Power capacitors

In electrical engineering, power capacitors are mainly used for :

• power factor improvement ;

• reduction of impedances in line series ;

• voltage regulation ;

• harmonic frequency filtering ;

• the network plug circuit ;

• starting single-phase motors ;

• protection of electric motors ;

• electrical energy storage.

• Five types of capacitors are available to meet user requirements:

  • Mixed capacitors: these consist of a sheet of paper and two sheets of plastic impregnated with a non-chlorinated liquid dielectric;

  • all-film capacitors: these consist of two or three sheets of plastic impregnated with a non-chlorinated liquid dielectric;

  • all-metallized-film capacitors: these consist of a metallized, non-impregnated plastic sheet;

  • all-film metallized and impregnated capacitors: these consist of a metallized plastic sheet; the coils thus formed are impregnated with a liquid or gaseous dielectric;

  • electrolytic capacitors.

  The latter, whose use is limited to starting single-phase motors, tend to belong to the field of electronics [32] . On the other hand, other types of capacitor are widely used on high-voltage (HTA and HTB) and low-voltage (BT) networks.

  This article deals in detail with capacitors designed to supply reactive energy to power grids or industrial plants.

• We use the terminology defined in IEC 871-1, the main terms of which are listed below.

  • Capacitor element (or element): a device consisting essentially of two electrodes separated by a dielectric.

  • Unit capacitor: set of one or more capacitor elements placed in the same enclosure and connected to output terminals.

  • Capacitor bank (or battery): set of individual capacitors connected so as to act together.

  • Capacitor: the term capacitor is used when it is not necessary to specify whether it is a single capacitor or a capacitor bank.