A low conductivity composite rotor for fractional pitch concentrated winding machines

Abstract

Fractional pitch, concentrated winding machines are recently enjoying attention due to their suitability as basis for fault tolerant machine designs. The concentrated nature of the armature current distribution yields significant rotor eddy current loss production due to the harmonics present in the airgap, leading to significant rotor loss in high power and high speed machines. By using carbon fiber for the retaining sleeve and plastic bonded magnets for rotor magnetization, rotor eddy current loss may be reduced. Both materials require certain tradeoffs between electrical, mechanical and magnetic properties but their high electrical resistivity makes them attractive for use in high speed, fault tolerant, electrical machine design.