Research on Torque Ripple of Multi-Phase PM Machine under Fault-Tolerant Condition

The influence factors of torque ripple under fault-tolerant condition are investigated from the aspects of magnetomotive force (MMF) harmonics and magnetic saturation for multi-phase PM machine. The armature MMF harmonic distributions under healthy and fault-tolerant conditions are obtained. Reconfiguration of the phase currents introduces some new harmonic components, which are featured as 5n and 5n±2 times. The introduced 12
^th
armature MMF harmonic interacts with the 3
^rd
rotor MMF harmonic, and this will cause 2
^nd
and 4
^th
torque harmonics. The torque ripple and torque harmonic distribution under different load conditions are further investigated to indicate the influence of magnetic saturation on torque ripple. Results show that magnetic saturation will increase the ratios of 2
^nd
and 4
^th
harmonics in torque, thus causing the increase of torque ripple.