Static gap BPS, was Static Spark Gap

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

Original poster: "Lau, Gary by way of Terry Fritz <teslalist-at-qwest-dot-net>" <Gary.Lau-at-hp-dot-com>

The BPS of a static gap is only remotely tied to the mains frequency.  With 
a 60 Hz supply, one would achieve 120 BPS only if the gap breakdown voltage 
was precisely set to the voltage that the cap would acquire after one 
half-cycle of power.  That sounds fine in theory, but it turns out that the 
actual breakdown voltage varies considerably with time, airflow, 
temperature, time since last breakdown, etc.  Variations in breakdown 
voltage will translate to variations in timing, i.e. no longer at peak 
voltage.  What isn't obvious is that if following a half-cycle of cap 
charging, if the voltage is too small to break down the gap, that charge is 
NOT wasted (where else would it go?).  Instead the cap forms a tank circuit 
with the power supply (NST) secondary inductance, and the energy in the cap 
is carried into the next half-cycle in the opposite polarity.

In any static gap circuit, the _average_ BPS will be governed by cap size 
and gap width.  Truthfully, I've never actually measured my gap's average 
BPS, though I have confirmed that the waveforms are as simulations predict 
- chaotic, and definitely not synchronized with mains peaks.  See 
http://www.laushaus-dot-com/tesla/gapsim.htm for simulated waveforms, and 
http://www.laushaus-dot-com/tesla/measured_waveforms.htm for a measured waveform.

I was surprised to hear Terry suggest that the BPS will ultimately work out 
to be roughly 200 BPS, or any particular number.  I know that the BPS is 
strictly dependant on cap size and gap width, so I'm not sure how such a 
generalization can be made.  Maybe I'll measure my minicoil's BPS tonight...

Gary Lau
MA, USA

 >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