Investigation of a Five-Phase E-Core Hybrid-Excitation Flux-Switching Machine for EV and HEV Applications

In this paper, to improve flux-regulation and constant-power speed range, a 10-stator-pole/18-rotor-pole five-phase hybrid-excitation flux-switching (HEFS) machine with “E”-core stator cell is proposed and analyzed. The topology and operation principle are investigated first. Then, the different armature winding connection methods are evaluated to reduce the total harmonic distortions of phase permanent magnet (PM) flux linkages. Furthermore, based on a simplified magnetic circuit, the analytical power-sizing equations are derived to determine the main design dimensions and parameters of E-core HEFS machines with given performance specifications. The electromagnetic performance, including the conventional static characteristics, such as phase PM flux, back electro-motive-force, cogging torque, electromagnetic torque, and flux-regulation capability, is analyzed by means of two-dimensional (2-D) and 3-D finite-element analysis to take end effect into account. The predicted results indicate that the proposed five-phase E-core HEFS machine exhibits improved flux-regulation capacity and wide range of speed regulation. The performances of HEFS machine are verified by experimental results on a prototype machine. Therefore, the HEFS machine is a promising candidate for electric vehicle and hybrid electric vehicle applications especially for direct-driven systems where the wide range of speed regulation and high-efficiency performance are crucial.