Combined complex permeance and sub-domain model for analytical predicting electromagnetic performance of surface-mounted PM machines

The paper presents a combined complex permeance (CP) and sub-domain (SD) model for predicting the open-circuit field, back-EMF, electromagnetic torque and cogging torque of surface-mounted permanent magnet machines. It significantly improves the computational speed since it is only required to solve a large equation set once, which otherwise needs to be solved for each rotor position in the SD model, and the hassle of numerical iteration in the conventional CP model is removed. The investigation shows the combined model has similar high accuracy to the conventional CP and SD models for the fundamental back-EMF and average torque, and predicts similar waveforms of cogging torque, torque ripple, and back-EMF harmonics to FE, but its accuracy is lower than that of the SD model in terms of the magnitudes of back-EMF and torque ripple harmonics.