1, control problems
After the successful production of the rare earth permanent magnet motor, the magnetic field can be maintained without external energy, but it is also difficult to adjust and control the magnetic field from the outside. It is difficult for a permanent magnet generator to adjust its output voltage and power factor from the outside. The permanent magnet DC motor can no longer adjust its speed by changing the excitation.
2, the cost problem
So far, because the price of rare earth permanent magnet motor is still relatively expensive, and the cost of this motor is generally higher than that of the electric excitation motor, it is necessary to use its high performance and operating cost savings to compensate. Therefore, permanent magnet motors are more suitable for low power applications.
3, demagnetization problem
The rare earth permanent magnet motor has strict requirements on the working environment. The rare earth permanent magnet material exceeding 180 °C will have irreversible demagnetization and failure conditions; and in the case of severe vibration or large temperature difference, it is prone to breakage and the like. In addition, rare earth materials are also susceptible to oxidative corrosion, which must be surface coated in order to be used. The rare earth permanent magnet motor is very sensitive to overload, and once it is overloaded, it will cause demagnetization of the permanent magnet material.
At the same time, the electromagnetic load of the rare earth permanent magnet material is very high. After the production, the magnetic field is difficult to adjust, and the power control system is much more complicated than the induction motor. Traditional motor design theory, calculation methods, and motor control systems cannot meet the development requirements of high-performance motors.
