Re: Richie - Garry's MMC cap failure explained.

["Tesla list" <tesla-at-xxxxxxxxxx>]

Original poster: Terry Fritz <twftesla-at-uswest-dot-net>

Hi Jon,

At 08:31 PM 12/2/2000 -0800, you wrote:
>
>Subject: Richie - Garry's MMC cap failure explained.
>
>
>> Original poster: Terry Fritz <twftesla-at-uswest-dot-net>
>>
>> Hi Richie,
>>
>> You may have hit on the exact problem.  These caps have ALL vacuum
>> deposited metal film layers.  There is no solid metal foil in them.  This
>> seems to be causing two problems.  The metal film does not seem to attach
>> to the end caps well.  The caps that are getting hot on only one side have
>> the foil breaking up at the end cap attachment.  This picture shows the
>end
>> cap area of a cap that had a "hot side".
>>
>
><snip>
>
>Geez Terry, the photos of those caps look just like my GE42l series caps,
>(0.22uf at 2kV). You remember, I sent  you one to test?
>I also had the same problem, (overheating at the end connection). I had to
>wire 30 of them in series to keep them happy.
>
>Jon

Your caps (I have it right here) have true metal foil electrodes.  However
the high currents that the end wires must take may be causing heating in
the center were this one failed.  At 0.22Uf, they have to take really high
currents that the thin wire leads and attachments may not be able to
withstand.  Perhaps at these higher values, we should be using like IGBT
snubbers that have those heavy straps for leads instead of wires.

Cheers,

	Terry