A Novel Design for Notch on Rotor Surface of Double-Layered Interior Permanent Magnet Synchronous Motor for Reducing Cogging Torque

摘要

Interior permanent magnet synchronous motors (IPMSMs) have the disadvantage that their many space harmonics on the air-gap magnetic flux density (Bg) cause a large cogging torque. To reduce the cogging torque, this paper proposed a novel design approach involving a notch on the rotor surface of a double-layered IPMSM. The proposed approach is based on the theory that the harmonic components of the cogging torque depend on those of the square of Bg. The ideal waveform of $B_{g^{2}}$, in which the major components of the cogging torque can be zero, was obtained theoretically. On the basis of this ideal waveform, the optimal notch position and notch width were determined. The optimal notch depth was calculated by FEA. The cogging torque of an IPMSM with an optimal notch was significantly lower. Moreover, the notch hardly affected the average torque under a load.