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Re: RQ Schematics
Subject: Re: RQ Schematics
Date: Tue, 22 Apr 1997 05:07:40 EDT
From: wb8jkr-at-juno-dot-com (Mark S Graalman)
To: tesla-at-pupman-dot-com
References:
1
On Tue, 22 Apr 1997 00:23:04 -0500 Tesla List <tesla-at-pupman-dot-com> writes:
>> >... 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
>
>
This possible resonant rise will exist in either case, the cap is
still
in parallel with the transformer high side the only exception
between the two is in the case of the gap across the transformer the
primary coil is also in the equation, but the primary inductance is
utterly insignificant in comparison to the inductance of the drive
transformer high side. But, gap across the transformer is the way
to go. The big problem with protection chokes is that the blasted things
ring like "little tesla coils" if they have too many turns and
thus a lot of self-capacitance, this is the big advantage of using
ferrite, lots of "L" small # of turns = no ringing.
Mark Graalman