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RE: first coil progress...



Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi,

At 08:03 PM 10/1/2006, you wrote:
..........

But if there IS a capacitor in parallel with the gap, but no primary
indictor, then there is indeed a problem.  The current through the
capacitor will not be inductively limited and may damage the capacitor.
But I'm still not sure that circuit Q plays any part.  I think the
hazard is over-current to the cap, not over-voltage.  How would the NST
be affected?


The hazard in enormous peak current blowing the relatively fragile end cap to foil connections out inside the caps... This also applies to be commercial caps.

In an off list thing, a person was having rouble with commercial caps failing in a non-TC but high voltage application. They had safety gaps directly across the caps that would fire at times. When they added big low value resistors in series with the safety gaps to control the current the problem was solved.

The current is simply the voltage (say 20kV) divided by the gap arc resistance (say 2 ohms) for a toasty 10,000 amps!! Inductance and series R of the metal work is probably not significant.

A spark gap directly across the primary cap and NST will create enormous high frequency harmonics!! Probably into the GHz range. The capacitor will look open load to those frequencies and I would imagine that the NST will absorb a lot of it!! I would not be surprised at all if the NST failed.

Cheers,

        Terry

..........
Regards, Gary Lau
MA, USA
........