A Novel Variable Impedance PM Fault-Tolerant Machine for Ultrahigh-Reliability Applications

This article aims to design and analyze a novel variable impedance permanent magnet (PM) machine for ultrahigh-reliability applications. In contrast to the existing conventional PM fault-tolerant machines, the automatic adjustment of the tooth-toroidal-leakage is applied by the special closed split tooth structure. With this design, the proposed machine presents low impedance in healthy condition and automatically changes to high impedance under turn-to-turn fault due to tooth-toroidal-leakage inductance being excited, which significantly suppresses short-circuit current and torque ripple. First, the topology and winding distribution of the proposed machine are presented. The automatic fault tolerance mechanism is revealed by developing an improved short-circuit model considering impedance variations. Then, the critical parameters of the closed split tooth are designed and optimized. Furthermore, the excellent electromagnetic and fault-tolerant performances of the proposed topology are verified by comparing with the conventional nonvariable impedance topologies. Finally, the prototype is built and tested where experimental results match well with the foregoing analyses.