How does a residual current circuit breaker work?

A residual current circuit breaker works by comparing the electricity entering the appliance with the amount of electricity leaving it. The current going into an appliance should equal the current exiting. If there is a difference, the residual current circuit breaker switches off the appliance.

A residual current circuit breaker, or RCCB, is basically a safety switch for an appliance. This type of circuit breaker is efficient and shuts off the electricity to the appliance faster than a fuse box or a miniature circuit breaker.

1. The current enters the appliance
The current flows into the appliance via the live wire of the power source. It generates a magnetic field around coils of wire within the circuit breaker.
2. The current leaves the appliance
The current leaves the appliance via the neutral wire. This also generates a magnetic field around coils on the neutral wire.
3. An iron pivot measures the attraction
The RCCB has an iron pivot that is equally attracted to both the live and the neutral wires, as long as the magnetic field is equal. If there is more power entering the appliance than exiting, the magnetic force on the live wire side is greater. If there is more power exiting than entering the appliance, the force on the neutral side is greater. If the magnetic force is uneven, the iron pivot is attracted to the side with the greater force. This results in a break in the circuit, which turns off the appliance.