Re: Variable capacitor

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "cd by way of Terry Fritz <twftesla-at-qwest-dot-net>" <vbprg1-at-hotmail-dot-com>

Instead of trying to eliminate the corona
how about eliminating the terminal failure heat effect
by flaring out the edges of the outer tube
and narrowing the edges of the inner tube.

Nice corona picture :)
Chris Dowdy

 > Without some special insulation at the edges of the metal plates the
 > electric field there is too intense. Corona forms, heats the dielectric,
 > and it soon fails. Oil may be a solution.
 > This is a variable tubular capacitor that I made recently. Could reach
 > 400 pF. Didn't last much.
 > Open as in the picture below, there was corona everywhere and the
 > dielectric surfaces started to become conductive.
 > http://www.coe.ufrj.br/~acmq/tesla/567c2.jpg
 > When I tried to eliminate the corona at the foil borders with a layer
 > of wax it failed in seconds with 20 kV at 300 kHz applied.
 >
 > Antonio Carlos M. de Queiroz
 >