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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: Wednesday, September 03, 1997 2:13 AM
To: Tesla List
Subject: Re: A Puzzle
Tesla List wrote:
>
> From: Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
> Sent: Tuesday, September 02, 1997 6:03 PM
> To: tesla-at-pupman-dot-com
> Subject: A Puzzle
>
> Greetings All,
> This is a genuine enquiry (no, I don't know all the
> answers regrettably). Last night, I replaced the large resonator in
> my work system with a much smaller one with the same sphere on top.
> I am using the same primary but k would be somewhat different.
>
> The large resonator is a 10" x 44" space wound job (Ctot about
> 26pF). The small resonator is 4" x 17" and with the same topload
> resonates at exactly the same frequency as the large one. This coil
> has around 1800 turns of wire one it and consequently its inductance
> is much higher (which it would have to be to resonate at 146kHz as
> its Ctot is much less than the larger coil). OK, I know the wire
> losses are a lot higher in the small one so on to the next bit of
> information.
>
> Under single shot conditions, the spark length is pretty much
> the same as the large resonator so that implies that output voltage
> is pretty much the same. Now that is reasonable because of higher
> losses and possibly reduced k probably compensated for by reduced
> total capacitance.
>
> The cruncher: The large resonator has created those rare long
> sparks measured well over 4 feet p-p. The little one is struggling to
> get to two feet p-p. This is with exactly the same primary coil and
> cap, energy and gap setting. This situation echoes someone recently
> switching from a 3" (?) coil to a 6" one. The air discharges from the
> terminal are a bit shorter with the small one suggesting the reduced
> capacitance might be a factor. I have not as yet taken any real
> measurements but will sometime today.
>
> The question: why? Any input sought, Ideas welcome from all.
> I'd like to hear from anyone, no matter how trivial you think your
> contribution might be.
>
> Regards All,
> Malcolm
Malcolm,
Larger diameter resonators certainly seem to provide better overall
performance. Some speculation...
Your smaller resonator probably has substantially lower Q as well as
significantly higher surge impedance (~70k ohms??). The first factor
will tend to lower its efficiency versus the larger coil. The higher
surge impedance will also limit the amount of "follow-through" current
after the streamer has punched a channel into the air. The degree to
which the secondary voltage collapses (after the initial transfer of
charge/energy to the streamer) will govern the degree to which the
streamer can extend itself.
A lower Zo coil should provide higher follow-through current for toroid
recharge AND streamer extension during a given bang. The current levels
required to support streamer growth are in the multi-ampere range. If
this level of current cannot be readily supplied, further extention may
need to await the next (lower) voltage peak on the damped wave, or even
for the next bang. Lower Zo (and Fo) coils may be able to get multiple
streamer extensions WITHIN a given bang through more efficient energy
replenishment to the top... ie, better matching for "air incineration".
Nothing's ever simple, is it! :^)
-- Bert --