Self-Healing in Metallized Film Capacitors: Theory of Breakdown Interruption

A theory of self-healing (SH) in metallized film capacitors (MFCs) is introduced. The interruption of the filamentary breakdown (BD) current in the thin dielectric insulation occurs when the thermally driven increase of the series impedance in the electrode metallization destabilizes the BD plasma arc. The interruption process can be described as a switching process which is self-induced by feedback via Joule heating. The theory is illustrated with an electric arc-like model for the BD current, coupled to the 2-D temperature-dependent RC transmission plane defined by the two metallization electrodes. A specific model realization is implemented in a multiphysics finite element method (FEM) simulation tool (COMSOL) and illustrated with a few results for electrodes with and without segmentation.