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KVAR Calculations

how to calculate kvar of any given load for unity power factor?

By Rajan Mane on 23 February, 2005 - 5:31 pm

By bill on 24 February, 2005 - 11:26 pm

By Dave on 8 April, 2006 - 7:54 pm

I think this person is confusing KW and KVAR. It seems that he/she thinks that if KVAR's in a system = 0 then there is no power flowing. This person fails to understand that Real power and apparent power are not the same for a system operating with a no unity power factor. This apparent power is simply circulating power due to the phase shift etween the source and the loads. This additional power that appears to be flowing requires the equipment to be rated higher than that for a system operating at unity. Obviously these circulating currents while real....produce no usefull work. It is the job of the EE to correct the load reactance as close as possible to unity to increase efficiency and reduce operational costs.

To my learned collegues I will add that this argument is overly simplistic. And that great things have been done either using existing or inducing reactive power into a system for a myraid of usefull puposes far beyond the scope of my simple explanation of a simple power system.

EE-Dave

By Steve Myres on 24 February, 2005 - 11:34 pm

Maybe I don't understand the question. If the power factor is unity, is the reactive power not by definition zero?

--

Steve Myres, PE

Automation Solutions

(480) 813-1145

By Anonymous on 24 February, 2005 - 11:49 pm

By Ganesh on 25 February, 2005 - 4:40 pm

i donno whether u r serious or jokin...

kvar = kv * sin (phase)

for unity pf, sin (phase)=0

hence, kvar=0

By DP on 27 February, 2005 - 2:02 pm

The calculation is the same for any other power factor, as cos phi is power

factor and the inverse cos of 1 is 0 you will find applying the calculation

that Kvar for unity power factor is................... 0

Do you know what the formula is????

DP

for a unity power factor there is no reactive power...

By Jose on 1 March, 2005 - 9:37 pm

If sion 0 is o and kvar is 0, how do we run motors?

What is then the use of a capacitive bank?

Regards

Jose

By Meir Saggie on 3 March, 2005 - 11:50 pm

Hi guys - oversimplification kills.

A motor draws a certain amount of inductive KVARs. In order for the utility company to see Cos phi of 1 (zero KVAR), we add an equal amount of capactive KVAR's that hopefully cancels out the motor inductive KVARs.

Meir

1 out of 1 members thought this post
was helpful...

Meir,

Hopefully you meant SOME of the motors' kVAR. "Zero" should never be the goal!

Regards,

Phil Corso, PE {Boca Raton, FL, USA}

[tal-2@webtv.net] (Cepsicon@aol.com)

By armando on 13 May, 2005 - 8:44 pm

For unity power factor, there will be no angle displacement between voltage and current. Both are in phase. when we say unity, we are refering to resistive load. If the load is reactive, then power factor will come into picture which is less than unity.

By mahesh on 28 January, 2012 - 8:22 am

how to calculate kvar of any given load for unity power factor? & method of calculation mfd\hz\volt\kvar

By Technical Assistant on 16 February, 2012 - 4:48 am