Performance Derating of Multi-Three-Phase PM-Assisted Synchronous Reluctance Motors in Open-Three-Phase Fault Condition

Multi-three-phase (M3PH) motor drives are experiencing increasing development in safety-critical applications since they can be configured as multiple three-phase conversion units operating in parallel, guaranteeing modular fault tolerance after an open-three-phase fault. Although most literature on M3PH applications considers induction or surface-mount permanent magnet (PM) motors, the development of interior PM (IPM) machines has gained more attention in recent years. Indeed, requirements like a wide constant power speed range, high power density and efficiency are now considered mandatory for propulsion applications. In this scenario, PM-assisted synchronous reluctance (PM-SyR) motors represent a key compromise among the potential IPM configurations as they satisfy the requirements above and minimize PM utilization. Currently, literature contributions are missing investigating the performance derating of M3PH PM-SyR motors in open-three-phase fault conditions. Therefore, this paper proposes a performance derating analysis of a 60 kW prototype by considering performance indicators like efficiency, torque ripple, power factor, and maximum torque per speed capability.