A high torque dual 3-phase permanent magnet vernier machine with strong fault-tolerance

The field modulation effect has been proposed and investigated in various electric machine topologies. Among them, permanent magnet vernier machines (PMVMs) have attained intensive research due to the high torque density and simple structure. However, the performance of PMVMs in terms of fault tolerance is seldom mentioned. This article proposes a novel dual 3-phase fault-tolerant PMVM with segregated concentric windings. Benefiting from the field modulation effect, the PMVM can generate high torque with low PM flux. The low PM flux also implies small fault currents in the short-circuit case. Therefore, the PMVM exhibits inherent good fault-tolerant capability without sacrificing torque performance. Two independent 3-phase modular winding sets are adopted to improve redundancy. To realize the physical and electrical isolation, each winding set is controlled by a standard 3-phase inverter. The healthy performance and fault tolerance of the proposed machine are evaluated by finite element analysis and verified by experimental tests. The results infer its advantages in healthy conditions and various fault scenarios, including open-circuit, short-circuit, and interturn short-circuit conditions.