Reasons for Burnout of Closing Coil of Moulded Case Circuit Breaker
1. Circuit breaker mechanism failure. When the circuit breaker closing control circuit is normal, the circuit breaker body of the conductive rod, drive rods such as jam, or because the circuit breaker operating mechanism is not well connected, and because the protective locking mechanism is not action, the vertex adjusted High, resulting in circuit breaker reflex, so that the closing core overload, causing the closing coil burned.

2. Auxiliary switch stroke position is not appropriate. At normal closing, thethe closing contactor of the circuit breaker is connected in series with the dynamic delay contact of the auxiliary switch. After closing, the auxiliary switch contact automatically cut off the closing circuit, the auxiliary contact can not open or pull the arc, closing contactor through the reclosing circuit or green light circuit to maintain, close the coil for a long time charged and burned.
3. Protection control device failure. The closing command is issued by the protection control device, if the protection device within the closing relay failure, or closing control circuit auxiliary switch contact action travel longer, resulting in closing instructions can not be promptly withdrawn, will make the closing coil Long time charged and burned.

4. Closing contactor failure. When the Molded Case Circuit Breaker is closed, because the closing current is relatively large, the control circuit can not directly control the closing coil, only through the closing contactor indirectly connected to the closing coil, so when the closing contactor failure, can not be disconnected , So that the closing coil power is too long, burn the coil. In addition, the closing contactor coil resistance becomes large, will close the contactor normal power when the suction force is insufficient, the main contact to produce arc, closing contactor contact resistance increases the main contact, indirectly affect the circuit breaker Closing the excitation current of the coil, so that the excitation force of the closing coil is insufficient, the core can not move normally, the closing coil is overloaded and burned.

5. Closing power supply capacity or closing control circuit of the wire resistance is too large, so close the moment the closing coil voltage below 80% of the rated voltage and burned.

Molded Case Circuit Breaker Prevents Closing Coil Burnout
1. To strengthen the closing contactor inspection and maintenance. Each minor repair, overhaul of the cycle to check the dynamic and static contact surface contact area, contact pressure and so on. The same time as the above-
2. Adjust the position of the auxiliary switch. 
3. The protection control device issued by the closing instruction time enough to make the closing coil work, and can be in the specified time to exit the closing instructions. 
4. Require the attendant in the permit before work, you must remove the control circuit fuse, and reclosing switch open circuit to avoid overhaul, the test process caused by closing the coil burned.