A fuse is an electrical safety device that has the capability to protect an electric circuit from excessive electric current. Fuses are destroyed during overload conditions, whereas circuit breakers are often used instead because they are not destroyed during overload conditions. It's cheaper to install fuses than circuit breakers, but since fuses need to be replaced and circuit breakers don't, fuses have a higher operational cost.
Houses have fuses in fuseboxes (see figure 1). Here are some helpful household tips for homes with a fuse box.
Fuses are designed to allow current through the circuit, but in the event that the current exceeds some maximum value it will burn out the wire, so that there is no longer a circuit. The current that will cause a fuse to blow is called the current rating. Fuses also have a voltage rating; this is the maximum voltage difference that the fuse can block. Once a circuit is open (broken), an applied voltage exists at the ends of the fuse, and if this voltage exceeds the voltage rating of the fuse, the air in the fuse may ionize and start conducting again, therefore leaving the circuit without a safety system.
Fuses are housed in fuse boxes (see figure 1) and listed in the table below.
|Cartridge||Contains a thin conductor designed to melt at a low temperature. Once the current reaches a level that can generate enough heat to match or surpass the designed melting point, the connection will break.|
|Blade||Contains two electrical connectors that plug into a circuit and a wire inside that will melt at a certain current.|
|Plug||Screwed directly into a standard fuse socket. To learn more about this type of fuse please see EPB.|
|Adapter||Referred to as a rejection base (also called type-S), it requires an adapter to fit into a standard fuse socket. Once it is installed it cannot be removed. Fuses with different current ratings will have different threads; therefore, they cannot be replaced with a fuse of a different current rating. To learn more about this type of fuse please see EPB.|
There are special fuses which handle short periods of overloads by deliberately reacting slowly, called time delay fuses. They can normally be found in a household microwave, which produces a current surge when it is turned on. See here to learn more about time delay fuses.
For further information please see the related pages below: