Analytical method for predicting air-gap magnetic field distribution of surface mounted permanent magnet machine with non-concentric magnetic poles

In this paper, a novel analytical method is proposed to predict the air-gap magnetic field distribution of surface mounted permanent magnet machine (SMPMM) with non-concentric magnetic pole (NCMP). The NCMP is parted into two sub-regions with different shapes in the radial direction, the magnetic field of which can be analyzed using different analytical models in the polar coordinate system. The governing equations and the associated boundary conditions are formulated and solved. The magnetic field distributions both in the radial and circumferential directions are calculated and compared with the finite element analysis results. By utilizing the proposed analytical method, the air-gap flux distribution of a prototype SMPMM is rapidly optimized for obtaining the maximum fundamental and minimum total harmonic distortion (THD).