stacked plate cap

To: tesla-at-poodle.pupman-dot-com
Subject: stacked plate cap
From: Tesla List <tesla-at-stic-dot-net>
Date: Mon, 21 Apr 1997 23:35:54 -0500
Approved: tesla-at-stic-dot-net
Subject:  stacked plate cap
  Date:   Mon, 21 Apr 1997 11:15:01 +1000
  From:   Ralph Down <rjdown-at-fan-dot-net.au>
    To:   Tesla List <tesla-at-pupman-dot-com>


I recently used one of the Tesla helper programs (Teslac- I think) to
design
a flat stacked cap using .1" thick  solid polystyrene and .01" thick
aluminium litho plates (used in printing). These are usually recycled,
but
if you approach a small printing firm, they will often part with 10 to
20
sheets.
The design for .01 uF required 20 plates 10" X 12", separated by the .1"
polystyrene.
I assembled the stack dry to test the capacitance using a cheap
multimeter
with a capacitance range and found it to be exactly as predicted (.01
uF).
Now here is the interesting bit.  When I finally assembled the unit, I
constructed a plexiglass container just slightly larger than the
assembed
stack so that I could submerge the unit in oil.  Having built a similar
cap
previously using aluminium foil and then  trying to get rid of the
trapped
air (unsuccessfully), I decided to assemble the unit in the enclosure
one
plate at a time and brush each plate with oil as it was stacked so as to
eliminate any air or dry spots. When all the plates were stacked, I
removed
the completed unit from the enclosure and used two 2 1/2" brass bolts
with
.1" washers between each aluminium plate pushed through previously
drilled
holes in the plates and tightened the whole stack with a brass nut.(This
then became one terminal with a wing nut to secure the cable).  I then
lowered the assembled unit into the enclosure & filled it with SUNISO
refrigeration oil (bought from local refrigeration repair shop for $30
for 4
litres.) I was very surprised when I again measured the capacity of the
completed unit - it was now .02 uF - a 100% increase in capacity due to
the
addition of the high dielectrc constant of the oil.  This cap has been
working for several months using 4 x 10kV 30 mA neon trannies in
parallel
with no problems whatsoever.  
Hope this is useful to someone.
Regards
Ralph Down
Today is the tomorrow you worried about yesterday....... and everything
is O.K.