Fault index current estimation and analysis for fault diagnostics in IPMSM under inter-turn short circuits

Abstract

This paper proposes an analysis of a fault index signal for internal permanent magnet synchronous machines (IPMSM) under inter-turn short circuits (ISC). Research has proven that the dynamic model of an electrical motor under ISC can be modeled as a healthy machine affected by a disturbance current representing the effect of the ISC. This current is equal to the product of the shorted turns ratio and the current flowing in the failure path. This signal has been used extensively for fault diagnostics. Having an understanding of how this fault index current affects the model of the IPMSM allows generating observer-based techniques to extract information of the fault index current and flux linkage estimation. A dynamic model for an IPMSM under ISC in combination with a fault index current observer is implemented in Matlab/Simulink; this model is validated with finite element analysis. The fault index current and sequence components analysis is studied to match previous work from other research. This work aims to accomplish two goals. The first is to show the observer-based estimation being effective in estimating ISC condition for several phases simultaneously and improve torque performance. The second, provide insight into the fault index current for diagnostics and show it as a generalized version of sequence component analysis. These goals produce better diagnostics and improve the control of the motor under ISC.