Real-Time Detection and Localization of Inter-Turn Short Circuits in Six-Phase PMSMs with Insulation Aging Analysis

Six-phase permanent-magnet synchronous machines (PMSMs) with asymmetrical stator windings are increasingly adopted in applications requiring high reliability and fault tolerance. However, the widespread use of wide-bandgap power devices increases the electrical stress on stator insulation, accelerating degradation mechanisms and raising the risk of interturn shortcircuit (ITSC) faults. In their early stage, ITSC faults may involve only a limited number of turns and a nonzero fault-path resistance, producing negligible deviations in terminal electrical quantities while still generating localized overheating and progressive insulation damage. This article develops a simplified analytical model to quantify the impact of ITSC faults in asymmetrical six-phase PMSMs. A combined theoretical and experimental investigation of insulation aging mechanisms leading to fault-path formation is carried out. The voltage harmonic components introduced by the fault are analyzed across the machine subspaces, providing a quantitative characterization of the ITSC signatures associated with resistance and back-EMF imbalance. Based on this analysis, a control-oriented diagnostic strategy is proposed, exploiting additional current regulators in selected synchronous reference frames to enable real-time fault detection, faulty-phase localization, and electrical severity estimation without additional sensors. Experimental validation on a dual three-phase PMSM prototype confirms the effectiveness of the proposed framework for online ITSC condition monitoring under steady-state and transient operating conditions.