Investigation of Cogging Torque Generation Mechanisms in Flux-switching Permanent Magnet Machines Based on General Air-gap Field Modulation Theory

An analytical approach is proposed for the cogging torque of a flux-switching permanent magnet machine based on the general air-gap field modulation theory. The modulation process is first investigated, and the cogging torque generation mechanism is analyzed based on the distribution of the air-gap magnetic flux density harmonics. Thus, the relationship between the air-gap field harmonics and the cogging torque is revealed, and the contribution of each harmonic to the cogging torque is calculated using the proposed method. Simultaneously, the characteristics of the cogging torque, including amplitude and frequency, are analyzed. Subsequently, the calculated cogging torque is compared with the simulated torque using finite element analysis. The two results exhibit considerable consistency, confirming the feasibility of the proposed method. Moreover, a prototype experiment is conducted, and the cogging torque is measured to verify the effectiveness of the proposed method.