Power Factor How To Calculate


What is Power Factor?

Power factor is the ratio of active power which is consumed by the load to apparent power supplied by the generating source. Power factor is a unitless no. which is cosine angle between actual power consumed to apparent power supplied.
Power factor is an indicator of the amount of power that is used to create actual by the load. power factor closer to 1(one) mean power supplied by the source is mostly consumed by the load. And losses as reactive power is minimum. for factor how to calculate, let first understand the basic term which is going to be used in it.

Power Factor Calculation

so,for power factor calculation first we must under stand following term.

1-Real power or Active power

Real power also called active power which is consumed by load or you can say this power performs work in the electrical system. This one is denoted by P.

Power Factor How To Calculate
Power Factor How To Calculate

2-Reactive Power

Reactive power is the loss in an electrical circuit that performs no work. It only flows from source to load sinusoidally. In reactive power, current and voltage are 90 degrees out of phase. It is denoted by Q.

3-Apparent Power

Apparent power is the actual phasor sum of real and reactive power. And its value is calculated by taking the RMS (ROOT MEAN SQUARE) value of current and voltage. It is denoted by S.

4-Power Factor Calculation
In case 3 phase motor how to power factor calculation –

power factor = P / S

Cos α =√3 VI Cos α / √3 VI

√3V I cos α= Real power consumed

√3V I= Apparent power supplied from generating source.

Apparent power= Real power + j Reactive power
Where apparent power = total power supplied from the source
Real power = energy consumed by the load (motor)
Reactive power= power is going to waste in the loss.


Suppose we have an 8 HP 3 Phase motor, by using a tongue tester or ammeter we took current which is found to be 11 amperes. For power factor how to calculate We know in case of 3 phase system voltage always will be 415V in the distribution network of India.

P= 8 HP= .746*8= 6 KW =6000 WATT


Cos α =√3 VI Cos α / √3 V I
= P / √ 3 V I


Cos α= P/ √3 VI

Cos α = 6000 W/ 1.732* 415 V* 11 A= 0 .75

POWER FACTOR= PF= Cos α = 0.75 this a way power factor how to calculate.

Now, In this article, we will discuss the basic concept of power factor also types of loads used in industries and what is leading, and what is the lagging power factor.
Let’s start with the basics of the power factor. The formula for power factor is the ratio of active power to apparent power. But what is that mean? Let’s take the example of beer.

Power Factor How To Calculate
Power Factor How To Calculate

We pay for beer, but inside the glass, there are both beers as well as foam for the more beer we have the least the foam there will be, so we get very good value for the money, but if it is vice versa, it’s a loss for us. This beer represents the true power or active power this is very useful for us and this foam represents reactive power which is a useless term. In actual industries, inductive loads are connected to the system due to which the reactive power inside the system increases. To overcome these capacitive loads are connected to the system which maintains the ratio of active the apparent power to the unity.
Let’s take another example of this beer.
In this figure , active power is equal to apparent power. That means in this case power factor is unity.

Power Factor How To Calculate

To know more about the power factor, you need to know the three basic terms which are current, voltage, and frequency. Let’s start with the current. Current is nothing but the flow of electrons or the conductor, and voltage is the driving force required for this flow. In laymen’s language, voltage forces current to flow to one conductor or a wire. The third term is frequency. If you understand the frequency, then you will know easily what is the power factor. Let’s take the example of the tube light.

Power Factor How To Calculate

This is the tube light to which two wires are connected. One is the phase, one is neutral. both phase voltage and current are flowing at 50 Hertz.
And what is 50 hertz are it’s a frequency? We all know that in India government-supplied electricity of 50 hertz. That means this tube light will turn on and turn off 50 times in a second.
This frequency can be varied by using a device called VFD. The full form of VFD is variable frequency drive. As I told you earlier, that 50 Hertz means your tube light will turn on and off 50 times in a second.
This graph will clear your inquiries about the statement I have made.

Power Factor How To Calculate

It represents the waveforms of voltage and the current flowing through the phase and concerning Neutral. It shows that the voltage and current start at one point and completes their cycle at one point. Only the half waveform as I’m showing indicates that the tube let is turn on and the other half is showing you the tube light is turned off. And that’s how the cycle of both current and voltage goes further 50 times in a second.

Further to know about what is leading and lagging power factor, you need to understand this type of loads used in industries due to which power factor varies.


The types of loads used in industries are resistive loads. Inductive load and the capacitive load. Let’s see one by one.

1-Resistive Load

The first one is resistor load. As I told you in the earlier example, that current and voltage both flow in the same way. Hence In resistive load, both current and voltage start and ends the cycles at the same point.

Power Factor How To Calculate
3-Inductive Load-

The next one is an inductive load. Sometimes what happens , Induction types of equipment which has their power factor which is less than one get connected to the system due to which current lag the voltage due to which power factor get disturbed to overcome the gap between the voltage and current capacitor Bank to be connected across the load which tries to close this gap and maintain the power factor close to unity.

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Power Factor How To Calculate
3-Capacitive load

The next one is capacitive load as sometimes what happens. the capacitive load gets increased while maintaining the inductive load at unity or near to the unit due to wish current leads the voltage.
This can be overcome by switching off one of the steps of the capacitor Bank.
Now I will show you some examples of leading lagging and unity power factors.

Power Factor How To Calculate

Lagging power factor

The first one is the lagging power factor in this energy meter is showing lagging power PF( Power factor), which is less than unity which means the inductive load inside the system has increased.


Leading power factor

The second one is the leading power factor. The leading power factor is denoted with the negative sign that means the capacitive load inside the system increased.

The unit power factor-

It is not possible to maintain an exact unity, but point ripening is a good power factor in this voltage and current are traveling together.

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