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Re: Tube coil makes sparks
Tesla List wrote:
> Original Poster: David Trimmell <davidt-at-pond-dot-net>
>
> At 04:18 PM 3/9/1999 , you wrote:
> >Original Poster: Brandywine <brandywine-at-writeme-dot-com>
> >
> >Fellow Coilers,
> <<>>Snip<<>>
> > There has been some debate over the usefulness of the MMC capacitor
> >arrangement. I am currently using 6-- 0.018 uF, 1600Vdc, Panasonic
> >metallized polyprop caps in series for the tank capacitor (result =
> >0.003 uF). They were mildly warm after a 5 minute run at 4000 Vac and
> >probably 4+ kW. I was hoping they would run stone cold. A permanent
> >setup could incorporate 24 caps in a series parallel arrangement, for
> >example. Despite the modest heating, I must tentatively conclude that
> >they are satisfactory for high power tube coil duty.
>
> Glad to here that you have had first light with this coil. I have been
> using the Panasonic caps also, I am using 10 of the 0.015 uFd-at-1.6KV in
> series wired so I can tap the last 4. They do perform well in my opinion,
> but they get warm after several minutes, although, even after the heating,
> they do not loose capacitance value, as do the doorknob variety. I must
> add that they are of great quallity, as mine have all measured within 2% of
> their rated value.
>
>
I should emphasize that the warming was quite modest after an extended run.
I said 5 minutes, but it could have been more like ten. I must assume that
temperature had plateaued and stabilized by then. Of course, this coil, which
I've named coil #1, is hardly optimized. If the caps survive 40" sparks, I'll
be happy. I suspect they will. Immersed in a bath of oil for cooling, they
should be bullet proof.
Finally, I should mention that only the tank caps heated. RF bypass and
grid-bypass caps were cold, as one would anticipate.
Dave H.