Reduction of Stator Core Loss in Interior PM Machines for Electric Vehicle Applications

Stator core loss of four interior permanent magnet (IPM) machines is studied for electric vehicle applications in this paper. The no-load air-gap density, core loss density, core loss harmonics, and the segregation of hysteresis and eddy current losses are investigated with finite-element analysis. The results show that the rotor surface shaping of a single-layered IPM machine and increasing the rotor magnet layers can reduce the stator core loss due to the harmonics of the rotor magnetomotive force. The stator core loss reduction effectiveness of rotor surface shaping is similar to a two-layered magnet configuration, but the reduction effectiveness is less than that the magnet layers increased to three numbers. An IPM machine with three-layered magnets rotor is prototyped to verify the analysis.