From: Paul
Date: Tue, 10 Oct 2000 08:19:14 +0100
Subject: [TSSP] Terry's modact results
Terrell W. Fritz wrote: > >> I would like to submit my paper at: > >> > >> http://users.better.org/tfritz/site/papers/modact/modact.html > >> > >> for perusal... Paul Nicholson replied: > >Good stuff Terry, a few comments... > >DC offset to the primary ring voltage - the gap is rectifying? > > Possibly. The gap is symmetrical but the initial spike may > cause the conduction to be offset for a time. Hmm, that's the problem, the primary time constant is too short to allow a constant DC offset to be sustained for this long, so either the gap is rectifying, or something non-linear in the V probe is introducing a bias, or perhaps this represents DC from the supply passing through the arc and we're seeing it dropped across the primary DC resistance. > >On secondary waveforms: > > > >The notches do coincide on this one. What's with the DC offset > >appearing in the secondary top voltage trace? Probe artifact? > >I see no way for the secondary to sustain DC for so long. > > That offset is very real. Apparently, negative charges arc far > more easily than positive charges so the net DC effect is seen. > Richard Hull also observed this effect. My ignition coil TC's > actually arc further in one polarity than the other due to this > effect. The DC charge is only there for a few hundred uS. Thats fascinating, if you're sure its not a probe artifact. Does the DC offset vanish if you operate at a level below breakout? > > > >Some arithmetic: > > > >Primary tank volts at trigger, 14kV, across 17nF gives > >a bang energy 1.67 Joules. > > > >Secondary peak top voltage 260kV across (16.7+10.3) pF > >gives 0.91 Joules. > > > >Therefore overall efficiency of energy transfer primary tank to > >secondary tank is 54%. Seems reasonable. > > I have posted a few detailed studies of where all the power is going in > such systems. This is close to our system of interest. > > Watts Percent > Power into coil 840 100 > Power in 50 foot cable 15.88 1.89 > Power in neon primary 30.47 3.63 > Power in neon secondary 38.2 4.55 > Power in NST filter 96.4 11.48 > Power in gap 156 18.57 > Power in primary cap 9.354 1.11 (7.5C temp rise) > Power in primary coil 76.08 9.06 > Power in secondary coil 71.84 8.55 > Power in self capacitance 14.95 1.78 > Power in terminal capacitance 8.49 1.01 > Power to arc 322.0 38.33 > TOTAL 839.66 99.96 Comparing the efficiency from the trace calculations with the efficiency obtain from your energy budget, the two come out nice and close, 54% and 46% respectively. I think you've got a good overall picture of operation here. > MicroSim is more than capable of doing transmission line models too. I > have tried this but the lumped models gave good results without the > dramatic calculation times needed for lossy coupled lines. Many of the > small harmonic features can be reproduced with T-line models however. You'll have a hard time simulating things with a standard transmission line model. They don't take account of either the non-uniformity or the longitudinal coupling. You'll be obliged to guess line constants that are in some sense average equivalents and so the end results won't be significantly more accurate than the approximations involved in applying a lumped model. > I hope this is all not straying too much from our topic here, but > I wanted to point these methods if they can be of help. No problem there! Reports of experimental results and techniques are very welcome. Theory is just conjecture without experimental support so the two must be developed together. I'll look forward to hearing about the next round of experiments. Cheers, -- Paul Nicholson, Manchester, UK. --
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.