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Ageing of self-healing polypropylene film capacitors by non-sinusoidal voltage

The goal of this work was to show ageing of capacitors with metalized polypropylene film by the sinusoidal and non-sinusoidal voltage and to find how the shape of the voltage waveform influences the ageing rate. A special device, which makes forming of the voltage of the fundamental and selected higher harmonic component possible, was used as a source for non-sinusoidal load. Capacitors with values from 10 nF to 47 /μF were tested. It was found that the ageing rate of capacitors loaded by the non-sinusoidal voltage is mostly a little bit higher in comparison with those when ageing was carried out by the sinusoidal load. The reason is faster degradation of the film electrodes under the non-sinusoidal voltage or higher temperature of “hot-spots” inside the capacitor.