[Prev][Next][Index][Thread]
Re: Capacitor Idea
Hello Chris, Steve, all,
I have been watching this post (cap in a safety jar) for some
time, but no one has commented on an obvious problem.
Let me make an ascii diagram of what you are thinking about.
Of course this is flat, so you will have to "see" it rolled up.
1.)
ALALALALALALALAL Grounded Al layer (Safety device)
GGGGGGGGGGGGG Glass jar
2.)
ALCALCALCALCALC 1st AL cap layer
PEPEPEPEPEPEPE 1st PE cap layers
ALCALCALCALCALC 2nd AL cap layer
PEPEPEPEPEPEPE 2nd PE cap layers
3.)
GGGGGGGGGGGGG Glass jar
ALALALALALALALAL Grounded Al layer (Safety device)
Part number 2 is rolled up (which is important to note!!).
This means the parts labeled "2nd" are on the inside!
Let me now make a "schematic" out of this:
-----||#------
The "#" represents the outer grounded plane. Chris, do
you now see the obvious problem? You are only shielding
one plane of the capacitor and in NO way will this save
your cap, if it is overvolted (strikes, kickback, etc). It canīt
save the cap, because it doesnīt short it in the event of an
overvoltage condition. As a matter of fact, if the inner
electrode sees overvoltage 1st (in respect to ground),
the electrons will zap right through your cap (to get to
that grounded plane). So your setup will actually promote
failure! Considering this and the problems others have
pointed out, I think it is safer and eaiser to make a nice
external safety gap that will breakdown at a specified
voltage. Even if your safety dielectric does NOT shatter
during a breakdown, the arc would change the dielectric
properties of the material and therefore alter the
breakdown voltage.
Coiler greets from germany,
Reinhard