Quenching

To: "'Tesla List'" <tesla-at-poodle.pupman-dot-com>
Subject: Quenching
From: Tesla List <tesla-at-stic-dot-net>
Date: Tue, 9 Sep 1997 18:52:28 -0500
Approved: tesla-at-stic-dot-net

From: 	Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: 	Tuesday, September 09, 1997 4:11 PM
To: 	tesla-at-pupman-dot-com
Subject: 	Quenching

Hi all,
         Having now rigged up a regulated compressed air line to the 
gap of my coil, I decided to check out what happened at various air 
flows. It was quite revealing. I suppose the experts have known this 
for years but for myself I discovered a concept I call "tuning the 
quench". I did some single shot tests at different airflows and 
monitored the response on the scope as well as observing the gap.

    With no airflow, the gap was relatively quiet and the discharge 
to a ground wire was what it was. With no breakout, the gap quenched 
at the fifth and sometimes sixth ringup depending on exact firing 
voltage (it was set to where it normally would be).
    Turning on _some_ air, the gap started to produce a soft "pop" 
and brightened a little. Generally, quench occurred a ringup earlier 
and output discharge increased.
    Turning on more air, the gap brightened some more, started 
getting louder and the output discharge was the same or a little 
shorter while the scope showed an average of another ringup 
disappearing.
    Without going through all the steps, I finally tried the air jet 
at full pressure. Now the gap was very loud and bright, output had 
sunk to a real low, and I actually achieved quench at the end of the 
second ringup with no breakout. It is clear this was a totally useless 
setting because while the quench looked excellent on the scope, the 
gap was dissipating the bulk of the power. This was borne out by the 
abysmally short discharge to the ground wire. BTW, the full air jet 
was so violent the spark was considerably displaced from the centre 
of the gap electrodes.

    On watching Richard Quick's video I was struck by the brightness 
and noise of the gaps with the various quenching systems he was 
using and yet it seemed that without that degree of airflow, the 
transformer fire in the gap just wouldn't go out. I commented to him 
that I thought there was a lot of power being chewed up there. Well 
it certainly seems so from this exercise. I now think that the degree 
of quench he was having to apply to stop power arcs was hindering the 
output of the coil. It seems to me that the way around this is to 
choose a bigger cap to load the supply more heavily so the air supply 
could be moderated to the point where it served the tuned circuits 
best.

    For my coil it looks as if a quite moderate air jet is best for 
tuned circuit behaviour. Question is: will it also be best for 
stopping transformer arcs in the gap? If more air is required to stop 
the arcing, it seems I could do better in matching the primary cap to 
the transformer. Be interested in comments anyone else has to make on 
this. The reason I mention all this is because I haven't heard of 
anyone actually setting the quench conditions for their coils in this 
way and it might prove useful for getting more bang for no extra buck 
in a number of cases.

Malcolm