Analysis and method of abnormal operation of electromechanical equipment installation test--《华强电子网

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During the trial operation of the installation and commissioning of electromechanical equipment, it is necessary to conduct an in-depth analysis of the faults occurring in the electromechanical equipment, quickly eliminate the faults, and ensure the normal operation of the mechanical equipment. This paper focuses on some abnormal phenomena that occur during the trial operation of electromechanical equipment installation, analyzes the reasons for the failure of the electromechanical equipment startup process, and puts forward some suggestions on how to solve these problems.
In line with the guarantee of the quality of the project, we usually start and debug the motor and the mechanical equipment it carries after the installation and construction of the engineering electromechanical equipment is completed. When commissioning and running, it is necessary for the construction unit personnel to perform regular operation on the equipment, and carry out long-term work trial operation according to the conditions and requirements of formal production or formal use. Only in this way can we better test the design of the equipment, further verify the quality of manufacturing and installation and commissioning, and verify the reliability of continuous operation of electromechanical equipment, so that users will have a good explanation for future users. However, in the process of commissioning the installation of electromechanical equipment, various problems often occur. We must understand it in advance, do a good job of prevention, and strive to deal with various anomalies in time to ensure the normal operation of the equipment. Operation. 1. Inspection during motor test operation 1.1 Before starting the motor, carefully check whether the insulation resistance is qualified, check whether the secondary circuit wiring is correct, and the inside of the motor should be dry, clean and free of debris. Observe whether the fastening bolt of the motor is loose, whether the bearing is short of oil, and whether the gap between the stator and the rotor is reasonable. Whether the setting values ​​of the fuses, contactors, circuit breakers, thermal relays, etc. are reasonable, and whether the wiring and transmissions meet the motor starting requirements.
1.2 After the motor is turned on, check if there is any abnormality, such as the motor can't start, the start is slow, and an abnormal sound occurs. During the startup process, as soon as an abnormality is found, immediately cut off the power supply shutdown check. Do not stand in the transmission part of the motor or near the sides of the dragging device, so as to prevent the rotating object from flying out and causing injury. The number of consecutive starts of the motor should not exceed 3-5 times to avoid overheating of the starting equipment and the motor.
1.3 During the test run of the motor, pay attention to check whether the rotation of the motor is flexible, whether there is noise, whether the rotation direction is correct, whether the power supply voltage is normal, and whether the current exceeds the rated current; check the motor casing with the electroscope to see if there is any leakage and Poor grounding; check whether the equipment driven by the motor is working abnormally; if there is any abnormality, stop it immediately and check it before operation. 2. Precautions during test run of the motor 2.1 In order to ensure the normal operation of the motor, it is necessary to pay attention to the cleaning of the motor, especially the terminal part of the motor, but the surface of the winding must not be neglected. Under normal circumstances, there should be no water droplets, oil stains and sundries on the surface of the motor. It is not allowed to get debris and water droplets to enter the inside of the motor, otherwise it will leave hidden dangers to the operation of the equipment. Regular maintenance should be carried out when using the motor, and the inside of the motor should be cleaned in time to replace the lubricating oil in time. During the test run of the motor, always pay attention to the air inlet, and there should be no other debris around it to prevent dust or water stains from being sucked into the motor. This can easily cause damage to the wire insulation layer and cause short circuit between turns. This causes an increase in current that causes the motor to burn out. Therefore, in the operation of the motor, it must ensure that it has sufficient insulation resistance, and also to ensure its good ventilation and cooling environment. Only by fully preparing for prevention can the motor be safe and stable during long-term operation, and reach a higher level. Good running effect.
2.2 The problem of motor overload operation is mainly caused by a series of reasons such as excessive drag load, or low voltage or mechanical jamming. If the motor is overloaded for too long, the motor will absorb a large amount of active power from the grid, causing the current to increase sharply, and the temperature of the motor will also rise. When operating at high temperatures, the motor is likely to cause aging failure of the insulation. Causes the motor to burn out. Therefore, during the operation of the motor, always pay attention to check whether the operation of the transmission is flexible and reliable, and whether the concentricity of the coupling meets the standard; and the flexibility of the gear transmission, if any jamming is found, it should be immediately Stop the operation and find out the cause and then continue the operation. 3. Motor trial run common fault analysis Motor common faults can be roughly divided into two categories: mechanical faults and electrical faults. Under normal circumstances, the fault that the staff is relatively easy to observe and discover is a mechanical fault, such as a fault occurring in a bearing, a fan blade, a core, a base, a rotating shaft, etc.; otherwise, a fault that is not easily found is collectively referred to as an electrical fault, such as a stator winding. Faults in conductive parts such as brushes are mainly electrical faults. Therefore, in order to correctly judge the fault of the motor, the motor must be carefully observed, studied and analyzed.
3.1 Vibration must first distinguish between the vibration caused by the motor itself, or the vibration caused by the poor transmission device, or the vibration transmitted from the mechanical load end, and check for specific conditions. The vibration caused by the motor itself is mostly due to the unbalanced rotation of the rotor, as well as the bearing damage, the bending of the shaft, the end cover, the base, the grounding of the motor installation, the installation is not in place, and the fasteners are loose.
3.2 The main reasons for bearing damage are: (1) improper assembly of the bearing, such as striking the inner ring of the bearing to cause the bearing to be worn, and unevenly tapping when the motor end cover is installed, the end cap and the outer ring of the bearing are too loose to run the outer ring. phenomenon. Whether running the inner ring or running the outer ring will cause the bearing temperature rise to rise sharply and burn. (2) Due to the axial misalignment of the stator and rotor core or the lack of precision after re-aligning the rotating shaft, the inner and outer rings of the bearing do not run on a cutting surface, causing the temperature to rise until it burns. (3) Because the temperature rise of the motor body is too high, and the bearing replenishing grease does not cause the bearing to be short of oil or even burned in time, or the bearing of different types of grease is mixed to cause bearing damage.
3.3 Three-phase current unbalance The fault of three-phase current unbalance is often caused by the imbalance of the external power supply voltage of the motor. The internal cause is mainly the short-circuit between turns of the winding or the wrong number of coils or the wiring error when the motor is re-wound repaired.
3.4 Phase loss operation In the three-phase power supply, as long as there is a phase disconnection, the motor will run out of phase. If it is in the stop state, it cannot be started because the combined torque is zero. The starting current of the motor is much larger than the normal operating current. Therefore, in this case, if the power is turned on for a long time or if the power is turned on frequently, the motor will burn out. When the running motor lacks one phase, if the load torque is small, the operation can be maintained, but the rotation speed is slightly decreased, and an abnormal sound is emitted. When the load is too heavy, the running time is too long, and the motor winding will be burnt.
3.5 Winding short circuit or grounding winding short circuit is divided into turn-to-turn circuit and phase-to-phase short circuit. Interphase short circuit is easy to cause fuse to blow. Circuit breaker tripping even affects the upper level switch and cause system failure; turn-to-turn short circuit is damaged due to poor performance of winding enameled wire insulation layer. Therefore, the phase conductors are directly touched, forming a low-impedance current loop, which increases the current between the turns and causes the wire package to heat up. Over time, the entire stator windings are overheated, and eventually the windings are destroyed by the sudden rise in heat. The short circuit between turns is the biggest cause of abnormal rise in motor temperature. The short-circuit fault can be judged by measuring the current under the condition of reducing the power supply voltage of the stator winding, and can also be measured by measuring its DC resistance. The ground fault is mostly caused by the insulation damage of the winding and the water in the motor. Before starting the motor, the first response should be made. The motor insulation is tested and qualified before it can be sent to run. 4. Conclusion With the continuous development of science and technology, electric motors and control equipment are also increasingly sophisticated, and the technical performance of electric motors and control equipment is also increasingly perfect. However, there are always some problems in the actual operation. We also need to accumulate experience in the usual work, find out the cause of the failure and analyze it, and take countermeasures in time. Regardless of the protection device, consider the overload protection device and the motor. The coordination of the overload protection device and the short circuit protection device. The commissioning of electromechanical equipment installation will result in an optimized return on investment, prolong the service life of the equipment, reduce production costs, avoid accidents and technical disasters. Therefore, before starting the motor, it is necessary to do a good job in advance preparation, carefully check the electrical appliances, Secondary circuit wiring, motor and mechanical devices, etc., and to analyze the abnormal phenomena in the test run, timely eliminate mechanical failures, and ensure the normal operation of the motor.