The circuit breakers are magneto-thermal devices that act in the protection of installations and electric motors against any overload and short circuit that may occur. These devices consist of a thermal trigger, bimetal, that acts in the situations of overload, and with an electromagnetic trigger, that acts in cases of short circuit.
Both systems are individually set to values appropriate for the protection of specific loads, as well as control circuits and small motors. Some types of circuit breakers are tripped free, so if the actuator is activated in the on position, internally the circuit breaker trips, for example.
By means of a very fast cutting device, the separation of the contacts is carried out very quickly. That is, the electric arc will be greatly reduced by special construction fire-extinguishing chambers in which the alternating short-circuit current will be interrupted before it passes through zero.
The contacts are designed with the use of special alloys based on silver, which provides a high security against the collage of the contacts and a high electrical durability. The circuit breaker needs to be specified through some well-defined quantities.