In this type of application capacitor duty contactor or power contactor are used to switch ON the capacitors as per the system is achieve power factor.

Automatic power factor correction is typical for large electrical systems with fluctuating load where it is common to connect number of capacitors to main power distribution station or substation. The capacitors are controlled by controller which continuously monitors the relative power demand. The relay connects or disconnects the capacitors to compensate for actual reactive power of the total load an

d reduce overall demand supply. Contactors are used to switch the capacitors ‘On’ and ‘Off’ in the system.