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When the three-phase stator windings of the permanent magnet motor (each with a difference of 120° electrical angle) are fed with a three-phase alternating current with a frequency off, a rotating magnetic field that moves at a synchronous speed will be generated.
In the steady state, the main pole magnetic field rotates synchronously with the rotating magnetic field, so the rotor speed is also the synchronous speed, the stator rotating magnetic field and the main pole magnetic field established by the permanent magnet remain relatively static, and they interact and generate electromagnetic torque, The drive motor rotates and performs energy conversion.
The permanent magnet variable frequency air compressor adopts a high-efficiency permanent magnet motor + inverter (PM motor). The screw host and the high-efficiency permanent magnet motor share the same main shaft. The motor has no bearing, the transmission efficiency is 100%. This structure eliminates the traditional motor bearing failure point and makes the motor maintenance-free.
The rare earth permanent magnet material has excellent magnetic properties. After magnetization, it can establish a strong permanent magnetic field without additional energy, which is used to replace the electric excitation field of traditional motors. , Reliable operation, small size, and lightweight. It can not only achieve high performance (such as ultra-high efficiency, ultra-high-speed, and ultra-high response speed) unmatched by traditional electric excitation motors but also can be made into special motors that can meet specific operating requirements, such as elevator traction motors, special motors for automobiles, etc.
The combination of rare earth high-efficiency permanent magnet motor with power electronic technology and microcomputer control technology has improved the performance of the motor and transmission system to a new level:
The high-efficiency permanent magnet variable frequency motor always maintains high efficiency under any load, saving more than 38% energy compared with ordinary motors and more than 10% energy saving to induction variable frequency motors.
After the motor is stopped, it can be started immediately, and it can be started and stopped infinitely without affecting the life of the motor. The starting current does not exceed 100% of the full load current.
Because the permanent magnet variable frequency motor has the advantages of low speed and high output torque, its variable frequency control mode is wider than that of the ordinary induction variable frequency motor. The permanent magnet variable frequency motor is 30% smaller in volume and 35% lighter in weight than motors with the same power, and easier to maintain. Therefore, improving the performance and level of the supporting technical equipment is an important development direction for the motor industry to adjust the industrial structure.
At present, the high-efficiency permanent magnet variable frequency motor is the best choice for a screw air compressor drive motor. It is more efficient and energy-saving than an ordinary three-phase asynchronous variable frequency motor!
