Re: Halloween night, CP cap {con,de}struction

To: tesla-at-pupman-dot-com
Subject: Re: Halloween night, CP cap {con,de}struction
From: Chip Atkinson <chip-at-pupman-dot-com> (by way of Terry Fritz <terryf-at-verinet-dot-com>)
Date: Mon, 02 Nov 1998 22:47:34 -0700
Approved: terryf-at-verinet-dot-com
No, there was nothing indicating anything about the service conditions
except for voltage (20,000).  There was the capacitance and serial number
indicating TC service, and a 10kv container dielectric strength, but
that's it.  

I'm not sure what you mean by failure mode, but I did unwind one of the
bad cells.  It had two spots where things failed.  One area is kind of all
melted together, and as I unwind each layer, I have to pull it apart and
there is material there.  The second spot is a cavity that is hollow.
There is no material here and only the edges are sealed together.  This
cavity is all black from carbonized plastic and oil.  As for the physical
cause such as a pin hole in the dielectric or a piece of dirt on a plate,
I have no idea, nor do I have any idea where to start looking for such a
thing as the evidence has been vaporized.

Chip


<<<< I happen to be a professional failure analysis engineer who has seen
many high power failures (just today! :-)).  Hopefully, I can get some of
the remains from Chip (30 miles away) and determine what the cause of the
failure was.  A group meeting in a few weeks should allow me to see the
horrible remains and determine what went wrong.  From Chip's description,
it sounds like pure over voltage breakdown but the "melted" areas need
personal examination.  Was it instant burning (over voltage) or prolonged
overheating (over dissipation)??  Heating failure is wide spread, starting
in the center and spreading out from the center of the cap pack.  Corona
failure is pronounced at the edges of the plates and other high field
stress areas.  Over voltage is fast and clean (just a boom). - Terry >>>>




=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
 Chip Atkinson 
 http://www.pupman-dot-com 
 --- If I can't fix it, I can fix it so it can't be fixed --
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

On Mon, 2 Nov 1998, Tesla List wrote:

> Original Poster: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz> 
> 
> HI Chip,
> 
> > Original Poster: Chip Atkinson <chip-at-pupman-dot-com> 
> <snip>
> > > Just for the record, CP stated on the outside of my units that they 
> > > are rated for 120BPS max.
> > > 
> > > Malcolm
> > 
> > Interesting.  These caps came from the first batch that Scott Meyers
> > ordered.  I bet that they didn't realize that they had to put that
> > stipulation on them until some other people toasted theirs.
> > 
> > Chip
> 
> Did they not state the break rate on yours? They did on my 
> original units. I believe they also did on their price list and 
> I also heard something to this effect when the purchase was being 
> organized.
>      We also know that they tested them at a rather low break rate 
> which wasn't even close to being representative of static gap 
> operation. I remember Robert Stephens commenting at the time. If they 
> weren't in a TC though that might have been reasonable to a degree as 
> they would have been subjected to lots of reversals.
>      Do you know what the failure mode was yet?
>      
> Malcolm
> 
>