Sensorless Standstill Diagnosis of Rotating Diode Open‐Circuit Faults in WFSSG via Current‐Vector Modulus

ABSTRACT

Open‐circuit (OC) faults in rotating diode rectifiers (RDRs) pose a severe threat to the operational safety and reliability of wound‐field synchronous starter/generator (WFSSG) systems. Although existing position‐sensorless diagnostic frameworks based on the rotor current vector modulus (CVM) are theoretically applicable to both rotating and stationary conditions, prior research has primarily established characteristic mechanisms, analytical relationships and threshold criteria specifically for rotating operation. Under standstill conditions, the DC components of the three‐phase rotor currents do not contribute to stator electrical signals due to the absence of time‐varying magnetic fields. Consequently, the DC components of the rotor current no longer contribute to the formation of stator‐side signatures, rendering the CVM mathematical expressions and fault criteria established under rotating conditions no longer applicable. To address theoretical gaps under standstill conditions, this paper analyses fundamental differences in feature formation between rotating and stationary states using electromagnetic induction laws. An analytical standstill CVM model is derived within the CVM framework, and characteristic indicators with identification thresholds are established for static detection. Experimental results validate the derived standstill CVM analytical model and the proposed diagnostic indices, demonstrating that the method can accurately and robustly identify dual‐diode open‐circuit faults in the rotating diode rectifier under standstill conditions.