Once the permanent magnet motor loses its magnetism, basically you can only choose to replace the motor, and the cost of maintenance is very high. How to judge whether the permanent magnet motor has lost its magnetism?
When the machine starts running, the current is normal. After a period of time, the current becomes larger. After a long time, the inverter will be reported to be overloaded. First, you need to make sure that the inverter selected by 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, you need to judge by back electromotive force, disconnect the head from the motor, perform no-load identification, and run it at no-load to the rated frequency. At this time, the output voltage is the back electromotive force. If it is lower than the back electromotive force on the motor nameplate by more than 50V, it can be determined that the motor is demagnetized.
1. Keep the permanent magnet motor working at rated current
The main reason for the overload operation of the permanent magnet motor is that the load is too large, the voltage is too low, or the driven machinery is stuck. 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, the temperature will rise, and the insulation of the permanent magnet motor will age at high temperature, and the magnet will lose magnetism. Therefore, during the operation of the permanent magnet motor, it is necessary to pay attention to frequently check whether the transmission device is flexible and reliable; whether the concentricity of the coupling is standard; the flexibility of the gear transmission, etc. If there is a lag phenomenon, it should be stopped immediately to find out the cause and troubleshoot before running again.
2. Frequently check whether the three-phase current of the permanent magnet motor is balanced
For the three-phase AC permanent magnet motor, the difference between the current of any one phase of the three-phase current and the average value of the other two currents is not allowed to 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 found out.
3. Check the temperature of the permanent magnet motor
Frequently check whether the temperature of the bearings, stators, casings and other parts of the permanent magnet motor has abnormal changes.
Whether the permanent magnet motor bearing is overheated or lacks oil. If the temperature rise near the bearing is too high, the machine should be stopped immediately for inspection. Check whether there are cracks, scratches or defects on the rolling element and raceway surface of the bearing, whether the bearing clearance is too large and shaking, whether the inner ring rotates on the shaft, etc. If any of the above phenomena occur, the bearing must be replaced before work can be carried out again.
4. Observe whether the permanent magnet motor has vibration and loud noise
If the permanent magnet motor vibrates, it will cause the load part connected to it to be non-concentric, resulting in an increase in the load of the permanent magnet motor, and overload operation will burn the motor. Therefore, during the operation of the permanent magnet motor, especially the high-power permanent magnet motor, it is necessary to frequently check whether the anchor bolts, end covers, bearing glands, etc. are loose, whether the grounding device is reliable, and solve the problems in time.
5.Keep the permanent magnet motor clean.
During operation, dust, water stains and other debris must not be allowed within 3m around the air inlet to prevent them from being sucked into the motor and forming a short-circuit medium, or damaging the insulation of the wire, causing a short circuit and burning the motor. Therefore, it is necessary to ensure that the permanent magnet motor has sufficient insulation resistance and a good ventilation and cooling environment to keep the permanent magnet motor in a safe and stable working state during long-term operation.
