Does the permanent magnet variable frequency air compressor never demagnetize? The answer is no. Demagnetization may occur when the equipment receives external force or improper operation by the user. When the permanent magnet variable frequency motor receives overload current, high temperature, severe vibration, etc., the equipment may experience irreversible demagnetization. Today, the editor will come to talk to you about how to avoid these situations.
1. Correctly choose the power of the permanent magnet motor
Demagnetization is related to the power selection of the permanent magnet motor in the frequency conversion air compressor. The correct selection of the power of the permanent magnet motor can prevent or delay demagnetization. The main reason for permanent magnet synchronous motor demagnetization is excessive temperature, and overload is the main reason for excessive temperature. Therefore, a certain margin should be left when selecting the power of the permanent magnet motor. According to the actual situation of the load, about 20% is generally appropriate.
2. Avoid heavy load starting and frequent starting
Cage asynchronous start synchronous permanent magnet motors try to avoid heavy load direct start or frequent start. In the asynchronous starting process, the starting torque is oscillating. In the valley of starting torque, the stator magnetic field demagnetizes the rotor pole. Therefore, try to avoid heavy load and frequent starting of the asynchronous permanent magnet synchronous motor of the air compressor.
3. Improve the design
3.1 Properly increase the thickness of permanent magnets From the perspective of the design and manufacture of permanent magnet synchronous air compressor motors, the relationship between armature reaction, electromagnetic torque and permanent magnet demagnetization should be considered. Under the combined action of the magnetic flux generated by the torque winding current and the magnetic flux generated by the radial force winding, the permanent magnets on the rotor surface are likely to cause demagnetization. When the air gap of the motor remains unchanged, the most effective way to ensure that the permanent magnet does not demagnetize is to appropriately increase the thickness of the permanent magnet.
3.2 There is a ventilation slot loop inside the rotor to reduce the temperature rise of the rotor and an important factor affecting the reliability of the permanent magnet motor is the demagnetization of the permanent magnet. If the rotor temperature rises too high, the permanent magnets of the variable frequency air compressor will have irreversible demagnetization. In the structural design, the internal ventilation circuit of the rotor can be designed to directly cool the magnetic steel. Not only reduces the temperature of the magnetic steel, but also improves the efficiency.