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KVAr and capacitance

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??

Reply to
colinstone
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At 220V 3ph 60 Hz, 3 55µF capacitors will draw 3 KVAr.

Reply to
Paul Hovnanian P.E.

Thanks - and at 400v 50Hz - UK 3 phase??

Reply to
colinstone

*>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

Reply to
daestrom

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