1. The voltage imbalance of three-phase power supply is large.

　　2. The stator winding has a serious inter-turn short circuit fault.

　　3. The bearing quality does not meet the requirements, or there are problems in bearing assembly, causing the coaxiality between the bearing and the bearing chamber does not meet the requirements.

　　4. Due to mechanical processing, the coaxiality of the bearing chamber and the stop of the machine base does not meet the requirements, or the coaxiality of the shaft bearing block and the outer circle of the rotor iron core does not meet the requirements.

　　5. The inherent vibration frequency of the whole mechanical structure of the motor is just consistent with the vibration frequency generated by the power operation, resulting in the resonance of the whole machine. This problem can sometimes occur in a frequency band when the converter is used to supply power.

　　6. The diameter of the bearing chamber is too large or too small, or there is a large taper.

　　7. The bearing at the movable end is not in the correct position of the bearing in the axial direction, or even "stuck" because the bearing cap and stop are higher than the design value, or the bearing chamber depth is not up to the requirements, and the distance between the shaft bearing blocks is large or small.

　　8. The placed corrugated spring is more or less, or the spring force is too large or too small, making the bearing at the movable end unable to move or move too much.

　　9. The rotor unbalance measurement exceeds the allowable value or the "horseshoe" phenomenon of iron core is more serious.

　　10. Uneven rotor air gap.

　　11. Axial alignment of rotor core is not aligned.

　　The rotor core is detached from the shaft. At this point, a large abnormal sound will be emitted, and at the same time, the rotation speed is low.

　　13. The rotor guide has serious slits or broken bars.

　　14. For the wound rotor motor, the rotor winding has a fault of phase break or near phase break (the reason may be that the brush is not in contact with the collector ring or broken line; The rotor outlet line is disconnected; The end of the rotor winding and the head cover off; Poor connection between collector and slip ring, etc. The fault cause is determined by measuring the dc resistance of the rotor circuit.

　　15. For the wound rotor motor, the rotor winding has severe turn-to-interphase short circuit fault. The fault cause is determined by measuring the dc resistance of the rotor circuit.

　　16. The rotor rotation is hindered due to the action of foreign body.

　　Key words: three-phase asynchronous motor, vibration

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