Hi Paul,
How much confidence do you have in those simulations? It basically
shows about 2/3 of the top voltage applied across the bottom 10% of
the winding, which sure looks like a recipe for failure.
Project update: After days of testing the rig, i discover another
secondary with a burn mark about the size of a dime. This time its
about 8" from the bottom of the coil. The coil was still functional,
and the damage appears to be localized. I suspect another shorted
turn that "self-healed".
BTW, here is a teaser video for the project:
http://www.youtube.com/watch?v=P37dmtwT2fM
Thats just footage from the start of the project using our old coils.
The rig we built for the event is quite breathtaking, now its just
gonna be an effort to keep it going for the 72 hours continuously that
they want these coils to run for. The secondary-coil-surgeon is in
the house!
Steve
Yes dispersion spreads the down-going transient although
it could still build up quite a high volts/turn near the
base. This has been discussed before as one possible
cause of racing arcs. Here is an animation of secondary
voltage distributions (July 2009, modeled on Marco
Denicolai's Thor system),
http://abelian.org/tmp/thor.anim1.gif
A normal ring-up of the secondary occurs until at 40uS
the topload is suddenly and completely discharged to
ground.
A slow-mo of the discharge,
http://abelian.org/tmp/thor.anim2.gif
During testing, our rig got rained on by a leaky roof.
... to bake out the water from the remaining coils
involved applying about 660W of power ...
Upon disection of the coil that had the bottom winding
fail, we found the wire was separated from the PVC form.
I guess this is a more likely explanation for the fault.
--
Paul Nicholson
--
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