Experimental Investigation of Self-healing Properties of Metalized Film Capacitors

The self-healing performance of metalized film capacitors is studied by building a repeated charging and discharging setup and a self-healing signal testing setup. The charging and discharging setup imitates the working condition of the metalized film capacitor. The process is repeated until the lifetime of the capacitor came to an end. During the experiment, the self-healing signal was detected and counted at the same time, which was achieved by building a self-healing signal detection setup. The self-healing signal detection setup was used to achieve the acquisition of self-healing waveforms and amplitudes and the number of self-healing signals. In the research, it was found that only the capacitance changed monotonously. The waveform of self-healing discharge has a certain regularity. In the initial stage of the aging test, the waveform is relatively regular, but when the aging test continues to approach the end of the capacitor's lifetime, the waveform is distorted, and the cause of the distortion is analyzed. When the performance of the capacitor continues to deteriorate, the frequency of self-healing discharges also begins to become more frequent, and the amplitude increases. Besides, by dissecting the capacitor, it can be found that the self-healing discharge point is mainly located at the margin. That means the field strength distribution at this place needs to be optimized.