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Re: Spark Gap Width



Original poster: "Gerry Reynolds" <gerryreynolds-at-earthlink-dot-net> 

Hi Chris,

There are two gaps to set.  The safety gap (one for each bushing of your
transformer where the ground of the safety gap connects to the chassis of
the transformer) is set with the main gap and TC primary circuit
disconnected.  It is adjusted to "just not fire" with the unloaded HV
transformer powered to the input voltage you expect to operate at(example,
140VAC using a variac).  The main gap can be adjusted using brass rod to
short out a gap or to tap into the string of pipes with your HV power.  The
increments in the total main gap setting will depend on the spacing between
each pipe pair.  I set my total gap spacing (using a 15KV/60ma source) to
.315 inch (9 gaps of 35 mils each). I am at an altitude of 5000 ft so your
results may vary.  I count on the safety gap to protect the NST and widen
the main gap until the safety gap starts firing then reduce it one gap.  I
also use a Cp of 1.6 * Cres to limit the resonant rise and to get about 120
BPS.

Gerry R.


 > Original poster: "Chris Fanjoy" <zappyman-at-hotmail-dot-com>
 >
 >    Perhaps this is a rather basic question, but I'm hoping someone can
 > enlighten this newbie. I've looked around on the web and haven't been able
 > to get much help.
 >    My specific question is, how does one determine what width of spark gap
 > is needed? Is there a specific guideline, such as so many mm per kilovolt?
 > This is for an air-cooled static gap BTW (actually several gaps in
series).
 >    Thanks for any advice.
 >
 >