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Re: Variable Quenching
From: gweaver[SMTP:gweaver-at-earthlink-dot-net]
Sent: Thursday, September 11, 1997 12:30 AM
To: Tesla List
Subject: Re: Variable Quenching
At 07:16 PM 9/10/97 -0500, you wrote:
>
>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
I have to agree with this 100%. I have a Richard Quick type spark gap with
a vacuum fan attached to it. I adjust the speed with a variac. Another
interesting point here is when I am using all 8 of the .025 gaps the system
works best with the fan running about 1/3 speed. If I reduce the gaps from
8 to 7 I then need to increase the fan speed a little for best system
performance. I can change the gaps again from 7 to 6 and again I have to
increase the fan speed for best spark output. If I am adjusted for 6 gaps
and change it to 7 or 8 and don't reduce the fan speed the spark gap has
trouble firing. The output sparks are much shorter and very different,
short fast moving with many small thin branches. If I reduce the fan speed
then the system output is back to normal with long sparks and streamers. I
have used this variable speed vacuum spark gap from 360 watts to 5000 watts
running at full speed at 5000 watts.
Gary Weaver