Asymmetric Rotor Surface Design in Interior Permanent Magnet Synchronous Motors for Torque Ripple Mitigation

Interior permanent magnet synchronous motors (IPMSMs) have broad applications due to their advantages of high torque and power densities. However, torque ripple in IPMSMs brings about undesired byproducts such as vibration and acoustic noise. This paper proposes an optimal asymmetric rotor surface design obtained by grid on/off search method to effectively reduce the torque ripple while maintaining/slightly increasing the average torque in an IPMSM. Genetic Algorithms (GA) has been applied to this method to achieve multi-objective optimization and to save simulation time. A two dimensional (2D) model is built in ANSYS Maxwell and has been analyzed using finite element method (FEM). Simulation results including flux distributions and forces acting on rotor surface, cogging torque, and total torque profiles are presented. Torque ripple of the optimal asymmetric design has been reduced by 77.46% while the average torque has remained unchanged as compared to the original design.