How many second it takes the fast blow fuse to blow?

The time it takes for a fuse to blow, either "fast blow" or "slow blow" is determined by the design of the fuse and is described in a table or graph provided by the manufacturer. In general, the higher the applied overload current, the faster the fuse will blow. Fast blow fuses can open in milliseconds, slow blow fuses can open in several seconds. The fuse used depends entirely on the application and what kind of circuit it is protecting.