The circuit breakers are magneto-thermal devices for protection of installations and electrical equipment against overload and short circuit. The contacts are made with the use of special alloys based on silver, which guarantees a high security against the bonding of the contacts and a high electrical durability. https://www.mrosupply.com/v-belts/v-belts/a-section/178164_a40_gates-rubber/ The circuit breaker needs to be pointed through some well defined quantities such as: Insulation voltage, nominal voltage, rated current, interruption capacity and type of drive.
They are equipped with a bimetal thermal trigger that acts in overload situations, and with an electromagnetic trigger that operates in the cases of short circuit. Both systems are individually set to correct values for protection of specific loads, such as control circuits, small motors, etc. Some circuit breakers are tripped free, ie if the driver is locked in the “on” position, internally the circuit breaker trips. Because of an ultra-fast cutting device, contact separation takes place in less than 1 ms. The electric arc is greatly reduced by special fire extinguishing chambers where the alternating short-circuit current is discontinued before it passes through zero.