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Re: Polyethylene Capacitors
Tesla List wrote:
>
> >From ed-at-alumni.caltech.eduWed Sep 25 23:10:02 1996
> Date: Wed, 25 Sep 1996 19:59:52 -0700 (PDT)
> From: "Edward V. Phillips" <ed-at-alumni.caltech.edu>
> To: Tesla-list-subscribers-at-poodle.pupman-dot-com, tesla-at-pupman-dot-com
> Subject: Re: Polyethylene Capacitors
>
> Rolled capacitors only have inductance if they are of the
> inserted-tab type. Extended (and soldered shorted) capacitors
> have very low inductance. Problem I see is how to with home-rolled
> capacoitors is how to solder the foil IF it is aluminum.
> Ed Phillips
Ed and all,
Soldering shouldn't be necessary. If you design the cap to have enough
foil protruding from ends of the roll, you can carefully flatten and
squeeze the foil layers after assembly then sandwich them tightly
between a pair of thicker aluminum pieces. You can use 1/8" x 1/2" or
1/8" x 3/4" extruded aluminum bar stock (available at the HW store) or
cut strips of aluminum flashing. Pre-drill matching holes and use either
nuts and bolts or sheetmetal screws to tightly clamp the aluminum foil
between the aluminum pieces. Sheetmetal screws are good since they will
"drill" through the foil layers - otherwise you may need to use an awl
to poke holes through the foil. Make sure that any aluminum shavings
created are captured and don't fall into the roll. You can then attach
heavy braid or strap to external terminations.
One potential problem with end-foil termination on a rolled cap is
insuring that trapped air can get out, and oil can get into all the
active area of the cap. You'll need to poke multiple relief holes into
the end foil to let oil in and the air escape. Drawing a partial
vacuum would speed this process...
Safe coilin' to ya!
-- Bert --