Abstract: An electric machine including a rotor shaft having an inner shaft core with a first composition and an outer shaft portion surrounding at least some of the inner shaft core. The outer shaft portion is fabricated from a material having a different composition than the inner shaft core. For example, the inner shaft core could be fabricated from a material having high thermal conductivity, such as copper, while the outer shaft portion is fabricated from a material with lesser thermal conductivity, but greater strength, for example steel. The two-material shaft with a highly thermally conductive core serves to conduct heat from the interior of the electric machine to the housing, or to an exterior apparatus or structure.

Abstract: An electric machine rotor including a shaft, a rotor back assembly surrounding a portion of the shaft, and a plurality of permanent magnets distributed at equal radial distance from the shaft around the rotor back assembly. The electric machine rotor also includes a gap between two adjacent permanent magnets and a thermally conductive material filing the gap. The thermally conductive material is in contact with the rotor back assembly between the two adjacent permanent magnets. The electric machine rotor also includes a heat transfer structure in thermal communication with the thermally conductive material, extending beyond an outer surface of the thermally conductive material to transfer heat away from the electric machine rotor.

Abstract: An electromagnet for an electric machine having a stack of laminations defining a tooth and a yoke segment, and an insulating bobbin surrounding a portion of the tooth of each lamination, such that each lamination is held against adjacent laminations by the bobbin. The disclosed electromagnets also have electrically conductive windings surrounding a portion of the bobbin; and an encapsulant fully encapsulating the bobbin and windings, wherein the encapsulant comprises a dielectric material and an additive to increase the thermal conductivity of the encapsulant.

Abstract: An electric machine having a rotor, stator and housing. The rotor includes a radially mounted array of permanent magnets and the stator includes a plurality of electromagnets radially positioned around the rotor. The machine includes a fluid circuit consisting of first and second cavities enclosed by the stator and positioned between the rotor and housing. The fluid circuit also includes an air gap between the stator and rotor and a plurality of ventilation channels extending through the rotor. The air gap and ventilation channels are in fluid communication with the first and second cavities. The rotor also includes an internal fan extending into the first or second cavity. When the rotor is caused to rotate with respect to the stator, the fan causes air or another fluid to circulate through the fluid circuit to cool the rotor.

Abstract: Methods and apparatus for enhancing the robustness and stability of an electric machine having a rotor, stator and housing. The rotor includes a radially mounted array of permanent magnets and the stator includes a plurality of electromagnets radially positioned around the rotor. The rotor is stabilized by providing a first thermally conductive dielectric encapsulant in contact with adjacent permanent magnets. The stator is stabilized by providing a second thermally conductive dielectric encapsulant in contact with adjacent electromagnets.

Abstract: An electric machine having a rotor, stator and housing. The rotor includes a radially mounted array of permanent magnets and the stator includes a plurality of electromagnets radially positioned around the rotor. The stator is encapsulated such that the stator encapsulant is in thermal contact with housing structures, for example the housing end plates. In some embodiments, the entire perimeter portion of the housing is in thermal contact with the stator or the stator encapsulant. The stator encapsulant provides for device robustness and thermal transfer from the stator to the housing. The thermal conductivity of the encapsulant may be enhanced by mixing an additive to the encapsulant to increase thermal conductivity.