What is the difference??
I have a table that tells me that I need 3 x 55uF to correct the power factor of a 5.5kW motor and www calculators come up with 3 KVAr??
KVAr and capacitance
Aug 17, 2007
3 Replies
At 220V 3ph 60 Hz, 3 55µF capacitors will draw 3 KVAr.
Thanks - and at 400v 50Hz - UK 3 phase??
*>Thanks - and at 400v 50Hz - UK 3 phase??
Xc = 1/(2*pi*F*C) = 1/(2*3.14*50*55e-6)= 57.9 ohms
Placed across line-line of 400V, Ir=400V/57.9ohms = 6.91 amps
VAR = 400V*6.91A * 3 = 8.29 KVAR
So you see the trouble with pf correction is you have to know how many VAR you need to correct the motor and then figure out the capacitance needed to 'generate' that VAR based on Voltage and frequency.
daestrom
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