From: Paul
Date: Thu, 16 May 2002 18:51:50 +0100
Subject: Re: [TSSP] Racing arcs
John wrote: > I tapped the primary at 14.5 turns with the 6" x 24" toroid, > and I got racing sparks about 1" from the top of the > winding, and also at about 1" or 2" from the bottom. These were > intense, and a "pop" sound was heard. > ...there was spark breakout during the above test. Hmm. That's interesting. When I was modeling the response of Thor to that initial burst of HF, the highest voltages seemed to occur a little way in from each end. I copied the graph to http://www.abelian.demon.co.uk/tssp/tmp/thor-hf.gif The horizontal axis is turns along the coil. LH axis = volts, RH axis=current. The red trace is the volts, and it's scaled for 4mA of base current. Thus for a 10 amp burst of HF, the 35 volts of that left hand peak is actually 35 * 10/0.004 = 87kV at 5% of the coil height, with similar at the top. I guess we'll only make sense of all this when we can get a TC carefully set up with base current and topvolts capture. If we can find a coil which can be tuned for breakout/ no-breakout/racing-arcs/no-racing-arcs then we can look and see (tcma) exactly what frequencies and amplitudes are present in the coil. I feel that we are making progress on this topic. We have plenty of candidate explanations for racing arcs, but we can't say which apply in any given case: Over driving, over coupling, severe tuning, HF ringing, discharge transients, dielectric polarisation. We ough to be able to narrow this list down by a close look at some base current waveforms. -- Paul Nicholson, --
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.