Inter-turn Short Circuit Ratio Estimation in IPMSMs Based on a Fault Index Current Observer

This paper proposes an approach to estimate the ratio between shorted and total turns in interior permanent magnet synchronous machines (IPMSM). When an inter-turn short circuit (ISC) occurs, a particular disturbance affects the motor. The proposed method estimates this disturbance using an observer; this estimated signal is used to obtain the short circuit ratio. The observers are based on a dynamic model of an IPMSM under ISC. The proposed technique has several advantages. The observer estimates the ISC disturbances even if multiple phases have ISCs. Torque recovery under ISC is possible with the proposed method. In addition, short circuit ratio is estimated separately for each phase, which makes it more flexible than other conventional methods such as sequence components analysis.