An Online Monitoring Technique for Partial Demagnetization Monitoring of Permanent Magnet Machines Based on Intermittent Short-circuit

Partial demagnetization threatens the reliable operation of permanent magnet synchronous machines (PMSMs). Online monitoring of partial demagnetization is critical to provide a fault pre-warning signal and avoid serious failures in the machine drive operation. In consideration of that the back electromotive force (back-EMF) is determined by the PM, this paper proposes a monitoring strategy for partial demagnetization based on the extraction of transient characteristic during the intermittent short-circuit controlling mode. The response current values are summarized for curve characterizing of back-EMF, which is significative for depicting the partial defect of magnet. Experimental tests are conducted to verify the accuracy and feasibility of the proposed method.