How to select Capacitor Bank for Electrical Panel.

The automatic power factor corrector unit ( APFC ) operate from the input from CT and if there is no load current, the control system operation will be in effective. But the actual pf will be low due to transformer inductance . So it is better to maintain some fixed capacitor in addition to the APFC .

The calculation of capacitor KVAR Will depend on the present and required pf .

In case your present pf is 0.7 ( Cos Φ1) and if you want to improve it

to 0.95 (Cos Φ2) the normal equation followed is :-

The kVAR = kW ( tan Φ1 - tan Φ2 )

The kVAR may be added and switched off in steps on both automatic and manual switching. You should check the PF meter also. It may not be operating properly.

Respected Sir,

Thank You for great reply, But till i have some queries if u send me Ur mail id / mobile no than i can contact you. I am also staying in pune & working in Minda Valeo Company.

Before adding more capacitance, look at the problem. I am surprise that 280 KVARS is not enough to compensate a 450KW load and improve the power factor. Can you give us numbers? We need to know the PF, the power... This band should be plenty even if you have many induction motors. The only loads that could demand such a high correction are welding machines and large DC motor drives. If you don't have much of those, you will not fix the real cause of your problem.

First is is OK to have a low power factor at low load. It doesn't cause any problem. If your utility is giving you a penalty, tell them to use a minimum threshold of the power factor meter or simply use the peak KVARs instead of the PF. This is a better measurement anyway. The PF is simply a ratio and doesn't mean much at low load.

Make sure that the PF meter you are reading is placed upstream of the capacitor bank to see its effect. Make sure that the controller is operating properly. Do you measure current in the capacitor banks?

Don't look for PF=1. Expect 0.9 to 0.95 as being good values. Also, if you over compensate your power factor will decrease in the leading direction. This could be your problem. Check the sign on your PF meter.

Finally, remember that too much capacitance can cause resonance problems that can be destructive for the plant sensitive equipment.

hai i am kannan, in my experiance you can go about 180 KVAR

Kannan

Would show you calculations how you came up with 180 kvar. You do not know the present power factor so how can you make this statement? Please describe you method.