality of longitudinal channels, each of the plurality of longitudinal channels being elongated along the first direction, and each of the plurality of longitudinal channels being in fluid communication with the jacket to allow fluid flow between the jacket and the plurality of longitudinal channels; and

[0055] wherein the rotor defines a plurality of interconnected channels, each of the plurality of interconnected channels directly interconnecting adjacent pairs of the plurality of longitudinal channels to direct the coolant from one of the plurality of longitudinal channels to another of the plurality of longitudinal channels, the jacket is disposed entirely within the shaft, each of the plurality of longitudinal channels is disposed entirely within the rotor, and each of the plurality of interconnected channels is disposed entirely within the rotor; and

[0056] The permanent magnet electric motor includes a plurality of pole pieces, each of the plurality of longitudinal channels has a first transverse end and a second transverse end opposite to the first transverse end, each of the plurality of longitudinal channels is formed as an arc extending from the first transverse end to the second transverse end, each of the plurality of longitudinal channels has a central angle, the central angle of each of the plurality of longitudinal channels is subtended by the arc extending from the first transverse end to the second transverse end, and the central angle of each of the plurality of longitudinal channels is less than degrees, and M is the number of pole pieces.

[0057] Technical Solution 16. A permanent magnet electric motor according to Technical Solution 15, wherein each of the plurality of longitudinal channels has a longitudinal channel midpoint between the first lateral end and the second lateral end, a first longitudinal channel distance from the first lateral end to the longitudinal channel midpoint is equal to a second longitudinal channel distance from the second lateral end to the longitudinal channel midpoint, each of the plurality of interconnected channels has an interconnected channel midpoint, each of the plurality of interconnected channels includes a first side end and a second side end opposite to the first side end, a first interconnected channel distance from the first side end to the interconnected channel midpoint is equal to a second interconnected channel distance from the second side end to the interconnected channel midpoint, each of the plurality of interconnected channels is shaped as an arc extending from the first side end to the second side end, each of the plurality of interconnected channels is angularly offset from an adjacent one of the plurality of longitudinal channels at an offset angle, the offset angle being defined as from the longitudinal channel midpoint of one of the plurality of longitudinal channels to the interconnected channel midpoint of an adjacent one of the plurality of interconnected channels, and the offset angle is equal to:

[0058]

[0059] Where M is the number of pole pieces.

[0060] Technical Solution 17. A permanent magnet electric motor according to Technical Solution 16, wherein each of the plurality of interconnected channels is shaped as an arc extending from the first side end to the second side end, each of the plurality of interconnected channels has a central angle, the central angle of each of the plurality of interconnected channels is subtended by the arc extending from the first side end to the second side end, and the central angle of each of the plurality of interconnected channels is less than degrees, and M is the number of pole pieces.

[0061] Technical Solution 18. A permanent magnet electric motor according to Technical Solution 17, wherein the rotor has a center, the rotor has an innermost rotor radius, the innermost rotor radius is defined as from the center of the rotor to the innermost rotor edge, each of the multiple longitudinal channels defines an innermost longitudinal channel end and an outermost longitudinal channel end opposite to the innermost longitudinal channel end, the outermost longitudinal channel end of each of the multiple longitudinal channels is farther away from the center of the rotor than the innermost longitudinal channel end of each of the multiple longitudinal channels, each of the multiple longitudinal channels defines an innermost longitudinal channel radius and an outermost longitudinal channel radius, the innermost longitudinal channel radius is defined as from the center of the rotor to the innermost longitudinal channel end, and the innermost longitudinal channel radius is equal to or greater than:

[0062] r + 5 mm; and

[0063] where r is the innermost rotor radius in millimeters.

[0064] Technical Solution 19. A permanent magnet electric motor according to Technical Solution 18, wherein each of the plurality of interconnected channels defines an innermost interconnected channel end and an outermost interconnected channel end opposite to the innermost interconnected channel end, the outermost interconnected channel end of each of the plurality of interconnected channels is farther from the center of the rotor than the innermost interconnected channel end of each of the plurality of interconnected channels, the rotor defines an outermost rotor edge, the outermost rotor edge is opposite to the innermost rotor edge, the outermost rotor edge is farther from the center of the rotor than the innermost rotor edge, the rotor has an outermost rotor radius, the outermost rotor radius is defined as from the center of the rotor to the outermost rotor edge of the rotor, each of the plurality of interconnected channels defines an outermost interconnected channel radius, the outermost interconnected channel radius is defined as from the center of the rotor to the outermost interconnected channel end of each of the plurality of interconnected channels, and the outermost longitudinal channel radius is equal to or less than:

[0065] R - 10 mm; and

[0066] Where R is the outermost rotor radius in millimeters.

[0067] Technical Solution 20. A permanent magnet electric motor according to Technical Solution 19, wherein the rotor defines a plurality of permanent magnet slots, each of the plurality of permanent magnet slots is sized to accommodate a permanent magnet, each of the plurality of permanent magnet slots has an innermost slot point, the innermost slot point is disposed at a position of each of the permanent magnet slots closest to the center of the rotor, and the distance from the outermost longitudinal channel end to the innermost slot point is greater than 3 mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The present disclosure will hereinafter be described in conjunction with the following drawings, wherein like numerals represent like elements.

[0069] Figure 1 A cross section of a permanent magnet electric motor according to one aspect of the present disclosure is schematically shown.

[0070] Figure 2 Schematically shows Figure 1 A perspective view of the rotor of an electric motor, showing the rotor end rings and rotor jacket.

[0071] Figure 3 Schematically shows Figure 2 Front view of the first lamination of the rotor.

[0072] Figure 4 Schematically shows Figure 3 Front view of the second lamination of the rotor.

[0073] Figure 5 Schematically shows a method according to one aspect of the present disclosure Figure 2 A perspective view of the rotor jacket of a rotor.

[0074] Figure 6 A perspective view of a rotor jacket according to another aspect of the present disclosure is schematically shown.

[0075] Figure 7 A perspective view of a rotor jacket according to another aspect of the present disclosure is schematically shown.

[0076] The foregoing and other features of the present disclosure will become more fully apparent from the following description and the appended claims in conjunction with the accompanying drawings. It should be understood that these drawings depict only several embodiments according to the present disclosure and should not be considered as limiting the scope of the present disclosure, which will be described with additional specificity and detail through the use of the accompanying drawings. Any dimensions disclosed in the drawings or elsewhere herein are for illustrative purposes only. DETAILED DESCRIPTION

[0077] Embodiments of the present disclosure are described herein. However, it should be understood that the disclosed embodiments are merely examples, and other embodiments may take different and alternative forms. The drawings are not necessarily drawn to scale; some features may be exaggerated or minimized to show the details of a particular component. Therefore, the specific structural and functional details disclosed herein should not be interpreted as limiting, but merely as a representative basis for teaching those skilled in the art to use the present disclosure in various ways. As will be understood by those of ordinary skill in the art, the various features shown and described with reference to any one of the figures may be combined with the features shown in one or more other figures to produce embodiments that are not explicitly shown or described. The combination of features shown provides representative embodiments for typical applications. However, various combinations and modifications of features consistent with the teachings of the present disclosure may be desirable for specific applications or implementations.

[0078] 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 referenced drawings. Terms such as "front," "rear," "left," "right," "rear," and "side" describe the orientation and / or position of parts of a component or element within a consistent but arbitrary reference system, which becomes clear by reference to the text and associated drawings describing the component or element in question. 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 meaning. Throughout the disclosure, the same or similar reference numerals represent the same or similar components.

[0079] Figure 1 1 shows a schematic cross-sectional view of a permanent magnet electric motor 100 configured to convert mechanical energy into electrical energy and vice versa. The electric motor 100 includes a shaft 102 extending along a longitudinal axis LX. The electric motor 100 also includes a rotor 104 mounted on the shaft 102. The rotor 104 is rotatable about the longitudinal axis LX in conjunction with the shaft 102. The rotor 104 defines an innermost rotor edge 106 and an outermost rotor edge 108 opposite the innermost rotor edge 106. The outermost rotor edge 108 is further away from the center CN (CN) of the rotor 104 than the innermost rotor edge 106. Figure 3 ). The innermost rotor edge 106 of the rotor 104 defines a shaft opening 111 that is sized to receive the shaft 102. The rotor 104 also has an outermost rotor edge 108 that is opposite the innermost rotor edge 108. The stator 110 is disposed about the outermost rotor edge 108 of the rotor 104. The electric motor 100 includes a stator 110 coupled to the rotor 104. The stator 110 is disposed about the rotor 104 and remains stationary relative to the rotor 104. The electric motor 100 also includes one or more flow dividers 113 that are at least partially disposed within the jacket 112 of the shaft 102.

[0080] The shaft 102 defines a jacket 112 configured to receive a coolant C (e.g., oil). The jacket 112 is disposed around the longitudinal axis LX to cool the shaft 102. The jacket 112 may have an annular shape to uniformly cool the shaft 102. In addition, the jacket 112 is elongated in a first direction X to cool the shaft 102 along its entire length. The first direction X is parallel to the longitudinal axis LX. The jacket 112 may be completely disposed inside the shaft 102 to effectively cool the shaft 102. The jacket 112 is in direct fluid communication with a coolant source 116. In this way, the coolant source 116 supplies the coolant C to the jacket 112. As a result, the coolant C flows directly from the coolant source 116 to the jacket 112. The coolant source 116 and the electric motor 100 together define the motor assembly 101.

[0081] The rotor 104 defines a plurality of longitudinal channels 114 in fluid communication with the jacket 112. Each longitudinal channel 114 is elongated along a first direction X to cool the rotor 104 along most (or all) of its length. Each longitudinal channel 114 is in fluid communication with the jacket 112 to allow fluid to flow between the jacket 112 and the longitudinal channels 114. Each longitudinal channel 114 is completely disposed within the rotor 104 to effectively cool the rotor 104. The jacket 112 is spaced apart from the longitudinal channels 114 along a second direction Y. The second direction Y is perpendicular to the first direction X.

[0082] The electric motor 100 further includes one or more flow dividers 113, each of which is configured to divide the flow of the coolant C between the jacket 112 and the longitudinal passage 114. To this end, each of the flow dividers 113 is disposed inside the jacket 112. Thus, a portion of the coolant C (e.g., oil) enters the jacket 112 and continues to flow along the entire length of the jacket 112, and another portion of the coolant C enters the longitudinal passage 114 (through the jacket 112) and flows along the entire length of the longitudinal passage 114, thereby allowing the shaft 102 and the rotor 104 to be cooled. Thus, the flow divider 113 allows the coolant C (e.g., oil) to flow from the jacket 112 into the longitudinal passage 14 and back into the jacket 112 to minimize the amount of coolant C flowing into the air gap of the electric motor 100, thereby minimizing rotation losses and coolant losses. The flow divider 113 also maximizes the amount of coolant C used to cool the rotor 104. As discussed above, the flow divider 113 is disposed inside the jacket 112 , leaving a gap between 0.05 mm and 0.5 mm. This gap range maximizes the amount of coolant C entering the longitudinal passage 114 while allowing enough coolant C to flow through the jacket 112 to effectively cool the rotor 104 and the shaft 12 .

[0083] Reference Figure 1 and Figure 2 The electric motor 100 also includes a plurality of inlets 118, each of which fluidically interconnects the jacket 112 to the longitudinal passage 114 ( Figure 1 ). At least one of the inlets 118 is directly connected to one of the longitudinal channels 114 to facilitate flow between the jacket 112 and the longitudinal channels 114. The electric motor 100 may include between 4 and 12 inlets 118, each inlet 118 having a diameter between 3 mm and 5 mm to evenly distribute the coolant C in the longitudinal channels 114 and enhance the dynamic balance of the coolant mass. The electric motor 100 also includes a plurality of outlets 120 that fluidly interconnect the jacket 112 to the longitudinal channels 114. The outlets 120 are spaced apart from the inlets 118 along the first direction X to allow the coolant C to cool a majority of the length of the rotor 104.

[0084] Reference Figure 2 , the electric motor 100 also includes a first end ring 122 and a second end ring 124 opposite the first end ring 122. The rotor 104 includes a first rotor end 126 and a second rotor end 128 opposite the first rotor end 126. The first rotor end 126 is spaced apart from the second rotor end 128 along the first direction X. The first end ring 122 is attached to the rotor 104 at the first rotor end 126. The second end ring 124 is attached to the rotor 104 at the second rotor end 128. The first end ring 126 defines a first end channel 130, which is one of the interconnecting channels 154. The second end ring 124 defines a second end channel 132, which is one of the interconnecting channels 154. The first end channel 130 may have an annular shape to facilitate the flow of the coolant C around the rotor 104. The first end channel 130 is aligned with the longitudinal channel 114 ( Figure 1 ) fluid is connected. The second end channel 132 may have an annular shape to facilitate the flow of coolant C around the rotor 104. The second end channel 132 is connected to the longitudinal channel 114 ( Figure 1 ) fluid communication. The first end channel 130, which is one of the interconnecting channels 154, can be directly connected to all the inlets 118 to facilitate the inlet 118 and the longitudinal channel 114 ( Figure 1 ) between the inlets 118. One of the inlets 118 may be directly connected to one of the longitudinal channels 114 to allow coolant C to flow from the first end channel 130 to the longitudinal channel 114 through the inlet 118. The second end channel 132 may be directly connected to all of the outlets 120 to facilitate the longitudinal channel 114 ( Figure 1 ) and the coolant flow between the outlet 120. At least one of the outlets 120 may be directly connected to one of the longitudinal channels 114 to allow the coolant C to flow through the outlet 120 ( Figure 1 ) flows from the longitudinal channel 114 to the second end channel 132. The electric motor 100 may have between 4 and 12 outlets 120, each outlet 120 having an outlet diameter between 3 mm and 5 mm, to evenly distribute the coolant C in the longitudinal channel 114, thereby enhancing the coolant mass dynamic balance and maintaining the coolant C in the longitudinal channel 114 to obtain optimized heat transfer performance.

[0085] Reference Figures 3 to 5, the rotor 104 can be at least partially formed by a plurality of laminations (i.e., a first lamination 134 and a second lamination 136). The first laminations 134 are stacked together to form a longitudinal channel 114. The electric motor 100 includes a plurality of pole pieces 138. Each pole piece 134 has a permanent magnet 140 and a permanent magnet slot 142. Although the drawings show a number of permanent magnets 140 for simplicity, each permanent magnet slot 142 receives a permanent magnet 140. Therefore, each permanent magnet slot 142 is sized to receive a permanent magnet 140. Each permanent magnet slot has an innermost slot point 144. The innermost slot point 144 can be disposed at a position closest to the center CN of the rotor 104.

[0086] When the first laminations 134 are stacked, the rotor 104 defines longitudinal channels 114. Each longitudinal channel 114 has a first transverse end 146 and a second transverse end 148 opposite the first transverse end 146. Each longitudinal channel 114 is shaped as an arc extending from the first transverse end 146 to the second transverse end 148. Each longitudinal channel 114 defines a central angle AL. The central angle AL of each longitudinal channel 114 is subtended by an arc extending from the first transverse end 146 to the second transverse end 148. The central angle AL of each longitudinal channel 114 is less than 138) to maximize the convection surface area, thereby enhancing cooling. The lower limit of the central angle AL of each longitudinal channel 114 can be determined based on the size requirements and / or limitations of the electric motor 100. Although the depicted embodiment shows eight pole pieces 138, the electric motor 100 can include more or fewer pole pieces 138.

[0087] The rotor 104 has an innermost rotor radius r. The innermost rotor radius r (in millimeters) is defined from the center CN of the rotor 104 to the innermost rotor edge 106. Each longitudinal channel 114 defines an innermost longitudinal channel end 150 and an outermost longitudinal channel end 152 opposite the innermost longitudinal channel end 150. The outermost longitudinal channel end 152 of each longitudinal channel 114 is farther from the center CN of the rotor 104 than the innermost longitudinal channel end 152 of each longitudinal channel 114. Each longitudinal channel 114 defines an innermost longitudinal channel radius 156 and an outermost longitudinal channel radius 158. The innermost longitudinal channel radius 156 is defined from the center CN of the rotor 104 to the innermost longitudinal channel end 150. The innermost longitudinal channel radius 156 (in millimeters) is equal to or greater than r + 5 millimeters (where r is the innermost rotor radius in millimeters) to optimize the coolant mass dynamic balance. The upper limit of the innermost longitudinal channel radius 156 of each longitudinal channel 114 can be determined based on the size requirements and / or limitations of the electric motor 100.

[0088] The rotor 104 has an outermost rotor radius R. The outermost rotor radius R (in millimeters) is defined from the center CN of the rotor 104 to the outermost rotor edge 108 of the rotor 104. The outermost longitudinal channel radius 158 is defined from the center CN of the rotor 104 to the outermost longitudinal channel end 152 of each longitudinal channel 114. The outermost longitudinal channel radius 158 (in millimeters) is equal to or less than R-10 millimeters (where R is the outermost rotor radius in millimeters) to maximize the convection surface area, thereby enhancing cooling. The lower limit of the outermost longitudinal channel radius 158 can be determined based on the size requirements and / or limitations of the electric motor 100. In addition, the distance PD from the outermost longitudinal channel end 152 to the innermost slot point 144 is greater than 3 millimeters to maximize the convection surface area, thereby enhancing cooling. The upper limit of the distance PD can be determined based on the size requirements and / or limitations of the electric motor 100. Each longitudinal channel 114 has a longitudinal channel midpoint ML between the first lateral end 146 and the second lateral end 148. A first longitudinal channel distance DL1 from first lateral end 146 to longitudinal channel midpoint ML is equal to a second longitudinal channel distance DL2 from second lateral end 148 to longitudinal channel midpoint ML. Longitudinal channel midpoint ML intersects a midpoint axis MX extending from center CN of rotor 104 to longitudinal channel midpoint ML.

[0089] Reference Figure 4 and Figure 5 , in addition to the end channels 130 and 132, the rotor 104 defines a plurality of interconnected channels 154 formed by the second laminations 136 (when stacked together). The interconnected channels 154 and the longitudinal channels 114 together define the rotor jacket 151. Each interconnected channel 154 directly interconnects a pair of adjacent longitudinal channels 114 to guide the coolant C from one of the longitudinal channels 114 to the other adjacent longitudinal channel 114. Each interconnected channel 154 is completely disposed inside the rotor 104 to effectively cool the rotor 104. Each interconnected channel 154 has an interconnected channel midpoint IM. Each interconnected channel 154 includes a first side end 160 and a second side end 162 opposite to the first side end 160. The first interconnected channel distance ID1 from the first side end 160 to the interconnected channel midpoint IM is equal to the second interconnected channel distance ID2 from the second side end 162 to the interconnected channel midpoint IM. Each interconnected channel 154 is shaped as an arc extending from the first side end 160 to the second side end 162. Each interconnecting channel 154 is angularly offset from an adjacent longitudinal channel 114 by an offset angle OA. The offset angle OA is defined as the distance from the longitudinal channel midpoint ML of one of the longitudinal channels 114 to the interconnecting channel midpoint IM of the adjacent interconnecting channel 154. The offset angle is equal to , where M is the number of pole pieces 138, so as to enhance the coolant mass dynamic balance.

[0090] Each interconnecting channel 154 defines an innermost interconnecting channel end 164 and an outermost interconnecting channel end 166 opposite the innermost interconnecting channel end 164. The outermost interconnecting channel end 166 of each interconnecting channel 154 is farther away from the center CN of the rotor 104 than the innermost interconnecting channel end 164 of each interconnecting channel 154. Each interconnecting channel 154 defines an innermost interconnecting channel radius 168 and an outermost interconnecting channel radius 170. The innermost interconnecting channel radius 168 is defined from the center CN of the rotor 104 to the innermost interconnecting channel end 164. The innermost interconnecting channel radius 164 (in millimeters) is equal to or greater than r + 5 millimeters (where r is the innermost rotor radius in millimeters) in order to maximize the convection surface area, reduce the rotor mass, and reduce the magnet temperature. The lower limit of the innermost interconnecting channel radius 164 can be determined based on the size requirements and / or limitations of the electric motor 100.

[0091] Each interconnecting channel 154 defines an outermost interconnecting channel radius 170. The outermost interconnecting channel radius 170 (in millimeters) is defined from the center CN of the rotor 104 to the outermost interconnecting channel end 166 of each interconnecting channel 154. The outermost longitudinal channel radius 170 is equal to or less than R-10 millimeters (where R is the outermost rotor radius in millimeters) in order to maximize convection surface area, reduce rotor mass, and reduce magnet temperature. The upper limit of the outermost longitudinal channel radius 170 can be determined based on the size requirements and / or limitations of the electric motor 100.

[0092] Each interconnecting channel 154 is shaped as an arc extending from the first side end 160 to the second side end 162. Each interconnecting channel 154 has a central angle AI. The central angle AI of each interconnecting channel 154 is subtended by an arc extending from the first side end 160 to the second side end 162. The central angle AI of each of the plurality of interconnecting channels 154 is less than degrees, and M is the number of pole pieces to enhance the coolant mass dynamic balance. The lower limit of the central angle AI of each interconnecting channel 154 can be determined based on the size requirements and / or limitations of the electric motor 100. Although the depicted embodiment shows eight pole pieces 138, the electric motor 100 can include more or fewer pole pieces 138. Figure 5 As shown, the first and second laminations 134 , 136 may be arranged to include interconnecting channels 154 only at the ends of the rotor 104 .

[0093] like Figure 6 As shown, the first and second laminations 134 , 136 may be arranged to include longitudinal channels 114 that are longer than the interconnecting channels 154 .

[0094] like Figure 7As shown, the first and second laminations 134 , 136 may be arranged to include longitudinal channels 114 having the same length as the interconnecting channels 154 .

[0095] Unless specifically stated otherwise, or otherwise understood in the context of use, conditional language such as "can," "may," "might," "could," "e.g.," etc., as used herein is generally intended to convey that some embodiments include and other embodiments do not include certain features, elements, and / or states. Thus, such conditional language is generally not intended to imply that one or more embodiments require features, elements, and / or states in any way, or to imply that one or more embodiments must include logic for deciding, with or without author input or prompting, whether such features, elements, and / or states are included in any particular embodiment or are to be executed in any particular embodiment.

[0096] In addition, the following terms may have been used herein. The singular forms "a", "an" and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, a reference to an item includes a reference to one or more items. The term "a" refers to one, two or more, and is generally applicable to selecting some or all quantities. The term "plurality" refers to two or more items. The term "about" or "approximately" means that quantities, dimensions, sizes, formulas, parameters, shapes and other characteristics do not need to be precise, but can be approximate and / or larger or smaller as needed, reflecting acceptable tolerances, conversion factors, rounding, measurement errors, etc. and other factors known to those skilled in the art. The term "substantially" means that the described features, parameters or values ​​do not need to be precisely implemented, but deviations or changes (including, for example, tolerances, measurement errors, measurement accuracy limitations and other factors known to those skilled in the art) may occur in an amount that does not exclude the effect that the characteristic is intended to provide.

[0097] For convenience, multiple items may be presented in a common list. However, these lists should be interpreted as if each member of the list was individually identified as a separate and unique member. Therefore, in the absence of contrary indications, any individual member of such a list should not be interpreted as a de facto equivalent of any other member of the same list solely based on their presentation in a common group. In addition, when the terms "and" and "or" are used in conjunction with a list of items, they are to be interpreted broadly, as any one or more of the listed items may be used alone or in combination with the other listed items. The term "alternatively" refers to the selection of one of two or more alternatives, and is not intended to limit the selection to only those listed alternatives or only one listed alternative at a time, unless the context clearly indicates otherwise.

[0098] Although exemplary embodiments are described above, these embodiments are not intended to describe all possible forms included in the claims. The words used in the specification are descriptive words, not restrictive, and it should be understood that various changes can be made without departing from the spirit and scope of the present disclosure. As mentioned above, the features of various embodiments can be combined to form other exemplary aspects of the present disclosure, which may not be explicitly described or shown. Although various embodiments may have been described as providing advantages or being superior to other embodiments or prior art implementations in terms of one or more desired characteristics, it is recognized by those of ordinary skill in the art that one or more features or characteristics can be compromised to achieve the desired overall system properties, depending on the specific application and implementation. These properties may include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, maintainability, weight, manufacturability, ease of assembly, etc. Therefore, embodiments described as being less ideal than other embodiments or prior art implementations in terms of one or more characteristics are not outside the scope of the present disclosure and may be desirable for specific applications.

Claims

1. A permanent magnet electric motor comprising: a shaft extending along a longitudinal axis; a rotor mounted on the shaft, wherein the rotor is rotatable concomitantly with the shaft about the longitudinal axis, the rotor defining an innermost rotor edge, and the innermost rotor edge is sized to receive the shaft; a stator electromagnetically coupled to the rotor, wherein the stator is disposed about the rotor and remains stationary relative to the rotor; wherein the shaft defines a jacket configured to receive a coolant, the jacket being disposed about the longitudinal axis, the jacket being elongated in a first direction, and the first direction being parallel to the longitudinal axis; and wherein the rotor defines a plurality of longitudinal channels, each of the plurality of longitudinal channels being elongated along the first direction, and each of the plurality of longitudinal channels being in fluid communication with the jacket to allow fluid flow between the jacket and the plurality of longitudinal channels, wherein the rotor defines a plurality of interconnected channels, each of the plurality of interconnected channels directly interconnecting adjacent pairs of the plurality of longitudinal channels to direct the coolant from one of the plurality of longitudinal channels to another of the plurality of longitudinal channels, the jacket is disposed entirely within the shaft, each of the plurality of longitudinal channels is disposed entirely within the rotor, and each of the plurality of interconnected channels is disposed entirely within the rotor, the permanent magnet electric motor further comprising a plurality of flow dividers located in the jacket of the shaft to direct the coolant into the jacket of the shaft, into the longitudinal channels of the rotor, and then back to the jacket of the shaft.

2. The permanent magnet electric motor according to claim 1, wherein: The jacket has an annular shape.

3. The permanent magnet electric motor according to claim 2, further comprising a first end ring and a second end ring opposite to the first end ring, wherein: The rotor includes a first rotor end and a second rotor end opposite the first rotor end, the first rotor end being spaced apart from the second rotor end along the first direction, the first end ring being attached to the rotor at the first rotor end, the second end ring being attached to the rotor at the second rotor end, the first end ring defining a first end channel, the second end ring defining a second end channel, the first end channel having an annular shape, the first end channel being in fluid communication with the plurality of longitudinal channels, the second end channel having an annular shape, and the second end channel being in fluid communication with the plurality of longitudinal channels.

4. The permanent magnet electric motor of claim 3 further comprising a plurality of pole pieces, each of the plurality of longitudinal channels having a first lateral end and a second lateral end opposite the first lateral end, each of the plurality of longitudinal channels being shaped as an arc extending from the first lateral end to the second lateral end, each of the plurality of longitudinal channels having a central angle, the central angle of each of the plurality of longitudinal channels being subtended by the arc extending from the first lateral end to the second lateral end, and the central angle of each of the plurality of longitudinal channels being less than degrees, and M is the number of pole pieces.

5. The permanent magnet electric motor according to claim 4, wherein: The rotor has a center, the rotor has an innermost rotor radius, the innermost rotor radius being defined from the center of the rotor to the innermost rotor edge, each of the plurality of longitudinal channels defining an innermost longitudinal channel end and an outermost longitudinal channel end opposite the innermost longitudinal channel end, the outermost longitudinal channel end of each of the plurality of longitudinal channels being farther from the center of the rotor than the innermost longitudinal channel end of each of the plurality of longitudinal channels, each of the plurality of longitudinal channels defining an innermost longitudinal channel radius and an outermost longitudinal channel radius, the innermost longitudinal channel radius being defined from the center of the rotor to the innermost longitudinal channel end, the innermost longitudinal channel radius being equal to or greater than: r + 5 mm; and where r is the innermost rotor radius in millimeters.

6. The permanent magnet electric motor according to claim 5, wherein: The rotor defines an outermost rotor edge, the outermost rotor edge being opposite the innermost rotor edge, the outermost rotor edge being further away from the center of the rotor than the innermost rotor edge, the rotor having an outermost rotor radius, the outermost rotor radius being defined from the center of the rotor to the outermost rotor edge of the rotor, each of the plurality of longitudinal channels defining an outermost longitudinal channel radius, the outermost longitudinal channel radius being defined from the center of the rotor to the outermost longitudinal channel end of each of the plurality of longitudinal channels, and the outermost longitudinal channel radius being equal to or less than: R - 10 mm; and Where R is the outermost rotor radius in millimeters.

7. The permanent magnet electric motor according to claim 6, wherein: Each of the plurality of longitudinal channels has a longitudinal channel midpoint between the first lateral end and the second lateral end, a first longitudinal channel distance from the first lateral end to the longitudinal channel midpoint is equal to a second longitudinal channel distance from the second lateral end to the longitudinal channel midpoint, each of the plurality of interconnecting channels has an interconnecting channel midpoint, each of the plurality of interconnecting channels includes a first side end and a second side end opposite the first side end, a first interconnecting channel distance from the first side end to the interconnecting channel midpoint is equal to a second interconnecting channel distance from the second side end to the interconnecting channel midpoint, each of the plurality of interconnecting channels is shaped as an arc extending from the first side end to the second side end, each of the plurality of interconnecting channels is angularly offset from an adjacent one of the plurality of longitudinal channels by an offset angle, the offset angle being defined as from the longitudinal channel midpoint of one of the plurality of longitudinal channels to the interconnecting channel midpoint of an adjacent one of the plurality of interconnecting channels, and the offset angle being equal to: Where M is the number of pole pieces.

8. The permanent magnet electric motor according to claim 7, wherein: The rotor defines a plurality of permanent magnet slots, each of the plurality of permanent magnet slots being sized to receive a permanent magnet, each of the plurality of permanent magnet slots having an innermost slot point disposed at a location of each of the permanent magnet slots closest to the center of the rotor, and a distance from the outermost longitudinal channel end to the innermost slot point being greater than 3 millimeters.

9. The permanent magnet electric motor according to claim 8, wherein: Each of the plurality of interconnected channels defines an innermost interconnected channel end and an outermost interconnected channel end opposite the innermost interconnected channel end, the outermost interconnected channel end of each of the plurality of interconnected channels being farther from the center of the rotor than the innermost interconnected channel end of each of the plurality of interconnected channels, each of the plurality of interconnected channels defines an innermost interconnected channel radius and an outermost interconnected channel radius, the innermost interconnected channel radius being defined from the center of the rotor to the innermost interconnected channel end, the innermost interconnected channel radius being equal to or greater than: r + 5 mm; and where r is the innermost rotor radius in millimeters.

10. The permanent magnet electric motor according to claim 9, wherein: Each of the plurality of interconnected channels defines an outermost interconnected channel radius, the outermost interconnected channel radius being defined from the center of the rotor to the outermost interconnected channel end of each of the plurality of interconnected channels, and the outermost longitudinal channel radius being equal to or less than: R - 10 mm; and Where R is the outermost rotor radius in millimeters.

11. The permanent magnet electric motor according to claim 10, wherein: Each of the plurality of interconnected channels is shaped as an arc extending from the first side end to the second side end, each of the plurality of interconnected channels has a central angle, the central angle of each of the plurality of interconnected channels is subtended by the arc extending from the first side end to the second side end, and the central angle of each of the plurality of interconnected channels is less than degrees, and M is the number of pole pieces.

12. The permanent magnet electric motor of claim 11 further comprising a plurality of inlets fluidly interconnecting the jacket of the shaft to the plurality of longitudinal channels of the rotor, the first end channel being directly connected to all of the plurality of inlets, at least one of the plurality of inlets being directly connected to one of the plurality of longitudinal channels to allow the coolant to flow from the first end channel to the plurality of longitudinal channels through the plurality of inlets.

13. The permanent magnet electric motor according to claim 12, wherein: The plurality of inlets includes between 4 and 12 inlets, and each of the plurality of inlets has an inlet diameter, and the inlet diameter is between 3 mm and 5 mm.

14. The permanent magnet electric motor of claim 13 further comprising a plurality of outlets interconnecting the jacket fluid of the shaft to the plurality of longitudinal channels of the rotor, the plurality of outlets being spaced apart from the plurality of inlets along the first direction, the second end channel being directly connected to all of the plurality of outlets, at least one of the plurality of outlets being directly connected to one of the plurality of longitudinal channels to allow the coolant to flow from the longitudinal channels to the second end channel through the plurality of outlets.

15. A permanent magnet electric motor comprising: a shaft extending along a longitudinal axis; a rotor mounted on the shaft, wherein the rotor is rotatable concomitantly with the shaft about the longitudinal axis, the rotor defining an innermost rotor edge, and the innermost rotor edge is sized to receive the shaft; a stator electromagnetically coupled to the rotor, wherein the stator is disposed about the rotor and remains stationary relative to the rotor; wherein the shaft defines a jacket configured to receive a coolant, the jacket being disposed about the longitudinal axis, the jacket being elongated in a first direction, and the first direction being parallel to the longitudinal axis; and wherein the rotor defines a plurality of longitudinal channels, each of the plurality of longitudinal channels being elongated along the first direction, and each of the plurality of longitudinal channels being in fluid communication with the jacket to allow fluid flow between the jacket and the plurality of longitudinal channels; and wherein the rotor defines a plurality of interconnected channels, each of the plurality of interconnected channels directly interconnecting adjacent pairs of the plurality of longitudinal channels to direct the coolant from one of the plurality of longitudinal channels to another of the plurality of longitudinal channels, the jacket is disposed entirely within the shaft, each of the plurality of longitudinal channels is disposed entirely within the rotor, and each of the plurality of interconnected channels is disposed entirely within the rotor; and wherein the permanent magnet electric motor comprises a plurality of pole pieces, each of the plurality of longitudinal channels having a first lateral end and a second lateral end opposite the first lateral end, each of the plurality of longitudinal channels being shaped as an arc extending from the first lateral end to the second lateral end, each of the plurality of longitudinal channels having a central angle, the central angle of each of the plurality of longitudinal channels being subtended by the arc extending from the first lateral end to the second lateral end, and the central angle of each of the plurality of longitudinal channels being less than degrees, and M is the number of pole pieces.

16. The permanent magnet electric motor according to claim 15, wherein: Each of the plurality of longitudinal channels has a longitudinal channel midpoint between the first lateral end and the second lateral end, a first longitudinal channel distance from the first lateral end to the longitudinal channel midpoint is equal to a second longitudinal channel distance from the second lateral end to the longitudinal channel midpoint, each of the plurality of interconnecting channels has an interconnecting channel midpoint, each of the plurality of interconnecting channels includes a first side end and a second side end opposite the first side end, a first interconnecting channel distance from the first side end to the interconnecting channel midpoint is equal to a second interconnecting channel distance from the second side end to the interconnecting channel midpoint, each of the plurality of interconnecting channels is shaped as an arc extending from the first side end to the second side end, each of the plurality of interconnecting channels is angularly offset from an adjacent one of the plurality of longitudinal channels by an offset angle, the offset angle being defined as from the longitudinal channel midpoint of one of the plurality of longitudinal channels to the interconnecting channel midpoint of an adjacent one of the plurality of interconnecting channels, and the offset angle being equal to: Where M is the number of pole pieces.

17. The permanent magnet electric motor according to claim 16, wherein: Each of the plurality of interconnected channels is shaped as an arc extending from the first side end to the second side end, each of the plurality of interconnected channels has a central angle, the central angle of each of the plurality of interconnected channels is subtended by the arc extending from the first side end to the second side end, and the central angle of each of the plurality of interconnected channels is less than degrees, and M is the number of pole pieces.

18. The permanent magnet electric motor according to claim 17, wherein: The rotor has a center, the rotor has an innermost rotor radius, the innermost rotor radius being defined from the center of the rotor to the innermost rotor edge, each of the plurality of longitudinal channels defining an innermost longitudinal channel end and an outermost longitudinal channel end opposite the innermost longitudinal channel end, the outermost longitudinal channel end of each of the plurality of longitudinal channels being farther from the center of the rotor than the innermost longitudinal channel end of each of the plurality of longitudinal channels, each of the plurality of longitudinal channels defining an innermost longitudinal channel radius and an outermost longitudinal channel radius, the innermost longitudinal channel radius being defined from the center of the rotor to the innermost longitudinal channel end, the innermost longitudinal channel radius being equal to or greater than: r + 5 mm; and where r is the innermost rotor radius in millimeters.

19. The permanent magnet electric motor according to claim 18, wherein: Each of the plurality of interconnected channels defines an innermost interconnected channel end and an outermost interconnected channel end opposite the innermost interconnected channel end, the outermost interconnected channel end of each of the plurality of interconnected channels being further from the center of the rotor than the innermost interconnected channel end of each of the plurality of interconnected channels, the rotor defining an outermost rotor edge, the outermost rotor edge being opposite the innermost rotor edge, the outermost rotor edge being further from the center of the rotor than the innermost rotor edge, the rotor having an outermost rotor radius, the outermost rotor radius being defined from the center of the rotor to the outermost rotor edge of the rotor, each of the plurality of interconnected channels defines an outermost interconnected channel radius, the outermost interconnected channel radius being defined from the center of the rotor to the outermost interconnected channel end of each of the plurality of interconnected channels, and the outermost longitudinal channel radius being equal to or less than: R - 10 mm; and Where R is the outermost rotor radius in millimeters.

20. The permanent magnet electric motor of claim 19, wherein: The rotor defines a plurality of permanent magnet slots, each of the plurality of permanent magnet slots being sized to receive a permanent magnet, each of the plurality of permanent magnet slots having an innermost slot point disposed at a location of each of the permanent magnet slots closest to the center of the rotor, and a distance from the outermost longitudinal channel end to the innermost slot point being greater than 3 millimeters.

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