Re: Spark Gap Auto Quenching/control

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Sean Taylor by way of Terry Fritz <twftesla-at-qwest-dot-net>" <taylorss-at-rose-hulman.edu>

Well, I don't quite understand exactly what youre saying, but this is what
I'm getting:

You have a typical TSG with a dimmer and cap, but in series with the
ignition coil primary, you want to place a triac to turn off the coil a
short time after turning it on so that the gap goes out, or quenches.

IF I have understood this correctly, then there are a few problems here:
An ignition coil fires when the magnetic field collapes on the core, i.e.
when the current through the primary is falling.  When using a
dimmer/capacitor, the sudden spike of current when the internal triac
switches on charges the cap and establishes a current through the primary.
The cap is then charged, and the dimmer has a (relatively) constant voltage
(its varying with the ac line, but it's rate of change is small compared to
the initial switching), and the cap discharges into the primary of the
ignition coil, and the magnetic field collapes, inducing a large current
into the secondary (current through a coil is proportional to the time rate
of change of magnetic flux through the core of the coil, iron for an
ignition coil).  The spark then fires, initiating an avalanche breakdown of
the air, allowing the main TC tank gap to fire.  Only when there isn't
enough current left flowing throught the spark gap does it cease to exist -
ie not enough current to keep the air ionized.  A wider gap will go out
sooner than a small gap because there is more air to ionize/keep ionized,
with currents equal.

The only way I can think of off-hand is to have your TSG blown out with a
small amount of air.  If it is fairly wide, a small amount of continuous
airflow would be able to help prevent the air from staying ionized and
continue to fire or power arc.

I have been working on a TSG controller using solid state electronics, and I
have made a few adjustments to it, getting it to work well, as well as a few
changes to the physical SG layout for a TSG.  I haven't done a whole lot of
experimenting yet, but the controller that I have made right now is
available at: http://www.rose-hulman.edu/~taylorss/tsg if you are
interested.  It looks fairly complicated, but if you use a dual timer (a
556) and a dual comparator/opamp (TL072), it can be fairly easy to build.

Maybe this was more of an answer than you wanted, or maybe I misunderstood
what you wanted to do, but I hope this made some sense . . .


----------------------
Sean Taylor
The Geek Group
G-2 #1204
Because the geek shall inherit the Earth! (c)
www.thegeekgroup-dot-org



----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, March 29, 2002 12:54 PM
Subject: Spark Gap Auto Quenching/control


> Original poster: "Cory Roussel by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<imcuddlycory-at-yahoo-dot-com>
>
> Hello coilers,
>
> I  have had this idea for a while mabey one of you
> will carry it out for me to see what happens... the
> idea is basically to intergrate a triggered spark gap
> (car coil/dimmersetup) and also a solid state resonant
> circut disruptor...  all the above means is, triggered
> spark gap, which by nature is normally longer than the
> normal spark gap length powered by a car coil with
> goes through a dimmer and some sort of ballasts ( i
> use caps) so it doesnt explode,  the idea is, the
> dimmer will make it fire at whenever in the phase you
> want from 0-90 degrees in the cycle so you want to
> make it fire at say 80-90 degrees, that would be the
> LOWest setting, so ok now you have a poorly or Not at
> all quenched triggered gap eh? ok now the second part
> of the idea is to have a power TRIAC built in series
> with the coil and the capacitor...  the triac should
> use ANOTHER switching setup (this will require a
> knowledge of electrical circutry and signal
> generation) which should remain ON during the entire
> process except to turn it OFF about 2 or 3 degrees
> after the gap fires, it should be turned back on
> before the 180 degree mark...  so basically you end up
> with a totally electrically controlled spark gap, that
> automatically quenches your spark!  this would be
> useful perhaps for large coils with big amperages or
> for MOTs...  the Power Triac could be replaced with a
> transistor or possibly a tube but this idea would
> prolly be a little expensive but it would DEFINately
> be worth a try..
>
> sincerely
>
> Cory Roussel
>
>
>
>