Torque Ripple Minimization of Seven-Phase Induction Motor under More-than-Two-Phase Fault

In respect to operation of seven-phase induction motors under open-phase faults, the single-phase fault and two-phase fault have been studied in prior-art. However, the seven-phase induction motor is able to operate under three-phase and four-phase fault, and how to suppress the torque ripple under these two cases is still not discussed. According to the steady-state model in terms of symmetrical components (SCs), there are six effective SCs producing the torque ripple during the open-phase faults. In this paper, the fundamental positive SC is kept constant based on the stator magneto-motive force invariance. By manipulating the other SCs, several current commands are deduced and the optimum control strategy with minimum torque ripple is selected. In addition, their average torque and efficiency are also evaluated. Finally, the effectiveness of the proposed strategy is verified through the simulation analysis.