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Re: Why does top capacitance work?
At 10:27 PM 2/10/97 -0700, you wrote:
>Subscriber: sfalco-at-worldnet.att-dot-net Mon Feb 10 21:49:24 1997
>Date: Sat, 08 Feb 1997 10:47:25 -0500
>From: Steve Falco <sfalco-at-worldnet.att-dot-net>
>To: tesla-at-pupman-dot-com
>Subject: Why does top capacitance work?
>
>I must be suffering from a misconception about top capacitance - i.e.
>the toroid. People talk about putting a larger toroid on top as a way
>to get a larger spark. The claim is that the larger toroid has to
>charge up to a higher voltage before breaking out.
>
>The problem I have with this, is that the coil will be resonating with
>an A.C. voltage, at 50 kHz or 100 kHz or whatever. So, won't the top
>capacitance charge and discharge at the same rate? I would think the
>average voltage would be zero. (I know I'm wrong here - I've seen the
>sparks!)
>
>So what is going on? Is there some sort of rectification effect here?
>Can anyone tell me what they think a plot of the voltage versus time
>would look like assuming we could hook a strip-chart recorder to our
>tesla coil and record the instantaneous voltage? Or do we get an
>oscillation that builds over time where eventually the swing exceeds
>the breakdown voltage? This seems like the most likely description to
>me.
>
> Thanks for any insights,
> Steve Falco
> sfalco-at-worldnet.att-dot-net
>
>Steve,
I have commented on this question several times in the past here. For what
its worth. The Toroidal effect is a factual occurance. The multiplicity of
mechanisms possible make a definitive statement almost impossible. Some
possible explainations are more or less plausible than others.
A strip chart recorder is far too slow in its action to be of much value to
use here. A digitizing storage scope would be of more value if it could
survive in the environment for long.
Really big coils, where the effect is most pronounced oscillate at around
50khz. Thus, the reversal of RF polarity occurs every 10 millionths of a
second. The DC time constant of a really large system toroid to ground
could be longer than this if air were the only path of breakdown. Not
necessarily the case. Electrostatically, the system can act as an electret
at times, as has been witnessed. Also the pumping and ionization of the air
as the coil builds to maximum spark output definitely has a rather long time
constant as is physically witnessed. Once a sort of "equalibrium" is
reached and max spark occurs, it is rather well maintained thereafter.
A key factor is that the coil itself must first be capable of breaking out
of the supplied toroid in the first place! A lot tend to forget this fact.
The coil along determines this final voltage value. The power into the
system per unit time and the toroid size determine the base current and thus
the output current for a given system. The air, surrounding condition, and
unusual only guessed at DC electrostatic effects further enhance the
"apparent effect" of what we call spark length.
Richard Hull, TCBOR