A method to distinguish local demagnetization and short-circuit faults of six-phase interior permanent-magnet machine based on voltage in synchronous frame

Short-circuit fault and local demagnetization faults are two common fault types of permanent-magnet machines, aiming to improve the reliability of multi-phase PM machines in safety-critical applications, a method to distinguish these two kinds of faults in six-phase interior PM machines is proposed. The voltage characteristics in synchronous frame of local demagnetization fault and short-circuit fault are investigated, and the influences of load current and internal power factor angle on the voltage harmonic characteristics are analyzed. To solve the problem of the interaction between the extracted harmonic amplitudes in integer and non-integer orders, the average and variance of the harmonic coefficients of the voltages in synchronous frame are utilized to distinguish two types of faults. Through comparing the fault indices under different load conditions of the six-phase interior PM machine, the distinguishing ability of the method is validated.