A new modular relieving-dc-saturation vernier reluctance machine excited by zero-sequence current for electric vehicle

This paper proposes a novel modular relieving-dc-saturation Vernier reluctance machine for electric vehicle application, which integrates merits of a robust structure, controllable excitation field, strong fault-tolerant capacity, and enhanced torque density, benefiting from its special relieving-dc-saturation design. In proposed machine, zero-sequence current establishes a modular magnetic path and functions as dominant excitation source for torque generation. Especially, slot permanent magnets are introduced into each module, which mitigates saturation effect in stator core caused by dc-biased flux with zero-sequence current source. Therefore, proposed machine can achieve enhanced torque density with relatively high current density. In this paper, machine structure and operation principle are illustrated in detail, with its electromagnetic performance evaluated by time-stepping finite-element analysis. It is revealed that, due to its relieving-dc-saturation ability, torque density of proposed machine is enhanced by about 20% with high current density.