Study on uncoupling characteristics of foil wire in metallized capacitors

Safety electrode can protect metallized capacitors from catastrophic breakdown. It plays a role in second protection which would help the metallized capacitors achieving better self-healing. The purpose of this paper is to analyze the disconnection mechanism of the small fuse of T-polypropylene safety foil, the energy of disconnecting the fuse in different width, and the relationship between the broken-down energy and time. The results of experiments indicate that the disconnection of fuse is caused by the small crack in fuse which is brought by the current heat, and the metallized layer will be evaporated as the crack becomes long enough to generate creeping discharge. The disconnection of different width fuse has little relationship with the thickness of polypropylene, but has clear relationship with the square resistance. The energy of disconnection will decrease with the increase of the time while current flows through the fuse.