Design and analysis of two six-phase hybrid-excitation flux-switching machines for electric vehicles

This paper designs two six-phase hybrid-excited flux-switching (HEFS) machines with E-core and C-core stator laminations, respectively, for electric vehicles (EVs). The iron bridges are adopted in stators to simplify the manufacturing process. First of all, focused on the flux-regulation capabilities, the steady-state and torque-speed (T-n) characteristics are discussed. Especially, the phenomenon that the E-core machine exhibits only the flux-weakening capability by field current is explained. Particularly, brief comparisons of the T-n characteristics are carried out between these two HEFS machines and their corresponding flux-switching permanent magnet (FSPM) structures. Then more attention is paid to fault-tolerant operations when open-circuit fault occurs to armature windings. Although the post-fault torque outputs can be effectively maintained, large unbalanced radial forces are generated on the rotor of E-core topology, since asymmetric armature loads are applied around air-gap. And this will further contribute to unfavorable torque ripples and vibrations. But the unbalanced radial forces can be avoided by adjusting the armature winding accommodations. Finally, the FEA predicted steady-state performances are validated by experimental measurements on two HEFS machine prototypes.