Re: The manufacture of capacitors

Tesla List wrote:
> >From MALCOLM-at-directorate.wnp.ac.nz Tue Dec 10 15:41:07 1996
> Date: Wed, 11 Dec 1996 11:32:39 +1200
> From: Malcolm Watts <MALCOLM-at-directorate.wnp.ac.nz>
> To: tesla-at-pupman-dot-com
> Subject: Re:  The manufacture of capacitors
> Hi Ed,
>         I presume 30kV is the peak rating?
> > Re: Oil dielectric capacitors
> >     Why not go the whole way and eliminate the solid dielectric
> > material between the plates?  I have an article in an old (circa
> > 1921) QST describing an 0.01 mfd, 30 kV capacitor using only oil
> > as the dielectric.  Quite a construction job  to get the plates
> > flat enough to avoid excessive average spacing, but genuinelyh
> > genuinely indestructable!!!!!!  By the way, this one worked at
> > the "special" wavelength of 350 meters, or about 857 kHz, so the
> > inductance must have been pretty small.
> What is the spacing between plates, and how many and what size for
> that capacitance?
> Malcolm


I have a classic old sprague pure oil dielectric unit of .005ufd -at-10kvac 
rating.  It is huge!  20" tall, 14" wide, 8" thick! (55lbs).  The plates 
are quite rigid and held appart by tiny ceramic spacers.  The oil sloshes 
around inside the unit.

There is a problem with too many pops or arc overs in these self-healing 
units.  The oil slowly carbonizes and the dielectric starts a conduction 
loss scenario.  This type of cap might be one of the most volumetrically 
inefficient capacitors in existence right after vacuum caps.  I would not 
recommend the construction of one to anybody!  Only a vacuum cap is the 
ultimate self healer with no problems!  Still the effort is fun.

Richard Hull, TCBOR