Comparative study of six-phase permanent magnet assisted synchronous reluctance motors with different winding

Abstract

Taking the winding displacement angle of a six-phase permanent magnet assisted synchronous reluctance motor (PMaSynRM) as the subject of this investigation, this paper reconstructs the stator into asymmetric and symmetric sixphase windings respectively while keeping the rotor design parameters and structure unchanged, and analyzes the differences in electromagnetic performance between the two motor configurations. By using finite element software, a comparative study is conducted on the stator magnetomotive force (MMF), inductance characteristics, load back electromotive force (back-EMF), torque output and fault-tolerant capability of the motors.The results show that compared with the symmetric winding, the asymmetric winding essentially eliminates the 5th and 7th order MMF harmonics, suppresses the load back-EMF harmonics and the 6th order torque ripple. As a result, the back-EMF total harmonic distortion (THD) is reduced by 14.8% and the torque ripple is decreased by 10%, leading to more stable steady-state operation of the motor.Owing to the higher salience ratio of the asymmetric winding, its average torque is increased by approximately 11% relative to the symmetric winding, which enhances the torque output capability of the motor. However, under the single-phase open-circuit fault-tolerant operating condition, the symmetric winding exhibits superior fault-tolerant performance. Its back-EMF THD is 28% lower than that of the asymmetric winding, and the output torque ripple is 33% lower. Therefore, the motor equipped with symmetric winding operates more smoothly under fault conditions.