Fuses protect important electronic circuits from being oversupplied with power--so much power that the other electronic components can be damaged as a result. A fuse is placed in a circuit and receives the same electric supply the protected circuit receives. If a unexpected surge in power is supplied to the fuse, the fuse element will burn away. This breaks the closed circuit, halting the power from going further to potentially harm other electronic parts. The fuse is how most electronics defend against this type of damage, and the kinds of fuses that are available vary depending on the use. Cartridge-type fuses are common and contain the fuse element within a closed space in the fuse. This type of fuse does not allow the electric current to be diffused outside of the cartridge when active.
Cartridge fuses have been in use for many years. Originally constructed from glass or ceramic, the cartridge contains a wire filament that, when exposed to a large amount of electric current, will burn away, cutting the power supply to the circuit. Glass cartridge fuses are little glass tubes with a metal wire inside capped by two metal ends. The two metal ends fit into a grasping base that the current passes through. Ceramic cartridges were similar, but the filament was encased in ceramic. Modern cartridge fuses are made from plastic and ceramic combinations and contain the filament inside the cartridge housing. For high-voltage applications, there are still ceramic and plastic-type cartridge fuses that can protect against extreme voltage variances, but the most common kind of cartridge fuse is found in automobiles. Look inside the fuse box of any motor vehicle to see scale versions of the different types of fuse cartridges in use today.
It was recognised in the 1800s that electricity could cause damage to parts when applied in high concentrations. The inventors of yesterday looked for the most reliable parts and tools to create the next great electronic tool. Much of the work was in creating enough electric power to run the equipment and how to protect it from too much. When experiments went bad, wires would burn and the circuit would be ruined. It didn't take long for the addition of fuse wires to be included into many important circuits to prevent such damage. The fuse was born, and it quickly became the best way to protect electronic parts from damage. What first started out as a piece of wire that was of a smaller gauge than the rest of the circuit has become a filament acting in the same way encased inside a housing.
A fuse should self-destruct before any large surge of electricity is sent into the rest of the circuit it protects. The right fuse will protect a circuit no matter what amount of power is needed to cause the fuse effect. Fuse filaments can be created in any size or shape. A fuse cartridge can be regulated and used in different circuits using fuses that are rated to protect from the current supplied. When too much power is supplied to a fuse, the filament burns and the circuit is broken.
Using the wrong fuse can harm your electronic circuit. When a fuse that is too large is inserted into a circuit, it can act as a resistor to the power supplied and reduce the normal amount of energy. This lack of power can create a draining effect on parts and eventually lead to damage. A fuse that is too large will also not break the circuit of a voltage that is high enough to harm components but not high enough to burn the fuse filament. A fuse that is rated too low will continually burn out and need to be replaced with the correctly rated fuse.
Cartridge fuses are rated and marked for use in the appropriately powered circuits. Cartridge fuses may be colour-coded or marked with the appropriate rate. Determine the correct size fuse filament for your circuit before inserting a fuse into the system for protection. Cartridge fuses are standardised, and the equipment they are used in can accept any correctly rated and shaped cartridge fuse for electronic security.
Kevin Sullivan, professor of automotive technology at Skyline College, understands the importance of new cartridge fuse technology and teaches this information to his students (see Resources). Automotive cartridge fuses are one of the most common electronic problems an auto owner will face, and knowing the best ways to diagnose and correct an electronic problem in a car is to know which fuses are working and which ones are not.