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Variable Quenching
From: Thomas McGahee[SMTP:tom_mcgahee-at-sigmais-dot-com]
Sent: Wednesday, September 10, 1997 2:46 PM
To: Tesla List
Subject: Variable Quenching
> 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
>
Malcolm,
On my vacuum quench gap systems I use a small variac to adjust the
vacuum from my AC/DC vacuum motor. I have found that I can "tune" the
system slightly by adjusting the air flow. If I turn the vacuum up
too high it causes the output spark to become wimpy and thread-like.
Best results are obtained with low to moderate vacuum. It is always
good to make as many parts of your system as variable as possible,
because each element affects the overall synergy in subtle ways.
When I have mentioned to others that I can slightly "tune" the system
this way they normally disregard this and say that it is probably not
really tuning but something related to the temperature of the copper
pipes. Nope. It is a genuine change in the quality of the gap system
that does in fact affect the actual tune point (if that is the proper
term to use here). It definitely affects the quality of the output
spark: its length and the color of the spark are both affected. As
you mention, Malcolm, it directly relates to the number of ringups
that occur.
As John Freau has pointed out, too much air blast and the poor gaps
have trouble firing in the first place. Some people refer to this as
over-quenching, but I agree with John that what we really have in
this case is a failure to fire as opposed to turning the spark off
too early.
So if anyone out there is using a vacuum spark gap and does not have
a variable damper plate or a variable speed motor to adjust the air
flow rate, then you are most likely NOT running your system
optimally.
Hope this helps.
Fr. Tom Mcgahee