The solution to the problem of demagnetization will prolong the service life of your air compressor.

Loss of excitation of permanent magnet variable frequency air compressor is a common problem. When the machine starts running, the current is normal, but after a period of time, the current becomes larger, and with the passage of time, the inverter will be reported to be overloaded. First of all, it is necessary to confirm whether the inverter model selected by the air compressor manufacturer is correct, and check whether the internal parameters of the inverter have been changed. If there is no problem with both, it needs to be judged by back electromotive force. Separate the nose from the motor, identify it with no load, and run it with no load to the rated frequency. At this time, the output voltage is back electromotive force. If it is lower than the back electromotive force on the motor nameplate by more than 50V, the motor can be determined to be demagnetized.

The following are several ways to solve the problem of loss of excitation:

1. The importance of motor power selection of permanent magnet air compressor

The demagnetization of permanent magnet variable frequency air compressor is related to the power selection of permanent magnet motor. Correct selection of the power of permanent magnet motor can delay demagnetization. The main reason of demagnetization of permanent magnet synchronous motor is too high temperature, and overload is the main reason of too high temperature. Therefore, when selecting the power of permanent magnet motor, there should be a margin. According to the actual situation of the load, about 20% is generally appropriate.

2. Improve the design

Reasonably increase the thickness of permanent magnets. From the viewpoint of planning and manufacturing of permanent magnet synchronous motor, the relationship among armature reaction, electromagnetic torque and demagnetization of permanent magnet should be considered. Under the combined action of flux generated by torque winding current and magnetic flux generated by radial force winding, the permanent magnet on the rotor surface will cause demagnetization. Under the condition that the air gap of the motor is constant, the most effective way to ensure that the permanent magnet does not demagnetize is to increase the thickness of the permanent magnet appropriately.

There is a ventilation groove loop inside the rotor to reduce the temperature rise of the rotor. The main factor affecting the reliability of permanent magnet motor is demagnetization of permanent magnet. If the rotor temperature rises too high, the permanent magnet will lose excitation irreversibly. In structural planning, the ventilation loop inside the rotor can be planned to directly cool the magnetic steel. This not only reduces the temperature of magnetic steel, but also improves the power.

3. Avoid overloading startup and frequent startup

Try to avoid asynchronous starting synchronous permanent magnet motor starting directly or frequently under heavy load. In the process of asynchronous starting, the starting torque is oscillating, and in the trough of the starting torque, the stator magnetic field has the effect of rebounding the rotor. Therefore, the overload and frequent starting of asynchronous permanent magnet synchronous motor should be avoided as much as possible.

In a word, the demagnetization of permanent magnet variable frequency air compressor is a problem that needs to be solved in time. Choosing the correct motor power of permanent magnet air compressor, improving the design and avoiding heavy load starting and frequent starting can effectively solve the problem of loss of excitation.

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