Design of IPMSM with Reduced Torque Ripple Through Advanced Sine-Shaped Poles

Asymmetric designs of IPMSM present reduction of the torque ripple and can improve the average torque when the machine is operating in the preferred rotating direction. This study proposes the rotation of the conventional sine shape in the rotor poles surface, in order to result in an asymmetric machine with reduced design parameters. The finite element simulations show that the sine-shaped poles reduce the harmonics in the electromotive force but increase the ripple in the cogging torque. The proposed design sightly increases the third harmonic in the electromotive force and reduces the torque ripple by reducing the cogging torque, and also increases the machine torque per ampere. A genetic algorithm was used to obtain an optimum solution with high average torque and low torque ripple, however, an even higher average torque and an even lower torque ripple can be obtained.