Spark Gaps

From:  Thomas McGahee [SMTP:tom_mcgahee-at-sigmais-dot-com]
Sent:  Saturday, April 11, 1998 9:02 AM
To:  Tesla List
Subject:  Re: Spark Gaps

> From:  Steve Falco [SMTP:sfalco-at-worldnet.att-dot-net]
> Sent:  Thursday, April 09, 1998 5:32 PM
> To:  Tesla List
> Subject:  Re: Spark Gaps
> > Static gaps will work great out to 5,000 watts if the builder has the
> > experience to apply them.
> > 
> > Richard Hull, TCBOR
> To what extent is this dependent on voltage and current?  E.g., I can
> get 5000 watts as 5kv -at- 1amp or 15kv at 1/3amp.  I would expect the
> static gap to work better in the latter case.
> 	Steve Falco

You adressed this to Richard Hull, but let me make a few observations:

When the voltage is lower your gap spacing has to be closer to allow the
gap to fire properly. With a lower voltage you generally end up using
a larger capacitor in the tank circuit. This means that you will also
have larger tank currents flowing when the gap finally fires. This in
turn translates into larger gap currents. This means more hot ions in
the gap, and greater gap erosion. 

Higher voltages allow you to use smaller caps, larger gap spacing, and
results in lower gap erosion with time.

You have probably noticed that the main spark gap can take quite a
beating with your .12 mfd capacitor and dual H&R transformers. A vacuum
gap is almost a necessity here, if not using a rotary.

By the way, you can ALSO process more energy in another way: When the
transformer has a large current capability, you can arrange things so
that you use a SMALLER capacitor and allow the gaps to fire at a much
lower voltage. This is usually accomplished by adjusting the speed
of a non-synchronous rotary gap. As you adjust the speed, you will
find that there are certain points at which the processed power
increases dramatically. This occurs, for instance, when the gaps fire
such that there are TWO gap firings per half-cycle. The transformer
is charging the cap to a lower voltage, but MORE OFTEN. Thus the 
actual processed power is increased. With a non-synchronous rotary
you can actually observe this effect quite readily, for when you
hit the right spot, the phasing will not be locked in, and so
you will see the output arcs slowly increase and decrease as the
phasing slips.

Because the H&R transformers are quite low as regards voltage, it
is best to run them matched to the cap such that resonant charging

Pole pigs and potential transformers operate quite well
when running with a rotary gap at higher BPS. Neons do not take the
abuse too well. It is usually a good idea to include a static gap
in series with the rotary gap, as this reduces the stresses on the
rotary and aids in earlier quenching.

Hope this helps.
Fr. Tom McGahee