Film capacitors are a kind of capacitor that utilizes a thin film of plastic as a dielectric. A sophisticated film drawing process makes the film very thin for these capacitors. Once the film is made for the capacitor, it is either metalized or left untreated. This depends mainly upon the applications and requirements of a capacitor. After that, electrodes are added, and then the assembly is mounted onto a case which gives it protection against environmental factors. Film capacitors have low inductance, high stability, and low cost. Because of such elements, they are used in many applications.
Types of Film Capacitors
There are many different types of capacitors like polyester film, metalized film, polypropylene film, Mylar capacitor, PTFE capacitor, etc. The key difference among all these capacitors is the material used as a dielectric, which is decided based on the capacitor's applications. Therefore, you must always be careful in choosing a capacitor for a specific application. Make sure that the dielectric material is the one that suits your application the best.
Polyester Capacitor
The polyester capacitor is also known as polyester film capacitor, and it is named so because the dielectric material is polyethylene terephthalate. This is also why this capacitor is sometimes called a PET capacitor. This capacitor is mainly used in general-purpose board-level applications, including bypassing, blocking, decoupling, and some noise suppressing applications. The dielectric material for these capacitors is primarily used to make capacitors required for high-frequency AC applications.
Polypropylene Capacitor
This is another type of film capacitor whose dielectric material is a polymer known as polypropylene, also known as PP capacitors. Polypropylene is a dielectric material mainly used for large and powerful capacitors. They are known to be used for high power and high-frequency applications such as pulse power discharge applications, induction heating, and AC capacitors for electric distribution.
PTFE Capacitors
The capacitors that use PTFE as their dielectric material are PTFE capacitors. This dielectric material is used for the capacitors required for applications that need low losses, good parametric stability, and high voltage ratings.
Characteristics of Film Capacitors
As already mentioned, film capacitors are used in various applications because of their superior characteristics.
- Since these capacitors are not polarized, they are suitable for power and AC signal applications.
- These capacitors can also be designed with highly accurate capacitance values to maintain the values longer than the other types of capacitors. Because of this factor, film capacitors age more slowly than the different types of capacitors. Therefore, film capacitors have a long service and shelf life and a low average failure rate.
- Film capacitors can also be manufactured with the highest precision capacitance, due to which they last longer than other capacitors.
- Film capacitors can tolerate voltages in the range of kilovolt and can also offer powerful surge current bursts.
- A particular class of film capacitors is manufactured that can withstand reactive power of more than 200 volt-amperes. This specific film capacitor is known as a power film capacitor.
- These capacitors may also have special screw-type terminals capable of withstanding high currents.
- Film capacitors are known to be bulkier than any electrolytic equivalents, which is an indication of SMT packages being available.
Precaution
Capacitors can sometimes burst if overloaded. This is a common occurrence in all types of capacitors; therefore, you should be careful.
