Capacitance Loss Analysis of Metallized Film Capacitors under AC Condition

With the rise of temperature and humidity, the electrode corrosion of metallized film capacitors under AC voltage becomes more significant. And the corresponding capacitance loss makes capacitors behave abnormally. This paper concentrates on the capacitance loss analysis of metallized film capacitors. Firstly, this paper establishes an experimental platform with a voltage of 305Vrms. The ambient temperature is 85 degrees C, 60 degrees C and 35 degrees C, respectively. And the ambient humidity is 35%, 60%, and 85%, respectively. Secondly, the mechanism of capacitance loss is studied based on experiment results and the anatomical analysis of the capacitors. Finally, the capacitance loss of the metallized film capacitor with the effects of temperature and humidity is studied. The results indicate that: (1) The process of capacitance loss can be basically divided into 4 stages. Each stage corresponds to different mechanisms;(2) The duration of the moisture ingress process decreases as humidity rises or temperature decreases, while the capacitance loss is accelerated with the rise of temperature and humidity.