Torque Ripple Reduction of Interior Permanent Magnet Machines using Asymmetric Q-axis Rotor

A torque-ripple reduction method using an asymmetric q-axis rotor for Interior Permanent Magnet (IPM) machines is presented. The design methodology for the asymmetric q-axis motor is presented based on an analytical equation that is validated through a 2-D Finite Element Analysis (FEA). The results showed that it could reduce the torque ripple by more than 70% at the expense of 3-4% average torque reduction compared to an optimized base model. The performances of the proposed method are compared with those of a base model and a step-skewed model to show the superiority of the asymmetric q-axis method. Additionally, the method does not require any extra manufacturing step and does not require any computationally extensive optimization technique as well. The proposed concept is also effective in reducing cogging torque substantially.