Wednesday, 28 August 2019

Smart Consumer - Understanding Power Factor

Understand the ‘Power Factor’ of your AC Load

Are you facing problems like a generator tripping due to Over Current Alarm or excessive black smoke?
Have you been advised to reduce the electrical load to suit the capacity of your generator?

If you are using a generator in a Factory, at a construction site or for any other commercial purpose, you may have faced such a situation. Most likely, you did not hire any electrical consultant to evaluate your electrical load before buying the generator.

A poor Power Factor (PF) might be the reason for these kind of problems. Keep reading for a fundamental understanding of what is a power factor.

The Beer analogy is the most popular and easy way to understand the Power Factor.

In a glass of beer there will be beer and also few inches of foam. You are paying for per glass of beer, therefore more beer and less foam is better value for money.

Let us compare this glass of beer with electrical power.

Glass of Beer                      = Beer + Foam
Apparent Power               = True Power + Reactive Power

True Power (Beer) is the power which we actually use, but Apparent Power (Beer + Foam) is the power we pay for.

Power Factor (PF)                            = True Power (kW) / Apparent Power (kVA)

Apparent Power (kVA) x PF          = True Power (kW)

The value of Power Factor will be between 0 - 1.

A Power Factor of 1 is best, but practically very difficult to achieve. A higher Power Factor value is always better.

There are various types of electrical loads. Broadly electrical loads can be divided into following three types.

1.       Resistive Load
2.       Inductive Load
3.       Capacitive Load

Pure Resistive, Inductive or Capacitive loads are never present in practical application, it is always a combination of different types of loads. Each type of load has different impact on the PF. 

Bad Power Factor

Bad Power Factor means more Reactive Power (foam of Beer) which is useless. Bad Power Factor reduces the capacity of Electricity Board supply lines. There is a provision of Penalty fees by the Electricity Board for having bad (very low) PF in your Loads. For domestic use there is no such penalty.

Commonly there will be more Inductive Loads which negatively affects the Power Factor.

Inductive Load causes Lagging Power Factor

Inductive Loads tend to hold back the current and results in a Phase shift between the Voltage and the Current. 

Capacitive Loads causes Leading Power Factor

This is opposite to the Inductive Load. Capacitive load tends to hold back the voltage, causing a phase shift.

Rectifying Leading Power Factor :- 

If you have a leading power factor caused by high capacitive loads ,

- Add Inductive Load to the circuit.

Pure Resistive Load causes Unity Power Factor – THE BEST

Pure resistive loads have a PF value of 1. There will be no phase shift between the Voltage and Current.

It means the Voltage and Current (in AC circuits) will cross the 0 value together at the same time.

Benefits after improving Power Factor

1.       Increase in efficiency of system and devices
2.       Low Voltage Drop
3.       Can use optimized size of Power Cable which will give a cost benefit.
4.       An Increase in available power
5.       Appropriate Size of Generators.
6.       Eliminate the penalty of low power factor from the Electric Supply Company
7.       Saving in the power bill
8.       Better usage of power system, lines and generators etc.

For further guidance or information on diesel/gas gensets visit our website at or call us at 1-800-419-1999

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