From: Paul
Date: Fri, 10 May 2002 07:38:45 +0100
Subject: Re: [TSSP] Secondary voltage stress factor
[static charge on secondary] Malcolm wrote: > I have a (spacewound 1:1) coil that exhibits this phenomenon > but has never flashed over in its life. Bart wrote: > I don't think the two are related. Ok. This racing arc stuff is maddening. > My secondary coupling ended up a little higher (0.145) and I got > racing arcs while testing the gap. We'd better have a look at the details of this system so that we can work out the voltage gradient associated with those racing arcs. Neither Bart's coil, nor John's, has a particularly high k factor. When I model the induced voltage due to various primaries, they just don't seem to generate the kind of concentrated EMF that would produce localised racing arcs as John describes: > the bottom 2" of the coil burned up in places from racing > sparks. With or without that extra 1/4" of secondary winding, the coupling is still pretty 'smooth'. Why should the bottom of the coil be clobbered like this? The most stressed part of the coil occurs quite a bit higher up. I'll throw another suggestion into the pot. At some high frequency the primary will be in half-wave resonance, grounded at both ends. Perhaps this or similar resonance is excited by the primary arc and couples HF energy into the part of the secondary close to the primary. Q: Do racing arcs ever occur on the third coil of a base-driven magnifier? -- Paul Nicholson --
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.