Maintenance and Maintenance of Three-phase Asynchronous Motor

Maintenance and Maintenance of Three-phase Asynchronous Motor
The motor should be monitored and maintained in operation, so that the working state of the motor can be known in time, abnormal phenomena can be found in time, and accidents can be eliminated in the bud. In the inspection of motors, we should use the methods of seeing, listening, touching, smelling and asking to know whether the motor is in normal operation. Usually, we should inspect the following points:

Look at:
Check whether the grounding protection of the motor is reliable, check whether there are cracks in the motor shell, check whether the foot bolts and end cap bolts of the motor are loose.
Check motor ventilation and environment. The motor and end cover should be kept clean and sanitary, the normal operation of the cooling fan should be guaranteed, the ventilation outlet should be smooth, and the external environment should not affect the normal operation of the motor. External ambient temperature should not exceed 40 C.
Check whether the working current of the motor exceeds the rated current (if there is an ammeter on site).
Listen:
Monitor motor noise for abnormal conditions.
Monitor the abnormal sound of motor bearings.
Touch:
Check whether the motor is overheated or not.
Check whether the motor has abnormal vibration.
Wen:
Check whether the motor emits abnormal odor.
Check whether the motor bearing is volatile oil odor.
Q:
Learn from the operator if there are any abnormal symptoms when the motor is running.
2. Standard for normal operation of three-phase asynchronous motor
1. When the three-phase power supply is balanced, the deviation between any phase of the three-phase current and the average value of the three-phase current should not exceed 10%.
2. When the ambient temperature does not exceed 40 C, the maximum allowable temperature rise of the motor in operation shall conform to the following table:
If the ambient temperature is between 40 and 60 C, the limit of temperature rise specified in the table above shall be subtracted from the value of ambient temperature exceeding 40 C.
3. The vibration value (double amplitude) of the motor in operation shall not be greater than the stipulations in the following table:
The maximum allowable value of radial yaw of motor axle extension shall not be greater than that specified in the following table:
4. The maximum allowable value of radial yaw of motor axle extension shall not be greater than that specified in the following table:
5. Three-phase asynchronous motor can operate continuously at rated power when rated voltage is less than 5%. If the voltage changes more than 5%, the allowable load of motor should be reduced.
When the operating frequency of the three-phase asynchronous motor driven by the converter is lower than the rated frequency, the output voltage of the converter will also be lower than the rated voltage. Pay attention to the code of mind cultivation, and learn Chinese medicine and explosion-proof knowledge. At this time, the output power will be lower than the rated power. Therefore, we should pay special attention to turning on or switching on the pump. Only when the pump can be switched evenly, smoothly and flexibly, can the frequency converter be started, and the given frequency should not be too small (not less than 20%). Otherwise, it may result in the operation of the converter, but the motor does not operate, so it is easy to cause the accident of burning the motor or the converter.
Repair of 3-phase asynchronous motor
1. Troubleshooting of three-phase asynchronous motor
In the daily patrol inspection of three-phase asynchronous motor, if any abnormal phenomena are found, besides corresponding treatment, they should be recorded in time and reported to the relevant leaders in time. Relevant technicians should timely detect the motor with abnormal phenomena, pay attention to the code of cultivating heart and mind, and learn Chinese medicine and explosion-proof knowledge. According to the relevant standards and experience of motor operation, the cause of motor abnormality is correctly judged and dealt with accordingly.
Common faults and treatment methods of three-phase asynchronous motor are as follows:
Click on the picture to zoom in.
2. Maintenance and repair of three-phase asynchronous motor
During the overhaul period, all production Motors should be properly maintained and repaired. The contents of maintenance and repair are as follows:
1) Dismantling and cleaning, inspecting motor windings, rotors, ventilation ditches and wiring boards.
Requirements: There is no obvious ash and oil stain inside the motor, no aging, loosening and discoloration of coils, cores and slots, and no detachment or breakage of cage rotor bars.
Method: Use clean and clean compressed air (no more than 200KPa) or "skin tiger" to clean, but do not break the winding.
2) Measure the insulation resistance of windings and dry them if necessary.
Requirements: The inter-phase resistance and ground insulation resistance of motor stator windings should be no less than 1K per volt.
Method: Remove the Y or delta connector of the motor and measure it with 500V megaohm meter by contacting the outlet head with the base and two different phases of the outlet head respectively.
Usually the measurement results are as follows:
The windings are normal. The measurement results meet the above requirements.
(2) The winding insulation is not good. The insulation resistance of three-phase windings measured by the above method is less than 0.38M, but not zero, indicating that the windings are not well insulated. To clean the drying winding, first blow and clean, then heat and dry with bulbs, electric furnaces, ovens, etc. to restore the insulation resistance to normal.
(3) Grounding of windings. Two of the three-phase grounding resistance measured by the above method have higher insulation resistance, while the other phase has zero insulation resistance, which indicates that the winding is grounded. Sometimes the pointer sways, indicating that the phase insulation has been broken down, but the wire and ground have not yet been secured. If the insulation resistance of this phase is very low but not zero, it indicates that the insulation of this phase has been damaged and there is the possibility of breaking down the grounding.
(4) Winding short circuit. The two-phase insulation resistance of the three-phase winding measured by the above method is zero or close to zero, which indicates the short circuit between the two phases.
The winding is broken. Measuring two ends of the same winding with megaohmmeter indicates that the winding is broken if the pointer reaches infinity.
3) Measuring DC of Winding