RE: Tesla Coil Blunders

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Gary.Lau-at-compaq-dot-com>

It is well known that the operating resonant frequency of a secondary with
streamers will be lower than the low voltage (streamerless) resonant
frequency, due to the fact that streamers and the ion cloud about the top
load will act to increase the terminal capacitance.  I used ETesla6 to
calculate my secondary frequency and it was dead-nuts on.  Only the physical
geometry and secondary DC inductance was needed, not R.  The operating
frequency with streamers was the "usual" amount lower - I just
experimentally tapped further out to find it, but didn't note exactly how
much lower it was.  

I would guess that to calculate this fudge factor in advance would require
an estimate of streamer behavior, something that's presently way too complex
to predict.

Gary Lau
Waltham, MA USA



>Original poster: "John H. Couture by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <couturejh-at-worldnet.att-dot-net>
>
>Tesla Coilers may be making the worst of TC blunders when doing
calculations
>for determining the operating resonant frequency of their coils. It is a
>well known fact that the calculated frequencies do not agree with the
actual
>operating test frequencies. Many important design decisions are based on
>this unique frequency so it is important that it be correct. To circumvent
>this problem a fudge factor is used for all TC computer programs but this
is
>only a bandaid for TC design.
>
>The equation that coilers use for finding the TC resonant frequency is
>
>      F = 1/(6.283 x sqrt(LC)
>
>The TC secondary circuit is an RCL circuit but the "R" is omitted by
coilers
>in the above equation which may be the worst of TC blunders. In the Tesla
>Coil Construction Guide page 5-1 the complete resonant frequency equation
is
>shown including the "R" parameter. It is also mentioned that the "R"
reduces
>the resonant frequency and if the "R" is large enough there will be no
>resonant frequency. In other words the "R" could be the reason the
operating
>frequency does not agree with the calculated frequency when the "R" is
>omitted.
>
>To my knowledge no one has ever determined how to find this very important
>"R" for an operating Tesla coil either by calculation or by tests. TC
>programs are hurting because of this lack of information.If anyone has any
>comments I would be interested in them.
>
>John Couture

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