Accelerated Damage in Metallized Film Capacitors Under Pulse Surge Combined With Rated DC Voltage

Metallized film capacitors (MFCs) have good self-healing performance and are widely used in pulsed power supplies, power systems, and aerospace equipment. The self-healing time of MFCs is often in the order of microseconds. When the pulsewidth of overvoltage is close to the self-healing time, MFCs are at risk of insulation failure. In this article, self-healing energy and time under pulse surge combined with rated dc voltage are investigated by analyzing the effect of the number of applied pulses on the capacitance loss, dielectric loss, and equivalent series resistance (ESR) of MFC. The correlation between the number of applied pulses and the capacitance loss of MFC at different repetition frequencies, pulse components, and temperatures is studied, fitting the 5% turning points of capacitance loss. The experimental results show that the multiple types of self-healing occur in an active period of one pulse under microsecond overvoltage. According to the level of injection energy and several typical waveforms from voltage and current, the self-healing process of MFC can be classified into effective self-healing, disruptive self-healing, and fatal self-healing. When effective self-healing occurs in the MFC, the performances remain stable for a certain time. As the number of tolerated pulses increases, disruptive self-healing and fatal self-healing significantly decrease capacitance value but increase dielectric loss and ESR.