Processes of Self-Healing in Film Capacitors in Overload Modes

The advantage of modern metallized film capacitors is high reliability caused by so-called ability to self-healing. Application of such capacitors in overload modes (at short lifetimes) can significantly improve their technical and volumetric characteristics. In spite of the fact that selfhealing had been investigated over the last decades, the existing theoretical notions and the reported experimental results did not led to the commonly accepted model of the process of self-healing. Moreover, there is no information on film capacitors performance in overload modes in the literature. In this paper, we present the results of experimental and theoretical study on processes of self-healing of film capacitors in overload modes. The capacitors’ testing method is proposed. The method allows to record events of self-healing over a wide range of voltages and times. It is shown that capacitors are able to operate at voltages 4-6 times higher than nominal value. The capacitors’ degradation mechanism is caused by multiple self-healing events that lead to the gradual accumulation of highly conducting zones near the breakdown channels. Model of single event of self-healing is developed. This allows estimating the energy of self-healing for different levels of applied voltage. It is suggested to use the value of cumulative energy of self-healing as a parameter for estimating the rate of degradation and predicting the film capacitor’s lifetime