Inter-Turn Short Circuit Diagnosis for Dual Three-Phase Machine Based on High-Frequency Voltage Injection Considering Series Winding Magnetic Coupling

Severe inter-turn short circuit (ITSC) faults in dual three-phase permanent magnet synchronous machines (PMSMs) often evolve from incipient faults with few shorted turns. Such minor faults are easily masked by factors like electromagnetic noise and load fluctuations, making early-stage diagnosis challenging. Furthermore, conventional diagnostic models often neglect the magnetic coupling between faulty and healthy turns, and the derived fault features remain susceptible to speed variations. To tackle these challenges, this paper employs high-frequency voltage injection to amplify fault characteristics and mitigate speed effects, proposing two distinct diagnostic methods. Method Ⅰ utilizes an equivalent circuit model that neglects magnetic coupling, employing the standard deviation (SD) of high-frequency voltage residuals as a fault characteristic value. To address this limitation, method Ⅱ accounts for the magnetic coupling between faulty and healthy turns within the series windings. It establishes a series winding magnetic coupling model, derives the relationship between high-frequency voltage residuals and fault characteristics, and constructs a speed-decoupled fault feature value FI to achieve the diagnosis of minor faults. Experimental results demonstrate that SD exhibits superior capability in distinguishing similar minor faults, whereas FI achieves more precise differentiation of fault severity under complex operating conditions owing to its speed-decoupling property.