Working Principle Of Molded Case Circuit Breaker

The main contacts of the low-voltage circuit breaker are closed manually or electrically. After the main contacts are closed, the free tripping 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 a short circuit or severe overload occurs in the circuit, the armature of the overcurrent release is energized, causing the free tripping mechanism to operate, and the main contacts to disconnect the main circuit.
When the circuit is overloaded, the thermal element of the thermal release heats up and bends the bimetallic strip, pushing the free tripping mechanism to operate, and the main contacts to disconnect the main circuit.
When the circuit is undervoltage, the armature of the undervoltage release is released, which also activates the free tripping mechanism, and the main contacts disconnect the main circuit.
When the shunt release button is pressed, the armature of the shunt release is energized, causing the free tripping mechanism to operate, and the main contacts to disconnect the main circuit