Re: did this fuse blow funny?

On Wed, 27 Jun 2007 16:59:07 GMT, Eeyore
<rabbitsfriendsandrelations@xxxxxxxxxxx> wrote:



"acannell@xxxxxxx" wrote:

i have a 1 amp , glass, fast blow, 1 1/4" fuse on the hot wire going
into a 65W SMPS. It blew on several units being tested, but its not
clear to me why. And the way the fuse "blew" was strange. Its seems
more like it "broke" off at the "weld" inside one of the metal cups.
You cant see where the fuse blew, but if you shake the fuse the
element bounces oscillates inside like a tuning fork. Its still
connected to one of the metal cups inside. Anyone ever see something
like this? There is no blackening of the glass or any other indication
the fuse blew.
And its not clear why a 1A fuse would blow on a power supply whos max
input current is supposed to be 72W. (60A inrush)

60A inrush and you're surprised it blew ?

I'm sure it should be a slow blow. Who specced the fuse ? Is it mounted in / on
the PSU itself ?
http://www.astecpower.com/products/datasheets/lp/lps50-M.pdf

It's not is it ? Was it your idea to use a fast blow fuse ?

I note also, on the board layout, that the printed fuse rating is
"T3.15A". This is a slow-blow 3.15A fuse. I expect that's a mistake of
some kind or another. It certainly shouldn't produce nuisance
tripping, if used.

2.5A also shows up in the neighbourhood. This kind of ambiguity in a
fuse label would make certification a pain.

I think you really need to examine the actual product in hand and get
a copy of the test files for the model in question.

RL
.

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