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From: roy@alanine.phri.nyu.edu (Roy Smith)
Newsgroups: sci.electronics
Subject: Can fuses get "worn out"?
Message-ID: <1990Dec14.171020.3615@phri.nyu.edu>
Date: 14 Dec 90 17:10:20 GMT
Sender: news@phri.nyu.edu (News System)
Organization: Public Health Research Institute, New York City
Lines: 19


	We had an air conditioning failure in our machine room a couple of
weeks ago.  Turned out to be the 1/3 HP induction motor in the blower had
died.  Seemed like some sort of internal short, since it just sort of hummed
but didn't turn, even with no load on it, and got *real* hot.  Anyway, they
replaced the motor, and yesterday, one of the 15A cartridge fuses protecting
it blew.  We replaced the fuse and the A/C came back on, but we're worried
that there is more to it that just a chance fuse failure.

	The motor only draws about 6A (yes, I know about startup surges), so
I think the fuses are the right size.  My current theory is that when the
previous motor died, it wasn't quite drawing enough current to blow the
fuse, but "damaged" it enough that two weeks later a normal startup surge
was enough to blow it completely.  Is this possible?  Do fuses act that way?
--
Roy Smith, Public Health Research Institute
455 First Avenue, New York, NY 10016
roy@alanine.phri.nyu.edu -OR- {att,cmcl2,rutgers,hombre}!phri!roy
"Arcane?  Did you say arcane?  It wouldn't be Unix if it wasn't arcane!"