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Re: Quenching


From: 	Peter Electric[SMTP:elekessy-at-macquarie.matra-dot-com.au]
Reply To: 	elekessy-at-macquarie.matra-dot-com.au
Sent: 	Friday, September 12, 1997 7:56 AM
To: 	Tesla List
Subject: 	Re: Quenching

Tesla List wrote:

> 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,

I found you post a bit confusing as my experience with static gap
quenching seems to be opposite to yours. I was running 15Kv 60Ma input
with a single static gap set at about 3/8" to 1/2" and a .015 Cap. I had
a compressor hooked up with a 1/4" nozzle and found the higher the
pressure from the compressor, the better the output from the coil. The
limit was at about 25PSI at which the compressor lost pressure too
rapidly to be much use. Also I found it difficult to hear the noise of
the gap over the incredible hissing from the airjet.

What current input were you using and were you using much lower voltages
in you setup?

Cheers,

Peter E.