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Re: Multi-Rolled Cap
Subject: Re: Multi-Rolled Cap
Date: Fri, 16 May 1997 09:36:06 -0400
From: "Thomas McGahee" <tom_mcgahee-at-sigmais-dot-com>
To: "Tesla List" <tesla-at-pupman-dot-com>
----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-poodle.pupman-dot-com
> Subject: Re: Multi-Rolled Cap
> Date: Wednesday, May 14, 1997 11:28 AM
>
> Subject: Re: Multi-Rolled Cap
> Date: 14 May 97 05:24:06 EDT
> From: Alan Sharp <100624.504-at-CompuServe.COM>
> To: "INTERNET:tesla-at-pupman-dot-com" <tesla-at-pupman-dot-com>
>
>
> Greetings All,
>
> I have been following the posts on
> building caps and I understand the
> advantages of putting caps in series.
>
> Let me represent 4 caps in series as
>
> -----||---||---||---||-----
>
> This is equivalent to:
>
> ----|||||------
>
> That is why not make a sandwich of 5 plates
> of Al foil seperated by polythene sheets.
> No connections are made to the 3 inner plates.
> This would be very dificult in a rolled cap,
> because of the number of layers. But easier
> in a flat cap. The layers would need to
> be staggered. Again showing only the foil:
>
> ----------------------------
> ------------------------
> ------------------------
> ------------------------
> ------------------------------
> ------------------------
> ------------------------
> ------------------------
> ----------------------------
> ------------------------
> ------------------------
> ------------------------
> ------------------------------
> ------------------------
> ------------------------
> ------------------------
> ----------------------------
>
Alan,
I don't understand why you are "staggering" the inner layers. As I
see it, the "end" plates would come out opposite sides as is usual,
and the "inner" plates would be smaller than the poly on ALL edges by
the same amount you would normally use for the sides of the "end"
plates. In other words, the inner plates would be smaller than the
poly on all sides.
I have done this, and it seems that it helps to distribute the charge
more evenly between layers. First the GOOD news: if you have flawless
poly, this even distribution is beneficial, as it causes the entire
area of the poly to be evenly heated/subjected to HV, etc. Now for
the really BAD news. Imagine that each sheet of poly has exactly ONE
flaw. The extra metal layers will interconnect the poly in such a way
that EVERY SINGLE ONE OF THE POLY FLAWS WILL COME INTO FULL PLAY.
Poof! In other words, it destroys the major GOOD reason for having
multiple poly layers in the first place. So I definitely DO NOT
recommend it!!!
> I think that this would save some material.
> and interconnections. And that it might be possible
> to prevent corona forming inside the cap,
> by reducing the electric field - oil will
> still be needed at the edges - where it can
> penetrate most easily.
>
> The inbetween foil layers are used to even out
> electric field - no current is drawn from them
> so I think cooking foil would do.
>
> This is just a thought - I haven't tried building
> caps yet - wait for the comments of the "old wise
> ones" before trying it yourselves.
>
> Have fun,
>
> Alan Sharp.
>
SNIPPED the stuff about buttered Cats!!! (Alan, you amaze me!)
I strongly suggest that anyone reading this post save themselves a
lot of aggravation and take my word for it that the extra metal
plates only AGGRAVATE the problem we are trying to overcome. I have
dimpled poly squares and then built up "defective" units that were as
much the same (defectively) as I could make them, with the defects
scattered at exactly the same places on each test cap. The ones with
the extra foil ALWAYS died at a lower voltage than the ones without
the extra metal plates. A little thought will tell you WHY this is
always so. Nature seeks out the *weakest* link, the *shortest* path,
the *easiest* way, even when it doesn't look to us like the weakest,
shortest, or easiest. WE have to *think* about it. Nature just does
it that way automatically. Putting the extra foil in there just gave
mother nature an express highway RIGHT TO the nearest defect. Not a
pretty sight!
Hope this post helps someone
Fr. Tom McGahee