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.