Polyester Capacitors

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Polyester capacitors (MKT): suitable for filtering, coupling and stability in general and industrial electronic applications.

It is a type of film capacitor, in this case polyester film, but first we have to know a little what a film capacitor or film capacitor is.

Film capacitors, plastic film capacitors, dielectric film capacitors or polymer film capacitors, generically called "film layers", as well as power film capacitors, are electrical capacitors with an insulating plastic film as a dielectric, sometimes combined with paper as a carrier for the electrodes. .

These dielectric films, depending on the desired maximum voltage or dielectric strength, are stretched in a special process to an extremely thin thickness and then electrodes are attached to them. The electrodes of the film capacitors can be metallized aluminum or zinc applied directly to the surface of the plastic film, or a separate metal foil. Two of these conductive layers are wound into a cylinder-shaped winding, generally flattened to reduce mounting space on a printed circuit board or pcb, or layered as multiple individual layers stacked together, to form a capacitor body.

A related type of component is the power (film) capacitor. Although the materials and construction techniques used for high-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. they are often classified separately, for historical reasons. As modern electronic equipment has acquired the ability to handle power levels previously the exclusive domain of "electrical power" components, the distinction between "electronic" and "electrical" power classifications has become less clear

Film capacitors are the most common types of capacitors and it belongs to a relatively large family of capacitors. The main difference between film capacitors and other types of capacitors lies in their dielectric properties. Some are listed below and to their left their different most common trade names:

Polyester (Mylar) MKT, MKTSH
Polystyrene PS
Polypropylene MKP, FKP
Polycarbonate PC
PM metallized paper

They are available in many values, tolerances from 10% to 0.01% and voltages up to 2000 volts.

In particular, polyester film capacitors are film capacitors that use a dielectric made from the polar thermoplastic polymeric material polyethylene terephthalate (PET), trade names Hostaphan or Mylar, from the polyester family. The small physical dimensions of PET film capacitors are the result of a high relative permittivity of 3.3, combined with a relatively high dielectric strength leading to a relatively high volumetric efficiency. This advantage of compactness comes with a few disadvantages. The capacitance temperature dependence of polyester film capacitors is relatively high compared to other film capacitors, ± 5% over the entire temperature range. The frequency dependence of the capacitance of the polyester film capacitors compared to the other film capacitors is -3% in the range of 100 Hz to 100 kHz in the upper limit. Also, the temperature and frequency dependence of the dissipation factor is higher for polyester film capacitors compared to the other types of film capacitors.

Polyester film capacitors are primarily used for general purpose applications or semi-critical circuits with operating temperatures up to 125 ° C.

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Polyester Capacitors