Fault-Tolerant Operation of Six-Phase Permanent Magnet Motor Drive With Open-Circuit Failures

This article proposes a novel six-phase permanent magnet (PM) motor drive with both phase and parallel redundancies for the highest level of a fault-tolerant operation. The proposed motor drive can continuously operate without any increased ripple torque up to four arbitrary phase open-circuit failures except for a single unique case where the two remaining phases are 180° apart. The proposed drive topology consists of three modular two-phase inverters, which provide individual phase current controllability for phase redundancy in the case of phase-leg open-circuit failures. Each two-phase inverter module can also independently produce constant instantaneous output torque for parallel redundancy in the case of inverter module failures. This article also introduces a novel phase current injection scheme for two-phase inverter operation with reduced neutral current for high drive system efficiency. The proposed scheme overcomes one of the main drawbacks of the conventional two-phase inverter, which is 40% higher amplitude of neutral current than that of phase current. The design and operating principle of the proposed six-phase PM motor drive are introduced, and the improved fault-tolerant operation capability is verified with simulation. A 3-kW laboratory-scale prototype is designed, and the ripple-free fault-tolerant operation with up to four out of six-phase open-circuit faults is demonstrated.