Capacitor instructions


I downloaded this from the ftp site.  It was in the rqdocs.zip file.

                          April 8, 1994

High voltage capacitor construction, by Bert Pool.

First of all important warnings and disclaimers:

High voltage  capacitors  are  very dangerous for several obvious
and some not-so-obvious reasons.   Most experimenters know that a
capacitor can retain a significant voltage even  after power has
been removed.

Discharge all  capacitors  with  a jumper cable before working on
them.  When  discharging large  capacitors,  the  jumper  cable
needs a high wattage 100 ohm resistor to limit discharge current.


Voltages and  currents  available  on  charged  capacitors can be
lethal.  Use common sense.  The  capacitors  described  here  are
sealed and  contain  mineral  oil.   While  mineral  oil  is  not
especially flammable, a catastrophic capacitor failure can result
in pressure  buildup and explosion if construction technique does
not allow for release of pressure.

Mineral oil will burn - a catastrophic capacitor failure can also
result in the release of oil which  could  ignite.   It is highly
suggested that  experimenters  keep  on hand a fire  extinguisher
rated for oil fires.

Also, it is suggested that oil filled capacitor banks be stood in
a metal pan large enough to contain the oil in case a capacitor
container is breached or oil is released.  This pan can prevent a
mess, as well as help contain a potentially nasty fire!

I have built over a dozen oil filled high voltage capacitors, and
I have  had  several  failures  due  to construction shortcuts or
material failures  and  I  have  NEVER  experienced  a  dangerous
buildup of pressure or a fire - but I know it  CAN  happen  and I
take measures  to be prepared for such an eventuality.  Many high
power Tesla coils use "power pole" transformers; these too are
filled with  oil  and  the  same  precautions  for  prevention of
explosion and fire apply here too.

As a high voltage experimenter,  you take full responsibility for
safe construction and operation of your capacitors and other high
voltage devices.

                  Be safe, be careful, use common sense!
  Keeping all these safety ideas in mind, presented  is  a  method for
  building home-brew polyethylene capacitors which serve very well for
  Tesla coils, ZPE devices, etc.

  The original design is not mine, it was conceived by Richard Hull of
  the Tesla Coil Builders of Richmond (TCBOR).  TCBOR has an excellent
  video showing step-by-step construction of this type of capacitor.

  Other available video tapes provide excellent info on Tesla coil and
  Tesla magnifier construction.  Richard  Hull  may  be contacted at:
                           7103 Hermitage Rd,
                           Richmond VA 23228.


A simple capacitor consists of two conductive plates separated by
an insulator.  Capacitance  is  determined by  the  area  of  the
plates, the  distance  between them and the "dielectric constant"
of the insulator between the conducting plates.

This dielectric constant is represented  by  a number called "K".
On the next page is a table of materials and their  "K" and their
puncture voltages taken from the "Radio Amateurs Handbook":

          MATERIAL               |   "K"          |  PUNCTURE
                                 |                |  VOLTAGE PER
                                 |                |  MIL
                                 |                |
          AIR                        1.0             240
          BAKELITE                   4.4 - 5.4       300
          BAKELITE, MICA FILLED      4.7             325 - 375
          FORMICA                    4.6 - 4.9       450
          WINDOW GLASS               7.6 - 8         200 - 250
          PYREX GLASS                4.8             335
          MICA                       5.4             3800 - 5600
          PLEXIGLASS                 2.8             990
          POLYETHYLENE               2.3             1200
          POLYSTYRENE                2.6             500 - 700
          PORCELAIN                  5.1 - 5.9       40 - 100
          QUARTZ                     3.8             1000
          TEFLON                     2.1             1000 - 2000

A vacuum or  air  has  a  "K"  of  1.   If you put a piece of teflon
between your plates (same spacing),  the  capacitance  will increase
2.1 times and it will handle at least 5 to 7 times as much voltage.

If you used  a  piece  of good quality glass, the capacitance  might
increase 8 times! (the voltage rating would increase only slightly).

The dielectric you  choose  will be determined by voltage, frequency
(if using a.c.), durability (glass  breaks  very  easily),  cost and
physical size.


The capacitors we will build use polyethylene.  Poly is very easy to
work with, does  not break, is inexpensive, readily  available,  has
very good a.c.  characteristics  (very  low loss), and has good high
voltage properties.  Mica would  be  even  better,  but  it  is VERY
expensive and is not readily available.

Glass is o.k. as far as availability and cost goes,  but it has very
high internal losses for Tesla coil use, compared to poly.  Glass is
also very fragile to work with.  I've made glass capacitors weighing
over 600 pounds -NEVER AGAIN!  You just can't beat making capacitors
out of polyethylene.

Purchase two sheets  of  polyethylene  sheet,  48  inches wide by 96
inches long.  Each sheet will be cut  lengthwise  into three sheets,
each 16 inches wide.  All together, you will have 6  pieces  of poly
16 inches wide  by  96 inches long.  This is enough material to make
THREE capacitors. (You will cut several more sheets if you choose to
use several thin layers of plastic instead of one single thick layer.)

The thickness of the poly sheets  is  determined  by the voltage you
will be placing  on  the capacitor.  You have to take  into  account
whether you are using d.c. or a.c.

If you are  using  d.c.  voltage,  calculate  your poly thickness by
using dielectric voltage rating of 600 volts per mil (one mil = .001
inch).  Some charts show that poly can handle 1200 volts per mil -
Tesla coil experience  shows  that  this  value  is NOT conservative
enough, even taking peak-to-peak values into account!

If you are using a.c., and especially with a Tesla coil, you have to
de-rate the voltage ratings on the  poly  or you will have capacitor
failure.  For Tesla coils using input transformers  from 9 kilovolts
up to 15  kilovolts,  use  90 mil thick polyethylene.  If your input
transformer is 7200 volts or less, you can use 60 mil poly.

*** Special construction note!  Once you have determined the
required capacitor dielectric thickness, it is MUCH better to make
your dielectric from several thin sheets of poly instead of one
single thick sheet.  Example:  If you need 90 mil thick poly, use
three 30 mil pieces stacked together to form a 90 mil dielectric. If
you use multiple layers the insulation will be MUCH more robust than
a single thick layer.  The reason?  If you were to use a single
thick layer of poly and it had a manufacturing defect, odds are that
the defect will extend all the way through the plastic.  High
voltage would force its way through the single defect to blow up
your capacitor.  If you have three or four thin layers stacked,
every sheet might conceivably have a defect,  BUT it would be almost
impossible for all of the defects to be lined up to allow the high
voltage to punch through.  Odds would be that while one sheet might
have a defect, you would still have several GOOD layers still
providing protection.  Professionally manufactured capacitors
usually use this secret of layering.

*** From this point on, where the text describes using "a" piece of
poly, you will probably instead be substituting three or even four
thin sheets of poly for the reason described above.  Keep this in
mind during the construction process!

The capacitor described, using .0625  inch  thick  polyethylene will
have a measured value of 0.0185 ufd with an a.c. working  rating  of
7500 volts r.m.s.***    A   .090  inch  thick  polyethylene  dielectric
capacitor will have a value closer  to 0.010 ufd, and can be used in
Tesla coil circuits using a power source up to 15 kilovolts a.c.

*** TCBOR suggests that .060 thick poly will work -at- 15,000
volts.  My experience shows this is not always true.  I
recommend 90 mil poly for 12,000 to 15,000 volt operation.

As any coil builder knows, the resonant peak voltages  go  WAY above
the source voltages!   You must design sufficiently thick poly
dielectric to handle this higher voltage.

Power  LOSS  in  one of these caps in a Tesla coil configuration is
LESS than 0.5  watt per cap!  Thus, they don't suffer from internal
r.f. losses which translate into heat failure.

A poly capacitor made with .060 poly should handle 36,000 volts d.c.
and the .090 thick poly job should easily handle 54,000  volts  d.c.
These are very  conservative  ratings  -  good  quality polyethylene
might handle twice these ratings.  Tesla coils, of course, use
alternating current.  The peak voltages generated in a resonant
Tesla circuit are incredibly hard on a capacitor.  This is why you
must "over-engineer" the voltage capabilities of your capacitors.

Capacitors may be  placed  in series  to achieve  higher  voltage
ratings, parallel for more capacitance.  Combination series/parallel
combinations may be used to achieve any desired capacitance and
voltage rating.

As an example, let's say you've built several 0.01 ufd capacitors
rated at 7,500 volts.  You make the deal of your life and acquire a
terrific 15,000 volt power transformer....only your capacitors can't
handle this voltage.  What to do?   Assuming your coil requires a
capacitance of 0.01 ufd, what kind of connections can you make to use
the capacitors on hand?

First of all, you could connect two caps in series, as shown below:

           c1          c2            0.005 ufd 15 kv capacitor
           ||          ||            made from two 0.01 ufd, 7.5 kv
  ---------||----------||------      capacitors
           ||          ||

You now have a capacitor rated at 15,000 volts...BUT the capacitance
is now only .005 ufd!  You increased the voltage rating, but placing
capacitors in series reduces the capacitance.  Now what?  We connect
two more caps in series to create another 0.005 ufd capacitor, then
we take our two 0.005 ufd caps and put them in PARALLEL.  We end up
with a 0.01 ufd capacitor rated at 15,000 volts:

                  c1    c2
                  ||    ||
          |-------||----||--------|              0.01 ufd, 15 kv
          |       ||    ||        |              capacitor made from
  --------|                       |---------     four 0.01 ufd, 7.5 kv
          |       ||    ||        |              capacitors
                  ||    ||
                  c3    c4

Because the transformer has an output of 15,000 volts, and we know
the PEAK voltages will be much higher than this, we might wonder
whether the capacitors we just wired together can handle the peak
spikes.  To reduce the chance of failure, we would be better off
placing THREE of our capacitors in series to achieve a voltage
rating of 7,500 times 3 or a total of 22,500 volts.  But what would
our capacitance be if we do this?  Right!  The capacitance will be
0.01 divided by three or 0.03333 ufd.  Guess what?!  We need to
parallel THREE sets of these caps to bring the capacitance back up
to 0.01 ufd:

                  c1    c2   c3
                  ||    ||   ||
          |       ||    ||   ||     |            0.01 ufd 22.5 kv
          |                         |            capacitor made from
          |       ||    ||   ||     |            nine 0.01 ufd, 7.5 kv
  --------|-------||----||---||-----|--------    capacitors
          |       ||    ||   ||     |
          |       c4    c5   c6     |
          |                         |
          |       ||    ||   ||     |
                  ||    ||   ||
                  c7    c8   c9

Using this method, you may build a capacitor rated for any
capacitance and at any voltage rating!  The down side is that you
can use up a LOT of capacitors!

We will make our conductive plates  out  of  aluminum roof flashing.
You can buy a fifty foot roll of 14 inch wide aluminum roof flashing
here in the Dallas area from Home Depot for about $22  (4-93).  This
is almost exactly  the  length  you  will  need for three caps.  The
aluminum flashing, by the way, is  about  10  mils  thick.  My local
Home Depot charged me  - $21.80 (4-93)

For a capacitor  container,  we use 6 inch diameter sdr 35 PVC  pipe 
cut into 19 inch lengths. 

PVC pipe comes in 13 foot lengths, $1.25 per foot, or $16.25 + tax
(2-93). You will also need flat "glue on"  pvc end caps for this
pipe; $4.40 each, or $26.40 for six (enough for 3 caps). Do NOT  get
the rubber gasketed end caps  - they are not flat on the end and the
seals will not hold up once immersed in oil.

You will also need pvc primer and cement to glue the end caps to the
pvc pipe.

You will also  need  some  1/4 inch  thick  clear  plexiglass  sheet
scraps, each piece large enough to cut a 6 inch diameter circle.

You will need plastic tie-wrap straps about 24 inches  in length, or
enough 12 inch straps to link together to form nine 24 inch long
straps.  Try to  get  straps  that do not contain metal teeth inside
the lock of the strap.

To make connection to the aluminum  plates  you  will  need some #10
screws, washers, and nuts.  You will need two split-bolt  electrical
connectors to go  on  the  top  of  each  capacitor  -  Home Depot,
$3.33 each.  You will  also  need  3 or 4 feet of high voltage wire
to  connect  the  split-bolt output connectors  to  the aluminum

You will need  two inexpensive radiator drain petcocks (valves) from
Chief Auto (#852079) for $2.99 each.   We  will  use these valves to
fill the capacitor with oil and/or attach a vacuum pump.

Finally, you need  a  very  high quality mineral  oil  to  fill  the
capacitor.  I use  SnapLube-100  from  Tulco Oil in Arlington Texas,
(817) 640-0051.

It comes in a five gallon re-sealable  pail  for  $43.10,  including
tax.  I've never  had  an oil related capacitor failure  using  this
oil. SnapLube 100 is a highly refined non-carcinogenic oil containig
no PCB's.  Stay away from PCB oils.  Any way, just  about  any  good 
quality, low moisture mineral oil will work in these capacitors.


BOTTOM PVC end caps:
Glue two  1/2 inch by 1/2 inch square pieces of plexiglass stock
three inches  long  across  the  inside bottom of the BOTTOM end
caps. Make sure these two strips are at least 1/4 inch away from
the walls of the plastic end cap!   You  have to allow space for
the wall of the pvc pipe to reach the bottom of the end cap.

The purpose of these spacers is to prevent the  rolled capacitor
from sitting  directly  on  the  bottom  pvc end cap.  The space
allows any moisture in the oil  to  settle  to the bottom of the
cap - the capacitor will sit on these plexiglass  supports above
the moisture contaminated oil.

PVC case:
Cut three  pieces  of  6  inch diameter pvc pipe 19 inches long.
Clean the pieces with alcohol.   Prime ONE end of each pipe with
pvc primer.   Immediately  swab bunches of pvc  cement  on  the
bottom 3  inches  of  each pipe.  Swab the inside walls of three
end caps which you prepared in the first step.  IMMEDIATELY push
an end cap onto the glue coated  end of each of the three pipes.
BOTTOMS!  As you push the bottom end caps on, twist them to help
insure a good seal.

Take the remaining three end caps which will  be  used  for  the
TOPS of  the  capacitors.   Using  a  saber  saw cut a five inch
diameter hole in the end of each cap. This will leave a 1/2 inch
pvc border  surrounding  the  hole.   Cut  three 6 inch diameter
circles out of your 1/4 thick plexiglass stock.

Next, we will score the TOP of the plexiglass with a sharp metal
scribe in the shape of a big X,  going from edge to edge.  Below
is a crude picture of these two cuts.  Make the  scribe marks at
LEAST 1/32 inch deep.

                          /\            \
     Cut two scribe      /   \         / \
     marks at right     |      \     /    |
     angles to each     |        \ /      | <-- TOP of plexiglass
     other.             |        / \      |     capacitor cover
                         \     /     \   /
                           \ /         \/

*************** Important Safety Note *******************
The purpose of the scribe marks is to provide starting
places for CRACKS to occur should the capacitor fail and
excess pressure occur.  The plexiglass will bow outward
and crack at the scribe marks, releasing pressure.  MAKE

Use pvc cement and glue a 6 inch plexiglass disk over the
hole you just cut in the end of the top cap. MAKE SURE
THE SCRIBE MARKS ARE ON TOP!  Do this for all three top
end caps.  You just created three TOP end caps with clear
windows in the ends!

*************** Safety Notes *************************
The plexiglass will seal to the pvc, but pvc cement does
not effectively bond plexiglass to pvc.  This is good!
Should the capacitor experience a pressure buildup due to
electrical failure we WANT the plexiglass to crack and
come loose and let the gasses out!  The plexiglass cover
also allows us to SEE a capacitor failure - the light
from the arc shines out!  The plexiglass cover serves as
at least two important safety needs!  Do NOT build a
capacitor without this or some other form of over-
pressure release mechanism!

*** Now let all pvc cement dry for 24 hours before doing
any additional work on the pipes or end caps!  See "PVC
CONTINUED" below  for  completion  of  the  TOP end caps
after the glue has dried.

Cut your aluminum flashing into six pieces, 14 inches
wide (natural width) by 93 inches long.  Use large
scissors to make cuts.  Cut all corners round (use a
fifty cent piece to mark the curves on the corners) to
reduce corona. Using a hand operated paper hole punch
(any office supply has these), punch a hole in ONE end
of EACH sheet, about 1/2 inch from the end, midway between
the end corners.  Take wet/dry sandpaper and sand all
burrs and rough edges off the flashing. Preparation of
the aluminum edges and corners is VERY important!  Any
burrs or roughness will result in capacitor failure!

Attach a length of high voltage wire to the hole in the
aluminum using a wire terminal and # 10 hardware.  The
wire should be about 16 inches long.  Do not do anything
with the other end of the wire yet.  Cut your screw off
as short as possible, very close to the nut.  DO NOT GET

Poly sheet:
Place sheets of newspaper on a carpeted foor.  Put one of
your poly sheets down on the newspaper and clean both
sides with paper towels and alcohol. Measure a line 16
inches from the edge.  Take a magic marker and draw a
line down the length of your sheet, 16 inches from the
edge.  Go to the opposite edge and do the same, drawing
another line down the length of the sheet.  Your poly
sheet should now be marked into THREE equal pieces, each
16" by 96".  Using a box knife, carefully cut along these
lines.  You will have three pieces 16" by 96" long.  When
you complete these two cuts, carefully set the three
pieces aside on a clean piece of paper.  Next, clean,
mark and cut your second piece of poly stock into three
pieces.  It is important that the poly you use is
scratch-free and umblemished!  Any imperfections can
cause capacitor failure.  You now have six 16" by 96"
pieces of poly (again, if you are layering your poly, you
will have several times this number of sheets.)

Place a 16" by 96" length of poly on your newspaper.
Place one of your aluminum sheets on top of this first
poly sheet.  Align the aluminum so that you have an even
1 inch border of poly showing all the way down it's 93
inch length.  Now scoot the aluminum towards the screw
end so that the aluminum hangs over the END of the poly
one inch.

          Note the 1 inch overlap of
          the aluminum end over poly!     | |
               | |=======================================
               | |                                      |
       Poly--->| |    Aluminum sheet #1                O|<--hole and
               | |                                      |   screw for
               | |                                      |   wire
               | |                                      |
               | |=======================================
    Left       |--------------------------------------|    Right

Place poly sheet #2 on top of the first aluminum sheet.
Align this poly exactly on top of the first poly sheet.'

Place the final aluminum sheet on top of the second poly
sheet.  The screw end should be on the far end of the
capacitor, OPPOSITE the first screw.

             | | Note the 1 inch overlap of the
                end of the aluminum over the poly!

             |======================================= |
             |                                      |  |<-  Poly sheet
   Hole & -> |O       Aluminum sheet #2             | |
   screw     |                                      | | (poly and alum
   for wire  |                                      | |  sheets #1
             |                                        |   |    omitted
             |======================================= |  for clarity)
   Left        |--------------------------------------|  Right

You should  have  a capacitor sandwich consisting  of,  from  the
bottom of the stack up, poly, aluminum, poly, and aluminum.  Make
sure that the screws on the two sheets of aluminum are NOT ON THE

Now carefully  roll  the  capacitor up, starting on the left end.
Make the core hole in the center  of  the  roll  about  2  inches
across.  Roll  the capacitor up as TIGHT as possible!   KEEP  THE
gets too close to the edge of the capacitor, high voltage can arc
around the  edge of the poly, causing  catastrophic  failure.   I
really suggest  getting  a helper to help keep  things  lined  up
straight as you roll!

Once the  capacitor  is  rolled up, you should have a cylinder 16
inches tall and about 4.5 to  5  inches  in  diameter.   If  your
capacitor is much over 5 inches in diameter, then  it  won't  fit
inside the PVC pipe.

Take three  plastic  tie-wrap straps and tie the rolled capacitor
up so that it can't unroll.  The two wires should come out of the
top of the capacitor - one from  the  inside  of the roll, one on
the outside.  Place a scrap piece of poly between the head of the
screw and  the  underlying  poly  sheet so that the  screw  won't
puncture the underlying poly sheet.


Carefully slide your rolled capacitor into one of the pvc
pipes, making  sure  the  wires  are  "up".  You should have
about a 1/2 inch space between the outside of your capacitor
and the inside wall of your  pvc  pipe.   The capacitor will
sit on the two plexiglass spacers which keep  the  capacitor
1/2 inch above the bottom of the end cap (see step one).

Take two of the split-bolt connectors and set them on top of
the plexiglass  window  on the TOP end cap.  The head of the
bolt will sit on top of the plexiglass.  Place the two bolts
opposite each other, about 5 inches apart.

        Split bolt ---->  /      O      \
                         /               \   <-- 6 inch round cap with
                        |                 |        5 inch plexi window
                        |                 |
                        |                 |
                         \               /
        Split bolt ---->   \     O      /

Mark the  plexiglass with a marker right around the edges of
the bolt where it sits on  the  plexiglass.  Next, clamp the
bolt in a vise.  Drill two holes through  the  head  of  the
bolts.  We  will  use  two 1.5 inch long # 10 screws through
these holes to attach the bolts to the plexiglass.

Take the plexiglass window and prepare to drill holes in it.
Place a drilled split-bolt on the plexiglass where we marked
it earlier, and mark the  new  hole  positions on the plexi.
Drill the two holes.  Coat the bottom of the split bolt with
epoxy and attach the split-bolt connectors to the plexiglass
window with  1.5  inch  # 10 hardware as shown  below.   The
epoxy is  important to prevent oil leaks. Place epoxy on the
screw threads where they  pass  through  the  split bolt and
where they pass through the plexiglass:

         ||     ||      <--  SPLIT BOLTS -->       ||     ||
         ||     ||                                 ||     ||
         || === ||                                 || === ||
         ====|====    < --- glop epoxy!    ----->  ====|====
      =======|=========================================|======   glass
     nuts ->===                                       ===
             |          <--   SCREWS  -->              |
             |                                         |

Note: each split-bolt is held on with TWO sets of screws and nuts!

Next, we drill and tap two holes in the plexiglass  window  for
our two  valves.   Locate  the  holes  for  the valves as shown
        Split bolt ---->  /      O      \
                         /               \   <-- 6 inch round cap with
                        |                 |        5 inch plexi window
        Valve holes --->| O             O |
                        |                 |
                         \               /
        Split bolt ---->   \     O      /

This arrangement keeps the split-bolts far apart, and the
two valves will be far enough away to prevent problems.

The holes for the valves should be slightly smaller than
the threaded portion of the valve.  Be very careful tapping
the plexiglass else it will split!

Coat the threads of the threaded end of the valves with
epoxy and screw the valves into the holes.  The epoxy will
seal the threads closed to the plexiglass and will prevent
oil leaks.  Do not get epoxy inside the valve itself!

Give the expoy a several minutes to dry.  Hold the end cap
over the top of the capacitor.  Test it to see how it fits
down over  the  6 inch pvc pipe.  Make sure the screws holding
the split-bolts do not come  too  close  to  the  top  of  the
capacitor.  Lift the end cap off the capacitor.  The wire from
the inside of the capacitor will connect to  a  screw  on  one
split-bolt connector;  the  other wire from the outside of the
capacitor will connect to the OTHER split-bolt connector.

Measure and  cut the wires  so  that  they  are  as  short  as
THE SPLIT-BOLTS.   Crimp and solder a round terminal connector
on the end of the two capacitor  wires.   Attach  each wire to
one of the split-bolts using another couple  of  #10  nuts and

Again, temporarily slide the top end cap on and check your
wires for fit.  If all looks ok, it is time to glue this
puppy on!

First, open both vlaves so air can go through them.  If you
forget this step, you won't be able to push the TOP down
over the pipe because of the trapped air!

Slather the outside top three inches of your pvc pipe with
primer. Coat the inside walls of the end cap with primer
too. Next, coat over the primer with lots of pvc cement.
Quickly push the cap on the pipe, twisting back and forth
to make a good seal.

Connect a vacuum pump to one of the valves with a length of
5/16 hose.  While running the pump, apply additional glue
around the lip of the cap where it touches the pipe. Listen
for the hiss of air getting sucked in.  If you find a leak,
add pvc cement until it stops.  Now is the time to find and
fix any leaks!  Once oil is introduced into the capacitor,
leaks cannot be sealed with cement - the oil will prevent

Once you are satisfied the capacitor is leak-tight, let it
sit for at least 24 hours to allow the pvc cement to

After the glue has completely dried, test the end caps for
complete seal one more time.  DO NOT TEST FOR LEAKS BY

Once you  are  satisfied the plastic-to-plastic seals are good
we can charge the capacitor with oil.  Run a 5/16 rubber hose
from one valve on the cap to a vacuum pump.  Pump the cap down
for one hour.  This will help boil out any residual moisture
and will help remove air from between the layers of poly and
aluminum.  Once it has been pumped down, run another 5/16 inch
rubber  hose  from  the other  valve down into the 5 gallon
pail of oil - but do NOT open this valve yet.  Turn your
vacuum pump on.  This will help to continue to produce a
condition of reduced pressure in the capacitor.  VERY slowly
open the oil valve just a tiny bit.  This will cause the oil
to flow up the hose from the pail through the oil valve into
the capacitor!

WARNING:  Do  NOT allow  oil to enter the vacuum pump or
permanent damage to the pump can result!

*** Be sure to slowly open the oil valve - the oil will want
to foam up and enter the vacuum pump.  Regulate the flow of
oil so that the oil does not foam. Stop the flow of oil once
the poly capacitor is under about 3/4 inch of oil.

Close the oil valve completely and let the vacuum pump suck
air out between the plates of the capacitor.  Again, the
oil will want to foam up from all the entrapped air, so you
will have to monitor the vacuum valve very closely to
prevent oil from foaming up and entering the vacuum pump.

After a half hour or so, most of the air will be out of the
capacitor - at least enough where you can open the vacuum
valve so that the vacuum pump is going wide open.  Be aware
that you will get air bubbles coming up out of the
capacitor even if you pump from now on 'til doomsday!

You will actually suck air THROUGH microscopic channels in the
pvc pipe and end caps!  Your goal is to get as much air out
of the capacitor as is practicable - usually a couple of
hours of vacuum pumping will do the job.

After the capacitor has been  thoroughly pumped down, shut off
the pump, disconnect the hoses.  Slowly open one of the valves
and let air into the space above the capacitor  to relieve the
vacuum.  Close   both  valves  on  the  capacitor  to  prevent
additional air and moisture from entering the capacitor.

Next comes the really hard part:  set the capacitor aside
for at least one week, preferrable two weeks.  Two or three
times a day, gently rock the capacitor from side to side.
This will help air bubbles to rise.  DO NOT AGITATE THE OIL!
The idea to remove air bubbles, not introduce more!

PUMPING IT DOWN!  If you do, entrapped air will cause it to
fail.  I have learned this the hard way!  The capacitor
needs to sit for one to two weeks to allow air to rise out
of the capacitor.  The number one reason for premature
failure of a new capacitor is due to running the capacitor
with pockets of air trapped between the layers.

To break in your capacitor do the following:

Wait the required week or two weeks (see above).

*** Open one or both of the valves to act as additional
pressure relief ports in case the capacitor does fail.

************ Important Safety Note **********************
Set up the capacitor in a protected outdoor area.  Make
sure kids, pets, nosey neighbors, etc. cannot get shocked
from the capacitor or test transformer.  It is important
that the chosen test sight be outdoors because the capacitor
will be on high voltage for an extended period of time, and
you probably won't be around should the capacitor fail.  If
the capacitor experiences a failure, and if power is not
IMMEDIATELY disconnected, there is a very real chance for
an oil fire!  Better the fire burn a hole in your lawn than
to burn your house or business to the ground!

Attach a neon transformer controlled by a Variac (variable 115
volt transformer) to the capacitor.  You may also use a
variable high voltage d.c. power supply, but the "hum" from
a.c. helps shake bubbles loose.  Slowly bring the high voltage
up to about 50% of the capacitor's rated voltage.  Let sit for
eight hours.  During this time, you will see additional air
bubble up out of the capacitor.

Air is a very real enemy!  After this 8 hour time, slowly
bring the voltage up to 75% of the rated voltage.  Let sit
another 8 hours. Finally bring up to rated voltage and let
sit for 30 minutes.  If the capacitor is going to fail, it
will usually do so by this time.

Failure can    result   from   poor   quality   or   imperfect
polyethylene, insufficient  poly  thickness,  burred  aluminum
edges, oil containing moisture (1 part water  in  10,000 parts
oil reduces  the  oil's  insulation  factor  by  50%  !!!)  or
entrapped air.   Insufficient   border   spacing   around  the
aluminum can also cause capacitor failure.

It is highly suggested that you open one of the valves on
the capacitor when using with a Tesla coil or other high
peak power source in case the capacitor should fail.

Having a valve open will vent a sudden build-up of pressure
from the gases which come from the vaporized plastic which
occurs when a capacitor fails.  Close the valves whenever
the cap is NOT in use to prevent moisture in the air from
entering the capacitor.

The capacitor should be stored and transported standing
upright.  If the capacitor gets turned on its side, the air
in the space above the capacitor will get back into the
layers of poly and aluminum - and you don't want to have to
go through the pump/wait process again!

Theoretically you could completely fill the capacitor with oil
- providing you left a way for the oil to expand and contract
with temperature changes, AND if you could build a 100% sealed
PVC container.   I assure you that doing this is harder than
one would suspect!  The pvc end caps may  seep  a tiny amount
of oil THROUGH the plastic - pvc is not nearly as impermeable
as we would be led to believe! Stand the caps upright in a
large metal pan to contain any oil leakage.

The pan should be large enough to contain all  the  oil stored
in one  of  the capacitors.  The pan will contain leakage, and
should you have a capacitor  container  failure  and oil fire,
the pan will contain the burning oil - definitely a plus!

Again, remember one reason why we put a clear plexiglass
window on the top of the capacitor: it lets you see when
you have a capacitor failure!  If the capacitor fails, the
high voltage arc will be visible through the clear window.

If you do have a capacitor failure, DISCONNECT POWER

************** LEARN FROM MY MISTAKES! ******************
Due to impatience, I did not let some of my capacitors sit for
a sufficient time before use, so they had air trapped in the
layers.  They failed. I built several capacitors with
poly which was not thick enough to withstand the voltage of my
transformer. They failed.  In every case I quickly
disconnected power.  Not once have I had a "catastrophic"
failure resulting in container failure or fire.  But I ALWAYS
keep a fire extinguisher rated for oil fires handy, just in
case!  So should you.

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