Online Fault Diagnosis for Multiple Open-Circuit Faults in Multiphase Drives with Current Harmonics

In the event of open-circuit (OC) faults, electric machines suffer from torque deviations and undesired radial forces causing vibrations and noise. In safety-critical applications, multiphase machines are utilized because of their higher degrees of freedom (DOFs) for OC fault mitigation in post-fault operation, enabling fault-tolerant operation and preventing the system from further damage. Therefore, a reliable and fast fault diagnosis is crucial to monitor the systems' behavior. In this paper, a real-time fault diagnosis method for multiple-phase OC faults is developed using only the measured current sensor signals that are inherently available due to the control task. The proposed fault diagnosis method is independent of fundamental wave assumptions and electric interconnection knowledge. Advantageously, the proposed method gives reliable fault diagnosis results even if the measured currents include higher harmonic orders, which is frequently the case for high-performance permanent magnet synchronous machines (PMSMs). Experiments on a test stand verify the immunity to false diagnosis under fast load changes and show the performance of the proposed fault diagnosis method in combination with a fault-tolerant control (FTC) strategy. Simultaneous and sequential triple OC faults are investigated for a twelve-phase (1 × 12) and a quadruple three-phase (4 × 3) PMSM at several operating points.