Re: NST current, was Filters & Chokes

["Jon Rosenstiel" <jonr-at-xxxxxxxxxxx> (by way of Terry Fritz <twftesla-at-xxxxxxxxxx>)]

Gary, John, All,

Using a 0.014uF tank cap with my 120bps SRSG I managed to pull 18A at 120Vac
using a modified 15/30 Jefferson, (every 3rd shunt was cut off giving about
43mA at 120Vac short circuit current). I couldn't understand why the coil's
performance rapidly  fell off and the NST was getting so hot. (When I later
removed the cover to inspect my submerged in oil NST it looked as though the
oil had been boiling!)  I then started experimenting with the SRSG's timing
and found another "sweet spot" where the spark output was better yet and the
input current dropped to 6A at 120Vac. This "sweet spot" was located 52
degrees ahead, (advanced), from the original setting that drew 18A.
Now my coil was "happy", it would seemingly run forever at this setting. No
performance drop off, no transformer overheating.

FWIW,

Jon



----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, November 15, 2000 6:39 AM
Subject: Re: NST current, was Filters & Chokes


> Original poster: FutureT-at-aol-dot-com
>
> In a message dated 11/14/00 9:45:51 PM Eastern Standard Time,
> tesla-at-pupman-dot-com writes:
>
> > Original poster: "Lau, Gary" <Gary.Lau-at-compaq-dot-com>
> >
> >  I use a standard unmodified 15/60 NST and the filter uses a pair of
1.6K
> >  113W resistors.  For a very long time I was puzzled at just how hot
these
> >  got.  By standard logic, the power is I^2 R, or .06^2 * 1600 =
5.76Watts.
> >  But after building a fiber-optic VI probe, I was able to scope the NST
> >  secondary current with a digital scope, which also performs true-RMS
> >  calculations.  Guess what?  My 60mA NST is pushing 184 mA, RMS.  It
appears
> >  that some unexpected things happen when charging an LTR cap,
speculation is
> >  that the current shunts saturate and allow far more current to pass.
So
> the
> >  184 mA causes a dissipation of 54 Watts per resistor.
> >
> >  Gary Lau
>
> Gary, all,
>
> I use a 12/30 NST with LTR cap, and it pushes about 50ma, but this
> only happens if I turn up the voltage to 140volts input using a step
> up type variac.  I seem to remember that you're using a step up
> variac also?  With a normal 120 volts input, my NST just gives the
> rated 30ma to the coil.  But if I use a matched size cap, then I can
> get 50ma with just 120 volts input.  I haven't tried 140 volts into a
> shorted output NST to see what the current is.  The 140 volts input
> probably has a lot to do with increasing the current.
>
> John Freau
>
>
>