A fuse is an electrical safety device that operates based on the Joule effect. When an electrical current passes through a wire, it generates heat with a power dissipation that is directly proportional to the square of the current (I²).
The fuse contains a specialized filament designed to melt at a specific temperature, which depends on the material properties, cross-sectional area, and a critical characteristic known as I²t. This melting point can vary slightly depending on the ambient temperature surrounding the fuse.
The body of the fuse, which encases the filament, contains different materials such as silica powder or air, depending on its specific technology. Depending on the design and size, the fuse can effectively prevent a large current from creating an electric arc between its terminals during a short circuit.
In essence, a fuse protects electrical circuits against overloads and short circuits, similar to a circuit breaker. However, there are several important distinctions to note:
- Unlike a circuit breaker, a fuse cannot be reset once it has blown
- In a three-phase circuit, a fault in a single fuse does not necessarily cut off the other phases
- Fuses are no longer authorized in new domestic electrical installations
- Fuses are more compact compared to circuit breakers with equivalent breaking capacity
When selecting a fuse, you need to consider:
- The current rating (calibre)
- The physical size of the fuse or fuse holder
- The type of fuse: fast-acting, time-delay, conventional (Gg), or motor (Am)
If you currently have fuses in your home, there's no immediate need for concern or replacement.
