"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."

本研究的工作内容与核心发现。本研究提出一种并联充磁局部偏心磁极组合（Local-Eccentric Magnetic Pole Combination with Parallel Magnetisation，LEMPC-PMs），其薄片状主磁极两侧对称布置有偏心辅助磁极。针对气隙不均问题，尤其是转子径向位移工况下的气隙不均问题，本研究通过在各子域内求解拉普拉斯方程与泊松方程，并结合相对磁导率与等效气隙函数，建立了开槽无刷永磁同步电机（Brushless Permanent Magnet Synchronous Motor，BPMSM）的子域解析模型。该模型可将转子径向位移明确纳入解析推导过程，进而得到气隙磁通密度的闭合形式表达式。通过有限元仿真验证了该解析结果的正确性。相较于传统磁极构型，所提出的LEMPC-PMs可降低气隙磁通密度的总谐波畸变率（Total Harmonic Distortion，THD），提升稳态磁悬浮力，并抑制电磁转矩与磁悬浮力的脉动率。