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Re: Maxwell 31159 cap on eBay
Original poster: Jim Lux <jimlux-at-earthlink-dot-net>
At 08:30 AM 6/22/2004 -0600, Tesla list wrote:
>Original poster: Ed Phillips <evp-at-pacbell-dot-net>
>Tesla list wrote:
> > Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com>
> > Your assumption is correct --- they are built differently. The difference
> > is a Maxwell trade secret that they will not reveal.
> > D
> OK - trade secrets can be very important. Presumably the capacitors
>with smaller reverse voltage ratings are built that way because they can
>be sold for a lower price and/or smaller in size. Any of that correct?
Indeed, Maxwell has trade secrets, but I will guess that they are in the
manufacturing processes, not the design. Any would-be pulse cap mfr could
buy a set of Maxwell caps of various types, saw them open and easily
determine what the dielectric materials are and the construction of the
What Maxwell has, and the would-be knock off mfr does NOT, is people and
procedures that enable them to consistently produce them. Even if Maxwell
were to publish all their design rules (and, frankly, I think they have,
over the years, published enough conference papers, etc. that lays out all
the stuff), I doubt that anyone else could use them to make capacitors that
are the equivalent. What Maxwell does not publish is things like how their
winding machines work, what tensions they wind at, how they test, how they
do the impregnation, and so forth.
There's a lot more to building any high performance widget than merely
having the bill of materials and the construction drawings.
What Maxwell also has is engineers who understand the specific applications
of their products to a variety of uses. They know how to specify designs
from their "library" that will optimally meet a particular need. Sure, one
could just use the catalog numbers and the derating curves and do it,
adding in some extra margin, but if you were an equipment manufacturer,
trying to reduce the BOM cost of your pulse cap containing widget, you'd
want some help selecting the part that is neither too big nor too small,
but, like chair size and temperature of porridge, just right.
In Maxwell's case, they have a certain range of "sub capacitor" units that
are easily producable (for them), and they have to series/parallel
mix/match them to get what the user wants, and it's not always achievable
(energy storage and inductance push in opposite directions for
instance). They also have all the test data needed to make rational life
predictions for their components, and can produce a test article for
accelerated test and have confidence in the results.