power factor capacitors
power factor capacitors
(OP)
power factor correction capacitors are rated in kvar
what is the formula that relates this to their value in farads
1/2.pi.fc gives xc but how is this related to kvar?
what is the formula that relates this to their value in farads
1/2.pi.fc gives xc but how is this related to kvar?






RE: power factor capacitors
Mike
RE: power factor capacitors
Is multiplier of 1000 correct?
If you have a 3 phase kVAR values, you need to use per phase voltage and divide the 3-phase KVAR value by 3 for per phase KVAR.
Or in other words:
Per phase Xc=Vph/Iph
Iph=KVAR/kV , use per phase values.
Xc= kV/(KVAR/kV)= kV^2/KVAR.
This turns out to be the same if you use 3 phase KVAR value and line to line voltage, as 3's cancel out.
Am I missing something?
RE: power factor capacitors
My bad...you can either account it to a typo or stupidity.
xc=kV^2*1000/MVAR=kV^2/kVAR
Mike
RE: power factor capacitors
Thanks. We will go with the typo!!!
Cheers!
RE: power factor capacitors
:)
RE: power factor capacitors
Xc = V/(kVAR/kV) = kV·1000/(kVAR/kV) = kV^2·1000/kVAR = kV^2/MVAR
RE: power factor capacitors
Mike
RE: power factor capacitors
thanks..I suspected i missed something..
Sorry , mparent and all...for creating confusion..but still worth the excercise..
RE: power factor capacitors
now the three capacitors are around 450uF each, connected in delta and rated at 48 KVAr
this doesnt work out unless i multiply the calculated KVAR per phase by root 3 is this right what is the formula for capacitance across each phase in a delta connection?
sorry to be a pain id like to get my head around it though
RE: power factor capacitors
Would you like an example?
A 3 phase 48 KVAR capacitor bank is connected delta on a 480 volt circuit. The load on each phase is 48 KVAR / 3 = 16 KVAR.
16 KVAR /480 = 33.3 amps.
The load on each line is 33.3 amps x root 3 = 57.7 amps.
When the capacitors are connected in wye (This will be a different set of capacitors with considerably more micro farads because of the reduced voltage )
Now 48 KVAR / 3 = 16 KVAR per phase.
16 KVAR / 277 = 57.8 amps. (In this case, the root 3 factor was used to convert 480 volts to 277 volts.)
We have about 0.17% rounding error. 277 should be 277.128
Hope this helps.
yours