A Unified Fault-Tolerant Current Control Approach for Five-Phase PM Motors With Trapezoidal Back EMF Under Different Stator Winding Connections

A unified approach for fault-tolerant current control of five-phase permanent-magnet (PM) motors with trapezoidal back EMF is proposed for open-circuit phase and line faults. In addition to conventional star connection, five-phase PM motors can be connected in two penta-type connections, pentagon and pentacle. In the proposed unified approach, a general solution for fault-tolerant currents is presented which uses only the fundamental and third-harmonic current components for the excitation of the healthy stator phases. The proposed approach is based on mirror symmetry of healthy phase current with respect to the fault location and it is optimized to increase output average torque while reducing torque pulsations and minimizing ohmic losses. A general parametric solution is presented which can be applied to five-phase motor drives with any fault condition and winding connection by selecting proper optimization constraints. It is shown that penta-type connection results in improved fault-tolerant capability in terms of maximum ripple-free torque due to the absence of zero-neutral current constraint. Experimental results are presented to verify the proposed solutions for fault-tolerant current control.