Views:6 Author:Site Editor Publish Time: 2020-11-09 Origin:Site
Metallized film capacitors are made of organic plastic film as the medium, metalized film as the electrode, and made by winding (except for the laminated structure). The films used in the metalized film capacitors include polyethylene, Polypropylene, polycarbonate, etc., in addition to winding types, there are also laminated types. Among them, polyester film factory media and polypropylene film media are the most widely used.
Metallized film capacitors are vapor-deposited a layer of metal film on the surface of polyester film instead of metal foil as the electrode. Because the thickness of the metalized film is much smaller than that of metal foil, the volume after winding is also larger than that of metal foil capacitors. It is much smaller. The biggest advantage of metallized film capacitors is the "self-healing" feature.
The so-called self-healing characteristic is that if the thin film medium has a defect at a certain point and a breakdown short circuit occurs under the action of overvoltage, and the metallization layer of the breakdown point can be formed by instantaneous melting and evaporation under the action of an electric arc-a very small void The metal area re-insulates the two pole pieces of the capacitor and can still continue to work, thus greatly improving the reliability of the capacitor.
Capacitors of this type of metallized film have a so-called self-recovery effect, that is, when the tiny part of the electrode is short-circuited due to the fragile electrical boundary, the electrode metal around the short-circuited part will be affected by the capacitor at the time. The electrostatic energy or short-circuit current causes a larger area to melt and evaporate to restore insulation, so that the capacitor resumes its role as a capacitor.