Asymmetric Slit Structure of IPMSM Rotor for High Torque, High Output, and Torque Ripple Reduction

This paper discusses asymmetric slit structures in a rotor that can reduce torque ripple as well as increase torque and output for concentrated winding interior permanent magnet synchronous motors. A motor with rotor asymmetric slits in forward rotation can reduce the torque ripple as opposed to a symmetric motor without asymmetric slits because of the effect of the asymmetric slits in increasing the instantaneous minimum torque. Furthermore, the more the outer diameter tip of the asymmetric slits is moved in the direction opposite to rotation, the smaller the torque ripple can be. In the reverse direction, torque ripple increases from forward rotation by the effect of asymmetric slits. However, by adding notches on the rotor core surface, the instantaneous maximum torque can be lowered and the torque ripple can be reduced.