RE: MMC - Sufficient Capacity?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com> 

It's not clear what "audio grade" caps are.  Many caps used for audio 
crossovers use Mylar film dielectrics, and this is not suitable for an 
MMC.  Audio applications do not need to support high pulse currents 
(despite what golden-eared audiophiles may believe) to the degree that 
Tesla coil caps do.  We would need to see a manufacturer/part number and 
spec sheet to be certain.

The number of caps you have in series may be a problem.  Each cap exhibits 
an equivalent series resistance (ESR).  A string of a few caps won't add up 
to much, but a string of 94-100 will be just that much lossier.  But this 
is uncharted territory; I can't be certain how significant this would be.

Adding different-valued caps in series will result in a non-equal division 
of voltages across the units in the string.  But since the "extra" units 
have a higher unit value, the voltage across them will be lower than the 94 
other units.

You may want to consider adding bleeder resistors across each cap.  While 
this will NOT result in an equal division of voltages, it will prevent 
residual charges from building.

BTW, the convention for ASCII representation of microfarads is uF, not 
mF.  In some circles, mF means millifarads.

Regards, Gary Lau
MA, USA


Original poster: Koen van den Berg <cerberus_rex-at-planet.nl>

Hello all,

I was hoping somebody can help me out with a 'problem' I've run in to. I'm
in the process of making an MMC. It consists of 94 audio grade caps in
series, rated at 160 V by 3.3 mf. This amounts to approx. 15 kV and 35 nf.
Will this be adequate considering my transformer (dual parallel 10 kV 50 mA
NST's)? I might be able to up the cap bank to 100 caps, all rated at 160 V,
but that would mean adding 6 caps that were made by the same manufacturer,
but aren't rated at the same capacitance. These are 160 V 4.7 mf caps. Is
my current MMC sufficient, should I add these extra caps or do I have to
take a totally different approach? Any help would be appreciated.

Thanks in advance

Koen van den Berg