Efficiency-enhanced DC-excited Vernier reluctance machine with reduced excitation coils for electric vehicles

Abstract

Due to its good mechanical robustness and field control capacity, the DC-excited Vernier reluctance machine (DC-VRM) is a promising candidate for electrical vehicle propulsion. However, the conventional design of this machine suffers from large excitation copper loss and leading to low efficiency, due to an identical distribution of DC excitation coils at the stator side. This paper proposes a novel efficiency-enhanced DC-VRM. The key technology is based on the flux modulation mechanism to reduce DC field coils and mitigate DC copper loss while keeping the excitation ability and power density not sacrificed. In this paper, the machine configuration and operation principle are introduced. A combination of the magneto-static finite element and the analytical method is used to quantitatively analyze the contribution of different harmonics on the phase EMF under two different DC layouts. The feasibility of the proposed topology is further verified by a transient finite element analysis, which proves that, with the same design parameters, the proposed design achieves higher back EMF and output torque per DC copper loss. Therefore, this new topology enhances efficiency and can be a more promising non-PM machine for EVs.