Re: ceramic capacitors

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: G Hunter <dogbrain_39560@xxxxxxxxx>

HV ceramic "doorknob" capacitors are not all the same.

Most are suitable only for DC filtering and small
signal work.  Pulse-discharge duty and/or RF power
amplifier duty tends to overheat or crack this type of
cap.

Some ceramic doorknobs are rated for RF and
pulse-discharge duty.  These are more rare and
expensive--of course!

Many ceramic doorknob caps exhibit rather extreme
temperature coefficient--they shift their capacitance
substantially with changing temperature--possibly even
enough to detune a Tesla coil.

Having spouted so much wisdom, I should also point out
that many coilers have successfully used ceramic
doorknob caps in Tesla coil tank circuits.  Not me
though.  The one time I tried it, the cheap Russian
surplus 40kv doorknob failed within seconds.  But I
know others have gotten them to work ok.

Cheers,

Greg

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: "Matthew Boddicker"
> <shmerpleton_town@xxxxxxxxxxx>
>
> I have been looking for an aternative for
> cornell-dubilier capacitors for a MMC and I was
> wondering if anyone has any knowledge with high
> voltage ceramic capacitors? My father is an
> electrical engineer and he believes that the
> dielectric should be able to with stand any
> current as long as the capacitor has the right
> voltage rating. He doesn't think that the
> frequency of the circuit could have a damaging
> effect on the dielectric.
>
> thanks,
> Matthew Boddicker
>
>
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