Re: Cap safety & spark gaps

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Christoph Bohr" <cb@xxxxxxxxxxxxxxx>

Hello Mike.

> Are you guys saying that if one
> has sufficient energy, and a resonant , or str cap, then charging
> voltage is dependent on spark gap length?
Sort of, of course resistive and other losses limit the effect, but under
mains resonant conditions, the voltage can and will rise very high.

>This explains why output gets bigger as one opens the gap.

Of course this effect does not beat energy conservation, you would get
lesser BPS, but each with higer energy. In some cases you can "rob" some
extra power from your transformer which yould not be availabel otherwise.
The increase in ouput might be somwhat related to the fact,
that TC's like high input voltages.
There is no real benefit in letting this happen, rather use a LTR
cap, which will give you equal or better performance and less
risk of blowing things up.

>So is this why a 35kV maxwell can
> blow with a 14.4 pig or PT?
This among other things. Mentioning 35KV Maxwell I think you refer
to the 37667 series, where the lacking ability of taking the large
voltage reversal is another problem which lets you not use the whole
DC rating without harming the cap.

>How does one keep there caps healthy in a
> ballast controled situation, where output is somewhat unlimited?
Hmmm safety gaps ;-)
The output is not unlimited. LTR as well as safe STR conditions can
be used, but while varying you ballast setting, you might sooner or
later hit the spot where resonant charging occours.
You wont notice that before it is too late, but a simple safety gap will
kick in the very moment the voltage gets to high...
cheap, simple, effective-

> I realize most ballasted coil configs use rotaries, but right now I'm
> using a sucker gap with my PT.
With RSG you usually use pretty big LRT with NST's or by far SRT
with pigs ( it will be hard to find a LTR for a pole pig running at 
full power )
unless you ballast your transformer very well, which I would suggest.
You can measure the complete ballast/pig setup and find where your cap
value settles to stay away from a resonant condition.
With your sucker gap your cap may be somewhat smaller, but can and
perhaps should be still LTR. Just make sure you do not open your gap to wide

However, I am not a pro and hope I have not given false advice.

best regards

Christoph Bohr