Working principle of molded case circuit breaker

The main contact of the low-voltage circuit breaker is manually operated or electrically closed. After the main contact is closed, the free release mechanism locks the main contact 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, while the coil of the undervoltage release is connected in parallel with the power supply
When a short circuit or severe overload occurs in the circuit, the armature of the overcurrent release will engage, causing the free release mechanism to operate and the main contact to disconnect the main circuit
When the circuit is overloaded, the thermal element of the thermal release device heats up, causing the bimetallic strip to bend, pushing the free release mechanism to operate, and the main contact disconnects the main circuit
When the circuit is under voltage, the armature of the undervoltage release device is released, which also causes the free release mechanism to operate, and the main contact disconnects the main circuit
When the shunt release button is pressed, the shunt release armature is attracted, causing the free release mechanism to operate and the main contact to disconnect the main circuit