Rare earth permanent magnet synchronous motor is mainly composed of rotor, end cover and stator.
Generally speaking, the stator structure of permanent magnet synchronous motor is very similar to that of ordinary induction motor, but the main difference is that the unique structure of rotor is different from that of other motors. The biggest difference of permanent magnet synchronous motor from the AC induction induction motors used by Tesla is the high quality permanent magnet poles (rare earth) placed on the rotors. Because there are so many choices of places to place permanent magnets on the rotor, permanent magnet synchronous motor (PMSM) are generally divided into three categories: built-in type, surface mount type, and plug-in type.
And the working principle is roughly the same, connect three phase current to the fixed motor stator winding, and the rotating magnetic field will be formed in the stator winding of the motor; because the rotor is installed with the permanent magnets, and magnetic pole of permanent magnet is fixed, rotating magnetic field generated in the stator will drive the rotor to rotate according to the magnetic pole principle that same poles attract and different poles repel.
Technical bottleneck of rare earth permanent magnet motor
1. Control problems
The permanent magnet motor can maintain its magnetic field without external energy, but it is very difficult to adjust and control its magnetic field from the outside.It is difficult for permanent magnet generator to adjust its output voltage and power factor externally.
2. Cost
Because the price of rare earth permanent magnet is still relatively expensive, the cost of rare earth permanent magnet motor is generally higher than that of electric excitation motor, which needs to be compensated by its high performance and savings in operating costs.So permanent magnet motor is suitable for low power occasions.
3. Problem of demagnetization
Rare earth permanent magnet motors have strict requirements on the working environment, and irreversible demagnetization and failure will occur when the rare earth permanent magnet materials exceeding 180℃; it is easy to break under the condition of severe vibration or large temperature difference; the material is easy to oxidize and corrode, so it must be surface coated before it can be used; rare earth permanent magnet motor is very sensitive to overload, and overload will lead to demagnetization of permanent magnet material.
Meanwhile, the electromagnetic load of rare earth permanent magnet motor is very high, and it is difficult to adjust the magnetic field after it is made; its power control system is much more complex than that of induction motors. Traditional motor design theory, calculation method and motor control system can not meet the requirements of high-performance motor development.
In a word, difficulties are numerous on the road of rare earth permanent magnet motor research and development. But the tireless efforts of engineers will eventually break the bottleneck, and customers will benefit from the convenience of technology.