Permanent magnet motor demagnetization reasons and preventive measures

Once the permanent magnet motor demagnetization, basically can only choose to replace the motor, the cost of repair is a large sum, how to determine the permanent magnet motor demagnetization, we continue to look down.
The machine starts to run with normal current, and after a period of time, the current becomes larger, and after a long time, it will report the overload of the frequency converter. First of all, you need to make sure that the air compressor manufacturer’s inverter selection 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 the counter electromotive force, the head and motor disengagement, no-load identification, no-load operation to the rated frequency, the output voltage is the counter electromotive force, if it is lower than the motor nameplate on the counter electromotive force of more than 50V, you can determine the demagnetization of the motor.

1. Keep the permanent magnet motor working under rated current.
   Permanent magnet motor overload operation, the main reason is due to the dragging load is too large, the voltage is too low, or the driven machinery stagnation and so on. If the overload time is too long, the permanent magnet motor will absorb a large amount of active power from the grid, the current increases, the temperature rises, the insulation of the permanent magnet motor at high temperatures will be aging, magnet steel demagnetization. Therefore, the permanent magnet motor in operation, we should 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 drive and so on. If you find that there is a stagnant card phenomenon, you should immediately stop to find out the cause of the fault and then run.
2. Often check whether the three-phase current balance of permanent magnet motor.
   Three-phase AC permanent magnet motor, the three-phase current of any one phase current and the other two currents of the average value of the difference is not allowed to exceed 10%, so as to maintain the safe operation of the permanent magnet motor, if more than that indicates that the permanent magnet motor has a fault, must be identified.
3. Check the temperature of the permanent magnet motor should always check the permanent magnet motor bearings, stator, shell and other parts of the temperature of any abnormal changes.
   Permanent magnet motor bearings whether overheating, lack of oil, if found near the bearings of the temperature rise is too high, it should be immediately shut down to check the rolling body of the bearings, raceway surface with or without cracks, scratches or defects, bearing clearance is too large shaking, the inner ring on the shaft with or without rotation. Any of the above phenomena, must update the bearing before working again.
4. Observe the permanent magnet motor with or without vibration and noise.
   If the permanent magnet motor vibration, it will cause the load part connected with it is not concentricity, the formation of permanent magnet motor load increase, overload operation, it will burn the motor. Therefore, permanent magnet motors in operation, especially high-power permanent magnet motors need to frequently check whether the ground bolts, end caps, bearing gland, etc. are loose, whether the grounding device is reliable, and find timely solution to the problem.
5. Keep the permanent magnet motor clean.
   Permanent magnet motor in operation, the air inlet around at least 3m does not allow dust, water and other debris, in order to prevent inhalation of the motor inside, the formation of short-circuit medium, or damage to the insulation of the wire, resulting in a short-circuit, burned out the motor, so to ensure that the permanent magnet motor has sufficient insulation resistance, as well as good ventilation and cooling environment, in order to make the permanent magnet motor in the long run to maintain a safe and stable working condition.