Maintenance and upkeep of three-phase asynchronous motors

Preparation and inspection before startup

1. Check whether the grounding of electric and starting equipment is reliable and complete, and whether the wiring is correct and good.

2. Check if the voltage and frequency indicated on the motor nameplate match the power supply voltage and frequency.

3. Before starting a newly installed or long-term disused motor, the insulation resistance of the winding relative to phase and relative to ground should be checked. The insulation group should be greater than 0.5 megaohms. If it is lower than this value, the winding must be dried.

4. The electric brush device on the collector ring of the wound rotor should be checked for normal operation and whether the electric brush pressure meets the requirements.

5. Check whether the motor rotates flexibly and whether the oil in the sliding bearing reaches the specified oil level.

6. Check if the rated current of the fuse used in the motor meets the requirements.

7. Check if all fastening bolts and installation bolts of the motor are tightened. After all the above inspections meet the requirements, the motor can be started. After starting the motor, run it without load for about 30 minutes. Pay attention to whether there are any abnormal phenomena in the motor. If abnormal conditions such as noise, vibration, and heating are found, measures should be taken. Only after the situation is eliminated can it be put into operation. When starting a wound motor, the starting variable resistor should be connected to the rotor circuit. For motors with electric brush lifting mechanisms, the electric brush should be lowered, the short-circuit device should be disconnected, the stator circuit switch should be closed, and the variable resistor should be turned. When the motor approaches the rated speed, lift the electric brush, close the short-circuit device, and the motor starts completely.

maintain

1. Electric motors should be kept clean regularly and no debris is allowed to enter the interior of the motor; The air inlet and outlet must be kept unobstructed.

2. Use instruments to monitor the power supply voltage, frequency, and load current of the motor. The power supply voltage and frequency must comply with the data on the motor nameplate, and the load current of the motor must not exceed the specified value on the nameplate. Otherwise, the cause must be identified, measures taken, and the adverse conditions eliminated before the motor can continue to operate.

3. Take necessary measures to detect the temperature rise of various parts of the motor.

4. For phase wound rotor motors, attention should be paid to the contact pressure, wear, and spark conditions between the brushes and collector rings. When the motor stops running, the switch in the stator circuit should be disconnected, and then the brush lifting mechanism should be turned to the starting position to disconnect the short-circuit device.

5. Regular maintenance of electric motors after operation is generally divided into two types: minor repairs and major repairs. Minor repairs are general maintenance and do not involve major disassembly of the motor starting equipment and the overall system. They occur approximately once a quarter. Major repairs involve disassembling all transmission devices and motor components, and conducting a comprehensive inspection and cleaning of the disassembled parts, typically once a year.