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Re: Corum's Resonator Theory




From: 	Malcolm Watts[SMTP:MALCOLM@directorate.wnp.ac.nz]
Sent: 	Sunday, November 02, 1997 3:47 PM
To: 	Tesla List
Subject: 	Re: Corum's Resonator Theory

Hi John,

> From:   FutureT[SMTP:FutureT@aol.com]
> Sent:   Friday, October 31, 1997 11:16 PM
> To:     tesla@pupman.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.  

I queried Mr Corum on that one and was completely ignored. To me this 
says that both their measurement techniques leave a lot to be desired
and that their calculation does as well. I pointed out to him that I 
can influence resonator Q by moving around it at a distance of more 
than 6 feet. Both Dr Rzeszotarski and I would have expected a Q of 
more than 200 with that particular coil.

> 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. 

That is *exactly* the problem. They are *drawings*, not scope photos 
as Mr Corum told me.

> 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??

My reading of that and that of at least one other on the list is that 
the y axis scale was changed to enlarge the drawing by 10x.

> 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.

When I asked them how I was met with a wall of silence. I told them 
that I had been using modern storage scopes and that I had seen 
nothing.

> 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.

Exactly my reasoning and that would be needed to take full advantage 
of the phenomenon if it existed. However, quenching the gap with all 
that energy bottled up is anything but a trivial exercise according 
to my experiments. Again, has *anyone* managed to do it without 
incurring terrible primary losses?
  
> > (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.

I would think so too. Perhaps Richard Hull might let us know what he 
has observed in his experimentation with the thyratrons?

Regards,
Malcolm