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Re: A Puzzle
From: Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
Reply To: bert.hickman-at-aquila-dot-com
Sent: Sunday, September 07, 1997 1:02 PM
To: Tesla List
Subject: Re: A Puzzle
Tesla List wrote:
>
> From: Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
> Sent: Friday, September 05, 1997 1:24 AM
> To: tesla-at-pupman-dot-com
> Subject: Re: A Puzzle
>
> Hello All,
> DR RESONANCE wrote:
>
> > From: DR.RESONANCE[SMTP:DR.RESONANCE-at-next-wave-dot-net]
> > Sent: Wednesday, September 03, 1997 11:36 AM
> > To: Tesla List
> > Subject: Re: A Puzzle
> >
> > Malcolm:
> >
> > I agree --- larger the resonator the better. There is a 20-25% gain going
> > from 3-4 inch dia to 6-10 inch dia resonators. This also scales up. Ed
> > Wingate's 24 inch dia. resonator works about 20% better than one of our
> > standard 18 in dia resonators. The larger resonators also seem to generate
> > a lot less standing waves kicking back into the pri side of the circuit.
> > Think big!!!
> >
> > DR.RESONANCE-at-next-wave-dot-net
>
> It is almost axiomatic that a large resonator is going to be running
> at a lower frequency as well. Cdistr scales with coil size. As well
> as that, wire size can be very large indeed which certainly makes Q
> scale with size depending somewhat on design. It would be most
> interesting to see whether the generally lower frequency is a factor
> in all this. My experience with the mini-coils suggest it might be.
> The thing I have been thinking is that the time it takes to establish
> an attached arc is not all that fast and spark gap figures are not
> greatly applicable to long sparks so book theory on gap speeds goes
> out the window. Witness the time it takes to establish a lightning
> channel for example. *If* the attachment is that slow to happen,
> perhaps a resonator sufficiently low in frequency (i.e. a large one)
> can add to the arc feed _directly_ by travelling wave rather than
> just relying on top capacitance for arc current. In such a case, the
> _full_ system capacitance is available as an on-tap feed rather than
> just Ctop.
>
> Just thinkin' out loud (yet again),
> Malcolm
Malcolm,
For larger systems this effect DOES seem to be occuring. Greg jus had an
interesting post, a portion of which is replicated below:
Greg said:
==========
"When I had my coil setup at the old warehouse in SF(see the July Nat'l
Geographic, Page 94), I installed two wide-bandwidth (20MHz) Pearson
CT's -- one on the secondary ground connection, and another around the
ground return wire for a suspended metal claw. The warehouse was rather
cramped, and the claw was only 10 ft. away, so power arcs were the
principal form of discharge. During a typical power arc, the peak
secondary base current ranged between 25 and 30A, and the waveform was
all but dead after 9 cycles. The peak current in the claw return was on
the order of 20A. The two waveforms seemed to be in phase, or very
nearly so. (possible skew from the chopping action on the scope?)
The RMS current (over 1 sec) for these waveforms was considerably less
of course, on the order of hundreds of mA."
It clearly sounds like Greg is seeeing not only the initial top load
capacitive surge, but also the follow-through of resonator-supplied
current during power arcs. Additional current is being supplied not only
from distributed self-C, but is also being electromagnetically coupled
from the primary through Zo of the secondary as well since the base and
claw current waveforms appear to be phased similarly. This might be
expected if a power arc from the previous bang is reignited on a
subsequent bang prior to full secondary ring-up. However, it may take a
large coil running at fairly high power to see this effect, particularly
over multiple RF cycles. I do know on single shots on my smaller coil
that ALL the secondary energy goes to zip if a power 'spark" occurs at a
point near the secondary voltage peak. In Greg's case, it appears that
power arcs ARE power arcs...
-- Bert --