Power Factor Definition and Applications

May 6 • General • 2073 Views • 3 Comments on Power Factor Definition and Applications

What is power factor???

It is characteristics of the alternating current (AC) circuits.Always between 0.0 and 0.1,the higher the number the greater the power factor.

power triangle

power triangle

SIGNIFICANCE OF POWER FACTOR

The significance of the it is that it lies in the fact that the utility companies supplies customers with volt-ampere but bill them in watts.The relationship is(watt=volt *ampere*power factor).It is clear that power factor below 1.0 require utility to generate more than minimum volt-ampere necessary to supply the power(watts).This increases the generation and the transmission cost.

Good power factor is considered greater than 0.85 or 85%.

What causes low power factor??

Since it is defined as the ratio of KW and KVA,we see that low power factor results when  KW is small in relation to KVA.The inductive loads causes large KVAR in the systems which includes-

Transformer

Induction motor

Induction generator(wind mill generators)

High intensity discharge lightening

These inductive loads consume major portions of the power consumed in the industries.Reactive power (KVAR)required by the inductive load increases  the amount of the apparent power(KVA) in the distribution system.This increase in the reactive and the apparent power results in the large angle and thus the cosine(or power factor) increases.

Definition and calculation

AC power has three components –

1,real power(P) measured in watts

2.apparent power(S) measures in volt amperes

3.reactive power Q measured in reactive volt

The power factor IS defined as-.

\frac{P}{S}

In case of perfectly sinusoidal waveform P,Q and S can be expressed as the vectors that form a vector triangle such that,

S^2\,\! = {P^2\,\!} + {Q^2\,\!}.

If  is the phase angle between the current and the voltage then the power factor is equal to the cosine of the angle

 |P| = |S| \left|\cos\varphi\right|.

Since the units are consistent ,the power factor is by definition a dimensionless number between -1 to 1.When the power factor is 0,the energy flow is entirely reactive and the stored energy in the load returns to the sourse in each cycle.When the power factor is 1 all the energy supplied by the source is consumed by the load.power factors are usually stated as lagging or leading to show the sign of the phase angle.Capacitive loads are leading and the inductive loads are lagging..

If purely resistive load is connected to the power supply,current,voltage will change the polarity in the step,power factor will be unity.

power factor waveform

power factor waveform

RELATED QUESTIONS-ANSWERS

1.DEFINE POWER FACTOR

It is characteristics of the alternating current (AC) circuits.Always between 0.0 and 0.1,the higher the number the greater the power factor

2.STATE THE POWER FACTOR VALUES DEPENDING UPON THE TYPE OF LOADS

When the it is 0,the energy flow is entirely reactive and the stored energy in the load returns to the source in each cycle.When the it is 1 all the energy supplied by the source is consumed by the load.These are usually stated as lagging or leading to show the sign of the phase angle.Capacitive loads are leading and the inductive loads are lagging.If purely resistive load is connected to the power supply,current,voltage will change the polarity in the step,it will be unity.

3.HOW IS THE POWER FACTOR RELATED TO KVAR?

Since it is defined as the ratio of KW and KVA,we see that low power factor results when  KW is small in relation to KVA.These inductive loads consume major portions of the power consumed in the industries.Reactive power (KVAR)required by the inductive load increases  the amount of the apparent power(KVA) in the distribution system.This increase in the reactive and the apparent power results in the large angle and thus the cosine(or power factor) increases.

Tell us Your Queries, Suggestions and Feedback

Your email address will not be published.

3 Responses to Power Factor Definition and Applications

  1. Rachita Mishra says:

    The power factor of an AC electrical power system is defined as the ratio of the real power flowing to the load, to the apparent power in the circuit,and is a dimensionless number between -1 and 1. Real power is the capacity of the circuit for performing work in a particular time.This is a good article which is about this power factor.

  2. Sounak Ghosh says:

    The power factor of an AC electrical power system is defined as the ratio of the real power flowing to the load, to the apparent power in the circuit,and is a dimensionless number between -1 and 1.This is an essential concept for those with an engineering background or science background students.This article is really helpful for understanding the concepts properly.

  3. Ritika Savita says:

    Power Factor is a very basic concept related to Electrical Engineering, which is also there in class XIIth Physics. It is an important characteristic of the power dissipated in the alternating currents.

« »