Detection of PMSM Inter-Turn Winding Faults Using DC Link Current in Field-Oriented Variable-Frequency Drives

This paper presents a method for detecting inter-turn short-circuit faults in motor windings using the inverter’s DC link current. The proposed approach leverages the fact that the second harmonic component of the DC bus current increases significantly under abnormal conditions. By analyzing the dynamic behavior of this second harmonic signal, the method enables fast, easily integrated fault diagnosis without requiring any hardware modifications. The experimental results verify the method’s effectiveness. At 500 rpm, a 5% partial short circuit produces a second harmonic component about 2.8 times larger than that of a healthy motor, while a 30% fault raises the ratio to about 3.6. The close match between theory and experiment confirms the accuracy and practicality of the proposed technique.