The circuit breaker is an essential component of your electrical installation. It is located in the electrical panel, upstream of your installation's electrical system. It is a device that primarily cuts off the electricity supply to protect circuits and electrical appliances from short circuits or overcurrent. A circuit breaker is essential in every electrical circuit because it protects not only the equipment but also the people in the area where the electrical circuit is located.
A circuit breaker works in a similar way to a switch. The main difference between these two electrical protection devices is that circuit breakers are designed to trip automatically.
When one of your circuit breakers detects a fault in your electrical circuit, it will ‘cut off the power’ to that circuit. You will then need to reset the circuit breaker to restore the electricity after detecting and eliminating the current leak.
What are the different types of circuit breakers?
In a conventional electrical installation, the main circuit breaker protects your home's electricity meter. It protects it in the event of overloads or short circuits. Other types of circuit breakers are also present in the electrical circuit:
- Branch circuit breakers: these are present in each area of your home.
- Residual current circuit breakers: protect people who come into contact with metal parts that are accidentally live.
More generally, there are two main types of circuit breakers: mechanical circuit breakers and electronic circuit breakers. The difference lies in the technology used to measure the current.
- Mechanical circuit breaker
A mechanical circuit breaker consists of several components:
- Magnetic detection coil (short circuit)
- Label holder
- Retractable tab
- Breaking chamber
- Neutral contacts
- Phase contacts
- Thermal detection bimetal strip (overload)
- Rail mounting clip
The current measurement for thermal protection (overload) is performed by the bimetal. This bimetal is sized to withstand a nominal current. The bimetal works in a simple way: as its name suggests, it consists of two blades made of different materials that expand at different rates depending on the temperature of the material. At nominal operating conditions, the two blades are of similar size. When the product heats up, one of the blades (at the bottom) expands while the other does not, causing the blade to round off and break contact.
Therefore, to generate different curves, different alloys are used.
The second important element of this device is the combination of a magnetic detection coil and a cut-off chamber.
Magnetic detection: current is passed through the circuit breaker in the form of a coil surrounding a fixed magnetic circuit. There is a moving part that opens when the current is sufficient. The coil generates a strong magnetic field that attracts the moving part. This is drawn towards the cut-off chamber (metal element).
When a strong current appears between two distant metal elements, an arc is created. The resistivity of the air is much higher than that of the conductive product, so the arc will be attracted to the path of least resistance. As the arc rises in the breaking chamber, it will encounter and split into smaller arcs. The more it splits, the lower its voltage and the less it can maintain itself. After several splits, it will extinguish.
- The electronic circuit breaker
The electronic circuit breaker retains the base of the breaking chamber, but everything else is done by electronic measurements and cards. This allows for more complex processing and thus closer to the operation of the installation (it is currently found on power distribution circuit breakers).
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