Re: Cap Formulas (fwd)

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Original poster: List moderator <mod1@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Wed, 13 Dec 2006 08:37:42 -0700
From: resonance <resonance@xxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Cap Formulas (fwd)




Sounds like a good solid plan.  Be sure to wear gloves and wipe your plates 
and dielectric down with acetone before winding.  Need to keep any oils 
out --- someone may have handled it before you received it.

Dr. Resonance



Hi Doc.

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)
2 Use aluminum flashing 20 x xx x .025 or better (max .030)
3 Use Sch 80 PVC tubing and end caps
4 Use a Robinair 4cfm vacuum pump
5 Sandblast the edges of the flashing while it is still in a tight
roll to round off and smooth all the edges
6 use acetone to bath and clean the flashing
7 use the compatible solvent to bath and clean the dielectric
      (Purchased in rolls)
8 use great to best impregnating oil
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)
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.
11 make a vessel as such that it will withstand a min vacuum of 25hg
12 Use 3/8 brass hardware for termination and epoxy or better for
sealing the terminations
13 Add a vacuum and oil fill port to the vessel
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.
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"
16 use nitrogen or the compatible inert gas on the fourth and final
pump down, fill the remaining space in the vessel with gas.
17 provide an externally mounted reservoir of gas for expansion and
contraction caused by changes of temp.
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.
20 once proven provide them to Tesla Junkies like us at a reasonable
price and to spec.!

What do you think, will it due?

Victor



-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Saturday, December 09, 2006 10:52 PM
To: tesla@xxxxxxxxxx
Subject: Re: Cap Formulas (fwd)

Original poster: List moderator <mod1@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Sat, 9 Dec 2006 20:11:37 -0700
From: resonance <resonance@xxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Cap Formulas (fwd)


In US units the equation is:


        C   =  KA/d x (n-1)


where C is in picoFarads

K is dielectric constant of the dielectric

A is total area of one plate in square inches

d is thickness of dielectric

You just insert your data and solve the above equation for area.


If you plan on using a pole xmfr I definitely would NOT use mylar.  I
recommend either PP (polypropylene) or PE (polyethylene) as a better
dielectric choice.  About 90 mil thickness if only one thickness, otherwise,

use multiple layers (5) of 20 mil sheets.  7 mil mylar will not last very
long on a pole xmfr.  RF currents produce heat and edge-tracking both which
can destroy a HF RF cap rapidly.

Also, if rolling your own, be sure to use extended foil construction.  Leave

a very generous margin on each dielectric edge (3 inch min on each side).
Wear plastic gloves as the salts on your skin are very conductive and will
cause your cap to "edge track" at RF frequencies --- the number one cause of

HV cap failures.  Vacuum evacuate the cap prior to adding the protective
xmfr oil.

If you need xmfr oil contact me off-list.  I carry it in 55 gal drums and
could supply a gallon.

Dr. Resonance




Can any one help me with calculating the required area (length of plates) to
make a rolled cap using the following;



20” wide by XX long aluminum flashing

24” wide x .007” thick x XX long Mylar film



With a dielectric constant of 3.0 and a puncture voltage of 7500v I figure
that I can make two 0.1uf @ 52.5kv for a total of 0.2uf for my 14.4kv 10kva
pig.

I will be immersing the roles in mineral oil.



Any ideas or comments?



Victor


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