High-frequency injection-based inter-turn short-circuit fault detection in SPM machines considering current closed-loop control effect

This paper investigates optimal injection signal parameters for high-frequency injection–based inter-turn short-circuit fault detection in surface-mounted permanent magnet synchronous machines under closed-loop current control. Theoretical derivations about the injection fault signatures reveal a signal enhancement effect induced by the current closed-loop control, which is found to be effective for reducing the undesired injection harmonics. Based on this phenomenon, an optimal injection frequency can be determined within a reasonable frequency range. This selection method of injection frequency is proven experimentally robust across different fault severities. Furthermore, the minimal injection voltage is obtained with respect to a minimal detectable fault case and a desired signal-to-noise ratio. The proposed injection frequency selection method can yield optimal injection frequency which reduces the negative impacts of injection; the proposed calculation method of the minimal injection voltage provides an analytical approach to evaluate the trade-off between the detectability of the inter-turn short-circuit fault and the cost of injection.