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[TCML] Fixing secondary strikes Re: Bad strike to a 12 inch traditional coil (somewhat terminal)

On 7/4/18 11:40 AM, David Rieben wrote:
Hi Phil,

My deepest condolences for your loss. I know it's JUST a secondary coil, but as a fellow coiler, I most assuredly feel your pain. On the bright side, at least you did manage to capture some truly spectacular footage of this secondary coil mishap. I have had this happen on rare occasion with the operation of my big coil, though fortunately, none of my mishaps turned out quite that severe! Only once did I actually have to repair some damage to the side of my coil and was able to get it back into full functioning mode via the repair. Since I must operate mine outside, I did have one occasion where the wind actully "blew" one of the streamers back into the side of my secondary coil, too. Lesson learned - although refraining from outdoor operation during rainfall is an obvious good rule, non-starters in windy conditions are also well advised.

I suppose this is a risk, that although may be small with a well-tuned and efficiently operating coil, is never completely absent. :^/

I wonder if we could figure out a way to segment a large coil vertically, so if a segment gets damaged, you can just rewind that segment. Just off the top of my head, I'm thinking about something like segments with a hundred turns or so. Could we come up with a way of making the connections in a "good" way. I'm almost thinking about how you using field grading rings on a Van de Graaff. You don't want a complete shorted turn, but you could terminate the winding in some sort of flat terminal on the "mating face" of a segment. You'd stack the segments, and then put some compression on it (threaded fiberglass rod?)

The other idea that comes to mind is if there is some way to "spread" the energy of the secondary strike.. Say your secondary were coated with a resistive (but still conductive) coating. Would that spread the current density enough to prevent burning through the insulation? Or a dissipative tube covering the secondary - not enough to "load" the secondary, but enough to "take the hit".

OR, what about a second helix, space wound, that extends the length of the secondary, with some suitable resistive conductor, so the voltage profile matches that of the secondary (so no protective helix to secondary arcs), but so it doesn't enter into the resonant circuit. The protective helix would be mostly capacitively coupled to the secondary, establishing the voltage.

What about something like a helix wound with wire, but with small gaps along the length.. the gaps don't break down normally, but if a streamer strikes, the gaps break down and provide a conductive (but lossy) path to the base.

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