Re: PFC caps

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

Original poster: "Steven Ward by way of Terry Fritz <twftesla-at-qwest-dot-net>" <srward16-at-hotmail-dot-com>




>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Re: PFC caps
>Date: Thu, 13 Jun 2002 23:00:23 -0600
>
>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??
> >
>
>
>
Well i know very little about power factoring.  So i ask the question:what 
size cap does a 12/30 NST need?  Also, im assuming to determine the power 
factor of my transformer, i would need to know the secondary current.  That 
is a problem since my ammeter is a clamp type and only reads down to a 3A 
scale.  So i cant get a decent measurement.  Could I just do a trial and 
error attempt??  Say start at 1/2 cap, like you said, then adjust the cap 
untill i get the least current draw?  I still dont know where to get these 
caps.

Thanks,
Steve Ward.

_