The role of film capacitors

What are the applications of film capacitors in power electronics?

The main applications for film capacitors in power electronics are identified and guidance given on how to select appropriate film capacitor types. Detailed calculations are then given for some example circuits showing how particular capacitors and their ratings are selected.

What are the different types of film capacitors?

Film capacitors are one of the most common types of capacitors used in electronics systems today. The most widely used types of film capacitors include polyester, polycarbonate, polystyrene, polypropylene, polysulfone, and Teflon capacitors. A comparison chart of various film capacitors is shown in Table 1.

Why is a film capacitor a good choice?

The inherent geometry of film capacitor structure results in very low ohmic losses and a very low parasitic inductance, which makes them especially suitable for applications with very high surge currents (snubbers) and for AC power applications, or for applications at higher frequencies.

What is a large power film capacitor?

Although the materials and construction techniques used for large 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 are often classified separately, for historical reasons.

Why are power capacitors different from film capacitors?

Although the materials and the construction of power capacitors are mostly similar to the smaller film capacitors, they are specified and marketed differently for historical reasons. The "film capacitors" were developed together with the growing market of broadcast and electronic equipment technology in the mid-20th century.

Why do film capacitors have a higher voltage?

The move to higher bus voltages also favors film capacitor types; the same energy is stored with smaller CV ratings at high voltage (due to the ‘squared’ in E=CV2/2) so less capacity is needed, and film types are available with kV ratings as required.