A novel spoke‐type PM motor with asymmetric rotor for low torque pulsation under MTPA control condition

Abstract This article presents a novel asymmetric spoke‐type rotor structure. It is used to reduce rotor magnetic flux leakage, torque ripple and no‐load back‐EMF distortion rate while increasing the motor output torque. The traditional method of optimizing torque pulsation is the inverse cosine function, which gives a sinusoidal distribution of the air‐gap magnetic field under no‐load conditions of the motor. The fundamental wave magnetic field of the air‐gap synthetic magnetic field under the load is offset from the no‐load air‐gap magnetic field. This paper presents the design theory and method of the new type of the asymmetric rotor. Asymmetric spatial harmonics are introduced to the rotor so that the motor has a sinusoidal distribution of the rated load air‐gap field under MTPA control. In order to verify the superiority of the new rotor, the performance of four different spoke‐type rotor structure motors under the same pole‐slot combination was compared. Finally, an experimental prototype is built to verify the theoretical reliability against the design of this paper.