Cap safety & spark gaps 2

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "MIKE HARDY" <MHARDY@xxxxxxxxxx>

First let me thank you guys (Christoph Bohr, Scot D, and Gerry  Reynolds)
for your kind detailed responses to my questions. The 'primer' of Garry's
is particularly usefull, as this is a very consise and usefull bit of 
info. I will need
to actually think a bit about it, but it's pretty clear.
I know I tend to go on a bit, but have a fixed idea that encompases a 
lot of stuff.
Esentially how to keep my hardware safe with max performance.
Interspaced below are some questions to these responses.

It was said;

If R is zero, (Q is infinite)  you would theoretically get infinite
voltage out or the RLC circuit (across the capacitor).  Typically for
NST's (I believe) the Q is about 5 or so.  PIGs have much lower R
resulting in higher Q's.  This means that if you use a 10KV NST, you
would have 50KV on the capacitor if operated at resonance with no
safety gap and nothing else fails.  With no capacitive load (open
circuit), the output of the transformer would be it's Vs_oc.  For Cp
values between 0 and Cp=Cres (where RLC resonates with the line
frequency), there is some voltage gain (we call resonant rise).  With
Cp=Cres you get the largest rise.  Once Cp becomes larger than Cres
(LTR - larger than resonance), the voltage gain starts
decreasing.  With a sufficiently large Cp, the voltage gain decreases
back to unity.  With Cp values even larger,  the voltage gain becomes
less than unity (the transformer can not charge the Cp to full voltage).

So is it ok to use a Cp larger than LTR? If the cap can't charge all
the way, doesn't it just act like a cap of suffucuent value?

and here was said;

 >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.

and I ask;

Don't these 373xxx caps have a 1000 bps rating? I thought these
where suitable for TC use. Then which caps are ok? How is voltage
reversal speced out?


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

and finally I ask;

How do I measure, and determine this 'safe' condition?



    ORIGINAL POST IS HERE

Due to the recent discussions on safety gap, and air breakdown
voltage, I need some clarification. 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? This explains why output
gets bigger as one opens the gap. So is this why a 35kV maxwell can
blow with a 14.4 pig or PT? How does one keep there caps healthy in a
ballast controled situation, where output is somewhat unlimited? I
realize most ballasted coil configs use rotaries, but right now I'm
using a sucker gap with my PT.