# Re: how to calculate power factor?

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#12168
Spir Georges GHALI
Participant

RAFI said:

Dear Friend,

In our plant we have load of 750kw  we are using 400kvar capacitor bank ….we are getting 0.91-0.97 pf sum tymes we are getting less pf like o.87….why getting like this>is capacitor bank has to increase ?

Dear Mr. Rafi ;

Firts, you should do the calculation, as I mentioned before for the same topic, to know if ” 400kVAR ” is enough or not for your installation.

In all case, there some reasons for your case that are :

– Normally, and depending to the connection's type of the controller, the Controller of capacitors is connected to ” one phase  or  2 phases ” accordingly the the connection's type, but allways with ” one Current Transformer ” that's installed on the same phase ( for the 1st connection type ) or on the third phase ( for the 2nd connection type ), that means the measuring of the angle ” φ ” is doing between the current of one phase only and the voltage.

– In some time we have on the same controller the value of PF ” 0.91  or  0.96  or  0.87 ” but we adjusted the controller to achieve ” 0.95 ” : as the methode of working of Capacitors bank is doing by a controller where it needs a time ( at least 50sec ) to Switch-On  or  Switch-Off ” the steps accordingly to the difference between the measuring value and the reference value, in these times it's possible to see on the controller a smaller or bigger value than the reference one.

– If you compare the PF value of the controller with the PF value mentioned on the Bill, there's certainly some difference, because the ” kVARh meter ” works on 3 phase for currents & Voltage.

Regards.