Design and Analysis of a Ferrite-PM-Assisted Hybrid Reluctance Machine for Electric Vehicle Propulsion

Reluctance machines with DC field coil in the stator is a competitive candidate for electric vehicle propulsion due to the elimination of rare-earth permanent magnets (PM), robust structures and controllable excitation. However, their torque density cannot be compared with PM machines. Introducing rare-earth PMs into reluctance machines can be an effective way to boost torque density, but the costs will greatly increase as well. To solve this problem, this paper proposes a hybrid reluctance motor using assistive ferrite magnets in stator slots. The introduced ferrite magnets operate based on the flux modulation effect for torque density improvement. It is revealed by finite element analysis, with ferrite magnets in stator slots, machine torque density and efficiency can be improved by 20.2% and 5.1%, respectively.