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: "Rob Judd by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
<canska-at-a5-dot-com>
 >
 >  > Original poster: "Mccauley, Daniel H by way of Terry Fritz
 > <teslalist-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>
 >  > How do you figure on 200 BPS???
 >  > I would think that with a static gap, the primary tank circuit is 
going to
 >  > charge up at 2 * 60Hz (positive and negative
 >  > peaks of the input 60Hz voltage) and static gap would discharge at some
 > peak
 >  > of these positive and negative peaks.
 >  > My calculations would say 120 BPS.
 >  > What am I missing???
 >  > The Captain

	The situation is no where near that simple.  For correct values of tank
capacitor and series charging inductance (either external to the coil or
internal as in the case of an NST) your statement will be correct.  In
general, as someone pointed out, the discharging tends to be chaotic.
You can see this quite easily with a SPICE-like simulation (I use
Electronic Workbench as I'm not a whiz on raw SPICE).  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.  Because
the leakage reactance varies with primary voltage (in the case of the
NST's I've measured the reactance appears to be highest for low voltage)
you can also experience other interesting effects as you vary the
transformer voltage; sort of like parametric oscillations.

	Terry has published quite a bit on this subject and he can probably
give you the archive reference.  Real coils exhibit the same sort of
behavior.

Ed