An Improved Subdomain Model for Magnetic Field Calculation of SPMSM Considering No-load Leakage Flux

Due to big leakage flux, the performance of permanent magnet (PM) motor will be much reduced. Especially for surface-mounted permanent magnet synchronous motor (SPMSM) with similar number of poles and slots, because the zigzag leakage flux is big and varies with the relative positions between stator and rotor, selecting no-load leakage flux coefficient with experience may cause a big calculation error to electromagnetic parameters by equivalent magnetic circuit model. Finite-element method (FEM) can directly calculate the coefficient, but entire process is time-consuming. Focusing on this problem, an analytical model of no-load leakage flux coefficient is proposed including air-gap leakage flux model and zigzag leakage flux model. Then, an improved subdomain model for magnetic field calculation of SPMSM is established, and the air-gap magnetic flux density, inducing flux linkage and line no-load back electromotive force (EMF) are calculated considering no-load leakage flux. To verify the improved model, an external rotor type SPMSM with 20-poles and 24-slots for bridge crane is designed and manufactured. Finally, the validity of improved model is verified by experimental test.