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Re HV Caps for a first Coil
>Original Poster: "Guy Bettina" <wilson-at-vossnet.de>
>
>Question : Is there an "easy" first time cap that does not invole lots of
>$$ and fiddling around with oil ? I will probably go for 1 or possibly 2 x
>6000v at 50mA giving either 6000v or 12000v at 50mA so I need about 0,02uF
>or less.
>
>I have read a number of the descriptions for stacked and rolled caps and
>they all sound messy / time consuming.
>
>What is an "extended foil construction"
Thanks for any hints and help.
Lots of $$ and fiddling around with oil. Yeah, that sums it up! But
seriously, that's the reason there's so much bandwidth on the topic on
this List. No one's found the perfect solution yet!
For cheap, there's salt water caps, but they're very poor performers,
plus messy with oil. Poly caps are great performers but costly for
materials, and require great patience to assemble, plus are easy to blow
if not constructed well.
It's frustrating, there's nothing in a well made poly cap that doesn't
appear in our kitchen trash every day. It's too bad there's not mass
market for these like car batteries, they'd be dirt cheap.
Re extended foil construction caps, most rolled poly caps have a wire
connected to one end of each of the aluminum plates, with the plates
being a spiral and adding a distributed series inductance, or ESL, to the
electrical properties. An extended foil construction capacitor is built
with the entire long edge of each plate connected to the output terminal,
so that the rolled plate does not contribute any series inductance. The
actual benefit of this reduced inductance isn't clear, I've not heard of
any actual comparisons, but it's got to be at least as good, and it
allowed me to use household foil instead of aluminum flashing.
Regards, Gary Lau
Waltham, MA USA