Electrical Equipment Control Circuit Overhaul Methods and Techniques

Electrical Equipment Control Circuit Overhaul Methods and Techniques

Circuit failure, the focus is to identify the point of failure, should not blindly tamper with. Prior to the overhaul, a detailed investigation should be conducted on the occurrence of the failure.

2.1 Look. First of all, based on electrical components such as contactors, time relays, temperature measuring instruments, etc., the principle of its analysis. Look again at whether the contacts are ablated or melted; whether the coils are hot or scorched; if the melt is blown; if the trip unit trips; if the connecting screws are loose. In short, this link is an initial inspection of the system failure, mainly to check some obvious appearance failures.

2.2 ask questions. Ask the operator about the operation of the circuit and equipment before and after the fault occurred, and the phenomenon at the time of the fault. If there is abnormal pyrotechnic and noise, is there any phenomenon such as frequent start-up, braking, forward/reverse, and overload before the fault occurs? Functions, methods of operation, normal phenomena, and failure procedures, and signs of trouble, etc., can often be used to obtain useful information.

2.3 smell the nose. Use an olfactory organ to sense the presence or absence of an electrical component that produces a hot, charred odor, which is useful for determining circuit fault conditions.

2.4 ears to listen. Listen to the circuit when there is no abnormal sound, such as vibration, friction, sound and other sound. In the premise that the circuit equipment can barely operate without expanding the fault, it can be powered on to start operation, listen to whether there is abnormal sound, and if any, the abnormal sound position should be determined as soon as possible and the power should be turned off quickly.

2.5 hand touch. Touch the electrical equipment to see if there is any heating phenomenon and whether the temperature rise is normal, so as to determine the cause of the temperature rise and find the fault point.

Through the preliminary judgment of the sensory sense, the cause of the fault phenomenon is analyzed, and the fault scope is gradually narrowed to determine the location of the faulty component.

3 electrical control equipment failure analysis search - detailed diagnosis

3.1 Find fault points based on the structure and working principle of the electrical equipment. When troubleshooting, you should start with the main circuit under the premise of clear electrical control principle to see if several motors that drag the device are normal, then check the contact system, thermal element, and fuse of the main circuit against the current direction. Whether there is a fault in the isolating switch and the line itself, and then check the control circuit's line connection, self-locking or interlocking contacts and electromagnetic coil according to the control relationship between the main circuit and the control circuit, and check whether the brake device and the transmission mechanism work. The normal range to find the fault site.

3.2 Check the fault range from the control circuit operation program. If the fault point cannot be found in case of a power failure, the electrical equipment can be checked for power. Before the power-on check, the main circuit must be cut off, the motor should be stopped, the controller or switch should be set to zero, the travel switch should be restored to its normal position, and then powered on. Use a multimeter to check if the power supply voltage is normal and there is no missing phase or serious failure. balance. Then, according to the control logic, it is checked step by step whether or not the components perform the required actions.

4 Electrical Equipment Maintenance Tips

4.1 first mechanical, rear electrical. In electrical control circuits, instructions are generally issued by mechanical switches (such as pushbuttons, travel switches, pressure switches, temperature nodes, etc.), followed by electrical control logic, and then by the mechanical mechanism to perform actions if the mechanical parts are interlocking mechanisms, transmissions, and If other parts of the operation fail, the device cannot operate normally even if the circuit is completely normal. Therefore, check whether the input and output of the control circuit are normal.

4.2 external debugging, after the internal processing. During inspection and repair, check whether the external button, limit switch, and status indicator are correct. Verify the normal response of the device under normal operation. If any abnormality occurs, first consider external solution, and then look at the internal control circuit. Under normal circumstances, Try not to open the appliance part of the device.

4.3 first static test, after the dynamic test. Static test refers to testing under the condition of non-energizing: such testing and overhauling usually does not cause the expansion of the fault, and then through the understanding of the equipment and the analysis of the drawings, the fault point is judged by the visual method and the instrument and meter method; and the dynamic Test refers to the test under power-on condition: if the static test cannot identify the fault point, or the operator cannot correctly describe the fault phenomenon of the equipment, the maintenance personnel should energize the equipment in the safe mode, and actively observe and analyze what happened. phenomenon.

4.4 First of all repair common problems, after the incurable diseases. The common faults and common faults of the equipment are high in the probability of faulty equipment. Usually the faults are repaired before the fault occurs. Usually, it is possible to do more with less. If it is found that it is not a common fault, then according to the principle of the equipment, the fault is seen.

5 Electrical Control Equipment Experience Maintenance Method

The commonly used empirical maintenance methods include component replacement method, comparison method, exchange method, circuit tapping method, temperature measurement method, heating method, segmentation method, and the like. For doubtful components, the above method can be used for verification. If the fault persists, it indicates that the fault point is not suspected, and there may be no problem with the component, but if the fault is removed, the circuit part related to the component is faulty and should be confirmed. In the actual maintenance, according to the specific circumstances, choose the appropriate method.

6 Conclusion

In the electrical control circuit, there may be more failures, some obvious, some hidden; some simple, easy to exclude; some complex and difficult to check. When overhauling faults, the above method should be used flexibly to eliminate faults in time to ensure normal production. During the overhaul, we should pay attention to written records, accumulate relevant information, constantly summarize experience and improve repair capabilities. Finding fault points and resolving faults to restore the equipment to normal operation can be said to complete only part of the work, to find out and analyze the cause of the fault, and to prevent the recurrence of similar or related phenomena in future work, which is the true purpose of maintenance.

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