Design and Analysis of Double-Air-Gap Flux-Modulated Permanent Magnet Motor Considering Leading Working Harmonics

In nature, to flux-modulated permanent magnet (FMPM) motors, the electromagnetic energy transmission is realized by abundant harmonics in the air-gap field. It means that, under the flux modulation effect, the harmonics in FMPM motors play an important role for motor performances. In this paper, by incorporating the concept of harmonics design into motor design process, a double-air-gap FMPM motor considering leading working harmonics is proposed and studied for potential applications of electric vehicles or electric tractors. First, the leading working harmonics are distinguished and chosen conveniently by evaluating the contributions of diverse harmonics to PM flux linkage. Then, a correlation design between the harmonic characteristics and geometric parameters is implemented based on the selected leading harmonics. In addition, the motor performances are evaluated by using the finite-element method, consisting of the air-gap harmonic analysis, no-load back-electromotive force, and torque performances. Finally, the theoretical analysis and computational results verify the effectiveness of the proposed motor.