Destruction! Blow Up! Eliminate! These are not pleasant words!
Unfortunately, when it comes to safety we have no other choices. In electrical industry, fuses are destroyed in order to protect lives or property.
Whenever there is a big fault in power lines, possibly caused by short-circuiting, fuses are very helpful to stop flow of current.
Unlike circuit breakers, fuses have no mechanical moving parts that can fail to operate. A fuse is just an electrical link in circuit that can melt very quickly whenever a certain temperature is reached.
Fuses have 4 things to do in a circuit:
1. They must sense faults 2. They must open quickly when a short-circuit occurs 3. They must also sense normal overloaded conditions, but must open if overload becomes excessive or prolonged. 4. They must not change or alter characteristic of current during normal operation.
Early types of fuses use lead wires, selected based on their diameters, connected to terminals. These types have some disadvantages. Whenever a fuse blows, molten metal spatters over equipment and could cause injury to people or cause fires, especially when arc was not confined.
Later, cartridge fuses replaced old lead wire fuses. These consist of non-conducting cylinders which contain soft metal fuse strips. The strips are connected to ends of cylinders by metal caps or ferrules. The entire cartridge fuse is mounted onto a matching fuse block.