[amluto]

IIUC the fuse is an electrically triggered explosive device. Badass, huh?

What's going on is that the current drawn while flooring a ludicrous vehicle is a largish fraction of the current that should cause an instantaneous fuse blow. A fuse that melts at a given temperature and heats up as I^2 R wasn't going to cut it. In the electrical distribution industry, you'd get a fancy circuit breaker with an electrical trip device and call it a day. This has two issues for Tesla. First, your average electrical trip device uses a current transformer, and those don't work for DC. Second, DC current is considerably harder to interrupt than AC, and the current the fuse needs to carry is in the kA range (I have no idea what the short circuit current is), so a circuit breaker would be rather large. Hence a fuse, with a little explosive inside, with an active circuit, presumably using a Hall effect sensor, the voltage drop across the fuse, or maybe just a reed switch.

(Hmm. It's nice when fuses and such don't need external power. I wonder if there's sufficient voltage drop across the fuse during a fault to power the circuit that blows the fuse? I bet there is. It could even be a very simple circuit like a Zener diode in series with a resistive heater that sets off the explosive.)

[tyingq]

Explosives in high current fuses is interesting, but not new or specific to Tesla. https://youtu.be/yTdngnsyNSE

[amluto]

I think that's the other way around. The fuses in that video trigger a tiny exclusive as a side effect of blowing. IIUC Tesla'a fuse blows because an explosive is triggered.