Re: Looking for run caps, urgent

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

transform the voltage and current from secondary to primary:
15000 * 0.120 = 1800 VA = 120V * 15A

Calculate Xl = 120/15  = 8 ohms
Assume that for total correction Xc = Xl, then calculate C
Xc = 1/ (60 * 2 * pi * C)
0.125/(60*2*pi) = C
.125 / 377 = 331E-6 Farad

Sure enough... 

But, as a practical matter, you probably don't need that much PFC.. After
all there is SOME resistive loading going on (you aren't running the
transformer into a dead short, so the primary C counteracts a fair amount
of the inductance (all of it if you run resonant..)), and it is generally a
bad thing to make your PFC exactly resonant, and an even worse thing to
make your system have a leading power factor (capacitive). 

If you were to assume (on no basis whatsoever) that your TC primary circuit
(the tank cap) knocks out half the inductance of the NST, the 1800VA input
to your NST is now half active and half reactive, for a power factor of
0.707 (that is, you are putting about 1300W into the coil, and also putting
in roughly 1300VAR of (lagging) reactive load). You want to get the PF to
somewhere around 0.85
(that is, around 270 VAR out of 1300) so you need about 1000 VAR of
compensation..

at 120V, 1000 VAR is 8.33 Amps, so the capacitive reactance you need is
around 15 ohms, which comes up around 180 uF, starting to get more
reasonable in terms of price.

I'd start with 100 uF and see how it works.. The reactive load presented by
a TC is somewhat strange in power factor correction terms.


Tesla list wrote:
> 
> Original poster: "Jonathan Peakall by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <jpeakall-at-mcn-dot-org>
> 
> Frank and other whow wondered,
> 
> I need 332uf because I have a 15/120 NST, and that's what the java TC
> designer prog. says I need. I sure hope that's right, as it looks like
> getting these caps is gonna be spendy.
> 
> Jonathan Peakall
> ----- Original Message -----
> From: Tesla list <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Monday, October 22, 2001 12:07 AM
> Subject: Re: Looking for run caps, urgent
> 
> > Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <PsychoticMinds1-at-aol-dot-com>
> >
> >
> >
> >         What do u need such a high uf of run caps for?
> >
> >
> >
> > Frank
> >
> >
> >