Electric machine rotor cooling systems and methods

An electric machine rotor comprising:

• 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, wherein at least one of the plurality of permanent magnets comprises a stack of laminations, with each with each lamination comprising a rare earth magnetic material;
• a plurality of gaps, with each gap being positioned between two adjacent permanent magnets;
• a plurality of thermally conductive encapsulant structures, with one thermally conductive encapsulant structure being positioned within each gap, wherein each of the thermally conductive encapsulant structures is physically separated from adjacent thermally conductive encapsulant structures;
• and
• a plurality of heat transfer structures, with at least one of the plurality of heat transfer structures extending beyond an outer surface of each of the plurality of thermally conductive encapsulant structures, wherein each of the plurality of heat transfer structures is in physical contact with no more than one of the plurality of thermally conductive encapsulant structures, and wherein each of the plurality of heat transfer structures is physically separated from adjacent heat transfer structures.