Pulse withstand capability of self-healing metalized polypropylene capacitors in power applications

Experiments performed on the end-edge contacts of polypropylene capacitors to determine whether the thermal effect is the main cause of their degradation are described. Current pulses with different wave-shapes but with the same value of the Joule integral were applied to the contacts, and the degradation levels were ascertained by measuring the tan δ variation, since degradation of the contacts results in an increase of the equivalent series resistance of the capacitor. The results obtained show only a partial dependence of the degradation level on thermal stress, revealing a contribution from the electrical and mechanical stresses