Analysis of Torque Capability for Permanent Magnet Machines With Magnetic Gear Effect

Permanent magnet (PM) machines have been widely applied in industrial applications due to the advantages of high torque density, high reliability, and high efficiency. In this article, the magnetic gear effect (MGE) in PM machines is investigated in depth. A comprehensive derivation of the torque-generating process is carried out and a quantitative analysis of the air-gap harmonics contributing to average torque under different configurational freedoms is studied. The improvement of torque capability for the PM machines with MGE is discussed. The electromagnetic properties of typical PM machines with MGE are analyzed based on the magnetic circuit analytical model, and the effectiveness of theoretical analysis is verified by finite element analysis and experimental prototype. It is shown that the PM machines with an independent modulation unit possess the characteristics of high torque density and large PM utilization rate. And the PM machines with tooth-pole modulation unit have strong overload capability.