Plate capacitor

 * Carbons Sent to: 102505.61-at-compuserve-dot-com

Quoting Scott Myers <102505.61-at-compuserve-dot-com>:

> I've recently come into a lot of .060 HDPE, for free.  So I am
> going to build a plate style capacitor.

> Question:  Has anyone built one of the using a material thinner
> than the aluminum flashing that is suggested by several 
> documents? Commercial capacitors use some pretty thin foils.  
> I am considering using heavy duty Reynolds Wrap. My 2 
> capacitors will have 110 - 7.25"x8" aluminum plates each.  
> These are small enough that I feel heavy duty aluminum foil
> should work.  The loss in Q should be immeasurable.  These 2 
> capacitors in series should provide appromately .025-.026 uF 
> good for about 24000 volts in a Tesla tank circuit. 

I didn't check your math, but all in all, this sounds reasonable.
Foil plates will work just fine in this application, and I can
offer a few tips: round all corners of the foil plates with a
pair of sharp sissors; stack the plates in a vertical
configuration that allows release of trapped air, even if you
intend to pump the cap down with a commercial vacuum pump; cover
with top quality mineral or transformer oil.

> Since I've never built one of these, I have one more question. 
> I assume that all one has to do is connect every other plate to
> a buss. Each buss is down opposite sides of the stack. Correct?

Close enough. What worked for me, though it did not make as
efficient use of the foil, was to cut out the plates with a very
sharp pair of sissors and include an extended tab to use for the
buss connection:
                                          |   |
                                          |   |
                                          |   |
                    /---------------------|   |
                  /                           | 
                  |                           |
                  |      ALUMINUM FOIL        |
                  |     CAPACITOR PLATE       |
                  |                           |
                  |                           |
                  |                           |
                  |                           |
                  |                           |
                  |                           |
                   \                         /

Multiple plates can be cut out at the same time by stacking
sheets of foil one atop another and cutting several plates at
once with the sissors. The plates are then separated and each
plate is inspected for flaws. All the plates may be cut with the
same template. When the capacitor stack is built, you simply
reverse the orientation of every other plate in the stack
so that the tabs extend out from opposite sides of the capacitor. 
All the left hand side tabs are then bundled together to form one
buss, the right hand tabs get the same treatment:

                   ___                     ___ 
                  |   |                   |   |
        BUSS -->  |   |                   |   |  <--BUSS
                  |   |                   |   |
                  | /-|-------------------|\  |
                  /                          \| 
                  |                           |
                  |         STACK OF          |
                  |       ALUMINUM FOIL       |
                  |     CAPACITOR PLATES      |
                  |                           |
                  |                           |
                  |                           |
                  |                           |
                  |                           |
                   \                         /

Hope this helps!

Richard Quick

... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12