Dongguan Langyi Electromechanical Technology Co., Ltd.

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Ten causes, hazards and treatment methods of motor vibration


Guide: The vibration generated by the motor will shorten the insulation of the winding and the bearing life, affecting the normal lubrication of the sliding bearing. The vibration force will promote the expansion of the insulation gap, so that the external dust and moisture will invade it, causing the insulation resistance to decrease and the leakage current to increase, even forming insulation. Puncture and other accidents.


Ten reasons for motor vibration


1. The rotor, coupler, coupling, and transmission wheel (brake wheel) are not balanced.


2. The iron core bracket is loose, the oblique key and the pin are loose, and the rotor is not tied tightly, which will cause the rotating part to be unbalanced.


3. The linkage part of the shaft system is misaligned, the center line does not coincide, and the centering is not correct. The cause of this failure is mainly caused by poor alignment and improper installation during the installation process.


4. The center line of the linkage part is coincident in the cold state, but after running for a period of time, the center line is destroyed due to deformation of the rotor fulcrum and foundation, and vibration is generated.


5. The gears and couplings connected with the motor are faulty, the gears are poorly engaged, the gear teeth are seriously worn, the wheel is poorly lubricated, the coupling is skewed, misaligned, the toothed coupling is toothed, the pitch is wrong, and the clearance is too Large or worn, it will cause a certain amount of vibration.


6. The structure of the motor itself is elliptical, the shaft is elliptical, the shaft is bent, the gap between the shaft and the bearing bush is too large or too small, and the rigidity of the bearing seat, the foundation plate, a certain part of the foundation and even the entire motor installation foundation is insufficient.


7. Installation problem, the fixing between the motor and the base plate is not strong, the foot bolt is loose, and the bearing seat and the base plate are loose.


8. Excessive or too small clearance between the shaft and the bearing bush can not only cause vibration but also cause abnormal lubrication and temperature of the bearing bush.


9. The load transmitted by the motor is transmitted, such as the fan driven by the motor and the vibration of the pump, causing the motor to vibrate.


10. AC motor stator wiring error, winding-type asynchronous motor rotor winding short circuit, synchronous motor excitation winding turn-to-turn short circuit, synchronous motor excitation coil connection error, cage asynchronous motor rotor broken strip, rotor core deformation caused by stator and rotor air gap Both cause the air gap flux to be unbalanced and cause vibration.


Harm of motor vibration


The vibration of the motor will shorten the insulation of the winding and the bearing life, affecting the normal lubrication of the sliding bearing. The vibration force will expand the insulation gap, and the external dust and moisture will invade it, causing the insulation resistance to decrease and the leakage current to increase, even forming insulation breakdown. Waiting for an accident. In addition, the motor generates vibration, and it is easy to cause the cooler water pipe to crack, the welding point to vibrate, and damage to the load machinery, reduce the accuracy of the workpiece, cause fatigue of all mechanical parts subjected to vibration, and loosen the anchor screw. Or disconnected, the motor will cause abnormal wear of the carbon brush and the slip ring, and even severe brushing will burn the collector ring insulation, and the motor will generate a lot of noise. This situation usually occurs in DC motors.


How to find the cause of vibration


In order to eliminate the vibration of the motor, we must first find out the cause of the vibration. Only by finding the cause of the vibration can we take targeted measures to eliminate the vibration of the motor.


1. Before the motor is not stopped, check the vibration of each part with the vibration meter. For the vibration part, test the vibration value in three directions of vertical horizontal axis. If the ground screw is loose or the bearing end cover screw is loose, Directly tighten, measure the vibration size after tightening, observe whether there is elimination or lightening, secondly check whether the three-phase voltage of the power supply is balanced, whether the three-phase fuse is blown, and the single-phase operation of the motor can not only cause vibration, It will also cause the temperature of the motor to rise rapidly, observe whether the current meter pointer swings back and forth, and the current swing phenomenon occurs when the rotor breaks. Finally, check whether the three-phase current of the motor is balanced. If problems are found, contact the operating personnel to stop the motor running in time to avoid burning the motor. damage.


2. If the motor vibration is not solved after the surface phenomenon is processed, continue to disconnect the power supply, uncoupling the coupling, and separate the load connected to the motor. Single-turn motor, if the motor itself does not vibrate, the vibration source If the coupling is not looking for a positive or load machine, if the motor vibrates, it means that the motor itself has a problem. In addition, the power-off method can be used to distinguish whether it is an electrical cause or a mechanical cause. When the power is cut off, the motor will not vibrate immediately. Vibration reduction, it is an electrical cause, otherwise it is a mechanical failure.


Overhaul for the cause of the failure


1. Overhaul of electrical causes:

The first is to determine whether the three-phase DC resistance of the stator is balanced. If it is unbalanced, it means that the welding part of the stator is welded, the winding is separated by phase, and the winding is short-circuited. If the fault is obvious, it can be insulated. The surface is burnt, or the stator winding is measured with an instrument. After confirming the short circuit between turns, the motor winding is re-routed.

For example: pump motor, the motor is not only vibrating, but the temperature of the bearing is also high. The small repair test found that the DC resistance of the motor is unqualified, and the stator winding of the motor has a phenomenon of open welding. After the fault is found by the elimination method, the motor runs normally.


2. Maintenance of mechanical reasons:

Check that the air gap is uniform. If the measured value is exceeded, re-adjust the air gap. Check the bearing, measure the bearing clearance, if it is not qualified to replace the new bearing, check the core deformation and looseness, the loose iron core can be bonded with epoxy resin glue, check the rotating shaft, repair the reaming of the curved shaft or directly straight shaft Then do a balance test on the rotor. During the trial operation of the blower motor overhaul, the motor not only has a large vibration, but also the bearing temperature exceeds the standard. After several days of continuous processing, the fault remains unresolved. When the team members helped to find out, the air gap of the motor was very large, and the level of the tile seat was not qualified. After the fault was found, the motor was successfully tested once after re-adjusting the gaps.


3. The load mechanical part is checked normally:

There is no problem with the motor itself. The cause of the fault is caused by the connecting part. At this time, check the basic level of the motor, the inclination, the strength, whether the center is correct, whether the coupling is damaged, and whether the motor shaft extension meets the requirements,etc.



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