Re: Power factor correction capacitors for MOTs

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "S&JY" <youngsters-at-konnections-dot-net> 

Well, that makes all the difference in the world!  Actually, your filter
caps on the secondary side of your MOTs will act like PFCs.  The cap value
is effectively multiplied to be considerably more, on the primary side, than
the capacitance of your filter.  You probably will not need any further PFC
correction in your primary circuit.
--Steve Y.

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, November 11, 2004 7:45 AM
Subject: Re: Power factor correction capacitors for MOTs


 > Original poster: "Borislav Trifonov" <bdt-at-shaw.ca>
 >
 > Does the load of the transformer matter?  I'm bridge rectifying and
 > filtering for DC output.  Should measuring the current draw be done with
 > the transformer loaded or not (I know it's drawing a good deal even
unloaded)?
 >
 >
 > Tesla list wrote:
 > >Original poster: "Virtualgod" <mike.marcum-at-zoomtown-dot-com>
 > >Here's a starting formula:  uF =        10^9             where F if line
 > >freq, V is line voltage, and C is the corrected kVA
 > >                                                 ------------- (C)
 > >                                                   2(pi)FV^2
 > >rating of the transfornmer (50% of VA rating for unmodded nst's). Since
you
 > >don't know and have no way to measure the uncorrected mots output VA
under
 > >load, probably be best to assume 50% efficiency for a ballpark figure,
use
 > >the previous formula, and then adjust the pfc by adding/removing
microwave
 > >oven caps in parallel, measuring the current drawn with a DMM. Whatever
uF
 > >draws the least current under load is what you need. I did this with a
 > >modded  7.5/32 (originally 7.5/20) nst and found about 40uF works best,
tho
 > >TC's are hardly sinusoidal loads, so the pfc will only help so much.
 > >Mike
 >
 >
 >
 >
 >