Stage-Wise Analytical Modeling of the Stray Magnetic Field in Surface-Mounted Permanent Magnet Synchronous Motors Under Mixed Eccentricity

Conventional subdomain methods face challenges in calculating the stray magnetic field of surface-mounted permanent magnet synchronous motors (SPMSMs) under eccentric conditions due to their inability to handle complex boundaries, leading to low computational efficiency. To address these issues, this paper proposes a cell-based Schwarz-Christoffel (SC) mapping method and a stage-wise calculation strategy to improve computational efficiency while maintaining accuracy. First, an analytical model (AM) integrating equivalent surface current, conformal transformation method is established. Based on magnetic field superposition, the load air-gap magnetic field is derived. Second, a stage-wise subdomain-based computational strategy is employed to decouple the magnetic field calculations for the air-gap region and the outer air region. The stray magnetic field is analytically modeled using SC mapping and separation of variables. Finally, the proposed method is validated through experiments on an 8-pole 18-slot interior-rotor SPMSM with mixed eccentricity. Results show that the TM achieves a computational error of only 3.49% and that the computational speed is 136 times faster than that of the finite element method (FEM).