Dynamic Process of Self-Healing in Metallized Film: From Experiment to Theoretical Model

Metallized film capacitors (MFCs) have been widely commercialized, and the insulation failure has become an important issue under high electric field. However, due to the self-healing characteristic, the MFCs offer a notable advantage in electrical insulation. This work aims to optimize the process of manufacturing in MFC in self-healing performance and explore the development process of self-healing in metallized film from experiment to theoretical model. In self-healing experience, the thickness of dielectric layer is negatively correlated with the performance of self-healing and winding tension in manufacturing is positive instead. The self-healing in metallized films have an incomplete but fierce combustion producing gas product like C2H6/CO and a large amount of H2. On the other hand, the self-healing process did not produce polar fragments/groups in dielectric layer, as indicated by Fourier transform infrared spectroscopy (FTIR). The SEM scan suggests a strong correlation between self-healing and carbonized area on the surface of dielectric layer. A small amount of metallic elements was found to remain in the self-healing area, with no metallic oxide particles. However, a large amount of graphite is composited in the clearing area along with a certain amount of element O. The simulation result of theoretical model built on plasma theory shows a depth of
$0.28~\mu \text{m}$
in carbon area, accounting for 5% of the 5.8-
$\mu \text{m}$
thickness of dielectric layer. In addition, the radius of carbonized area in dielectric exceeds the evaporated area in metallized layer by 1.5 times.