On Open-Phase Faults in Multi-Three-Phase Drives

Drive architectures utilizing multiphase machines offer a robust solution for high-reliability systems. Multiphase drives can be monitored with advanced fault signature analysis for fault diagnosis, and in principle, they feature an intrinsic fault-tolerance capability. However, the fault tolerance must be effective and must be assessed with a methodology that allows analysis in terms of performance and limits. Postfault algorithms can also be embedded in the drive control to enhance behavior under fault conditions. The architecture of current controllers and related tuning parameters have a significant impact on the performance of motors in the presence of faults. These factors should be considered in fault analysis for improved accuracy. This study focuses on open-phase faults for multi-three-phase drives, providing a guideline for the development of an analytical model to analyze the fault-tolerance capability with or without postfault control (PFC) strategies. Postfault behavior is investigated in terms of peak current, Joule losses, torque ripple, and peak phase-to-phase voltage compared to the healthy operation of the electric drive. The analytical results and experimental tests conducted on a laboratory prototype confirm the efficacy of the proposed methodology.