Optimal current waveforms for five-phase permanent magnet motor drives under open-circuit fault

This paper presents a new solution for calculating optimal sinusoidal current waveforms for five-phase permanent magnet motor drives under open-circuit fault condition. The current waveform obtained in this study minimizes the total stator ohmic loss under single-phase open-circuit fault. Closed form expressions are derived to calculate the optimal fault-tolerant sinusoidal currents. A concept to relate the fault-tolerant currents in the spatially symmetrical phases is introduced. Instantaneous power-balance theory is applied for the derivation of the optimal current set. The new optimal solution is compared with the existing solution reported in the literature. It is found that the optimal current set produces less stator ohmic loss than the existing solution. Finite element analysis results of a five-phase IPM are presented for validation of the new solution.