RE: High Voltage but Low Current fuses...Why ? ? ?

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

Original poster: "Mccauley, Daniel H by way of Terry Fritz <teslalist-at-qwest-dot-net>" <daniel.h.mccauley-at-lmco-dot-com>


May sound like a dumb question, but can you explain to me why you would
need a high voltage fuse for tesla coiling?
If your goal is to provide fusing to the output of a pole transformer or
similar, then fusing should be placed on the
input side instead on the 240VAC etc...

Trying to design a fuse (esp. a high voltage one) is a daunting task in
the least.
Contrary to most people's belief, fuses are EXTREMELY complex devices.
Not something you can just take a piece of wire and
make a simple fusible link out of.

The Captain



 > Hi,
 >
 > Apparently, there is a need for a "Tesla coiling fuse".  The
 > mid-voltage
 > fuses and all are not right for "our stuff"...
 >
 > The key is that we do not need to break a "sustained" 4000
 > amps or anything
 > like that.  A say 5 amp continuous AC current, 0.25 amp,
 > 30,000 volt fast
 > blow fuse is what we need.  Not really hard to make, but none
 > of the big
 > guys seem to make a high voltage fuse that is designed to work with
 > "little" currents...
 >
 > We make take a 4000 amp "hit" from a big impulse cap, but
 > then the current
 > falls to like 100mA in our case...
 >
 > I think I got a new project ;-))
 >
 > Cheers,
 >
 >          Terry
 >
 >
 > At 09:43 PM 7/15/2003 -0400, you wrote:
 > >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.
 > >
 >
 >