A low power factor increases the current, which results in an increase in losses and causes a decrease in the efficiency of the system. Hence, it is necessary to improve the power factor of the system, in order to ensure economic transmission and distribution of electric power.

The lagging reactive components of current can be compensated by connecting a device having leading currents in parallel with the load, called a capacitor.

Power factor correction can be achieved by, 
1. Static capacitor
2. Synchronous condenser
3. Phase advancer

The phase advancer supplies exciting ampere turns to the rotor circuit at slip frequency. The phase advancer is mounted on the same shaft as the main motor.

The capacitor has leading currents and partly or completely compensates these lagging reactive components of load currents. This results in an increase in the power factor of the load.