Before the before the invention of three phase power factor meter it was very difficult to calculate the power factor of three phase system.

So a electrical engineer devised a mathematical formulae to calculate the power factor of three phase system using the reading of to wattmeters.Now in this experiment it became possible to identify the power increasing factors in a load and to counter the inductive effect of the load capacitive loads could be added and again power factor could be increased to unity.

Like in our household systems in India the motor that are installed at homes for pumping up water from the MCD supply has a resistive+ inductive load in it.This causes the power at the input to maximise and cause increase in bill.

To reduce the power power factor of the system should be brought closer to unity, to achieve this objective there is capacitor bank connected at the input of the three phase mains supply.This auto correction capacitor bank corrects the power factor automatically based on the nature of the load.

To demonstrate this concept better I have attached the youtube link.I hope you will appreciate my blog.