Analytical Calculation of Loaded Torque for SPM Machines Based on an Improved Equivalent Surface Current Method

In order to calculate the torque of the parallel magnetized eccentric pole shaping surface-mounted permanent magnet (SPM) machines under different load conditions accurately and quickly, an improved equivalent surface current method is used to treat the PM, and the loaded air-gap magnetic field of the SPM machines is calculated by combining the subdomain method and superposition principle. The surface of PMs is divided into several infinitesimals by the improved equivalent surface current method, each representing a currentcarrying conductor. The current value and position of each current-carrying conductor can be easily solved by transforming the local coordinate system into the global coordinate system. Therefore, the improved equivalent surface current method has the advantages of simple calculation and fast computation speed. The analytical method is used to calculate the torque under different loaded conditions, and the correctness of the analytical calculation is verified by comparing it with the finite-element analysis and the experimental method.