1. The room temperature is too high
2. Poor heat dissipation
3. Overload
4. Overvoltage, undervoltage or unbalanced voltage
5. Frequent start and stop or frequent forward and reverse rotation
6, lack of phase 7, the fan is broken or the air inlet and outlet are blocked
8. Bearing lack of oil
9. The machine is stuck and blocked
10. The load moment of inertia is too large and the starting time is too long
11. Short circuit between turns
12. The internal wiring of the new motor is incorrect
3. The star-delta wiring is wrong
14. Star-delta or self-dual step-down start-up load restart time is long or abnormal conversion due to failure
15, the motor is damp
16. Broken bar of squirrel cage asynchronous motor rotor
17. The rotor winding of the wound asynchronous motor is broken or the resistance is unbalanced
18. Rotor sweep
19.The harmonics of the power supply are too large, such as large rectifier equipment, high-frequency equipment, etc. nearby
20. The magnetic flux of the motor core after multiple maintenance is reduced
21. Some motors have poor winding technology
Analysis method of the cause of motor heating failure: When analyzing the motor heating failure, use a non-contact infrared thermometer or the temperature measurement gear of a multimeter (multimeter with temperature measurement), and measure the temperature of the motor end cover when the temperature exceeds the ambient temperature by more than 25 ℃ , Indicating that the temperature rise of the motor has exceeded the normal range, and the temperature rise of the general motor should be below 20°C. The direct cause of the motor heating is due to the large current. The relationship between motor current I, motor input electromotive force E1, motor rotation induced electromotive force (also called back electromotive force) E2, and motor coil resistance R is: I=(E1-E2)÷R, I increases, indicating R becomes smaller or E2 is reduced. The decrease of R is generally caused by a short circuit or an open circuit of the coil. The reduction of E2 is generally caused by the demagnetization of the magnetic steel or by the short circuit or open circuit of the coil.
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