Current Residual Double Normalization Fault Diagnosis Method for Interturn Short-Circuit Fault of PMSM Servo System

The stator interturn short-circuit fault can cause great harm to the permanent magnet synchronous motor (PMSM), necessitating timely diagnosis to mitigate the damage. Under servo conditions, the variation of the speed, torque, and amplitude and frequency of electrical signals of PMSM present challenges to fault diagnosis. This article proposes a double normalization interturn short-circuit fault diagnosis method. The healthy PMSM current is calculated using a linear extended state observer, subtracted from the faulty PMSM current to generate the residual. Considering the existence of model errors, the second harmonic current residual is converted into a dc component in the negative sequence rotating frame, such that the impact of model parameters is reduced. Since the current residual is directly related to the fault current and short-circuit turns ratio, whose amplitude and frequency will change under the servo conditions, the current residual is first divided by the voltage to normalize the amplitude; then the dc component is extracted by angle integration to normalize the frequency change. The effectiveness of the proposed method is verified by experimental results.