Causes and treatment methods of motor vibration

In industrial production, motors play a crucial role in equipment, providing power for the operation of production equipment. However, in the process of use and testing, the motor will also have some abnormal conditions, especially severe vibration, which will not only damage the equipment, but also greatly increase energy consumption. So what are the reasons for the abnormal vibration of the motor?

Causes of motor vibration

1. Unbalanced rotors, couplings and transmission wheels (brake wheels) can cause motor vibration.

2. Loose iron core support, failure of oblique keys and oblique pins, and weak binding of the rotor will also cause imbalance in the rotating part.

3. The shaft system of the linkage part is misaligned, the center lines do not coincide, and the alignment is incorrect. Failure problems are mainly caused by improper centering and installation during installation.

4. In the cold state, the center lines of the linkage parts coincide. However, after running for a period of time, due to the deformation of the rotor fulcrum and foundation, the center lines are damaged and vibrate.

5. The gears and couplings connected to the motor are faulty, the gears are badly occluded, the teeth are severely worn, the gears are poorly lubricated, the couplings are skewed and misaligned, the tooth shape and pitch of the gear couplings are incorrect, the gap is too large or the wear is serious All will cause certain vibrations.

6. Structural defects of the motor itself, such as elliptical journal, shaft bending, too large or too small gap between the shaft and the bearing bush, insufficient rigidity of the bearing seat, foundation plate, part of the foundation and even the entire motor installation foundation.

7. Installation problems, such as the motor and the base plate are not firmly fixed, the anchor bolts are loose, the bearing seat and the base plate are loose, etc.

8. If the gap between the shaft and the bearing bush is too large or too small, it will not only cause vibration, but also cause abnormal lubrication of the bearing bush and increase in temperature.

9. The load driven by the motor conducts vibration, such as the vibration of the fan or water pump driven by the motor, causing the motor to vibrate.

10. The stator wiring of the AC motor is wrong, the rotor winding of the wound asynchronous motor is short-circuited, the excitation winding of the synchronous motor is short-circuited between turns, the excitation coil of the synchronous motor is connected incorrectly, the rotor bar of the cage-type asynchronous motor is broken, and the deformation of the rotor core causes the stator and rotor gas. The gap is uneven, causing the air gap magnetic flux to be unbalanced and vibrate.

Solution for motor vibration

01. The clearance between the tiles or bearings is too large

If the gap between the tiles is too large, it can be adjusted by reducing the gasket at the tile mouth to keep the gap at the top of the tiles at about one thousandth of the shaft diameter. If there is a gap between the upper tile cover and the tile back at this time, you can add gaskets to tighten it. If the bearing clearance is too large, it can be solved by replacing the bearings.

02. The two ends of the shaft are not concentric

First measure whether the bearing seats at both ends are coaxial and adjust to the same axis. If the shaft is not concentric, it must be machined to ensure concentricity.

03. Insufficient shaft stiffness or unbalanced rotor

If the stiffness of the shaft is found to be insufficient, the shaft should be processed using high-strength materials and replaced to increase the stiffness of the motor shaft. If the rotor is unbalanced, it must be adjusted on a dynamic balancing machine to achieve the level of balancing accuracy.

04. Vibration caused by vibration of working machines

The vibration of the working machine is often transmitted to the motor, so it is necessary to find out the cause and eliminate its impact on the motor. For example, when the fan is unbalanced, vibration will be transmitted to the motor through the coupling.

05. Poor coupling alignment

The working machine is connected to the motor through a coupling. If the alignment is not good, axial vibration will occur. At this time, the pin should be removed, the coupling should be aligned, and the gauge should be set to make the radial runout, end face runout and clearance meet the standard requirements to reduce vibration.

06. The motor base is loose or insufficiently rigid.

When the motor anchor bolts are loose, the vibration damping capacity decreases and the motor vibration increases. Just tighten them. Sometimes because the base is uneven, blindly tightening will deform the motor, changing the running accuracy of the motor and causing vibration, which can be solved by adding shims to adjust. If the base is not rigid enough, you can increase the rigidity of the base by adding reinforcement or replacing the base.

07. The air gap of the motor is uneven

When reinstalling, the air gap of the motor should be adjusted. However, after running, the air gap of the motor will be uneven due to vibration, looseness, discomfort of the stopper and other reasons. At this time, the air gap must be adjusted so that the error is less than 5%.

08. Axial center deviation of stator and rotor

When the axes of the rotor and the stator do not coincide, the changing magnetic field will pull the stator to move back and forth, resulting in axial vibration. At this time, you need to cut the coupling, start the motor, wait until it is stable, then determine the position of the coupling, and then align it according to this position to solve the resulting vibration.