RE: Cap Formulas (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: List moderator <mod1@xxxxxxxxxx>



---------- Forwarded message ----------
Date: Wed, 13 Dec 2006 15:20:56 -0500
From: "Lau, Gary" <Gary.Lau@xxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: RE: Cap Formulas (fwd)

Why would it be useful to remove oils from handling, if it will
ultimately be submerged in oil?

But more importantly, rolled caps have gone the way of the buggy whip.
While you may have a relatively good way to build them, no one will want
them.  No coiler who is aware of the state of the art of coiling is
going to buy a DIY rolled cap over an MMC, and it's doubtful that the
price or reliability could be made competitive with an MMC.  The only
appeal of a DIY rolled cap is that YOU made it, with no charge for your
labor.  If someone else makes it, their significant labor and equipment
investment is not free, and no personal pride.  Then there's that nasty
business of if you make and sell it, does it come with any sort of
warrantee?

Most HV commercial caps are made of multiple sections wired in series,
to keep any one section from seeing too high a voltage.  I think
something to do with corona inception voltage - an unavoidable situation
where a dielectric of any quality or thickness will degrade and fail if
exposed to the corona that occurs if the voltage is too high.  A rolled
cap must take the same thing into consideration.

Gary Lau
MA, USA

> 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
> 
> 
> --
> No virus found in this outgoing message.
> Checked by AVG Free Edition.
> Version: 7.5.432 / Virus Database: 268.15.15/579 - Release Date:
12/7/2006
> 1:31 PM
> 
> 
> 
> 
> 
> 
> --
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.5.432 / Virus Database: 268.15.15/581 - Release Date:
12/9/2006
> 3:41 PM
> 
> 
> --
> No virus found in this outgoing message.
> Checked by AVG Free Edition.
> Version: 7.5.432 / Virus Database: 268.15.16/582 - Release Date:
12/11/2006
> 4:32 PM
> 
> 
> 
> 
> 
> 
>