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What Are The Reasons for Motor Vibration?

Aug. 04, 2021

The reasons for motor vibration are many and complicated. Large pole count motors above 8 poles will not cause vibration due to manufacturing quality problems. So what causes the motor to vibrate abnormally, and how can we repair it? Synchronous Motor Manufacturer tells you how to judge and fix the problems.

 Synchronous 8 to 40 Poles Motors

Harm of motor vibration

The vibration of the motor will shorten the life of the winding insulation and bearing, affect the normal lubrication of the sliding bearing. Look at the 3 Phase Motor, the vibration force will promote the expansion of the insulation gap, so that the external dust and water will invade it, resulting in the reduction of insulation resistance and the increase of leakage current, and even the formation of insulation breakdown and other accidents. In addition, vibration motor, vibration and easy to make the cooler water pipe crack, vibration welding points, at the same time can cause load mechanical damage, reduce the precision of workpiece, can cause all the mechanical parts by vibration fatigue, can make the anchor bolt is loose or broken, motor and can lead to abnormal wear of carbon brush and slip ring, brush can appear even serious fire and burned collector ring insulation, Electric motors will make a lot of noise, as is often the case with DC motors.


Some causes of motor vibration

1. Unbalance of rotor, coupler, coupling and transmission wheel (brake wheel).

2. Loose core support, inclined key, loose pin failure, loose rotor binding is not tight will cause the rotating part of the imbalance.

3. Motor driven load conducts vibration. For example, the vibration of the fan and water pump driven by the motor causes the vibration of the motor.

4. The shaft system of the linkage part is not centered, the center line is not coincident, and the centering is not correct. The main reason for this failure is the installation process, to the bad, improper installation caused.

5. The gear and coupling associated with the motor are faulty, the gear bite is bad, the gear tooth wear is serious, the wheel lubrication is bad, the coupling is skewed, misplaced, the tooth shape of the gear coupling, the tooth pitch is wrong, the clearance is too large or the wear is serious, will cause a certain vibration.

6. Defects of the structure of the motor itself, ellipse of the shaft neck, bending of the rotating shaft, too large or too small gap between the shaft and the bearing bush, and insufficient stiffness of the bearing seat, foundation plate, some part of the foundation and even the entire motor installation foundation.

7. Installation problems, the motor and the foundation plate is not fixed firmly, the bottom bolt is loose, the bearing seat and the foundation plate is loose, etc.

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

9. The clearance between the shaft and the bearing bush is too large or too small. It can not only cause vibration, but also cause abnormal lubrication and temperature of bearing bush.

10. The AC motor stator connection is wrong. Short-circuit of rotor windings of winding asynchronous motor, short-circuit between turns of excitation windings of synchronous motor, incorrect connection of excitation coils of synchronous motor, broken rotor bars of cage asynchronous motor and uneven air gap between stator and rotor caused by deformation of rotor core all lead to imbalance of air gap flux and thus cause vibration.


Low voltage high power squirrel cage motor


Maintenance for the failure

Electrical reasons

First is whether the measured stator three phase dc resistance balance, such as imbalance, explain the stator wire welding parts have open welding phenomenon, disconnect phase winding points to look up, whether there is another winding interturn short circuit phenomenon, such as fault obvious can see from the surface of the insulating sear, or use the instrument measuring the stator winding, after confirm the turn-to-turn short circuit, the motor winding to logoff.

Mechanical reasons

Check if the air gap is even. If the measured value exceeds the standard, readjust the air gap. Check bearings, measure bearing clearance, replace new bearings if unqualified.

Other reasons

When the connection part is wrong, it is necessary to check the basic horizontal plane of the motor, incline, strength, center alignment is correct, whether the coupling is damaged, and whether the motor shaft extension and winding meet the requirements.


Contact ZCL Group to wholesale any kinds of motors you want such as permanent magnet synchronous motor and explosion-proof motors. Our manufacturing plant has a professional technical service team. The team members have professional technical level and rich experience in on-site service of mechanical operation. It can use the professional technical level to deal with various motor faults that occur during the installation, operation and failure of the machine, and can complete the technical service support at a faster speed to ensure the normal production and operation of the user.

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