An open-circuit fault diagnosis method for PMSM drives using symmetrical and DC components

In this paper, a diagnostic method based on symmetrical and DC components is presented for multiple open-circuit faults (OCFs) in a three-phase permanent magnet synchronous motor drive. The remaining phase currents under faulty situations are theoretically analyzed based on the Fourier series method and the mechanism of torque generation. To evaluate the asymmetry and discriminate fault types, the magnitude ratio of the positive sequence to the negative sequence of phase currents is designed as a fault detection index. Thereafter, the DC components of the phase currents in different reference frames are utilized to locate faults. Specifically, the polarities of the DC contents in the natural reference frame are utilized to locate a single OCF and two OCFs in different legs. Two OCFs in the same leg are diagnosed by evaluating the signs of the phase currents in the dq reference frame with a negative rotating direction. The simulated and experimental results validate the effectiveness of the developed method in fault detection and robustness against operating point and motor parameter variations.