Space-vector models for torsional vibration of cage induction motors

Electromagnetic response of induction motors to torsional vibration is studied using space-vector and finite element (FE) models. Comparison of the results shows that the skin effect in the rotor bars plays an important role and the basic space-vector model has to be updated to a double-cage or triple-cage model. The results of the higher order models agree well with those of the FE analysis as long as motors with semi-open rotor slots are studied. In case of closed rotor slots, the saturation of the iron bridges on top of the bars causes problems in modelling accuracy.