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RE: TESLA COIL REVISED
Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com>
>Original poster: "Trans-world" <jaro-at-surfside-dot-net>
>you make some good points. I'm glad that you agree that the 1:50
>primary/secondary ratio would be the way to go for SOLID-STATE Tesla
>coils, because feeding the primary coil with the resonant frequency of
>the secondary would build up the output voltage to any level, only
>limited by resistance and leakage losses.
I said no such thing. A 50-turn secondary would result in a very high
resonant frequency. Since AC resistance increases with frequency, such
a coil would have a higher resistance than one operating at a lower
frequency. The lower Q would probably result in inferior performance.
>As to the classic coil that Tesla was using, I think he was correct
>when he said that using a thick wire secondary could build up voltage
>to any level. It seems to me that it was his experience and applied to
>the BIG coils that he was using. Of course that may not apply to small
>1-foot diam. coils. Why? Perhaps because small coils have smaller
>inductance and with it much higher resonant frequency.
Mr. Tesla would frequently communicate in less than scientifically
accurate terms, so as to impress and attract investors. Do you really
believe that any thick wire coil he made could build up to ANY voltage?
A billion volts?
>It could be that the spark-gap discharge isn't fast enough or efficient
>enough to feed a secondary that resonates at MHz frequencies. Or the
>thick wire secondary still produces excessive losses at these very high
>frequencies. So, as I noted in a previous email, the answer for small
>Tesla coils would seem to be using a thick wire secondary, PLUS a
>100-200 turn tertiary coil to reduce that high frequency.
>As to the brush-like discharge, that's what Tesla saw as THE difference
>between his coil and other high voltage sources. So if you build a HV
>coil that doesn't have such discharge, you've built a high voltage
>coil, but it's not a TRUE Tesla coil.
The generally accepted definition of a Tesla Coil is a high frequency
air-core double-resonant transformer which produces high voltage. I
have never heard of a further distinction constraining the type of
discharge. There are many well circulated photos of Mr. Tesla with
lightning-like discharges from his coils. Are these not Tesla Coils?
>By the way, you said that in a classic TC, resonant rise does not
>occur. Is there any experimental data supporting that?
One must first understand what resonant rise is. With resonant rise,
energy must be _continuously_ applied to a system, at its resonant
frequency. Like with a person pushing another on a swing, giving small,
equal pushes, once per swing, the swing-amplitude grows with each push
(until the other person falls off or discharges). This is what happens
in a CW coil. But in a spark gap coil, there is only one big whopping
initial push as the gap fires, and things go downhill from there as the
energy transfers to the secondary. Pri-sec resonance is necessary to
transfer the "push" energy to the secondary side, but it does not employ
resonant rise, because there is only a singular application of energy,
and each successive application of energy (spark gap firing) does not
build on the energy of the previous application.
It may not be obvious to some that the energy from each gap discharge,
or "bang", is dissipated completely before the next bang and does not
build on previous bangs. It is, and this has been proven countless
times through actual circuit scopings. Terry Fritz composed a paper
comparing simulated and measured waveforms in his coil, and it plainly
shows that all energy has been dissipated before the next bang. See
Regards, Gary Lau