## Disadvantages of Low Power Factor

Power factor play an important role in AC circuits and power dissipation depends on this factor. For instant, we know that;
Power in a Three Phase AC Circuit = P = √3 V x I CosФ
And Current in a Three Phase AC Circuits = I = P / (3 V x CosФ)
I ∝1 /CosФ….… (1)
Also,
Power in a Single Phase AC Circuits = P = V x I CosФ
And Current in a Three phase AC Circuits = I = P / (V x CosФ)
I ∝ 1/CosФ……… (2)
It is clear from both equations (1) an (2) that Current “I” is inversely proportional to CosФ i.e. Power Factor. In other words, When Power Factor increases, Current Decreases, and when Power Factor decreases, Current Increases.
Now, In case of Low Power Factor, Current will be increased, and this high current will cause to the following disadvantages.
1.) Large Line Losses (Copper Losses):
We know that Line Losses is directly proportional to the squire of Current “I2
Power Loss = I2xR i.e., the larger the current, the greater the line losses i.e. I>>Line Losses
In other words,
Power Loss = I2xR = 1/CosФ2 ….. Refer to Equation “I ∝ 1/CosФ”….… (1)
Thus, if Power factor = 0.8, then losses on this power factor =1/CosФ2 = 1/ 0.82 = 1.56 times will be greater than losses on Unity power factor.
2.) Large kVA rating and Size of Electrical Equipments:
As we know that almost all Electrical Machinery (Transformer, Alternator, Switchgears etc) rated in kVA. But, it is clear from the following formula that Power factor is inversely proportional to the kVA i.e.
Therefore, The Lower the Power factor, the larger the kVA rating of Machines also, the larger the kVA rating of Machines, The larger the Size of Machines and The Larger the size of Machines, The Larger the Cost of machines.
3.) Greater Conductor Size and Cost:
In case of low power factor, current will be increased, thus, to transmit this high current, we need the larger size of conductor. Also, the cost of large size of conductor will be increased.
4.) Poor Voltage Regulation and Large Voltage Drop:
Voltage Drop = V = IZ.
Now in case of Low Power factor, Current will be increased. So the Larger the current, the Larger the Voltage Drop.