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FW: Corum's Resonator Theory
From: FutureT[SMTP:FutureT-at-aol-dot-com]
Sent: Friday, October 31, 1997 11:16 PM
To: tesla-at-pupman-dot-com
Subject: Re: Corum's Resonator Theory
In a message dated 97-10-30 20:09:31 EST, you write:
<< snip>
> (3) The re-arrangement of current (which it is claimed would result
> in a voltage rise over the lumped situation) has not been observed by
> anyone I know. Personally I have captured waveforms using a
> storage scope many, many times and not once have I ever seen a
> hint of this, breakout conditions or no. In fact, I will touch on
> this problem in point (4) below. Perhaps someone has seen it.
> If so, please, please post.
Malcolm, all,
This may be of interest to those who have not read the below
mentioned paper.
The Corums write on page 11 of their paper "Tesla Coils: 1890-1990
100 years of cavity resonator development", that they measured the
output voltage of a TC having a 24" dia secondary, 780 turns of #10
copper wire, top loaded with a 24pF ball, and resonant at 67 kHz,
and they found the predicted and measured coherence time to be
about 71uS. The TC's predicted and
measured Q was 60. The next couple of pages show drawings
that show the energy transfering back and forth between primary
and secondary for about 308uS before the gap quenches. Then
they show the voltage increasing about 10 times higher almost
instantly, then gradually rising to almost double again within 5
RF cycles which is the coherence time. (Perhaps the drawing
is showing the primary voltage up to 308uS, then the secondary
voltage after that...this might explain the ~10 times voltage rise??
However I don't think this is what they mean, because they
mention that the voltage rise is so great, that it is hard to show
on the graph, also the heading says "Voltage across VC2", and
a drawing on the previous page refers only to the secondary also.)
They do not mention
whether or not the coil is sparking at the time, but they do say
that anyone can measure this voltage rise effect on their coils.
They go on to say that they tested other resonators and found
similar results.
I have not seen any voltage rise in either sparking, or non-breakout
conditions after the gaps quench, in any of my coils, but see below.*
It seems to me that if this was happening (rise), we should be able to
select a toroid size that would permit break-out *only* after spark
quench, dependent on degree of ionization of streamer roots, etc.
> (4) As most will be aware, trying to quench a gap under no breakout
> conditions is a notoriously difficult exercise. However, the
> implication is that a voltage rise should be observed *any time* the
> gap is quenched, no matter how little energy remains as long as it is
> not zero. Once again, has anyone ever seen it?
Yes, the implication is as you stated based on the above paper, and
I have not seen any such rise. Using a transistor in place of a spark
gap, *I have seen a very slight rise for 1 cycle or so after "quench",
but I attribute this to the built-in diode within the transistor allowing
another half cycle of RF to pass after the "quench". I would have to
re-check my work, since my set-up was crude.
> According to Mr Corum, it is this extra rise that is the secret
> of a "true" Tesla Coil. I repeatedly queried him on quench issues and
> came up against a brick wall in trying to extract an answer. How many
> people who have examined coil waveforms in minute detail believe that
> you can cut a gap off when all the energy remains bottled up in the
> system (e.g. ideal first notch quench without discharge)? If Mr C's
> theory is correct and this can be done, then I think we are in for a
>treat. If not...... None of my coils have ever done it including the
> one with the difficult-to-break-out-of topload I posted on in the
> last couple of days. In attempting to do this, I blew a *jet* of
> compressed air through the gap. No voltage rise was observed on the
> scope from the time the gap was cutoff and to make matters worse, the
> gap losses roughly doubled according to both a discharge test and
> the scope not to mention the gap flame and noise.
Using a transistor or H2 thryratron in place of a spark gap may be
useful for these measurements I would think, since they can
"quench" without breakout. Even if the thryratron shuts off *too
soon*, it should still give valid results for this work.
Regards,
John Freau
> If anyone has observations, measurements, comments etc. I for one
> would love to hear them. This post is done as much to advance my own
> understanding as it is an attempt to clarify the issues. I would just
> like to observe two things - the distributed model fails to predict
> the resonant frequency if one uses lumped L and lumped C, and from
> the diagrams I have seen in the Corum's papers, they are considering
> a *balanced* line as a model. Does that make any difference? (I plead
> with those into scalar theory not to make an issue of this). Mr Corum
> states that Maxwell and other conventional engineering theory are all
> that is needed to predict resonator behaviour.
>Thanks for listening,
> Malcolm
>>