A Study on Torque Ripple Reduction of Hysteresis Motors According to Stator Slot Structures and Rotor Geometries

The geometry variation of the semi-hard magnetic material in the rotor of a hysteresis motor does not affect the magnetization pattern itself; however, it influences the poles of the hysteresis ring. In this paper, the magnetization pattern caused by the geometric variation of the rotor ring in a hysteresis motor is formulated, and the corresponding torque ripple and output characteristics are analyzed. Moreover, the number of notches in the rotor is determined analytically based on the developed formulation. The developed analytical model is expected to be effectively utilized for torque ripple reduction design in hysteresis motors.