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RE: first coil progress...

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Gary,

Excellent observation!
I tried the model I had for my big old coil without a secondary (just set coupling to zero). The RMS current only went from 7 to 8 amps though. For my small coil, the RMS primary current goes from 5.7Arms to 6.8Arms. So in that case, you could run the primary system alone just fine!
In general, spark gap losses are so high I don't think the bare primary RMS current will really go up that much. There is no notch effect which also helps to reduce the RMS current. So running a primary without a secondary on a conventional spark gap coil should not be too terrible.
Of course, never directly short a fully charged Tesla coil cap!! Without the inductor there to limit the current, cap damage is guaranteed!
Also, SISG and electronic drive circuits might really hate to run open load. If normally they only dissipate 20 watts in an IGBT, but suddenly are forced to 100W, something could easily blow. 

Cheers,

        Terry



At 07:30 AM 10/1/2006, you wrote:

Hi Dr.:

I agree wholeheartedly with your advice, but not the rationale.

If one does not have a suitable load on a coil, the issue is that the
power drawn from the wall won't have anyplace "safe" to go.  By safe, I
mean into bright, noisy, pretty sparks coming from the top load.  If
that power isn't going into sparks, it HAS to go somewhere else.  It
will for the most part be burned up in the gap (i.e. the gap will run
MUCH hotter), but additionally, it will heat up the capacitor, and
that's the gotcha.  The peak cap current will be unchanged, but the RMS
current will be much higher.

While the primary circuit Q will indeed be higher without the presence
of the secondary, this won't result in the primary voltages getting any
higher.  In a continuously excited (CW) coil, higher Q would result in
higher voltages, but in a disruptive (spark gap) coil, each bang rings
completely down to zero before the start of the next bang.  The ringdown
time will be longer without the load, but the starting voltage and
ending voltage of each bang will be identical.

Regards, Gary Lau
MA, USA

> Original poster: "resonance" <resonance@xxxxxxxxxxxx>
>
>
>
> Never run it without a pri/sec load.  Without a load the circuit Q
> factor will rise to a very high value producing overpotentials that
> will blow your caps and xmfr.
>
> With a load it will run a bit cooler.
>
> Dr. Resonance
> ----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
> To: <tesla@xxxxxxxxxx>
> Sent: Friday, September 29, 2006 11:40 PM
> Subject: first coil progress...
>
>
> >Original poster: Slurp812 <slurp812@xxxxxxxxx>
> >
> >I have a few pics of my progress so far.
>
><http://www.flickr.com/photos/slurp812/>http://www.flickr.com/photos/sl
urp812/
> >
> >I also have one question. If the spark gap stays cool now, without a
> >primary/secondary , can I expect much difference when I do get it
> >all put together?
> >
> >
> >
>
>