Investigation on performances of insulation materials for inverter-fed traction motors

In order to investigate the degradation phenomena of the electrical insulation of stator windings stressed by non sinusoidal applied voltages, an experimental activity has been carried out on specimen subjected to repetitive unipolar pulse voltages. The effect of the application of such voltages has been studied by recording, at different aging stages, the dielectric properties (ε and tanδ) of the insulating material and by detecting the partial discharge activity when applying a sinusoidal (50 Hz) voltage. Furthermore, the introduction of diagnostic tools based on PD detection has made it possible the classification, recognition and location of defects, which might give the basis for assessing new design criteria and new standards for the electrical insulation of components subjected to distorted wave shapes.