MMD (not another acronym!)

• To: tesla@pupman.com
• Subject: MMD (not another acronym!)
• From: "Mike Nolley" <mnolley@mail.slc.edu> (by way of Terry Fritz <twftesla@uswest.net>)
• Date: Tue, 07 Mar 2000 18:49:46 -0700
• Approved: twftesla@uswest.net
• Delivered-To: fixup-tesla@pupman.com@fixme

    As preparation for the diode bulk buy, I have a few questions for the
learned ones about diode failure.  Do hv diodes fail open, or closed?  If they
fail open, then a single-string MMD would not catastrophically fail, if it were
encapsulated--  It would just turn off.  The problem with this is related
to the
encapsulation--the diodes would be hard to replace.  If on the other hand they
fail closed, I think it would be fairly likely that a single-string MMD would
fail quickly, if it were rated close to supply voltage.
    My second question is, how much should the MMD be over-rated--*given* the
use of an R-C network (which I presume any diode-user would need by default).
     Multi-string MMD's seem to be impractical for size reasons, and silly to
boot as the 1kv, 6A diodes would seem to be sufficient for any system under 84
kva ; )
      Thanks for any, and all responses.
                    --Mike

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