stacked plate cap

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
a flat stacked cap using .1" thick  solid polystyrene and .01" thick
aluminium litho plates (used in printing). These are usually recycled,
if you approach a small printing firm, they will often part with 10 to
The design for .01 uF required 20 plates 10" X 12", separated by the .1"
I assembled the stack dry to test the capacitance using a cheap
with a capacitance range and found it to be exactly as predicted (.01
Now here is the interesting bit.  When I finally assembled the unit, I
constructed a plexiglass container just slightly larger than the
stack so that I could submerge the unit in oil.  Having built a similar
previously using aluminium foil and then  trying to get rid of the
air (unsuccessfully), I decided to assemble the unit in the enclosure
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
the completed unit from the enclosure and used two 2 1/2" brass bolts
.1" washers between each aluminium plate pushed through previously
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
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
with no problems whatsoever.  
Hope this is useful to someone.
Ralph Down
Today is the tomorrow you worried about yesterday....... and everything
is O.K.