Power Factor Correction Methods

• Power factor maintenance  is the most important consideration in electrical power system. 
• Power factor is defined as the cosine angle between voltage and current.
• If this power factor(P.F) is not maintained nearer to unity , then it will lead to power factor penalty( i.e electricity bill increases due to consumption of more current in household non linear loads due to decrease in P.F) and enormous voltage drop in the transmission lines.
•  Now, we are going to see various power factor improvement methods one by one.

1. Static capacitors
2. Synchronous condenser 
3. Phase advancers 

1.Static capacitors:

• As we know that, most of our loads are inductive load which is considered as a non linear load( voltage and current are not in phase) .
• In inductor, the current lags behind  the voltage by 90 degree. Now, the point is how to make the current to be Inphase with voltage.
• In capacitor, the current leads the voltage by 90 degree. Here,is the solution, if we add capacitor in parallel with the inductive load, the resultant current is almost nearer to the voltage.

• Group of capacitors connected together to form a capacitor banks.

• Here, is the phasor diagram to show how capacitor aids in increasing the power factor.

2.synchronous condenser:

• A synchronous motor takes a leading current when over excited and therefore behaves as a capacitor.
• An over excited synchronous motor running on no load is known as synchronous condenser.

• When such a machine is connected in parallel with the supply, it takes a leading current which partly neutralizes the lagging current of the inductive load.
• Thus, the power factor is improved.

3. Phase advancers:

• Phase advancers are used to increase the power factor of induction motor.
• The stator exciting current of the induction motor lags behind the voltage by 90 degree.
• So, an external AC exciter is connected to the rotor circuit of the motor.
• It provides exciting campers turns to the rotor circuit at slip frequency.
• Now induction motor is said to be operated on leading power factor like an over excited synchronous motor.
• Thus, power factor is maintained.