TSSP: List Archives

From: "Terrell W. Fritz"
Date: Thu, 03 May 2001 18:02:51 -0600
Subject: Re: [TSSP] Time domain modeling

Hi Paul,

If it is of any help, I wrote up some testing I did on the effects of k
with various gaps and scope traces at:

http://hot-streamer.com/TeslaCoils/MyPapers/sgap/sgap.html

If one save the pictures of the scope traces and looks at them with a real
veiwing program, they look much better.  An HTML conversion thing...  I may
be able to fix that now with FrontPage...

I should point out that today, three years later, such measurements can be
made with far higher precision!

Very excited about this new stuff you are doing!!!

Cheers,

	Terry

At 07:09 PM 5/3/2001 +0100, you wrote:
>Hi All,
>
>Gosh, this time domain modeling stuff does open up a lot of
>avenues of investigation. I'm just sitting down to another
>evening with the code, but even when I'm at work, thoughts
>keep coming back to the problems and possibilities.
>
>For example, I've always assumed that breakdown of the sec
>is likely if k is taken too high, due to the induced EMF
>from the primary exceeding the turn-turn breakdown of the
>secondary.
>
>Havn't got a full picture yet, but other possibilities
>arise. The familiar pri-sec beat is the sum of two 
>normal modes, more or less equally excited by the initial
>bang. For small k, the modes are close and very similar
>sec I distribution I(x) for each, but of opposite sign, relative
>to Ipri. So with equal amounts of each, the two sec I(x) cancel
>out to around zero, and the two Ipri add up to the amount
>required for the bang. As k increases the modes move apart and
>also change shape. Cancellation is now no longer perfect, and 
>thus higher modes need to go into the pot in order to recover
>the match to the initial conditions. Energy in the higher
>modes has a roughly proportionally higher voltage gradient
>on the secondary, eg 3/4 wave has almost 3 times the volts
>per metre than 1/4 wave, for the same terminal voltage. Hopefully
>we'll be able to tell if this mechanism contributes to 
>difficulties of using high k. We'll also soon be able to see
>if the conical primary makes life easier in this respect - we
>might expect its 'smoother' application of EMF to couple
>less to the higher modes. Sorry for the handwaving, just a
>few thoughts. The math and computations should spell this out
>more rigorously.
>
>I wrote:
>> > >The reason I ask is that, depending on just how
>> > long the arc
>> > >discharge path can be considered to be grounding
>> > the top of the
>> > >coil, it looks like quite a substantial amount of
>> > energy can be
>> > >transfered into one of the higher modes, to be
>> > trapped there.
>
>Boris wrote:
>> Correct.The freq. of power discharge depends on a
>> isotropic C, physical size of isotropic capacity(not
>> just on C but there is difference wether toroid
>> /sphere etc.used),density of coil turns and I suspect
>> to some extent on geometry of outter path to ground
>> coil discharges into.
>
>Yes, but I'm not too concerned with the high frequency 
>components of the arc itself - I wouldn't know where to
>start to calculate these. Just that, while the arc is
>present, the solenoid is effectively grounded at both
>ends, with an appropriate set of modes for this boundary
>condition, and the longer this condition persists, I think
>the greater is the energy is transfered from the two main
>modes into higher order resonances. When the discharge
>ends and the top short is released, the original grounded
>base modes are restored and the energy remaining in the
>coil is once again redistributed, this time amongst the
>original mode set. Can't say for sure yet, but I don't 
>think the energy winds up back in the original main two
>modes, but is more spread out than before the discharge.
>
>> Terry's former experimental coil has shown power arc
>> impedance about 2kohm for 3.5" arc.
>> System I tested in Croatia by estimation of heat
>> consumption of watter resistor,has shown an average
>> impedance of more than 8000 ohms  for 17" arc.
>> Dale Hall's single pulse operated coil with 24"*8" top
>> toroid gave about 500-1000 ohms for 20" arc.
>
>Quite some variation there, going to take some effort to
>get a general picture. I think that the load impedance will
>end up being the dominant limiting factor in ultimate accuracy,
>more so than, say, Q factor, and therefore we are justified in 
>reducing the accuracy of the modeling itself. So I've been
>using around 200 steps rather than around 500 steps as used
>up to now by tsim.
>
>Cheers All,
>--
>Paul Nicholson,
>Manchester, UK.
>--


Maintainer Paul Nicholson, paul@abelian.demon.co.uk.