MMC Packing (Was Re: MMC Design UK Bulk Order)

To: tesla-at-pupman-dot-com
Subject: MMC Packing (Was Re: MMC Design UK Bulk Order)
From: "Reinhard Walter Buchner" <rw.buchner-at-verbund-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Thu, 08 Jul 1999 07:40:47 -0600
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Hi Malcom,

> Original Poster: "Malcolm Watts" <malcolm.watts-at-wnp.ac.nz>
> Perhaps a note of caution might be in order if you consider packing
> caps in like this:

> > Original Poster: wwl-at-netcomuk.co.uk (Mike Harrison)
> > radial. Radials in nice rectangular cases might be easier as you can
> > stack them on their backs, maybe glue together or sit them in a
> > 'tray', and solder the pins together, making a nice rectangular
>> block shape. No need for a PC board

> Apart from thermal considerations it might pay to watch the case
> insulation ratings.

I think thermal considerations are MORE of a problem, than
the insulation ratings. Here is a pictorial of an MMC (as
always, use a fixed font to view):

B ABCDEFGH B 1
B ABCDEFGH B 2
B ABCDEFGH B 3
B ABCDEFGH B 4
B ABCDEFGH B 5

B are the bus connectors
A is the first cap in each string
B is the second cap in each string
C-H likewise
# is the string number

For my comments, we will assume that the voltage is
distributed equally among the caps. So, there is no
voltage difference among the A-H colums (not rows!).
The voltage across A(1) is the same as across A(5).
So you don´t need to worry about the insulation from
string to string (for each single cap) as long as you
don´t stagger the caps. The voltage difference from
A(x) to B(x) (the caps next to each other) is also zero
as they are directly connected, so the insulation will
not be overstressed here, either. There will be a
voltage difference between (for example) A(x) and
C(x). In the demo case, this will be applied volts (V)
divided by 8. The only voltage increase (in respect
to ground, tho), that I can see, which *might* be a
problem is the continiual increase from from the bus
connection on the left side going (along the caps) to the
right. In other words, cap A is 1/8 the total voltage above
ground, cap D is 4/8 (or 50%) of the total voltage above
ground and so on for the rest of the string. However, this
is a problem you have to deal with in ANY capacitor
setup. So, as I don´t think I´m telling you anything new,
what exactly do you mean by "case insulation ratings",
Malcom?

a bit puzzled in germany,
Reinhard