Mitigation of Interturn Short Circuit Fault Based on Axial Split Phase Permanent Magnet Synchronous Machine

Abstract

In order to solve the problem that three-phase PMSM cannot operate under interturn short circuit (ITSC) fault, an ITSC fault mitigation scheme based on three-phase axial split phase permanent magnet synchronous machine (ASP-PMSM) is proposed in this paper. The ASP-PMSM has inherently superior fault isolation capability among phases, high inductance and low copper loss induced by ITSC current, which greatly reduces the fault severity and difficulty of fault mitigation from machine structure. The inherently low fault severity of ASP-PMSM leaves space for postfault torque production. Therefore, it does not need the phase current to be totally injected to d-axis. As a result, the operation of three-phase PMSM under ideal ITSC fault can be realized while maintaining more than half of rated torque. In order to find out the most serious fault condition for different winding types, the influence of the number of parallel strands and the SC turn ratio on the severity of ITSC fault is investigated by theoretical analysis (TA) and finite element analysis (FEA) for the first time. And the effectiveness of the fault mitigation for the ASP-PMSM with different number of parallel strands is investigated by FEA. Finally, a three-phase prototype of ASP-PMSM is served as an example to verify the validity of analysis above. The ITSC current and temperature at different SC turn ratio and operating conditions are tested. The test results are consistent with that of TA and FEA. It is verified that the proposed fault mitigation scheme can realize the postfault operation of three-phase PMSM.