Study of Changes in the Dissipation Factor of PP Film Capacitors Caused by Heat Treatment

The coefficient of variation of the dissipation factor of PP (polypropylene) film capacitors was examined in dependence on the time of heat treatment and the frequency. Five groups of PP film capacitors from five manufacturers were taken under test. Every group was composed of twenty capacitors. The nominal capacitance of the capacitors was 0.1 μF and the maximum operating voltage 275 V AC. All capacitors were of the type X2. The heat treatment was carried out at the temperature of 100 °C for a total time 22 983 hours. The dissipation factor was inspected in the frequency range of 1 kHz – 1 MHz. The courses of the coefficient of variation of the dissipation factor of every group of capacitors were compared mutually. It was found that the inspection of the variation coefficient can be good additional information to the monitoring the loss factor.