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Re: MMC advice



Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com> 


If you have a 30 kV DC rating divide by 2.5 to get the equiv. AC rating.

Example,   30 kV DC / 2.5 = 12 kV Erms rating for the string

BTW, these are not my rules --- Beau Meskin, Pres. of PCI, developed this
rating method with considerable work in his cap lab which is well-equipped
to measure corona formation, etc, etc.  He said in all commercial work both
his company, Maxwell, CSI, and most other cap mfgrs use 3 x DC pulse rating
for the equiv. AC rms rating.

The main problem is corona formation at the edge of the foil.  If you exceed
these ratings you will definitely be getting corona formation (no
exceptions) and eventually the cap will fail.  It's only a question of time,
and in the case of MMC's, which one in the string fails.

Yes, as Dan pointed out, you can push them, but if they fail right when you
need the machine to work properly (Teslathon, haunted house, etc.) then you
end up with egg on your face  -- you become the "bumbling engineer" not the
shining knight.

We usually use the 2.5 times rule and so far have had no failures or
intermittant problems.  As a former TV technician (in the 60's) I can tell
you the intermittant type failures are the worst --- they drive you
partially crazy trying to ascertain the exact problem not to mention the
tremendous waste of your time.

At only $3 per cap why take chances?


Dr. Resonance

Resonance Research Corporation
E11870 Shadylane Rd.
Baraboo   WI   53913
 >
 > So what are you really saying?  Take your transformers AC voltage and
 > calculate peak.  Multiply this by 2-2.5 and then divide by the
 > individual cap DC rating to give number of caps per string?
 >
 > Cheers, Chris (NZ)