Molded case circuit breakers(MCCB) can automatically cut off the current after the current exceeds the trip setting. Molded case refers to the use of plastic insulators as the outer shell of the device to isolate the conductors and the grounded metal parts. Commonly used rated currents are as follows: 16, 25, 30, 40, 50, 63, 80, 100, 125, 160, 200, 225, 250, 315, 350, 400, 500, 630A.
Working principle:
The main contacts of the 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 attracted, 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 contact disconnects the main circuit.
When the circuit is undervoltage, the armature of the undervoltage release is released, which also activates the free tripping mechanism and disconnects the main circuit.
When the shunt release button is pressed, the armature of the shunt release is attracted, the free tripping mechanism is activated, and the main contact disconnects the main circuit.
Post time: Jul-26-2024
