What is a miniature circuit breaker and its working principle

Miniature circuit breaker, referred to as MCB (Micro Circuit Breaker/ Miniature Circuit Breaker), is the most widely used terminal protection appliance in building electrical terminal power distribution equipment. For single-phase and three-phase short-circuit, overload and overvoltage protection up to 125A, including single-pole 1P, double-pole 2P, three-pole 3P and four-pole 4P.
A circuit breaker refers to a mechanical switching electrical appliance that can make, carry and break current under normal circuit conditions, and can also make, carry and break current for a certain period of time under specified abnormal circuit conditions.
working principle:
Miniature circuit breakers are composed of operating mechanisms, contacts, protection devices (various releases), and arc extinguishing systems. The main contacts are manually operated or electrically opened. After the main contacts are closed, the free trip mechanism locks the main contacts in the closed position. The coil of the overcurrent release and the thermal element of the thermal release are connected in series with the main circuit, and the coil of the undervoltage release is connected in parallel with the power supply. When the circuit is short-circuited or severely overloaded, the armature of the overcurrent release is pulled in, so that the free release mechanism operates, and the main contact disconnects the main circuit. When the circuit is overloaded, the thermal element of the thermal trip unit will heat up, bending the bimetal, thereby pushing the free trip mechanism to act. When the circuit is undervoltage, the armature of the undervoltage release is released. And the free trip mechanism is also actuated.

Post time: Aug-29-2022