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Re: How good are MMC caps ;-))



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



I don't think it is a regular occurence.

I built dozens of small size coils (less than 40 inch spark) and we never use any resistors across the caps. I have never observed a charged cap from AC after shutdown.

Dr. Resonance



Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>

I agree that coronal rectification is the most likely explanation, as a
non-linear process is needed and that's the only plausible one that
comes to mind.  But I don't think it is due to differences in component
layout.

Reviewing my experimental results posted at
http://www.pupman.com/listarchives/2004/January/msg01310.html, I
miss-spoke - the cap value differed between trials with different cap
types.  But to summarize the results:
Charge? Cap type/value
No (4) CD942C 0.1uF/2000V No (4) BC Components 383-MMKP 0.1uF/1600V
Yes! (4) BC Components 376-MMKP 0.047uF/1600V

The CD caps are the axial units we all know so well, and no residual
charge was observed.  The two different BC caps were radial-lead box
caps with identical case sizes and assembly geometries
(http://users.rcn.com/laushaus/tesla/minicoil_files/mmc.jpg).

The only other non-linear process I can think of is dielectric breakdown
and puncture, but I hate to think that it happens so regularly!

Regards, Gary Lau
MA, USA


> Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx> > > Tesla list wrote: > > >Original poster: "Lau, Gary" <Gary.Lau@xxxxxx> > >Bleeding and balancing are two unrelated things. > >The mechanism by which unequal charges remain on individual MMC caps is > >not understood. It is not due to unequal capacitance values. In my > >experiments, some capacitor types are prone to developing these charges, > >and others are not, using exactly the same cap values and test circuit. > >I have no idea what causes this difference. > > Probably corona at the interconnections, effectively adding rectifiers > across the capacitors at random positions (or systematically, depending > on how asymmetrical the construction of the connections around each > capacitor is). > > Antonio Carlos M. de Queiroz > >