Rotor skew pattern design and optimisation for cogging torque reduction

Abstract

This study examines the effects of different rotor skew patterns on the cogging torque, the excitation torque ripple, the average torque, and the axial force in an interior permanent magnet synchronous motor. A genetic algorithm is used to minimise the cogging torque for different skew patterns based on analytical functions. The optimal design obtained is verified with finite element analysis. The results show that the linear skew patterns reduce the cogging torque, but increase the axial force. Four- and five-step symmetric skew, herring-bone skew, and five-step W-shaped skew patterns provide an adequate reduction in the cogging torque and axial force, but they have higher excitation torque ripple compared with the linear skew pattern.