A Robust and Practical Approach to Estimate the Number of Shorted Turns in PMSM With ITSC Faults

This article puts forward a novel method to estimate the fault severity index and consequently the number of shorted turns in permanent magnet synchronous motors (PMSMs) with interturn short circuit (ITSC) fault. In this method, the machine is excited with dc current at standstill conditions to obtain the winding resistance seen by the d-axis of the machine. The estimated d-axis resistance contains useful information pertaining to the fault severity index and is used to extract the fault severity index and the number of shorted turns in the faulty motor. The proposed method enables the estimation of fault severity index without complex machine modeling and extensive experiments with different machine prototypes, or finite-element analysis (FEA) models to analyze the relationship between the machine currents and short-circuit current. To enhance the accuracy of the estimation algorithm, this article addresses practical issues associated with inverter nonlinearity effects such as distortion voltage due to deadtime effects and voltage drops across the switching devices and proposes method to estimate the fault severity index that is immune to the aforementioned issues. Determining the fault index is critical in order to design appropriate mitigation techniques, as well as defining a safe operating area for the machine to avoid further damage to the winding. To verify the efficacy of this algorithm, experiments are conducted on a three-phase PMSM with artificial taps that imitate the behavior of ITSC fault, and the results which demonstrate the practicability of this algorithm are presented.