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Re: How to rise the secondary? (fwd)



---------- Forwarded message ----------
Date: Fri, 10 Jul 1998 23:37:10 +0000
From: "John H. Couture" <couturejh-at-worldnet.att-dot-net>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: How to rise the secondary? (fwd)


  Richard, et al -

  I agree the TC operating conditions are different from the instrumented
conditions. The capacitance due to streamer loading, etc. would change the
capacitance (Cs) of the secondary circuit and change the operating
frequency. However, my tests indicate this change is very small. 

  A much larger change in capacitance occurs when the toroid, etc . is
mounted on the TC. The change in toroid capacitance from the calculated free
space capacitance can be as much as 30%. This can create a large change in
operating frequency. The calculated free space capacitance should not be
used to calculate the operating frequency without a correction for the
toroid being mounted on the TC.

  My TC computer program ignores the streamer loading, etc, capacitance
because I did not have this information when the program was being
developed. However, the tuning indicated  by the program varies little from
the actual tuning of the operating coil when the corrected free space
capacitance of the toroid is used. This would indicate the streamer loading,
etc. capacitance has little effect.

  Do you (or R. Hull) have any test data that would show how much the
streamer loading, etc. capacitance is and how much it affects the operating
frequency after the toroid mounting capacitance change is taken into
consideration? As I indicate above the operating frequency change for only
the streamer loading, etc. should be very small.

  I like to look at the longest sparks as the condition where the TC input
energy equals the output energy plus the losses. When the losses are the
lowest the maximum energy appears in the secondary circuit and the sparks
are the longest. In other words the longest sparks happen when the maximun
energy at the maximum potential occurs on the topload. The length of the
first spark depends on the potential and additional sparks are then modified
by the ionozation of the air. The energy and potential are related by
    Joules = 1/2 Cs Vs^2
This should be multiplied by an efficiency if one can be determined.
Note that a large amount of power can mean large currents and low potential
producing short sparks.

  John Couture

-----------------------------------------------------

At 11:50 AM 7/9/98 -0600, you wrote:
>
>
>---------- 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:
>
><snip>
>>  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
>on
>>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
>new
>>total secondary capacitance (Cs) will be the true total capacitance. The
>new
>>toroid capacitance being used will be the true capacitance of the toroid
>>when mounted on the TC.
>
><snip>
>
>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
>
>