Loss Reduction of Five-Phase Induction Motor With Third Harmonic Injection Throughout Widest Torque Range Under Open-Circuit Faults

The harmonic injection and fault-tolerant control can significantly increase the torque density and dependability of induction motor systems without raising the hardware cost. In terms of fault-tolerant control, the conventional maximum-torque strategy (MTS) and minimum-copper-loss strategy (MLS) are commonly used in motor systems to, respectively, realize the widest postfault torque range and the minimum copper loss. However, the classical MTS and MLS cannot simultaneously maximize the torque range and minimize the copper loss and are not applicable to induction motors with harmonic injection, which underutilizes the potential capability of the motor under faults. To address this situation, this article provides an efficiency-optimized MTS (EOMTS) for five-phase induction motors with third harmonic injection (FPIMs-THI) to minimize the copper loss for each torque value throughout the widest torque range. The optimal flux distribution is basically guaranteed, and the degrees of freedom are saved by neglecting minor magnetic field components. The relative relationship of the phase currents can be adaptively adjusted to the load conditions. In this way, the postfault torque range and efficiency of FPIM-THI are synergistically optimized. The proposed EOMTS is validated in an FPIM-THI for the typical open-circuit fault conditions. Experiments demonstrate the validity and effectiveness of EOMTS.