Novel Effective Torque Analysis Method for Interior Permanent Magnet Synchronous Machines

Effective torque performance for interior permanent magnet synchronous machines (IPMSMs) has always been a concern for designers. In order to seek the mechanism of effective torque generation in IPMSM, this article proposes a novel effective torque analytical method (AM) featuring the armature reaction magnetic field (AR-MF) calculation method. For AR-MF, a combination method, which dq-axis current excitation is separately and then jointly taken, is utilized to analyze the airgap flux density, especially tangential component. Meanwhile, the effects of the permanent magnet magnetic field (PM-MF) and the rotor magnetic barrier on the AR-MF are separately considered by the rotor slotting and pole-cap coefficient. Then, based on flux densities, the general expression of effective torque is derived by using Maxwell stress tensor. Through the harmonic analysis, the contribution of harmonic flux densities to the effective torque is investigate, and thus, the mechanism of effective torque is revealed. In particular, the contribution of harmonic flux densities is caused by the slotting effect. Finally, the validity of the AM is verified by finite element (FE) and experiments.