Re: [CAD_CAM_EDM_DRO] Re: Stepper Dissasembly

I keep trying to figure out what would happen if one put a fuse in the
output of a chopper drive.

I'm thinking perhaps it wouldn't accompish anything, because the fuse
blows (melts) due to heat, and the chopper would limit the average
current even if it couldn't prevent extremely brief spikes of
extremely large currents when shorted. So I'm thinking the fuse would
not blow.

So the question is, what happens to the power MOSFET? I recall being
told these devices are actually a bunch of tiny MOSFETs on the same
die, and perhaps this makes them delicate (in more than the gate-oxide
sense) so that they get damaged by brief overcurrent spikes that would
not affect a fuse.

Which raises the question of some sort of fast acting 'silicon fuse'.
But at that point, I'm tempted to say, power MOSFETs are actually
pretty cheap, just use them as a fuse and replace them if they blow...

Chris

--
Christopher C. Stratton, stratton@...
Instrument Maker, Horn Player & Engineer
22 Adrian Street, Somerville, MA 02143
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