As a key protection device in the electrical system, the correct operation and maintenance of low-voltage circuit breakers are essential. Aiming to help electrical engineers and technicians diagnose and handle associated problems more efficiently, this article will go in depth on the typical reasons why circuit breakers cannot be closed and their solutions as well as the judgment and processing of “refusal to close” errors.
UEM5Z1 Electronic MCCB Circuit Breaker
1. The circuit breaker cannot be closed, and the reasons why the circuit breaker cannot be closed
①. The undervoltage coil does not work (the voltage is normal) (solution–replace the undervoltage coil);
②. Press the closing button, and the closing coil does not work when it is energized (solution–replace the undervoltage coil);
③. The closing button has poor contact (solution: replace the closing button);
④. Burn out of the control circuit fuse; test that the control circuit is normal and there is no short circuit; then, replace the fuse; ⑤. The circuit breaker does not store energy; thus, be sure the voltage of the motor control power supply is ≥ 85%).
⑥. The closing electromagnet control power supply voltage is less than 85% (solution–the closing electromagnet power supply voltage must be ≥ 85%);
⑦. The closing electromagnet is damaged; replace the closing electromagnet;
⑧. The secondary circuit of the drawer-type circuit breaker has poor contact (solution – shake the drawer-type circuit breaker back to the “on” position. Find out whether the secondary circuit is consistently connected;
⑨. The universal conversion switch is in the stop position (solution – turn the switch to the left power supply or right power supply);
2. Judgment and treatment of “refusal to close” fault
The “refusal to close” problem arises essentially throughout the reclining process and closing operation. This kind of flaw is more damaging. For instance, if the backup power supply circuit breaker fails to close, the accident will be expanded even if the backup power supply is needed to be rapidly used in an accident. The reason for judging the circuit breaker “refusal to close” and the treatment method can generally be divided into three steps.
① Check whether the previous refusal to close was caused by improper operation (such as releasing the control switch too quickly, etc.), and close it again with the control switch.
② If the closing is still unsuccessful, check the conditions of various parts of the electrical circuit to determine whether the electrical circuit is faulty. Turn the control switch to the “closing” position to find whether the closing iron core runs normally. The inspection items are: whether the closing control power supply is normal; whether the closing control circuit fuse and the closing contactor are in good condition; whether the contact of the closing contactor is normal.
③ If the electrical circuit is normal and the circuit breaker still cannot close, it means that there is a mechanical failure. Stalled the circuit breaker and let the dispatcher know for maintenance’s purposes.
Following the aforesaid initial assessment helps one ascertain whether mechanical or electrical breakdown is the cause. Common mechanical and electrical circuit problems are detailed here.
2.1 Typical electrical problems
Should the red and green lights not be on prior to the closing operation, the control circuit is either disconnected or lacks control power supply. Whether the operating voltage is normal, whether the fuse is blown, whether the anti-trip relay is normal, whether the auxiliary contact of the circuit breaker is in good contact, etc., you can find whether the supply of control power and the components on the complete control circuit are normal.
When the green light flashes after the operation is closed, but the red light is not on, the instrument has no indication, the horn sounds, and the circuit breaker mechanical opening and closing position indicator is still in the opening position, it means that the position of the operating handle does not correspond to the position of the circuit breaker, and the circuit breaker is not closed. The typical causes are improper contact; the closing contactor does not work; the closing coil fails; the closing circuit fuse blows.
When the circuit breaker is closed, the green light goes out, the red light is bright for a moment and then goes out, the green light flashes again and the horn sounds, indicating that the circuit breaker automatically trips after closing. The explanation may be that the circuit breaker is closed on the fault line, therefore the protection action trips or the mechanical failure of the circuit breaker cannot keep the circuit breaker in the closed position.
Should the green light flash or go out following the closure of the operation, the red light is not on; rather, the meter indicates that the mechanical opening and closing position indicator is in the closed state, therefore closing the circuit breaker. The possible reason is that the auxiliary contacts of the circuit breaker are in poor contact, such as the normally closed contacts are not disconnected, the normally open contacts are not closed, causing the green light to flash and the red light to not light up; it may also be that the closing circuit is broken or the closing red light is
2.2 Frequent mechanical flaws
① The transmission mechanism connecting rod is loose and falls off.
② The closing iron core is stuck.
③ The mechanism does not return to the pre-closing position after the circuit breaker is opened.
④ The tripping mechanism is tripped.
⑤ The closing electromagnet action voltage is too high, so that the hook cannot be hung.
⑥ The opening connecting rod has not returned.
⑦ The mechanism is stuck, and the shaft pin of the connecting part falls off, causing the mechanism to close empty.
⑧ Sometimes the circuit breaker performs multiple opening and closing actions continuously when closing. At this time, the auxiliary normally closed contacts of the switch are opened too early.
UEM5Z1 Electronic MCCB Circuit Breaker
Starting with both mechanical and electrical elements, methodically examining the reasons the circuit breaker cannot close helps to diagnose and address the issue more successfully. The failure of any link— mechanical linkage and electromagnet, operational mechanism, control power supply, or mechanical linkage and electromagnet—may compromise the circuit breaker’s usual operation. Thus, the key to guarantee the safe and steady running of the electrical system is regular inspection and maintenance as well as prompt treatment of failures.
Post time: 7 月-18-2024