MET Films

Film Capacitors are used in almost all electronic circuits. They store energy and discharge it when needed. Important applications for film capacitors include electronic filtering for linear and switching power supplies; decoupling and bypass of electronic signals for circuits and circuit boards; and frequency control, timing and conditioning of electronic signals for a broad range of applications.

Film capacitors are constructed of electrodes (the capacitor plates) with plastic dielectric material in between.
The type of electrode used determines whether the capacitor is a metalized film or a film/foil type.
Metalized capacitors have a self-healing behavior as an key characteristic by its construction. Self healing is the ability to recover after a dielectric breakdown.
Due to their construction, very thick electrodes, film/foil capacitors can carry higher currents than metalized types,
but are much larger in volume. These capacitors cannot recover after a breakdown.
Therefore In some constructions double side metalized plastic film is used as electrode to replace the foil.
The plastic material has only the function of carrier: the self healing properties are maintained and the current carrying capability is increased a lot in comparison with single metalized types.
Depending on the AC voltage in the application, single or series constructions are used. In a series construction two or more sections are placed internally in series in one capacitor. Single section capacitors are normally used for products with an AC rating up to 300 Vac.
Series constructions are used for higher voltages. The end connection of the capacitor cell to the outside circuit is realized by metal sprayed end connections wherein lead wires or tabs are welded.

Finally the capacitor cells can be protected for severe environmental conditions or to withstand passive flammability. Encapsulation with epoxy materials in plastic boxes is common used for fixed outline dimensions. Epoxy dipped capacitors have a more rounded and easy to handle shape. All these encapsulations are flame retardant materials fulfilling the UL 94 classification system.
Axial types are typically of the wrapped end construction. An extra wrapped film and epoxy at the end connections protects the cell. For high power film capacitors as well aluminum housings in a can-format are common.

Main applications:

Power supplies

Systems and installations for power factor correction

High voltage DC (HVDC) transmission systems

Inverters for solar energy installations

Inverters for traction applications

Equipment and systems of consumer electronics and communications technology

Ballasts for LED lighting systems

Ballasts for xenon lamps in motor vehicles

EMC filters

Film Caps (DC-Link)