Investigation of on-loaded performances of hybrid-excitation flux-switching brushless machines for HEV/EV applications

The HEFS machines were proposed by reducing the permanent magnet (PM) length of a flux-switching permanent magnet (FSPM) machine and introducing a set of field windings into the saved space. Thus, the HEFS machines shares the identical motor laminations, meanwhile different PM and field winding locations. Based on 2D finite element analysis (FEA), this paper is focused on the comparison of electromagnetic performances of the HEFS machines with more attention paid to open-circuit flux-regulation capabilities and torque capabilities. Hybrid conditions employing Ferrite and NdFeB are discussed, respectively. Both the predicted airgap flux-densities and phase flux linkages under field currents reveal that different configurations of magnets and field windings have distinct influences on the flux-regulation capabilities. And compared to FSPM machines, reducing the magnet length can result in significantly reduced torque density in the HEFS machines. Overall, the HEFS machine having magnets located adjacent to the air-gap exhibits strongest flux-regulation and torque capabilities. The FEA predictions are validated by experimental measurements on the prototype machines.