1, room temperature is too high,

2, heat dissipation

3, overload

4, over-voltage under-voltage or imbalance

5, frequent start-stop or frequent and reversing

6, lack of phase

7, the outlet fan is bad or into the wall

8, bearing the lack of oil

9, mechanical jam blocked

10, moment of inertia of the load is too large, the startup time is too long

11, turn-to-turn short circuit

12, new motor internal wiring is wrong

13, star delta

14, star triangle or the step-down start negative load start time is long or not normal transformation because of malfunction

15, motor be affected with damp be affected with damp

Article 16, squirrel-cage asynchronous motor rotor is broken

17, break or wound rotor asynchronous motor rotor winding resistance unbalance

18, rotor bore

19, power harmonic is too big, near a large rectifier devices, for example, high frequency equipment

20 and maintenance of motor core flux decreases for many times

21, some motor winding process

22. The motor temperature generally is unlikely to be bearing problem, unless the bearing temperature is too high.