Cogging Torque Reduction Technique by Considering Step-Skew Rotor in Permanent Magnet Synchronous Motor

This paper deals with the cogging torque reduction in surface-mounted permanent magnet synchronous motors with overhang by considering the step-skewed rotor method. Firstly, optimal step-skew angle of the rotor is determined not only to minimize cogging torque but also to meet the required output torque. Furthermore, each rotor stack length should be appropriately adjusted to reduce the cogging torque more effectively in the way to make the axial directional flux density distribution on each stack uniformly. The analysis reveals that the proposed step-skew method is useful in minimizing cogging torque, and the experiment results show the validity of the cogging torque reduction model selected by analytical results.