28 Nov
2013
28 Nov
'13
12:10 a.m.
On Nov 27, 2013, at 17:26, John Wilson <wilson at dbit.com> wrote:
Showing my dumbness: how critical are voltage ratings on fuses?
Since the fuse has close to no voltage drop across it, it seems as if
the voltage is really none of its business until it blows, and even then
it just needs to have enough dielectric strength to be sure it really
won't conduct, and I would think any glass tube would be OK up to many
hundreds of volts ... Unless what we're really talking about is the film
of former fuse filament (the F.F.F.F.) that flashed onto the inside of
the tube when the fuse blew. Which seems very fancy.
A fuse voltage rating generally refers to its rated dielectric strength.
Thus a 120v fuse will stave off at least 120v when it's blown.
I've never heard of a 25v fuse, but a 120v fuse should be fine;
what makes the fuse blow is the I^2*R dissipated power.
- Dave