Metallized film capacitors are capacitors made by using organic plastic films as the dielectric and metalized films as the electrodes. In addition to the winding type, there are also laminated types. The films used in metallized film capacitors include polyethene, polypropylene, and polycarbonate. Among them, polyester film media and polypropylene film media are the most widely used.
Metallized film capacitors have a self-healing effect. Assume that when a small part of the electrode causes a short circuit due to the fragile electrical boundary, the electrode metal surrounding the short circuit part will cause a larger area of melting and evaporation to restore insulation due to the electrostatic energy or short circuit current carried by the capacitor at that time. , Make the capacitor return to the role of the capacitor again.
Metallized film capacitor is a layer of metal film deposited on the surface of the polyester film instead of metal foil as the electrode. Because the thickness of the metallized film layer is much smaller than the thickness of the metal foil, the volume after winding is also larger than the metal foil type capacitor. Much smaller. The biggest advantage of metallized film capacitors is the "self-healing" characteristic, which greatly improves the reliability of capacitor operation.
In principle, there is no short-circuit failure mode for metallized film capacitors, and many short-circuit failure phenomena occur for metal foil capacitors. However, compared with metal foil capacitors, there are two disadvantages: 1. The capacitance stability is not as good as that of foil capacitors. This is because metallized capacitors are prone to loss of capacity under long-term operating conditions and reduce capacity after self-healing. 2. The ability to withstand large currents is poor because the metallized film layer is much thinner than the metal foil.
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