A Computationally Efficient Subdomain Model Based on Modified Equivalent Currents for Magnetic Field Prediction of SPM Machines Considering Saturation Effect

Traditional subdomain models based on equivalent currents cannot consider the actual permeability of permanent magnets (PMs) and can only analyze one pair of equivalent currents each time. Besides, a lot of slots in surface-mounted PM (SPM) machines are a burden for fast calculation of the models. This article proposes a computationally efficient subdomain model based on modified equivalent currents to address these special issues. The actual permeability of PMs can be taken into account by the modified equivalent-current model. Furthermore, all equivalent currents in PMs can be analyzed altogether instead of a pair of equivalent currents, which can significantly improve the calculation speed. Meanwhile, the number of slots analyzed in the proposed model can be considerably reduced using the odd periodic boundary condition. Besides, this model can consider the magnetic saturation of machines. It is applied to a nine-phase SPM machine, and its correctness is verified by the finite-element analysis (FEA) and experiments. The calculation speed using the proposed model is more than 290 times faster than the FEA for the case study. The main contributions of the work are to improve the equivalent-current method and enhance the computational efficiency of subdomain models.