Method for Analyzing the Vibration Causes of Three Phase Asynchronous Motors

There are many reasons that can cause vibration in three-phase asynchronous motors, but vibration is common in 2-pole, 4-pole, and 6-pole motors. Motors with a large number of poles above 8 poles will not cause vibration due to the quality issues of the motor itself.

The causes of motor vibration can be simply judged from the vibration values in the following three aspects:

1. Large horizontal vibration and unbalanced rotor;

2. Large vertical vibration and uneven installation foundation;

3. Large axial vibration and poor assembly quality of bearings.

The above are just simple judgments, which should be based on the on-site situation and combined with the above factors to find the true cause of motor vibration.

To find the cause of motor vibration, the following methods can be used:

1. Disconnect the motor from the load, test the motor on air, and detect the vibration value.

2. If the vibration of the motor during the air test does not exceed the standard, and the vibration with load exceeds the standard, there are two reasons:

① Significant deviation in alignment;

② The residual imbalance of the rotating components (rotor) of the main engine overlaps with the phase of the residual imbalance of the motor rotor. After docking, the residual imbalance of the entire shaft system at the same position is large, resulting in a large excitation force that causes vibration.

3. Check the vibration value of the motor foot. The vibration value at the foot plate should not exceed 25% of the corresponding position of the bearing. If it exceeds this value, it indicates that the motor foundation is not a rigid foundation.

4. The vibration of only one or two diagonally opposite feet exceeds the standard, and the tightening of the foundation bolts causes deformation and vibration of the machine base.

5. Tighten all four anchor bolts, and the vibration value of the motor still exceeds the standard. At this time, check whether the coupling installed on the shaft extension is flush with the shaft shoulder. If it is uneven, the excitation force generated by the excess keys on the shaft extension will cause the horizontal vibration of the motor to exceed the standard.

6. The vibration speed does not exceed the standard, and the vibration acceleration exceeds the standard. Only the bearings can be replaced.

7. The rotor of a bipolar high-power motor may deform due to poor rigidity, and may vibrate when not in use for a long time. This is the reason for poor storage of the motor.

8. The motor vibration of sliding bearings is related to the assembly quality of bearing pads. It is necessary to check whether the bearing pads have high points, whether the oil inlet of the bearing pads is sufficient, whether the bearing pad tightening force, bearing pad clearance, and magnetic center line are suitable.

9. The vibration of the Y-series box motor should pay special attention to axial vibration. If axial vibration is greater than radial vibration, it poses great harm to the motor bearings and can cause shaft holding accidents.

10. After the rotor is dynamically balanced, the residual imbalance of the rotor has solidified on the rotor and will not change. The vibration of the motor itself will not change with changes in location and working conditions, and vibration problems can be handled well on the user's site.

Zhejiang Jinsu Motor Co., Ltd. is an enterprise that manufactures various types of DC, AC, and three-phase asynchronous motors. The company covers a total area of over 30 acres and currently employs more than 150 employees; Having a modern garden style factory building and introducing excellent and efficient production and testing equipment from both domestic and international sources, we aim to create a sustainable manufacturing enterprise that provides customers with excellent products and services. As a modern enterprise that integrates scientific research, production, sales, and service, we are committed to building a sustainable business.