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RE: Many dry caps in series



I'd imagine that with a little ingenuity you could build the caps
without welding, use twice the length of foil that you need for each
capacitor so that the "odd" sheets of one capacitor become the "even"
sheets of the next.
It would mean less flexibility (must always be in series) but it would
be the lowest cost and resistance.

> ----------
> From: 	Tesla List[SMTP:tesla-at-pupman-dot-com]
> Sent: 	Saturday, October 31, 1998 8:13 AM
> To: 	tesla-at-pupman-dot-com
> Subject: 	Many dry caps in series
> 
> Original Poster: Gary Lau  30-Oct-1998 1345 <lau-at-hdecad.ENET.dec-dot-com> 
> 
> Dear List:
> 
> Several weeks ago I proposed doing away with the oil immersion of poly
> caps by constructing it as MANY caps in series.  Since no one appeared
> to
> have first-hand experience doing this, I took it upon myself to
> conduct
> an experiment to test this.  I built a scaled down version, using two
> layers of 4 mil Home Depot Poly between each foil plate-pair, in a
> flat
> plate construction, times 20 sections.  The total capacitance measured
> only 47pF, but my goal was only to see if any signs of corona were
> present.
> 
> I ran this test cap in parallel with my .01uF cap on my TC for about 2
> minutes, intermittently, and looked for signs of corona, but saw none.
> The cap was constructed with each plate wrapping around a corrogated
> cardboard spacer, so the edge of each foil plate was plainly visable.
> I also inspected one of the sections for discoloration of the poly at
> the
> foil edge and saw none.
> 
> It's clear that using only a single layer of thin poly between plates
> is
> asking for trouble as surface defects in the poly are very common.
> Hopefully the use of two sheets between plates will guarantee a
> puncture-proof dielectric.  
> 
> My original plan was to use 20 extended foil rolled caps in series,
> but
> after attempting rolling this with two thin poly sheets between
> plates,
> gave up in utter frustration.  Instead I'll use flat plate
> construction.
> 
> Has anyone had experience trying to spot-weld standard .75 mil kitchen
> aluminum foil?  Each of my proposed 20 flat plate segments will have
> 34
> sheets of foil, 12" wide, extending from the poly that needs to be
> connected to the 34 sheets from the next segment.  Spot-welding sounds
> neat if it can be done.
> 
> Gary Lau
> Waltham, MA USA
> 
>