Open-Circuit Fault Diagnosis Strategy for Five-Phase Permanent Magnet Fault-Tolerant Servo Motor Drive Systems Based on Phase Voltage

When the five-phase permanent magnet fault-tolerant servo motor (PMFSM) for aerospace is in the typical condition, rotating over a small position angle range, the motor phase current fluctuates up and down in a small range rather than presenting a sinusoidal waveform. Therefore, the current-based open-circuit (OC) fault diagnosis strategy would be ineffective. The OC fault diagnosis strategy based on the lower power switch voltage and line voltage can only diagnose the power switch OC fault, but not the winding OC fault. Therefore, we propose an OC fault diagnosis strategy based on phase voltage to solve the problem that the present OC fault diagnosis method cannot effectively diagnose the OC faults of power switches and windings under the typical condition of servo motors. The proposed strategy can diagnose not only the single power switch OC fault but also the single winding OC fault under the typical condition. In addition, the proposed strategy can also diagnose OC faults in multiple power switches, OC faults in multiple windings, as well as mixed OC faults in windings and power switches. The simulation results verify that the proposed strategy can quickly and accurately diagnose the OC faults of power switches and windings under the typical condition. The phase voltage diagnosis method used in this paper is the first to be used in the fault diagnosis of five-phase motors. Two thresholds are set by combining the phase voltage to diagnose the winding fault and the power switch fault respectively.