A Two-Step Online Diagnosis Strategy for Open-Phase Fault in Doubly Salient Electromagnetic Motor Drives

Open-phase fault is a common fault in motor drives and occurs as the phase winding is disconnected or one leg of the converter bridge fails, which may generate significant torque ripple and reduce the output torque of the motor. To enhance the reliability of the system, this article proposes a two-step online diagnosis strategy for open-phase faults in doubly salient electromagnetic motor (DSEM) drives. In the first step, the occurrence of open-phase fault is detected based on the variation of active phase currents under normal and fault conditions. In the second step, the differentiation of two fault types (phase-winding open-circuit faults and two-switch open-circuit faults in the same bridge leg) as well as the localization of the fault phase winding can be realized by analyzing the variation of the zero-sequence voltage component (ZSVC) in the fault sector. And combined with the two-phase energization characteristic of the DSEM, the fault bridge leg can be localized based on the changes of the working phase currents within the fault sector and its subsequent sector. Finally, the effectiveness of the proposed method is experimentally verified on a 12/8-pole DSEM system.