Capacitor Bank Calculations

Please review your calculations and the total concept of power factor.

YOU have a half megawatt generator and you're asking for help. (Or really an anonymous opinion.)

YOU have the generator. How can it have a p.f of 0.7? (Unless you're out of synch with the grid)

Is the power factor leading or lagging?

Typically it would be considered that the load has the power factor issue, not a generator.

Is your generator a "synchronous" machine? (If yes, then you might investigate the impact of changing the relative phase of the excitation voltage. If no, then it really shouldn't be connected to grid.)

If you had a motor, the answer would be relatively simple.

power factor of load .7

Ihave only one generator without network,load power factor .7Lagging,and i have motors

What is meant by type of connection?

KVAa = KVA Cos Φ

KVAr = KVA sin Φ

Also there are quite a few threads on pf compensation. take some time to go through them.

What is the load ? 0.7pf looks to be too lo for any properly designed system, unless it is under quite significantly under-loaded, and then the KVA too will be low.

And why that number 0.92?

_{Is it a homework?}

It is homework.

Dear Mogahed,

Would you please to consider other comments related this subject. I give you the KVAR required without knowing your maximum and minimum loads.

Generator rating 500 kVA. PF1 = 0.7 and PF2 required = 0.92.

Based on data above:

angle of fi1 = 45.573 degree (from PF1 = 0.7), and angle of fi2 = 23.074 degree (from PF2 = 0.92).

KVAR required = kVA x PF1 x [tan(fi1) - tan(fi2)]

= 500 kVA x 0.7 x [tan(45.573) - tan(23.074)] = 207.97 kVAR.

Regards,

RSM

You can not apply PF correction directly to generator, it is applicable only for the load.

Required KVAr= KW(Tan phi1-Tan phi2)

KW= Desired Load

Phi1=Cos^-1 initial pf angle

phi2=Cos^-1 desired pf angle

determine the point of connection capacitor bank after main circuit breaker

Dear Mr.mogahed,

You have not mentioned the power leading whether it is leading or lagging. if it is lagging, the solution is simple to add capacitor near to load. If it is leading the capator to be removed. In both cases the value of KVAR will remain same. the basic equation you know it.

DHAYANANDHAN.S,

INDIA.