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tesla coil top loads and rough edges
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Pirateguy:
i m wondering, would covering a rough edge on a tesla coil top with some kind of insulator improve anything?
T3sl4co1l:
How rough, and how insulating?

Projections need to be a sizable fraction beyond local curvature to matter, in terms of reducing the voltage where corona or breakout occurs.  Just because it's made of sharp metal that will cut your hand open if you fondle it, doesn't necessarily mean it's electrically worse. :)

There are three kinds of treatment you can apply, to insulate or smooth it out:
- Metal: smooth over it directly, say with aluminum tape.  This brings up the nearby material and reduces sharpness of the area.
- High quality insulator, strong but low-k: a lot of layers of polyimide tape, say, or a goopy silicone rubber or something.  Local curvature is not significantly affected, so some corona will still be produced by the point, at a somewhat higher voltage.  This puts a lot of stress on the material, hence demanding high quality.  (Polyimide has excellent corona resistance.)  The current drawn by the corona, from the surface of the insulator (more correctly, a dielectric barrier discharge), is the current flow that's able to drop so much voltage across the insulator, and thus prevent the point from breaking out quite as early.  Note that, if it does break out, the insulator is screwed, nothing can withstand direct plasma. ;D
- High-k insulator: not sure what material would count here -- presumably one could make, like, ceramic-loaded tape, analogous to fridge magnets (plastic loaded with ferrite), but with dielectric material instead.  Anyway, this has the effect of bringing up the nearby surface again, but with an insulator rather than a conductor.  Because the k is large, the internal voltage drop is small (but not as nearly zero as for a conductor).  This acts like an intermediate between the two cases.  Breakout will still occur, much as with the conductor case, which isn't such a great thing for any nonmetallic material you'd place here... :)

So, in conclusion: maybe, it depends. ;D

Tim
Pirateguy:
ok well what we are talking about here is mini coils with top loads made from soda cans
and i was wondering about the thin edge of where i cut it.

i gave it a good sanding, and for the insulator i was thinking of maybe the mantle of some wire
or just running the edge through some epoxy.

but if i understand correctly this isn't really an issue at a small and relatively low powered scale?
Simon123:
Made from soda cans?

Will that provide proper capacitance?
Pirateguy:
i am copying something i saw in a video.
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