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Re: RQ Schematics
Subject: Re: RQ Schematics
Date: Mon, 21 Apr 1997 21:55:15 -0400
From: "Thomas McGahee" <tom_mcgahee-at-sigmais-dot-com>
To: "Tesla List" <tesla-at-pupman-dot-com>
CC:
<alfred.skrocki-at-cybernetworking-dot-com>
----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-poodle.pupman-dot-com
> Subject: Re: RQ Schematics
> Date: Monday, April 21, 1997 1:20 AM
>
> Subject: Re: RQ Schematics
> Date: Sun, 20 Apr 1997 18:19:29 +0500
> From: "Alfred A. Skrocki" <alfred.skrocki-at-cybernetworking-dot-com>
> To: Tesla List <tesla-at-pupman-dot-com>
>
>
> On Fri, 18 Apr 1997 08:50:08 -0400 Thomas McGahee
> <tom_mcgahee-at-sigmais-dot-com> wrote;
>
> >... Oh, what the heck! My own personal favorite is any circuit that
> > has the main spark gap across the transformer.
>
> Thomas, this arrangement has always intrigued me when in illustrations
> of the arrangement with the spark gap across the transformer we see
> the safety gap also across the transformer. What intrigues me is that
> the safety gap will never fire! The operating gap will always be
> smaller than the safety gap otherwise the 'safety gap' will become
> the running gap! Consequently in the arrangement with the spark gap
> across the transformer the safety gap is a waste of time, or one
> could say there is NO SAFETY in that arrangement.
>
> > People who put the capacitor directly across the transformer are
> > unnecessarily jeapordizing their neons.
>
> How!? If you have a safety gap across the transformer and the spark
> gap is in series with the transformer it will be totally protected
> UNLIKE the condition of the spark gap and safety gap being
> across the transformer where the safety gap CAN'T fire! In the
> arrangement you describe the only function the safety gap would serve
> would be to protect someone from opening up their gap way too far!
Precisely, Alfred! I am in total agreement with about 95% of what you
say.
And you don't think that people sometimes open up their main gaps too
far?
In the search for ever bigger and nastier sparks, it happens all the
time.
Some of the coilers out there can tell you that they have their safety
gaps
firing several times a minute.
Your objection about the safety gaps seems to assume that the safety gap
and the main gap are in parallel. 'Taint necessarily so. Many people use
RF
chokes between the neon and the main gap. Believe me, the voltage that
develops across such a choke can be enormous. Like very heavy, white
angry
sparks about an inch long! Got chokes? try putting a little temporary
"spark gap" across one of the beasts using some #21 bare wire, and watch
the sparks fly! Watch the metal melt! Stand in awe at the savagery of
the
nasty white sparks! (We are assumimg the Tesla coil is operating and
hurling huge discharges into the ceiling of your garage).
The logical conclusion of your paragraph above is that in the
arrangement
where the main spark gap is across the transformer, there is no need for
a
separate safety gap. OK, let's look at that conclusion as if it were
correct. You are objecting because with this arrangement we get to
*eliminate* a part? Save time and money? Use the parts for some other
purpose? You consider this a negative? (Scratch, scratch....) Hmmmm.
That
looks like a positive point to me. :)
But enough with the jesting!! The main special reason why the capacitor
should *not* be across the transformer has to do with resonant rise.
This
is a condition where low frequency resonance between the neon
transformer
and the tank capacitor causes the voltage across the transformer to rise
SIGNIFICANTLY above its rated voltage. I think many of us forget that,
or
are ignorant of that fact. Hey, coilers, the resonant frequecy of the
tank
circuit is not the *ONLY* resonance in effect in your Tesla coil! Or why
else do you think you can pull that main spark gap back REALLLLY far and
sometimes sustain some pretty long main spark gap arc??? Or why is it
that
you can sometimes get your Tesla coil to operate with only 30 volts
coming
out of the variac??? Resonant rise. Number one killer of neons.
Initiating
cause of arcover and burnt windings and fried neons.
Hey, try a simple experiment if you have a meter that can measure 40KV
AC.
Connect your neon alone up to the meter and measure the voltage. Then
connect JUST your tank capacitor in parallel with the neon and measure
the
voltage now. Aw, what the heck, guys, I don't want any of you to blow
your
neon up or totally trash your beloved capacitor just to prove that there
is
a really good reason not to have too much resonant rise in your circuit,
so
use a variac and only put in about 60 VAC for each of the above trials.
Now, on some Tesla coils things will look fairly normal, but on other
Tesla
coils, the voltage will appear about DOUBLE. Maybe Barry Benson or some
of
the other coilers that have experienced the effects of resonant rise
will
come forward and put in their two cents worth here. There *IS* a
difference
in what voltage the transformer "sees" when you wire the capacitor up
differently. Placing the capacitor directly across the transformer *CAN*
set up a resonant rise that quite easily exceeds the breakdown voltage
of
the neon. Pole pigs are oil immersed and take the abuse without
blinking.
By the way, remember all that talk about "matching your transformer to
the
capacitor"??? Well, if you have done that, then you have most likely set
up
a 60HZ resonance between the transformer and the capacitor. Now, such
resonance can be VERY useful... but it can also put voltages across your
neons that are MUCH higher than you dreamed! Ah, the wonders of the
resonant circuit!!!
The resonant rise can be bad or good, depending on how you look at it.
Alfred, the resonant rise can actually be beneficial in circuits using
things like 5KV neons. Assuming that the 5KV neon can take fairly
continuous 10KV RMS voltage, that is. I have been doing a lot of
research
on the question of neon demise, and resonant rise is often the
unsuspected
culprit.
> In the arrangement with the capacitor across the transformer and a
> safety gap across the transformer with the operating gap in series we
> have full protection from high voltage surges and kick-back to the
> transformer for this would fire the safety gap!
OK, I admit that a REALLY GOOD safety gap helps much to remove the
danger
associated with the capacitor across the transformer. But, tell me... is
your safety gap as robust as your main spark gap? If not, then you may
be
in for a nasty surprise somewhere down the road. Not EVERY spark gap can
absorb the full current stored in the tank capacitor. I wonder what
happens
then??? To the transformer that is in parallel with the safety gap, that
is. Poof.
There are multiple ways of looking at most things. In the arrangement
where
the main spark gap is across the transformer, the transformer will
actually
still see the capacitor across itself. Check it out for yourself. When
the
spark gap is not firing, the capacitor is connected across the
transformer
via the very LOW 60HZ resistance of the Tesla primary. Ah, so you ask,
then
EVEN in this arrangement the capacitor is across the transformer. The
answer is YES!!! But the difference is that there is also this very
MACHO
Spark Gap designed to take huge surgees of obscene current levels
without
vaporizing (too much or too long...) :) This SAME Macho Spark Gap
shunts
the nasty super-currents through itself, thus saving the frail and
feeble
neon for yet another surge of sixty cycle current. (or 50 Hz current for
the European coilers out there). I hope that the picture is becoming
clearer.
> The only condition
> the gap would not protect against is a total short of the capacitor
> but the neon transformer is designed to take a dead short for a
> limited period of time besides that condition would cause excess
> current flow in the primary which would trip the protective breaker
> that should be in the primary circuit.
The current limiting in the neon is built in, and actually does *not*
cause
excessive primary current. Increased current, yes, but not excessive
current. In normal use driving a neon gas tube, the neon transformer is
actually running in current limited mode all the time. The output
voltage
of a 12KV neon when actually driving a neon tube is disgustingly low.
Something like one or two KV MAX.
Neons have their problems, and always will. Or, as Ed Wingate would put
it:
Enough with the stinking neons and the H&R transformers... be a man, buy
a
pole pig, and abuse it all you want. You can hardly kill the beasts. Ed
sounds like a pretty up front macho guy to me, and I have begun
searching
for a pole pig or potential transformer. When I find one that has a low
enough price tag I'm going to buy that sucker, throw a couple of $45
Variacs and arc welders and a clothes dryer in series with the input
side,
and build a three-phase Twin Tesla coil connected up to a 100 KiloJoule
50KV 200 mfd military surplus infinite duty cycle pulse capacitor
(charged
by a model T Ford spark coil left over from my high school science fair
project 30 years ago, and a string of 10,000 1N914 diodes that I got
real
cheap at a ham fest in Hohokus, NJ) that will blast holes in my
fluorescent
light fixtures at a distance of several feet! Of course I will post
pictures for everyone else to salivate over. Pictures of me with a light
bulb in my mouth standing next to my four foot diameter 15,000 RPM
Salient
Pole bi-synchronized variable speed counter-rotating air cooled 2 HP 5
inch
thick teflon coated G10 compressed air operated optimally quenched
rotary
spark gap with brass fitted non-thoriated pure tungsten inserts
aerodynamically shaped to produce maximum air turbulence, arranged in a
semi-elliptical pattern of fibonacci related prime number segments with
multiple vacuum quenched modified Richard Quick static series gaps using
water-filled solid copper electrodes a la Bert, in a search for pure
synergy. The design was lifted verbatim from a tape soon to be released
by
TCBOR, and is based on work by John, Ringo, Malcolm, Ed, Fred, Jim,
Michael, Richard, Richard, Billy, Bob, Bert, Bert, Bert, and Ernie. If I
left anyone out I am sorry. :)
A final note. I mentioned tongue-in-cheek that a discussion of Tesla
circuitry would most likely lead to some heated discussions. I hope,
Alfred, that you and any other coilers that prefer the
capacitor-across-the-neon circuit do not take any offense at my remarks
above. I do not want such discussions to generate heat, but rather
light.
You made some excellent and insightful remarks in your post. One can,
indeed, run a decent Tesla coil with the capacitor across the
transformer.
I have done it many times myself. I have a few coils in which I do it
that
way *on purpose*, to make advantageous USE of the resonant rise. But
there
are new coilers out there that may be totally unaware of the potential
(pun
intended) resonant rise and how it can cause a poor neon transformer to
arc
over internally. If such a discussion helps them to see the issue a bit
more clearly, then our mutual jousting and jesting may be of some use
after
all! Enjoy!
Fr. Tom McGahee