When the machine starts running, the current is normal. After a period of time, the current becomes larger. After a long time, the inverter is overloaded. First of all, it is necessary to confirm that the inverter of the air compressor manufacturer is correct, and then confirm whether the parameters in the inverter have been changed. If there is no problem with both, it is necessary to judge by back electromotive force, disconnect the machine head from the motor, perform no-load identification, and run at no-load to the rated frequency. At this time, the output voltage is the back electromotive force, if it is lower than the motor nameplate. The motor can be demagnetized by the back electromotive force of 50V or more.
1. Keep the permanent magnet motor working at rated current
The permanent magnet motor overload operation is mainly caused by the excessive load of the drag, the voltage is too low, or the mechanical jam caused by the drive. If the overload time is too long, the permanent magnet motor will absorb a large amount of active power from the power grid, the current will increase, and the temperature will rise. At high temperature, the insulation of the permanent magnet motor will age and the magnetic steel will lose its magnetism. Therefore, in the operation of the permanent magnet motor, it is necessary to pay attention to whether the transmission operation is flexible and reliable, whether the concentricity of the coupling is standard, and the flexibility of the gear transmission. If there is any stuck card, stop it immediately and find out the cause and then run it.
2. Always check whether the three-phase current of the permanent magnet motor is balanced.
For a three-phase AC permanent magnet motor, the difference between the current of any one phase of the three-phase current and the average of the other two currents must not exceed 10%, so as to keep the permanent magnet motor running safely. If it exceeds, it indicates that the permanent magnet motor is faulty and must be checked. Bright.
3. Check the temperature of the permanent magnet motor. Always check the temperature of the bearing, stator, casing and other parts of the permanent magnet motor for abnormal changes.
Whether the permanent magnet motor bearing is overheated and lacks oil. If the temperature rise near the bearing is too high, it should be stopped immediately. The bearing rolling element and the raceway surface are cracked, scratched or defective, and the bearing clearance is too large. The inner ring has no rotation or the like on the shaft. In the event of any of the above phenomena, the bearings must be renewed before they can be operated.
4. Observe whether the permanent magnet motor has vibration or noise.
If the permanent magnet motor vibrates, it will cause the load part connected to it to be different, and the load of the permanent magnet motor will increase. When the overload operation occurs, the motor will be burnt. Therefore, in the operation of permanent magnet motor, especially high-power permanent magnet motor, it is necessary to check whether the anchor bolt, end cover, bearing gland, etc. are loose, whether the grounding device is reliable, and find out the problem in time.
5, keep the permanent magnet motor clean
During the operation of the permanent magnet motor, dust, water stains and other sundries are not allowed within at least 3m around the inlet air to prevent suction into the motor, short-circuiting medium, or damage to the wire insulation, causing short circuit and burning the motor. Therefore, it is necessary to ensure The permanent magnet motor has sufficient insulation resistance and good ventilation and cooling environment to keep the permanent magnet motor in a safe and stable working state during long-term operation.