The no-load current of the small permanent magnet motor is small, because the no-load current of the permanent magnet motor does not include the excitation current. For the load current, the same load current, the load current of the permanent magnet motor does not include the excitation current, so the corresponding loss is small, and the efficiency of the motor will naturally be high. The magnetic poles of permanent magnet DC motors are difficult to manufacture, and there are some problems with ferroboron permanent magnet materials. In fact, the saving of permanent magnet materials is also very limited.
Therefore, it is still a direction to strengthen the research on the improvement of the magnetic properties and processing properties of such economical motor ferrite permanent magnet materials. A synchronous motor in which the stator generates a rotating magnetic field and the rotor is made of permanent magnet material. In order to realize energy conversion, a synchronous generator needs a DC magnetic field, and the DC current that generates this magnetic field is called the excitation current of the generator. Permanent magnet motors, especially rare earth permanent magnet motors, are simple in structure and reliable in operation. Small size, light weight; small loss, high efficiency; the shape and size of the motor can be flexible and so on. Therefore, the application range is extremely wide, covering almost all fields of aerospace, national defense, industrial and agricultural production and daily life.