“…Using the changes in torque spectrum and the track diagram of a torque ripple, Hong et al [9] detected PM demagnetisation by analysing the characteristic quantity of the output torque for a motor under fault. Yoo et al [10] proposed a demagnetisation diagnosis method based on locked rotor test results to detect PM demagnetisation through the locked‐rotor torque and current of the motor. Accordingly, He et al [11] proposed a robust demagnetisation fault detection method in PMSM based on sliding observer.…”