ECN Forum Forums Technical Discussion Electrical Theory and Applications Sizing Power factor caps?

That I did. Currently I'm lucky enough to commute by train, which is pretty nice except for every once in awhile when something happens. But I'm wandering off topic again.

Radar

Update...

POCO does charge a PF penalty on KW usage. They have minumums that must be met, yet they are hidden, and was a real bugger getting this info from them:

1-185KW must maintain a PF of .80 or better
185-2500KW .90 or better

And this is both on GS(commercial) services as well as HT(high voltage transmission) services.

So, then..I was able to retrieve bills that show the PF of the place ranges from .69 to .76 from 12 months ago.

Would you attempt to size PF caps from the .69 to say a .90. That would push the PF from .76 to .97, wouldn't it?

What would happen if you corrected the .69, to say .93, and then when the loads changed, it forced the .76 either at unity or slightly above?

Dnk..

"So, then..I was able to retrieve bills that show the PF of the place ranges from .69 to .76 from 12 months ago.
Would you attempt to size PF caps from the .69 to say a .90. That would push the PF from .76 to .97, wouldn't it?"

You need to maintain a PF of 0.90 or better.
Use the kw load at 0.69 and correct to 0.90 or better. Check the load at 0.76 and using the capacitors installed, see what the caps correct the PF at that load.


[This message has been edited by Bob (edited 03-02-2006).]

Ok here I go again.

I think I got it but need more help..

Using the following givens;
255Kw load
PF .7
V=4160
60Hz

I get the following results:
To correct PF to unity
39mf caps
current in the caps 62a

To .9 PF
21mf caps
current 33a in caps

To .8 PF
11mf caps
current 16 in caps

This should be right, but I need the help in going backwards. If I correct from .7 to .8 and use a 11 mf cap, how do I calculate the change when the load goes from .7 to .75?

I got something wrong in my sheet and can't figure this one out...

I plan on using switching units, but still want to know how to figure it out...

Thanks..

Dnk....