Space Harmonics and Saturation Interaction in Fault-Tolerant Induction Machine Drives Due to a Zero-Sequence Stator Current

Postfault operation strategies for three-phase squirrel cage induction machine drives enable increased fault-tolerance in the case of inverter faults. However, in strategies that apply a zero-sequence stator current, additional space harmonics interact with the fundamental wave. This article studies these space harmonics and the occurring saturation interaction with the main system based on two different induction machines. For illustration, and to support the analysis with quantitative results, it exemplarily investigates the effects of this saturation interaction on the flux linkages and the torque during the postfault operation of a rotor flux-oriented drive.