Polypropylene film capacitors are a commoncapacitor used in electrical equipment. They are made of two pieces of thin plastic film, charged with electrodes as the dielectric. They can replace electrolytic capacitors in applications where the voltage is above 500V.
There are two main formats of polypropylene film capacitors. They're distinguished by the type of dielectric (insulating) material used. Firstly, film foil has two metal foil electrodes separated with two plastic films. Whereas metallised film has two very thin layers of metallisation, with plastic film as the dielectric. To get the desired electrical characteristics you need, such as stability or ability to withstand high voltage, you can choose different film materials for the dielectric layer.
Because of their high tolerance and voltage resistance, polypropylene film capacitors are used in a wide range of electric applications. These include switching power supplies, high voltage circuit applications, lighting ballast systems and circuits with high peak current levels.