Comparative Investigation of Hybrid Excitation Flux Switching Machines

In this paper, the effect of partitioned stator (PS) structure and iron flux bridges in hybrid excitation flux switching (HEFS) machines is comprehensively discussed and compared. Firstly, the operating principles of four HEFS machines with single stator and PS respectively with and without iron flux bridges are described. Then an equivalent lumped parameter magnetic circuit model is developed to analyze the characteristics of PS structure and iron flux bridges. In order to achieve a fair comparison among different HEFS machines, the multi-level design optimization method is used to obtain the optimal parameters efficiently, based on which the electromagnetic performances of four machines are comprehensively evaluated by using 2D finite element analysis (2D-FEA). The results reveal that the machines with PS structure can exhibit not only a better flux regulation capability but also a higher torque density than conventional HEFS machines. Moreover, by adopting iron flux bridges, enlarged wide constant power speed region (CPSR) can be achieved, but the PM utilization will be slightly sacrificed.