Working Principle of Metallized Film Capacitor

Posted by Super User on Aug. 08-14.2015

Metallized film capacitors adopt the polyester film or polypropylene film as the dielectric, and Zn-Al alloy, as electrode, was coated to the film surface by vacuum evaporation deposition method. The capacitors come into being after non-inductive & non-polarity winding. Metallized film capacitors holding the solid characteristics of high voltage proof, high insulation resistance, better impedance frequency features(smaller parasitic inductance ), lower ESR, high capacitance stability and low loss tangent value (dissipation factor).

Capacitors are consist of two polarity plate separated with dielectric filling between them, basically there is no electricity current passing through unless the middle dielectric is over-shocked.

While connecting the capacitor to a DC loop circuit, a short charging process will occur. This process will last until the positive & negative polarity plate are fully charged with electricity (capacitor terminal voltage equals the power voltage.) After then, there will be no more current traveling and herewith a conclusion is drawn: Capacitor is DC isolated. While connecting the capacitor to an AC loop circuit, a same charging process will occur & the process stops while the capacitor voltage equals the power supply voltage, after that, the power voltage begins to descend, capacitors begin to discharge; when the power voltage is ascending reversely, the capacitor recharging reversely accordingly, then discharge reversely! Through these steps the capacitor charges & discharges alternatively just as the AC current travels, herewith a conclusion is drawn: Capacitor is AC allowing/unblocking.

In a word, capacitor are “DC blocking, AC allowing.” Capacitors are widely used in electronic circuits for blocking DC while allowing AC to pass. In analog filter networks, they smooth the output of power supplies. In resonant circuits, they tune radios to particular frequencies. In electric power transmission systems, they stabilize voltage & power flow.


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