Analysis of PM Volume Reduction Methods for Hybrid Excitation Switched Flux Machines

Due to the high cost of the rare-earth permanent magnet (PM) materials, the PM volume is a critical factor in determining the material cost of the hybrid excitation switched flux (HESF) machines. In this paper, two PM volume reduction methods for HESF machines are proposed by removing the PM bottom part which contributes little to the PM flux-linkage. The key performances of HESF machines applied with the PM volume reduction methods are comparatively investigated by using the finite element analysis, including the flux regulation capability and on-load average torque. It is found that the proposed PM volume reduction methods could reduce the material cost of the machine by up to 20.7%, and the flux regulation capability can increase from 45.96% to 57.38%. As for the on-load average torque, it can be increased by >4%. All the analysis are confirmed through the finite element analysis.