Electrode-end contact degradation of metallized polypropylene capacitors in power applications

An explanation of the disconnection of `sprayed ends´ from the electrode edges of metallized polypropylene capacitors is given. Experimental observations using transparent cells and post-test analyses of the end-edge contacts show that the disconnection is due to erosion caused by electric sparks. The sparks are a consequence of the irregular nature of the contacts and of high intensities of the current flowing through them. Results of laboratory tests show that the degradation of the contacts is related to the peak value of the current pulses, in agreement with the above explanation. In addition, the results confirm that the degradation is not related to the energy content of the applied pulses