"Research on the BPMSM with Local-Eccentric Magnetic Pole Combination and its Air-gap Magnetic Field Analytical Modeling"

"What we did and what we found. We propose a Local-Eccentric Magnetic Pole Combination with Parallel Magnetisation (LEMPC-PMs), in which a wafer-shaped main pole is symmetrically flanked by eccentric auxiliary poles. To address the non-uniform air-gap condition, especially under rotor radial displacement, we establish a subdomain analytical model for the slotted BPMSM by solving the Laplace and Poisson equations in each subdomain and incorporating the relative-permeability and equivalent-air-gap functions. This enables rotor radial displacement to be explicitly introduced into the analytical derivation, yielding closed-form expressions for the air-gap flux density. The analytical results are validated by finite-element simulations. Relative to conventional pole configurations, the proposed LEMPC-PMs is shown to reduce the total harmonic distortion (THD) of the air-gap flux density, enhance the steady-state magnetic suspension force, and suppress the ripple ratios of both electromagnetic torque and magnetic suspension force."