Unbalanced Magnetic Force Calculation Based on Subdomain and Magnetic Circuit Hybrid Model in SPM Machines

This paper presents a nonlinear calculation method for unbalanced magnetic force (UMF) in surface-mounted permanent magnet (SPM) machines based on subdomain and magnetic circuit hybrid model (SMCHM). The hybrid model transforms the nonlinearity effect in stator core to equivalent current on the edges of slots. The current densities are obtained by magnetic circuit (MC) and applied to boundary conditions in improved subdomain model of SMCHM. The UMF of SPM machines can be calculated by the predicted nonlinear flux density distributions in air-gap based on Maxwell stress tensor. The excellent accuracy of this nonlinear UMF calculation method based on SMCHM is validated by finite element (FE) method. Besides, it also significantly improves computational speed compared to FE method.