From: Paul
Date: Fri, 17 Nov 2000 20:41:10 +0000
Subject: Re: [TSSP] Primary gap questions
Paul wrote: > >Looking at some of Terry's scope traces in > > > > http://hot-streamer.com/TeslaCoils/MyPapers/spark1/sparkgap.html > > > >we seem to be seeing the gap extinguish and re-ignite on > >every zero crossing of the primary current - is that correct? Terry wrote: > Wha... You think I make this stuff up :-))) > > The zero crossing spikes are very real. As the current flow > reverses, the gap goes out and has to be re-lite with a bit of > a bang. For some reason I always assumed that AC arcs kept their ionisation between half-cycles. The fact that they are mini-bangs means that the breakover voltage is lower than for the gap starting from 'cold', so something survives over the zero-crossing. I guess at higher frequencies most of the ionization would remain from cycle to cycle and there would be less of a hiatus as the current reversed. Barry wrote: > There ought to be an initial loss due to channel formation > (resistive loss). All in all, does this formation loss contribute much to gap loss? Barry wrote: > Succeeding losses are possibly caused by plasma maintenance, > ionizations and reionizations at the voltage reversals, and > cathode spot formation and reformation on the opposite electrodes > at voltage reversals. I suppose that energy must be taken continuously to maintain ionisation as heat and light are lost from the gap. Can losses be reduced by surrounding the gap with a reflective cylinder? If the gap is operated at a higher air pressure, I believe the breakdown voltage goes up. Does the Vcond also go up with increasing pressure? Barry wrote: > ...a scheme that I am still pondering... > two spark gaps...each gap is isolated by a high voltage high > "pulse" current diode...force the gaps to be unidirectional.. Perhaps a single gap could be placed across the DC terminals of a bridge rectifier to achieve the same effect? -- Paul Nicholson, Manchester, UK. --
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.