Plastic film capacitor
In film capacitors, plastic film is used to construct the dielectric and aluminum or zinc is used to construct the electrodes of the capacitor. Film capacitors are also known as plastic film capacitors or film dielectric capacitors. Plastic film capacitors are mainly used in circuits where low loss and high insulation resistance is required.
Plastic film capacitor definition
Plastic film capacitor is a capacitor that uses plastic film as the dielectric and aluminum or zinc as the electrodes to store electric charge.
What is dielectric?
Dielectric is the insulating material placed between the electrodes of a capacitor. Dielectric materials are chosen based on their ability to allow electrostatic attraction and repulsion. Good dielectric materials are poor conductors of electricity. However, they allow the electrostatic field.
In plastic film capacitors, polyester, polypropylene, polyethylene terephthalate, and polyphenylene sulfide are commonly used as dielectrics.
Types of plastic film capacitors
Film capacitors are classified into two types:
Film-foil capacitors
Metallized film capacitors
Film-foil capacitors
The film-foil capacitor is made of two plastic films or sheets; each is layered with thin aluminum metal foil or sheet. The plastic sheets and aluminum sheets are then rolled in the form of a cylinder and wire leads are attached to the both ends of aluminum sheets. Polyester, polypropylene, polyethylene terephthalate, and polyphenylene sulfide are commonly used as dielectric in film capacitors. In plastic film capacitors, aluminum sheets acts as electrodes and plastic sheets acts as dielectric.
The film-foil capacitor is made of two plastic films; each is layered with thin aluminum metal foil.
Metallized film capacitors
In metallized film capacitors, the aluminum sheet or foil is replaced by a layer of metal vacuum deposited on the film layer. The most commonly used metal layer is aluminum or zinc that is extremely thin.
In metallized film capacitors, the aluminum foil is replaced by a layer of metal vacuum deposited on the film layer. The most commonly used metal layer is aluminum or zinc that is extremely thin.The plastic film layers made of synthetic material act as dielectric and the aluminum layers act as electrodes. The major advantage of film dielectric capacitors over natural dielectric capacitors is that the plastic film is synthetic or artificial. Therefore, we can able to increase thickness and heat resistance of the dielectric. In other words, we can change the thickness and heat resistance of the plastic film capacitor.
Applications of film capacitors
The various applications of film capacitors include:
A/D converters
Filters
Motor run
Peak voltage detectors
Advantages of film capacitors
High stability
Low cost
Low losses even at high frequencies
