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Re: capacitor question - rell.com order



Original poster: "Dmitry (father dest)" <dest@xxxxxxxxxxx>

> Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>
>
> No, this is wrong thinking.  Penny wise but dollar foolish.
>
> You need to allow at  least Erms x 2.5 to 3.0 for safe Erms performance.
>
> They use Erms x 3.0  to obtain the correct Edc pulse rating for all their
> high voltage reversal caps.

"Erms x 3.0" is equal to "Upeak * 2.12" - the same rule is used at derating
of commercial pulse caps, which don`t use "self healing", but 942 caps
use this technology.

http://www.pupman.com/listarchives/2005/Jul/msg00419.html

"1. Self Healing - MMC capacitors can be driven to twice and sometimes 3
times their rated DC voltage before they arc over internally. Due to their
construction, MMC capacitors will self heal and continue to operate even
after thousands of over voltage hits. This is pretty important since many
coilers have "accidents" and things that arc the caps. Mica caps are
destroyed after just "one" hit as are many other types of caps. Although it
has been done, it is very difficult to destroy an MMC from over voltage."

"5. Peak voltage - For Tesla coils, we can use the DC rated voltage value
and ignore the AC voltage rating. This is due to the short pulsed nature of
Tesla coils and the very short clock time that the caps are run. Dielectric
ion inception damage is just not a problem for us in the case of Tesla
coils"

do you negate all that Terry said?