Load switch in a circuit breaker - Solutions - Huaqiang Electronic Network

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The circuit breaker is a kind of load switch with short circuit and overload protection function, and its short circuit protection function is realized by electromagnetic coil. Because of its perfect protection function, it is easy to repair and use, and it is widely used in power systems. This paper describes the causes and preventive measures for the breaker closing and closing coils.
The cause of the breaking of the opening coil is that the capacity of the closing power supply is decreased or the wire resistance of the closing control circuit is too large, so that the voltage at both ends of the closing coil of the closing moment is lower than the rated voltage by 80% and burned.
Measures to prevent the closing coil from burning
1. Strengthen the inspection and maintenance of the closing contactor. Every time minor repairs, periodic overhauls, check the surface contact area of ​​the moving and static contacts, contact pressure and so on.
2. Adjust the position of the auxiliary switch.
3. The closing command time issued by the protection control device is sufficient to make the closing coil work and can exit the closing command within the specified time.
4. The operator is required to remove the control circuit fuse before the permit work, and open the reclosing switch circuit to avoid the burning of the closing coil during the inspection and test.
1. Mechanical failure of the opening electromagnet. When the coil is loose, the electromagnet is displaced when the circuit breaker is opened, causing the iron core to jam, causing the coil to burn out; or because the active stroke of the iron core is short, when the power supply of the opening circuit is turned on, the core top does not open the tripping mechanism to make the coil energize for a long time. burn.
2. The circuit breaker refuses to divide. When the control loop is normal, the fault that the circuit breaker appears to be rejected is the linkage mechanism problem. If the apex is improperly adjusted, the force of the circuit breaker opening the iron ejector shall not cause the mechanism to trip in time; or because the protective locking mechanism does not move, resulting in The coil is overloaded, causing the trip coil to burn out.
3. The stroke of the auxiliary switch opening state is not properly adjusted. When the circuit breaker is in the open state, the auxiliary switch should be adjusted to be within the travel range of the open state. However, when adjusting the parameters such as the circuit breaker opening distance and overtravel, the initial state of the circuit breaker opening is not adjusted accordingly, which will cause the auxiliary switch to not normally switch the opening circuit, and the opening coil will be burned.
4. The brake control circuit auxiliary switch contact is improperly used. When the closing time of the circuit breaker is extremely short, which is much smaller than the opening time of the circuit breaker, the circuit breaker will be closed in the future when the tripping is reached. At this time, the delay action of the time delay contact will lose its meaning. On the contrary, in the process of opening the delay contact, due to the small insulation gap of the auxiliary switch dynamic and static contact, the arcing phenomenon often occurs, which will cause the contact of the auxiliary switch to burn, and then the brake coil is burned.
5. Protection control device failure. The opening command is issued by the protection control device. If the opening relay in the device is faulty, or the opening of the auxiliary control switch of the opening control circuit is large, the opening command cannot be exited in time, and the opening coil will be long. Time is charged and burned.
6. The circuit of the opening circuit is too large. The insulation of the opening coil circuit is reduced, or the control circuit has a small wire diameter, which causes the resistance to be too large, so that the voltage drop of the opening control circuit is large, and the voltage does not reach the value of the opening action of the coil, so that the opening coil is charged and burned for a long time. .
Measures to prevent the brake coil from being burnt
1. Change the delay moving contact of the opening circuit to a pair of moving contacts. Check the contact of the auxiliary switch and the arm screw of the auxiliary switch frequently, and adjust the position of the auxiliary switch correctly to make the auxiliary switch and open circuit. The device is closed and the position is correctly and effectively matched.
2. Fix the opening coil and check the iron core of the opening coil frequently.
3. The time of the opening command issued by the protection control device must be able to make the opening coil work, and it must be able to exit the opening command in a short time.
4. In the annual maintenance work, the linkage mechanism of the circuit breaker should be properly adjusted, and it is often checked whether the free tripping of the circuit breaker is normal. Whether it can be reliable between 30% and 65% of the rated voltage during the low voltage operation test. Tripped.
The cause of the closing coil burnout
1. The breaker mechanism is faulty. When the circuit breaker closing control circuit is normal, the inner conductive rod and the transmission link of the circuit breaker body are stuck, or the connection of the circuit breaker operating mechanism is not good, and the apex is biased due to the non-action of the protective locking interlocking mechanism. High, causing the circuit breaker to refuse to close, causing the closing core to overload, causing the closing coil to burn.
2. The position of the auxiliary switch stroke is improper. When the switch is normally closed, the coil circuit of the closing contactor of the circuit breaker is connected in series with the breaking delay contact of the auxiliary switch. After closing, the auxiliary switch contact automatically cuts off the closing circuit, the auxiliary contact can not be opened or pulled, and the closing contactor is self-maintained through the reclosing circuit or the green light circuit, and the closing coil is charged and burned for a long time.
3. Protection control device failure. The closing command is issued by the protection control device. If the closing relay in the protection device fails, or the closing stroke of the auxiliary control switch of the closing control circuit is long, causing the closing command to fail to exit in time, the closing coil will be closed. Burned for a long time with electricity.
4. The closing contactor is faulty. When the circuit breaker is closed, the control circuit cannot directly control the closing coil because the closing current is relatively large. The closing coil can only be indirectly connected by the closing contactor. Therefore, when the closing contactor fails, it cannot be disconnected in time. Make the closing coil energized for too long and burn the coil. In addition, the coil resistance of the closing contactor becomes large, which causes the closing force of the closing contactor to be insufficient when the current is energized normally, and the main contact generates a pulling arc, and the contact resistance of the main contact of the closing contactor increases, indirectly affecting the circuit breaker. The excitation current of the closing coil causes the energizing force of the closing coil to be insufficient, the iron core cannot operate normally, and the closing coil is overloaded and burned.