Polypropylene (PP) Film Capacitors
Polypropylene film capacitors have a dielectric made of the thermoplastic, non-polar, organic and partially crystalline polymer material Polypropylene (PP), trade name Treofan, from the family of polyolefins. They are manufactured both as metallized wound and stacked versions, as well as film/foil types. Polypropylene film is the most-used dielectric film in industrial capacitors and also in power capacitor types. The polypropylene film material absorbs less moisture than polyester film and is therefore also suitable for "naked" designs without any coating or further packaging.
The temperature and frequency dependencies of electrical parameters for polypropylene film capacitors are very low. Polypropylene film capacitors have a linear, negative temperature coefficient of capacitance of ±2,5 % within their temperature range. Therefore, polypropylene film capacitors are suitable for applications in Class 1 frequency-determining circuits, filters, oscillator circuits, audio circuits, and timers. They are also useful for compensation of inductive coils in precision filter applications, and for high-frequency applications.
Most power capacitors, the largest capacitors made, generally use polypropylene film as the dielectric. PP film capacitors are used for high-frequency high-power applications such as induction heating for pulsed power energy discharge applications, and as AC capacitors for electrical distribution. The AC voltage ratings of these capacitors can range up to 400 kV.