Open-Phase Fault Diagnosis in Six-Phase PMSM Drives Based on the Harmonics of the Measured Secondary Subspace Currents

Multiphase machines are ideal candidates for application in electric drives for critical applications. Since they can operate with open-phase faults (OPFs) without requiring extra hardware, the fault detection is important to reconfigure the control strategy. Hence, this paper proposes a new signal-based diagnosis method to detect OPFs in six-phase permanent magnet synchronous machine (PMSM) drives based on the measured currents mapped into the secondary subspace, which do not contribute to the production of flux or torque. The proposed OPF diagnosis method measures both the mean value and the amplitude of the second harmonic of the secondary currents in the rotor reference frame to detect and identify an OPF. Moreover, the proposed method is unaffected by current harmonics due to non-sinusoidal back-EMF and due to deadtime effects in the power converters, which map as a sixth harmonic of the secondary currents in the rotor reference frame. The simulation results demonstrate the ability of the proposed method to correctly detect and identify OPFs independently of the drive operating conditions.