Need Help With Capacitor

 * Original msg to: Oldradio-at-cheney-dot-net
 * Carbons sent to: usa-tesla-at-usa-dot-net

Quoting "James M. Watson" <oldradio-at-cheney-dot-net>:

> Hello Richard.

> I am about to begin constructing my first capacitor, and 
> another bit of doubt has popped up.  I will be constructing a 
> flat stacked plate capacitor, with the plates being discs made
> from aluminum flashing; the housing will consist of 10"OD PVC 
> sewer pipe (previsions for pressure build up will be made). 

This sounds OK. You won't have much of a problem with pressure
rise, and as I mentioned there is no need to prepare the PVC pipe
container. Just make sure it does not leak... Will you turn it on
it's side when it is done, or pull the air out of the stack with
a vacuum pump?

> The dielectric will be three layers of .030 polyethylene.  Each
> plate will have a small tab which I will attach to either an 
> aluminum or copper bus bar.  The closest point between any two
> opposing plates will be where this tab comes out of the 
> dielectric.  Do you think that 1" separation at this point 
> would be enough to prevent fringing, considering that I will be
> using mineral oil, and the input will be 15kV? 

This sounds like it will work fine. If you are worried about
flashover beneath the oil you can mount an extra safety gap
across the capacitor terminals. The safety gap can be set for the
same width as the closest points between your conductors under
the oil. Given that the dielectric strength of oil is
considerably higher than air, the air gap across the capacitor
terminals will fire before the oil dielectric breaks down.

> Would an aluminum bus bar serve well (1/4" thick x 3/4" = 
> wide)?   Is there any problem with using PVC sewer pipe for the
> housing? 

The bussing sounds heavy enough, depending of course on the value
of the capacitor and peak current the bussing is required to
handle. At these frequencies the bussing does not need to be so
thick as is does wide. Your charging amperage will be measured in
miliamps at 50/60 AC, which any reasonable conductor will handle
without worry. Your pulse discharge is going to oscillate
however: a smooth wide strap will have the lowest resistance to
this type of energy.

As I mentioned, the only care you need to take with the container
is to make sure it won't leak... If you intend to pump the cap
down to remove air it must withstand the vacuum.

Richard Quick

... If all else fails... Throw another megavolt across it!
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