In the event of a short circuit, the main difference between a circuit breaker and a fuse is that a circuit breaker can be reset (either manually or automatically). It is designed to operate without suffering any damage. Thanks to its evolving and varied technology, circuit breakers can be adapted to specific situations. On the other hand, if a fuse blows, your only option is to replace it completely.
What is a fuse?
A fuse is a technology that works based on the Joule effect. It contains a filament that melts at a specific temperature depending on the material used. Its cross-section gives the fuse a characteristic linked to the Joule effect: I²t.
As previously mentioned, the filament will melt at a given temperature, and therefore the melting current can vary depending on the ambient temperature.
The body of the fuse (surrounding the filament) contains different elements depending on its technology: silica powder, air, etc. Depending on the technology used and the size of the fuse, it can prevent a very large current from passing through via an electric arc (short circuit) between its two terminals.
Different filament materials produce different types of fusion.
Example: 'aM' for motors and 'gG' or 'gF' for standard applications.
If a fault occurs on a single fuse in a three-phase circuit, the other phases remain connected. It's also worth noting that fuses are now prohibited in new installations in the domestic and residential sectors.
What is a circuit breaker?
A circuit breaker is an electromechanical or electronic protective device. Its function is to interrupt the electric current when an incident occurs in an electrical circuit. It is capable of interrupting overcurrents.
Overcurrents are categorized into overloads and short circuits:
- An overload is an increase relative to the normal operating current, which causes conductors and devices on the line to overheat and can eventually cause a fire.
- A short circuit is a significant increase in current due to contact between a phase and neutral, or between two phases.
Depending on its design, a circuit breaker can monitor one or more parameters of an electrical line.
It consists of:
- A magnetic part that provides protection against short circuits via the switching chamber.
- A thermal part that provides protection against overloads via a bimetallic element or an electronic component.
The different types of circuit breakers
- The magneto-thermal circuit breaker provides protection against both short circuits and overloads.
- The magnetic circuit breaker only protects against short circuits.
- Thermal protection (thermal relay) only provides protection against overloads.
