Capacitance Loss Mechanism and Prediction Based on Electrochemical Corrosion in Metallized Film Capacitors

For the metallized film capacitors (MFCs) designed to maximize the self-healing performance in the event of overvoltage, electrochemical corrosion is the major capacitance loss (CL) mechanism especially under high temperature and/or high humidity. In this paper, the electrode corrosion evolution is analyzed by dividing the process into anode and cathode reaction. In order to investigate the CL characteristics, three types of MFCs are stressed with 305 VAC under different temperature and humidity. Based on the corrosion mechanism and distribution analysis, a staged CL prediction method is proposed. The results indicate that the typical CL curve can be divided into 4 stages which are characterized by the reaction rate coefficient and the capacitance loss exponent derived from the experimental data.