RE: Cap Formulas (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Gerry Reynolds <greynolds@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Thu, 14 Dec 2006 19:17:43 -0800
From: Anthony R. Mollner <penny831@xxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: RE: Cap Formulas (fwd)

One comment to make is that commercial caps are sometimes put under vacuum
at temperature. They're cooked AND pumped at the same time.

-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Thursday, December 14, 2006 5:12 PM
To: tesla@xxxxxxxxxx
Subject: RE: Cap Formulas (fwd)


Original poster: Gerry Reynolds <greynolds@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Thu, 14 Dec 2006 17:06:04 -0700
From: Terrell Fritz <terrellfone@xxxxxxxxxxxxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: RE: Cap Formulas (fwd)

Hi Victor,

So you "aren't" going to make an MMC ;-))  Ok...  Here are some thoughts...

>.....
>Here is the process that I was intending on doing to make my caps,
>
>1       Use the BEST dielectric available
>       (Compromise of best properties to cost)

Polypropylene.  No other real choice aside from Teflon.  In oil,
polyethylene "might" stay cool, but the price is the same so might as well
use polypropylene for 10X lower dissipation.

>2       Use aluminum flashing 20 x xx x .025 or better (max .030)

It could be "very" thin from an electrical point of view.   In oil it is
usually 1kV/mil radius.

>3       Use Sch 80 PVC tubing and end caps

I assume that is the heavy big kind.  Caps have been ruined from a small
drop where the thinner plastics crack.  Beware that if it does short of
fail, you want it to be able to vent overpressure so it does not turn into
a bomb!!

>4       Use a Robinair 4cfm vacuum pump

Any mechanical pump will be fine.

>5       Sandblast the edges of the flashing while it is still in a tight
>roll    to round off and smooth all the edges

Cool!

>6       use acetone to bath and clean the flashing

Acetone eats and dissolves almost anything...  Aluminum is fine but
everything else it touches it will dissolve.  Use nitrile gloves and don't
breath it.  Beware that the stuff you buy at the hardware store is of
"questionable" purity.  I think it is also used to make methamphetimines so
if you buy ten gallons of it you are going to attract some attention
there.  Not a big deal but be prepared to explain...

http://www.stopmeth.com/made.htm

>7       use the compatible solvent to bath and clean the dielectric
>       (Purchased in rolls)

Isopropyl alcohol.  92% USP form the drug store.  It would probably work
fine on the metal and case plastic too.  Beware the HV oils are usually
boiled under vacuum to remove water before use.  We installed some HV
transformers (big ones) and that was a major operation!!  A tanker truck
with the oil and two more for vacuum / boiling to fill it...

>8       use great to best impregnating oil

USP mineral oil is fine.  It is very "clean" and safe to soak one's self
in.  Commercial oils for electrical stuff always have "mysterious"
additives.

>9       Design and build a machine that will wind two plates and two layers
>of                      dielectric simultaneously with proper back tension
>to provide a very       tight roll. (14-20" wide flashing and 18-24"
>dielectric)

:-))  Sounds harder to make than the cap :o)

>10      the termination will be provided on both ends of each plate
>(totaling       four 1.5" strips) by cutting the sheet and folding the
strip
>in the  proper direction to create connections that exits on one end.

Beware that aluminum quickly forms a very nasty very insulating oxide layer
(30 minutes) so connections have to "bite" into the metal an be "air
tight".  Sand the connections first and crank the bolts down solid.  Never
use "casual contacts" with aluminum even in oil...  That is what plagued
the "cap buy" of years back...

>11      make a vessel as such that it will withstand a min vacuum of 25hg

Probably 30 inches unless you are in Colorado at 5300 feet like me
;-))  But you might want to hold that vacuum a long time without
significant bending of the vessel.  I think the plastic size you are using
is very strong though so no big deal.  Beware that if it implodes it will
be "mean"...  Of course, if the oil or any thing is "hot", the strength of
plastic goes to zero fast...

>12      Use 3/8 brass hardware for termination and epoxy or better for
>sealing         the terminations

:-))  Quality epoxy should do well.  "Test" it first!!

>13      Add a vacuum and oil fill port to the vessel

Vacuum it "first".  There is a lot of water vapor in there so vacuum the
dry vessel to remove moisture in it like auto air conditioning systems
do.  You should also boil the oil to remove water from it...  Small amounts
of H2O in insulating oils is a GIANT problem!!!  In the power industry like
one of those five alarm fires:

http://teslamania.delete.org/frames/frameindex.html

The firemen like to "watch" those fires :o)))   Nothing they can do...

>14      after the roll is made, terminated and sealed in the vessel
>         I will pump it down to 25hg and then draw in the oil.

They often use craft paper to help the oil penetrate in between the
layers...  You can actually get "high vacuum" "bubbles" in there that are
very conductive.  "Vibration" helps to drive them away.  This is a pretty
messy issue!!

>15      after the first pump down and fill I will do it again two more
times
>or until there is about 2" of room left in the top covering the roll    at
>least by 2"

Might just keep the filled cap with oil under vacuum for "days" with
vibration and heating/cooling...  Hard to know what is best there and if it
really helps in those low volume situation.  If you were making a bunch,
then it would be a "design of experiments" thing...

>16      use nitrogen or the compatible inert gas on the fourth and final
>pump    down, fill the remaining space in the vessel with gas.

"Don't" use "argon" ;-))  N2 is fine and probably already comes "dry".

>17      provide an externally mounted reservoir of gas for expansion and
>contraction caused by changes of temp.

Ok.  But beware that if it blows, a LOT of pressure might have to get out
fast.  It really needs a "safe way" to "blow up"....

>18      break her in at 1/4 power then 1/2 power then at 3/4 power and the
>real glory of full power! (14.4kv @ 10-15kva pig)using a dummy primary  and
>SRSG @ 480bbp.

:-))))

>19      Provide a few to a select few at material cost to test and abuse.

That's asking for trouble :o)))

>20      once proven provide them to Tesla Junkies like us at a reasonable
>price and to spec.!

Not even the people that make caps every day have gotten there yet ;-))

>What do you think, will it due?

Hope it works good!!!  If not, make an MMC :O))))

Cheers,

         Terry



>Victor
............