Re: PFC caps

["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>



Tesla list wrote:
> 
> Original poster: "Steven Ward by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<srward16-at-hotmail-dot-com>
> 
> Hello
> 
> I am running my coil from a reconditioned NST.  It had to have windings
> re-wound on the primary, and the core has some small gaps that i could not
> fix.  So this means that it draws a bit too much current.  It was a 12000/30
> unit.  I have removed 10 shunts from each pack of shunts(40 total).  The
> transformer now draws 7.5+Amps, depending on operation(can raise to about
> 8A).  I am interested in power factoring.  I have a few main questions:
> 
> What size cap do i need?

If you have removed shunts, you have also reduced the "equivalent series
inductance" that a power factor correction capacitor would be compensating
for.  

To know what size cap you need you need to know what the power factor of
your transformer is now (in operation...).. You can measure the leakage
inductance fairly easily by standard transformer measurements (short the
output, measure the current, etc.)

With that information, you'll have a starting point for correction.


But, to get you started, you KNOW that it will need less PFC than an
unmodified 12kV 30mA transformer would.  Since the original transformer
probably drew around 3 Amps, a ballpark would be to start with half the
capacitance you'd use on the 12/30.
> 
> Who is a good supplier?

> 
> Will PFCing reduce heating of the primary coil?(it gets rather warm)
PFC might reduce heating of the transformer a bit (less RMS current for the
same power out)..
It won't change the TC primary at all.
> 
> Is there anything else im missing out on with this whole deal??
>