Vector Control of Nine-phase Permanent Magnet Synchronous Motor under Symmetrical Fault Condition for Derating Operation

The superior fault-tolerant operation capability is the most important characteristic of multi-phase motors, which are applied in integrated electric ship propulsion systems. In this paper, a nine-phase permanent magnet synchronous motor (PMSM) composed of three sets of three-phase windings is regarded as the research object. Once an open-circuited fault occurs, the whole set of symmetric three-phase winding containing the fault phase can be cut out of operation. First, the mathematical model of the nine-phase PMSM is established. Second, the output torque matching the propeller load is calculated with symmetrical fault. Third, the symmetrical fault-tolerant derating operation is realized by vector control. The simulation results confirm the validity and the efficiency of the symmetrical fault-tolerant derating operation for a nine- phase PMSM.