The setup behaves like a large number of individual capacitors connected in parallel, thus reducing the internal ohmic losses ( ESR) and the parasitic inductance ( ESL). This contact keeps all current paths to the entire electrode very short. However, a disadvantage of metallized construction is its limited current surge rating.Ī key advantage of modern film capacitor internal construction is direct contact to the electrodes on both ends of the winding.
With this basic design, it is possible to make high quality products such as "zero defect" capacitors and to produce wound capacitors with larger capacitance values (up to 100 μF and larger) in smaller cases (high volumetric efficiency) compared to film/foil construction. This configuration can have "self-healing" properties, in that dielectric breakdowns or short circuits between the electrodes do not necessarily lead to the destruction of the component. A very thin (~ 0.03 μm ) vacuum-deposited aluminum metallization is applied to one or both sides to serve as electrodes. Metallized film capacitors are made of two metallized films with plastic film as the dielectric.Advantages of this construction type are easy electrical connection to the metal foil electrodes, and its ability to handle high current surges. Each is layered with a thin metal foil, usually aluminum, as the electrodes. Film/foil capacitors or metal foil capacitors are made with two plastic films as the dielectric.There are two different types of plastic film capacitors, made with two different electrode configurations: In general, film capacitors are not polarized, so the two terminals are interchangeable. Overview of construction and features įlattened winding of a "naked" film capacitor before encasement, with a view of collateral metal contact layers ("schoopage") and attached terminalsįilm capacitors are made out of two pieces of plastic film covered with metallic electrodes, wound into a cylindrical shaped winding, with terminals attached, and then encapsulated.
9.2 Safety and EMI/RFI suppression film capacitors.8.5.2 Dissipation factor (tan δ) and ESR.8.5 Impedance, dissipation factor, and ESR.8.2.1 Frequency and temperature changes in capacitance.8.2 Capacitance standard values and tolerances.6.8 Paper (film) capacitors (MP) and mixed film capacitors.6.5 Polytetrafluoroethylene (PTFE) film capacitors.6.4 Polyphenylene sulfide (PPS) film capacitors.6.3 Polyethylene naphthalate (PEN) film capacitors.6 Characteristics of film materials for film capacitors.5 Dielectric materials and their market share.2.4 Internal structure to increase surge ratings.2.3 Internal structure to increase voltage ratings.2.2 Self-healing of metallized film capacitors.1 Overview of construction and features.In the past, the boundary between these two families was approximately at a reactive power of 200 volt-amperes, but modern power electronics can handle increasing power levels. As modern electronic equipment gained the capacity to handle power levels that were previously the exclusive domain of "electrical power" components, the distinction between the "electronic" and "electrical" power ratings has become less distinct. Although the materials and construction techniques used for large power film capacitors are very similar to those used for ordinary film capacitors, capacitors with high to very high power ratings for applications in power systems and electrical installations are often classified separately, for historical reasons. Ī related component type is the power (film) capacitor. Film capacitors, together with ceramic capacitors and electrolytic capacitors, are the most common capacitor types for use in electronic equipment, and are used in many AC and DC microelectronics and electronics circuits. Two of these conductive layers are wound into a cylinder shaped winding, usually flattened to reduce mounting space requirements on a printed circuit board, or layered as multiple single layers stacked together, to form a capacitor body.
The electrodes of film capacitors may be metallized aluminum or zinc applied directly to the surface of the plastic film, or a separate metallic foil. The dielectric films, depending on the desired dielectric strength, are drawn in a special process to an extremely thin thickness, and are then provided with electrodes. Plastic film capacitors potted in rectangular casings, or dipped in epoxy lacquer coating (red color)įilm capacitors, plastic film capacitors, film dielectric capacitors, or polymer film capacitors, generically called film caps as well as power film capacitors, are electrical capacitors with an insulating plastic film as the dielectric, sometimes combined with paper as carrier of the electrodes.