Re: Static Spark Gap

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ed Phillips by way of Terry Fritz <teslalist-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
 >
 > Original poster: "Stephen Conner by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>
 >
 > At 12:23 24/04/03 -0600, you wrote:
 > >Original poster: "Ed Phillips by way of Terry Fritz <teslalist-at-qwest-dot-net>"
 > ><evp-at-pacbell-dot-net>
 > >  If the LC product
 > >is high enough you can get the situation where the spark is at  60 bps
 > >(this can result in core saturation), or at sub multiples of 60 bps.  In
 > >other words, the circuit is "counting down".  I've observed the effect
 > >with a real coil when I have used a variac to get the input voltage to
 > >the transformer very close to that at which the gap won't fire.
 >
 > I noticed that too when using a NST with a resonant cap. I could get the
 > firing rate down to about 1bps with the variac at 50V (240V supply).
 > Unfortunately this practice is not to be recommended because a very high
 > circulating current is flowing in the NST all the time. After a minute or
 > so the NST got very hot. It died soon after, although I'm not sure if there
 > was a connection :(
 >
 > Steve C.

	I don't understand why your transformer got very hot unless you had
your gap set much wider than that required to "just break down" with
rated input voltage and no capacitor across it.  What's happening to
cause the low spark rate is that the voltage across the
transformer/capacitor is increasing due to resonance and, since the Q is
of the order of 15 or 20, it takes a number of cycles to build up to the
gap firing voltage.  I wonder if the transformer failure was due to too
wide a gap?  Was the failure a short in the secondary?

Ed