Electromagnetic Performance Analysis of Interior PM Machines for Electric Vehicle Applications

An interior permanent magnet (IPM) machine with del + U shape rotor topology is proposed and its electromagnetic performance with typical V shape and del shape for electric vehicle (EV) applications are compared. The pole-arc to pole-pitch ratios are optimized to maximize the fundamental air-gap flux density and minimize its total harmonic distortion (THD) of all the three IPM machines by the finite element (FE) method. It can be obtained that del + U shape rotor topology has the lowest THD of the air-gap flux density. The back electromotive force and its THD orders, cogging torque, torque density, torque ripple, d-and q-axis inductances, saliency ratio, and iron loss of three machines are analyzed and compared. It is demonstrated that the del shape IPM machines have the highest average torque, and the torque ripples of the V shape and del shape machines are almost the same. The del + U shape IPM machine has the lowest torque ripple and iron loss with only a little reduction of average torque. Finally, the del + U shape IPM machine is prototyped to verify the results of the FE analysis.