Research On The Influence Of Interlayer Air On The Performance Of Metallized Film Capacitors

Metallized film capacitor can work under high electrical stress because of its excellentself-healing properties. It is commonly used in pulse power system for its high energydensity and reliability. In its manufacture process, dry-type metallized film capacitor willbring in air. The air exists between dielectric layers. Due to electrochemical corrosion andpartial discharge, the air between layers will influence the performance of the capacitor.Metallized film capacitor under AC electrial stress will suffer a degradation onelectrode. The degradation phenomenon is mainly because there is electrochemicalcorrosion caused by the air. Based on the study of electrochemical corrosion, this paper hasproposed a new way of heat-treatment, which is in vaccum condition. The new way ofheat-treatment can restrain the degradation effectively.The paper analyzes the breakdown mechanism of the air between layers. Study work ismainly about the double-layer dielectric system, which is made up of air and film. Theorialand simulation work is done on the air between layers when the capacitor is under DC highvoltage. Based on the analyzation of pulse discharge experiment, an effective solution toreduce the effect of air is proposed.To improve the performance of the double-layer dielectric system, a study work isdone on the impregnation of the capacitors. The study work shows that capacitors undervacuum condition or AC condition can get fully impregnated. The life of impregnatedcapacitors can be3to4times of that of dry-type ones. The teardown analyzation of theimpregnated capacitors shows that the outer layers and the middle layers of the capacitorare well protected after impregnation, and self-healing probability on these layers is greatlyreduced. Because the innner layer is under high stretching force during manufacture process,it maynot be fully impregnated. The capacitance loss of the impregnated capacitors ismainly on the inner layers.The result of this paper, which is meaning to improve the energy density and reliabilityof the capacitors, can be referenced on the improvement of the manufacture of capacitors.