Re: How to rise the secondary? (fwd)
---------- Forwarded message ----------
Date: Thu, 9 Jul 1998 18:02:13 +0100
From: R M Craven <craven-at-globalnet.co.uk>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: How to rise the secondary? (fwd)
John Couture, in reply to Bill the arcstarter, wrote:
> You are correct in saying that "the really tricky one is Cs". The Cs
>includes the toroid cap which is changed to an unknown value when mounted
>the TC. However, the true Cs and toroid capacitances can be found after the
>TC is built and tested to find the true operating frequency. You then vary
>the toroid cap value in repeated manual calculations with the several
>parameters involved until the test frequency shows up in the output. The
>total secondary capacitance (Cs) will be the true total capacitance. The
>toroid capacitance being used will be the true capacitance of the toroid
>when mounted on the TC.
Whilst this is all established, the fact is that the operating conditions
are different from instrumented conditions, and additionally operation at
full power is different from operation at lower powers.
Richard Hull and many others, myself included, commented ages ago when we
were all discussing toroid sizes, optimums, expressions for calculating
toroid capacitance. The apparent increase in total secondary C due to
streamer loading, brush discharge and localised ionisation, mean that the
topload "looks" more capacitive than when output effects are not occurring
by which I mean St Elmo's fire through brush discharge through to arcs).
That is why people recommend doing a static setup based on calcs, then
running at lower power, then empirically tuning the pri out a couple of
turns. Then, the loading effect that occurs as topload "activity" increases,
causes the self-res freq. of the sec to lower, and match the already
intentionally-lowered primary frequency.
As for longer sparks, it's a question of minimising all of the spurious
"effects" and concentrating all of the available power into one channel,
keeping it alive, and promoting it before it can extinguish. That is why
there are differences between achieving a maximum potential difference on
the topload, and getting the longest sparks. They aren't the same thing! It
is through-power that is the goal.
Richard Craven, Malvern, England