Open-Circuit Fault Diagnosis Method for Dual Three-Phase PMSMs Based on Optimized Current Features

Dual three-phase permanent magnet synchronous machines (DT-PMSMs) have great application potential in aerospace actuation systems due to their high fault-tolerant capabilities. However, stator winding open-circuit faults (OCFs) represent a critical threat to the operational reliability of machines. Conventional diagnostic methods often rely on complex machine models, and their diagnostic results are frequently affected by torque and speed fluctuations, limiting their effectiveness in dynamic scenarios. In contrast, diagnostic approaches utilizing harmonic subspace current features allow for the direct observation of electromagnetic asymmetries and offer high potential for rapid identification. This paper proposes a fast and accurate OCF diagnostic method for both single-phase and two-phase faults based on optimized harmonic subspace current features. By establishing the intrinsic mapping relationship between the z1-z2 harmonic subspace and the fundamental current plane, fault features with low sensitivity to load variations are constructed. Specifically, the incorporation of a bias term δ effectively resolves the numerical singularity inherent in 180° spatially apart OCFs, enabling the identification of all fault types. Furthermore, the diagnostic features are refined via adaptive filtering and partial-cycle averaging to suppress impulsive spikes and minimize detection latency. Experimental results at 2000 r/min demonstrate that the proposed method precisely identifies and localizes faults within 1/10 to 1/5 of an electrical cycle, providing an accurate and efficient solution for aerospace actuators.