The pyrotechnic fuse (pyrofuse) is the main high voltage fuse in EVs. Unlike a normal fuse that opens the circuit on its own when it burns up, the pyrofuse is directly controlled by the cars computer. When the computer determines the circuit needs to be broken, it triggers a small explosive charge that breaks open the busbar inside the fuse. (Blown pyrofuse from a Model 3. You can see the center section has been blown open.) There are other styles but the new Tesla ones are the most simple.