Re: capacitor question - rell.com order

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>


Even though the puncture thru the dielectric is "self-healing" 
operating them in the manner you describe will not stop the corona 
and tracking at the edge of the foil.  Excessive operation in this 
manner will actually melt the dielectric near the edges and 
"self-healing" will not occur with such large damages.

Do it right the first time and you won't have to spend hours 
searching for a bad cap.

You can't ignore the pulsed rating.  Beau Meskin has been making this 
type of cap for over 30 years and he says he just shakes his head 
every time he hears these claims.

But, if you have a lot of time on your hands to make repairs, why not 
just run them at the DC rating ......?

I was only trying to save the experimenter some time and grief.


Dr. Resonance
----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Friday, August 19, 2005 9:56 AM
Subject: 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?