Power Factor

[ptonsparky]

Photo of 43B while checking PF. Can you tell by this information what size PFC is needed to correct it to +.9?
(IDK, so this is a B style question vs A.)

Loads are multiple fan motors on a feeder. Individual PFC will not happen but up to four may be a go. One for each group of fans.

Loads are 3phase 480v FWIW. Reflection on right covers the 100A scale

 

[charlie b]

With 29.5 kW, a pf of 0.9 would make the KVA value equal to (29.5)/(0.9), or 32.8. Next step is to find the third leg using Pythagorean formula. KVAR squared equals 32.8 squared minus 29.5 squared, so KVAR equals 14.3. You add 27.6 KVAR of capacitors, and you will get your .9 pf.

 

[lielec11]

With 29.5 kW, a pf of 0.9 would make the KVA value equal to (29.5)/(0.9), or 32.8. Next step is to find the third leg using Pythagorean formula. KVAR squared equals 32.8 squared minus 29.5 squared, so KVAR equals 14.3. You add 27.6 KVAR of capacitors, and you will get your .9 pf.

I got the same results...

 

[ptonsparky]

Nice!!

That goes onto my Formulas Spread Sheet the next chance I get!

Thanks

 

[Ingenieur]

have
29.5/51.2 = 0.58
41.9 kvar

want
29.5/newkva = 0.9
newkva = 32.8

from kva = sqrt(kw^2 + kvar^2)
32.8 = sqrt(29.5^2 + newkvar^2)
newkvar = sqrt(32.8^2 - 29.5^2) = 14.3 kvar

need to add 41.9 - 14.3 = 27.6 kvar

 

[ptonsparky]

Nice!!

That goes onto my Formulas Spread Sheet the next chance I get!

Thanks

What do you suppose I found when I got around to adding a Capacitors page?

Yup, an in detail, fill in the knowns and get the unknowns. Guess I haven't had to worry about PFC for a few years.

 

[Besoeker]

Nice!!

That goes onto my Formulas Spread Sheet the next chance I get!

Thanks

The algebra is not altogether complex. But beware of harmonics.

 

[ptonsparky]

The algebra is not altogether complex. But beware of harmonics.

Even have some of that in there.

	Hz	KVAsc	KVAR
H (HARMONIC FREQ)	22.17	491.35	1.00
	15.67	491.35	2.00
	12.80	491.35	3.00

That and I have an email this morning inviting me to read a white paper on "How PFC Capacitors Affect Harmonic Levels" @powerermonitors.com.

Study time again.

Have I ever mentioned I'm counting days to retirement and an EC business is available?

 

[Besoeker]

Even have some of that in there.

	Hz	KVAsc	KVAR
H (HARMONIC FREQ)	22.17	491.35	1.00
	15.67	491.35	2.00
	12.80	491.35	3.00

That and I have an email this morning inviting me to read a white paper on "How PFC Capacitors Affect Harmonic Levels" @powerermonitors.com.

Study time again.

Have I ever mentioned I'm counting days to retirement and an EC business is available?

Sub harmonics. Those that are multiples of supply frequency are usually more troublesome for PFC. We are a 50Hz country and most put detuning reactors with a resonant frequency of 225Hz so a bit below 5th. I designed for 177Hz. A bit more expensive but it did the job.