Re: MMC or Maxwell? Which is better?

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

Original poster: Crow Leader <tesla-at-lists.symmetric-dot-net> 

On Sat, 28 Feb 2004, Tesla list wrote:

 > Original poster: "S & J Young" <youngs-at-konnections-dot-net>
 >
 > Guys - let's call a truce.  A Maxwell capacitor IS AN MMC!  The only
 > difference is there are typically more caps in series and more strings in
 > parallel to achieve more reliability, and they are packaged in a nice metal
 > oil-filled box with nice HV feed-through insulators.  So we are talking
 > home-made vs commercially made MMCs.

They're not quite the same.

More strings in parallel won't increase reliability in a non-self healing
cap. Film/foil caps tend to fail short, vs. open for metallized ones. Any
shorted section is a bad thing, but can be avoided by proper ratings in
the first place.

I doubt you will find a corona inhibiting impregnant in a cornell dublier
cap, or 2" wide copper foil for internal terminations, or solid foil and
polypropylene vs. metallized films + foil as in the CDE 942 series. With
the CD caps, you lose current carrying ability, RF current handling
ability, corona inhibiting, cooling from the impregnant and the
reliability or way fewer connections.

If one were to still argue that you NEED hybrid caps to have self healing
for reliability, take a look at utility company power factor capacitors.
They are made to last 20+ years, nonstop from below freezing to hot summer
temps out in the sun. What may be the "cadillac" of these caps, from
Cooper use all film and foil construction, extended foil, and crimps, to
eliminate failed solder joints (soldering aluminum foil can be done, and
I've seend a few caps where it failed). There is no self healing ability,
they are made to last their design life the first time. It's fairly
impressive. I belive the BIL starts at 95kV for them as well, even for the
ones rated several kV.

KEN