Re: High Voltage but Low Current fuses...

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "David Speck by way of Terry Fritz <teslalist-at-qwest-dot-net>" <dave-at-davidspeckmd-dot-org>

Chris,
Actually, most standard fuses do fail with time, even when operated within 
their specified ratings.  There are microscopic cracks and inhomogenieties 
in the fuse bar which get locally hotter than the rest of the material, 
thus further propagating the defect.  Eventually, the defect lowers the 
functional rating of the fuse, and the fuse blows, frequently with the 
turn-on current rush, or just during normal operation.  That's one reason 
that critical equipment usually has a spare fuse in a holder right next to 
the working one.
Dave


>I would think that would work here, too, only with pen springs or 
>similar.  But that's probably more complex than a simple weight.  The 
>weight mustn't be too large or it could promote a premature failure over 
>time - copper creeps when hot.