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Re: Air as di-electric
Tesla List wrote:
>
> Subscriber: kukkonen-at-cc.hut.fi Thu Jan 2 23:04:23 1997
> Date: Fri, 3 Jan 1997 01:38:57 +0200 (EET)
> From: Kristian Ukkonen <kukkonen-at-cc.hut.fi>
> To: tesla-at-pupman-dot-com
> Subject: Air as di-electric
>
> I've lately been seriously thinking about spending some valuable
> lab space for a "definitely-not-space-efficient" capasitor. The
> good this would be the fact that it could be virtually impossible
> to destroy without melting steel BIG TIME..
>
> So, it's a plate-cap using steel plates separated 10mm from each other.
>
> It would mean that the capasitance, using 2000mm*330mm plates would be
> 0.5841nF *(n-1), where n is the amount of plates. Using just 41 plates it
> would be about 23nF. using 1mm thick plates the total mass would be about
> 200kg. The cost would be 45FIM (9usd) for a plate 1000mm*2000mm which
> would get converted to 3 plates. This would mean 14 of those big plates
> and 630FIM (130usd) - propably less - usually price for steel is 2FIM/kg
> at "surplus"stores.
>
> The total size of the thing would be 2m*.33m*.41m "only".
> Plus the fixture keeping the thing intact.
>
> Quite reasonable. Does not require much FLOOR space. :)
>
> Would be (trans)portable and moveble with some wheels under it.
>
> So, the question is: dry air etc. break at something like 4kV/mm. That
> would mean 40kV rating for that monster. Thinking reasonably it could
> work with the 20kV pig I have.
>
> In reality? Does someone out there know? for sure?
>
> At least it would be INDESTRUCTABLE.
>
> Adding a blower below the thing would make any arcs act like in a jacob's
> latter - and I could actually put kind of jacob's ladders to the top of
> the plates - between each pair of plates. It would quench any arcs caused
> by cap "breakdown".
>
> So, before buying those plates of steel and starting to spend some disks
> with the disk grinder cutting plates to pieces and sending molten pieces
> of steel around:
>
> Opinions? Am I forgetting something? Will there be HUGE corona between
> plates - causing losses and breakdown at much less than 4kV/mm ? Something
> else? I may need to put some plates of plexi between edges of plates..
>
> It could be made tunable by inserting pieces of plexi (or PP) between
> plates..
>
> I could build a tank around it too - and fill it with dry N2 or
> something fancier. It would make it a potential bomb though.
>
> Thanks,
>
> Kristian.
>
> ---------------------------------------------------------------------------
> | Kristian Ukkonen | Do as thou wilt shall be the whole of the law |
> | kukkonen-at-alpha.hut.fi |_____ Chance favours the prepared mind |-------
> | http://www.hut.fi/~kukkonen | Fear is the mind-killer |---------
> ----------------------------------------------------------- 42
Kristian,
Forget it! Corona at 20kv will be tremendous and breakdwon will occur at
10mm spacing at that level in the oscillatory circuit. Air is one of the
poorest of dielectrics, It is unpredictable and never stable. I would
prove this to myself with some casually placed aluminum or steel plates
on hand by setting them up in a much smaller capacitor setup and firing
away to verify what I say.
Richard Hull, TCBOR