Inter-turn Short Circuit Ratio Estimation in IPMSM Based on a Fault Index Current and Magnet Flux Linkage Observer

This paper proposes a method to estimate an internal short circuit (ISC) on interior permanent magnet synchronous machines (IPMSM) that is robust to changes in the magnet flux linkage. The machine operation under ISC can be modeled using a key variable defined as the fault index current (FIC). In order to develop an FIC model, accurate machine parameters are required. It will be shown that an error in the magnet flux linkage estimation causes the observer output to deviate significantly and accurate FIC prediction is not feasible. A modified topology is proposed which can keep the estimation of the magnet flux linkage and hence estimate the FIC with minimum error. This modified topology is compared with finite element analysis and is shown to be in good agreement.