US Patent 11056942 Electric machine rotor cooling systems and methods

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.