Investigation of Optimal Split Ratio in Brushless Dual-Rotor Flux-Switching Permanent Magnet Machine Considering Power Allocation

This paper investigates an optimal split ratio for a brushless dual-rotor flux-switching permanent magnet (BDR-FSPM) machine. Based on the design theory of conventional FSPM machine, the split ratio of the BDR-FSPM machine is deduced and redefined. And the crucial factors which have close relationship with the split ratio are determined, consisting of power split ratio, magnetic loading, PM pole width, and stator pole width. To conveniently explore the optimal split ratio, the response surface method is purposely utilized for conducting optimization, where the magnetic loading and output torque are chosen to be the objectives. In addition, considering the application requirement of hybrid electric vehicles, the concept of power allocation is proposed and integrated into the optimization process of split ratio. Then based on the optimal split ratio, the machine performances are analyzed in detail, including air gap flux density, back-electromotive force (EMF), coupled-EMF, and torque performances. Finally, a prototyped BDR-FSPM machine is manufactured and tested to verify the validity of the proposed split ratio optimization and machine design approach.