Plate Caps of PCB

Subject:  Plate Caps of PCB
   Date:  Thu, 17 Apr 1997 20:03:40 +1000
   From:  Phil Chalk <philoc-at-ozemail-dot-com.au>
Organization:  Secure_Logic
         To:   tesla-at-pupman-dot-com

-----Original Message-----> 
> From:         Tesla List> 
> Sent:         Saturday, April 12, 1997 5:32 AM> 
> To:           tesla-at-poodle.pupman-dot-com> 
> Subject:      Stacked capacitor (fwd)> > 
> Date:         Thu, 10 Apr 1997 16:31:20 -0600> 
> From:         "Phillip M. Jarvis" <jarvisp-at-bee.d93.k12.id.us>> 
> To:           tesla-at-pupman-dot-com> 
> Subject:      Stacked capacitor> 

>I just made a stacked cap with 16oz. copper (measured thickness is 25> mils) and 6 plates 
>each with 206 sq. inches of area. 120 mil> ployethylene dielectric and light mineral oil as 
>the drowning agent.

Hi all,

I've been thinking of making a stacked cap from fibreglass PCB.  I read
it has a Dielectric
Constant (K) of about 5 (5.2), and a puncture voltage of 700V/mil.  The
stuff I use is about
1.6mm thick, or about 63 mils, for 44kV.  This may be optimistic, but it
could probably be
conservatively rated around 30kV or so. Using back-to-back pairs of
single-sided board, you
could double the voltage rating.

I won't bore you here with the construction details, but I've got it
sussed. So, I figure
I'm not the first person to have thought of this - I wonder if anyone
here has actually made
one ?

Also I'd like someone to tell me, if cost were no object (which it is !)
which would be
THE BEST dielectric material for TC work ?  I have just bought some 69mm
(2.75") dia. clear 
acrylic tube, 3mm (~ 1/8") wall.  A 1.83m (6ft) length was a mere $55.00
!  This is for my
_first_ coil. A 2m length 0f 200mm (8") dia. 5mm (1/4")wall, inc tax, is
a tad under $400
so I decided against it for the 'big coil'  

What I mean, though, is for stacked plate caps.  All the talk is about
polyethylene for its
low dielectric loss.  Would any of: mylar, polycarbonate, polypropylene,
polystyrene, PTFE
(Teflon), acrylic, etc be any improvement - albeit costly ?  The list I
saw quoted the
puncture voltage of mylar at 7500V/mil.  If this is not a typo, that
makes it look pretty
attractive for TC caps.

Has anyone ever tried silicone oil in caps ?  Or know of its HV
properties ?  It's used in
e.g. high-quality brake-fluids, as I believe it has very good
anti-hygroscopic properties.

But mainly I'm wondering about PCB caps - any comments ?


Phil Chalk.