Frequently Asked Questions

We hope to give you an easy explanation of what Power Factor Correction (PFC) Capacitor is, why one need PFC Capacitor, and to answer frequently asked questions


Question 1 : What is a capacitor ?

Question 2 : What is Power Factor ?

Question 3 : What causes low Power Factor ?

Question 4 : Why Improve your Power Factor ?




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What is a capacitor ?

A capacitor is an electric device that can store electric charge which can be used later for different useful purposes..


What is a Power Factor ?

Yes, now we are ready to ascertain what power factor is

Before understanding power factor, we will go through some basic definitions:

REAL , reactive and Apparent Power


Real Power (P) :

Real Power also called "Working Power" or "Actual Power" or "Active Power" and is measured in unit of Watts. This is the power actually required by the equipment to perform useful work.

Reactive Power(Q) :

Reactive Power is the power that is requied in case of Inductive Load( magnetic equipment) such as motors, relay, transformer etc. Reactive Loads dissipate zero Power, yet they drop voltage and draw current gives the decipative impression that they actually do dissipate power.

This "Phantom Power" is called reactive power and is measured in unit of VAR (Volt- Amp- Reactive). The reactive power is required to produce the magnetic flux.

Apparent Power (S) :

The combination of Reactive and Real Power is called Apparent Power, and it is product of circuit's Voltage and current, without reference to Phase angle. Apparent Power is measured in the unit of Volt- Amps (VA).

In other words Apparent Power is the "Vectorial Summation" of :













The three type of Powers - real, reactive and apparent power relates to one another in
trignometric form, which is called as power triangle in figure below:









Power traingle relating apparent power to active power and reactive power.

Let us understand Power Triangle in simple analogy ....







To understand power factor, visualize a horse pulling a railroad car down a railroad track. Because the railroad ties are uneven, the horse must pull the car from the side of the track. The horse is pulling the railroad car at an angle to the direction of the car's travel. The power required to move the car down the track is the working (real) power. The effort of the horse is the total (apparent) power.

Because of the angle of the horse's pull, not all of the horse's effort is used to move the car down the track. The car will not move sideways; therefore, the sideways pull of the horse is wasted effort or nonworking (reactive) power.

The angle of the horse's pull is related to power factor, which is defined as the ratio of real (working) power to apparent (total) power. If the horse is led closer to the center of the track, the angle of side pull decreases and the real power approaches the value of the apparent power.

Therefore, the ratio of real power to apparent power (the power factor) approaches 1. As the power factor approaches 1, the reactive (nonworking) power approaches 0.

Power Factor = Real Power / Apparent Power

= KW / KVA

For example, using the power triangle illustrated below, if





Real power = 100 kW

and

Apparent power = 142 kVA

then

Power Factor = 100/142 = 0.70 or 70%.

This indicates that only 70% of the current provided by the electrical utility is being used to produce useful work.


"Note that in an ideal condition look heavy load analogy :

KVAR would be very small (approaching zero)
KW and KVA would be almost equal (Need not to waste any power along height)
The angle formed between KW and KVA would approach zero
Cosine ø would then approach one
Power factor would approach one.

Power factor of an ideal system should be 1.0

However, sometimes, our electrical distribution has a power factor much less than 1.0."

Low power factor is expensive and inefficient. Many utility companies charge you an additional fee if your power factor is less than 0.9. Low power factor also reduces your electrical system's distribution capacity by increasing current flow and causing voltage drops.



What causes low Power Factor ?


Low power factor is caused by inductive loads (such as transformers, motors, high intensity discharge lighting, induction generators-wind mill generator etc.), which are the major portion of the power consumed in industrial complexes.

Unlike resistive loads that create heat by consuming kilowatts, inductive loads require the current to create a magnetic field, and the magnetic field produces the desired work. The total or apparent power required by an inductive device is a composite of the following:

Real power (measured in kilowatts, kW)

Reactive power, the nonworking power caused by the magnetizing current, required to operate the device (measured in kilovars,     kVAR)

Reactive power required by inductive loads increases the amount of apparent power (measured in kilovoltamps, kVA) in a distribution system. The increase in reactive and apparent power causes the power factor to decrease


Why improve your Power Factor ?


There are several different reasons to improve Power Factor. Some of the benefits of improving power factor are as follows:

Curtail Utility Bill

Recall that inductive loads, require reactive power, causes low power factor.
This increase in required reactive power(KVAr) causes an increase in required apparent power(KVA) which is supplied by utility.

So, with the facility of improved power factor, Utility can supply more loads without actually increasing the installed capacity.

So, a facility's low power factor causes the utility to have to increase its generation and transmission capacity in order to handle this extra demand.

By lowering your power factor, you use less KVAr. This results in less KW, which equates to a dollar saving from the utility.


Eliminating Power Penality & Getting Incentive

Utilities usually charge an additional fee when their power factor is less than 0.9. In fact some of the utilities are also offering Incentives if power factor is above 0.95.

Thus, one can not only avoid the additional fees but also get the incentive.


Increased system Capacity

By additing capacitor (KVAr ) to the system, the power factor is improved and the KW capacity of the system is increased.

For Example, a 1000 KVA transformer with an 0.6 Power factor, provides 600 KW of power to main bus bar

By increasing the power factor to 90%, more KW can be supplied for the same amount of KVA.

The KW capacity of the system increases to 900 KW.

Reduced system losses

Uncorrected power factor causes power system losses in your distribution system. By improving your power factor, these losses can be reduced. With the lower system loss, one can also able to add additional load to the system.