Open-Circuit Fault Diagnosis in Multiphase Brushless DC Motor Utilizing Zero-State Conservation Equation

This article proposes an open-circuit fault (OCF) diagnosis method for symmetrical multiphase brushless dc motor (BLDCM) drive systems, utilizing the zero-state conservation equation (ZSCE). The method addresses the limited fault recognition capability of existing technologies for OCF diagnosis in multiphase motors, as well as the difficulties in fault feature extraction and the complexity of diagnostic algorithms under nonideal conditions characterized by nonsinusoidal current waveforms. To overcome these challenges, the proposed method derives the multiphase current ZSCE and extracts the transient current features of the motor under fault conditions, utilizing the conservation relationship before and after the fault. This method enables rapid detection and identification of both open-switch faults in inverter power devices and open-phase faults in motor windings. Furthermore, by analyzing the positive and negative values of the derived ZSCE, the fault switch can be located, providing detailed information for fault diagnosis. The method offers rapid diagnostic speed, operates independently of control strategies and motor parameters, and exhibits high robustness to variations in speed and load. It is also effective under nonideal working conditions with nonsinusoidal current waveforms. Finally, experimental results conducted on a nine-phase BLDCM with various OCF types validate the effectiveness and robustness of the proposed method.