The permanent magnet motor uses permanent magnets to generate the motor's magnetic field. It does not require excitation coils or excitation currents. It has high efficiency and simple structure. It is a good energy-saving motor. With the advent of high-performance permanent magnet materials and the rapid development of control technology, the application of permanent magnet motors will become more extensive.
The development of permanent magnet motors is closely related to the development of permanent magnet materials. China is the first country in the world to discover the magnetic properties of permanent magnet materials and apply them to practice. More than two thousand years ago, China made a compass using the magnetic properties of permanent magnet materials, which played a huge role in navigation, military and other fields, and became one of the four great inventions of ancient China.
The first motor in the world that appeared in the 1820s was a permanent magnet motor whose excitation magnetic field was generated by permanent magnets. But the permanent magnet material used at that time was natural magnetite (Fe3O4), which had a very low magnetic energy density, and the motor made from it was bulky, and was soon replaced by an electric excitation motor.
With the rapid development of various motors and the invention of current magnetizers, people have conducted in-depth research on the mechanism, composition and manufacturing technology of permanent magnet materials, and successively discovered carbon steel and tungsten steel (the maximum magnetic energy product is about 2.7 kJ/m3 ), cobalt steel (maximum magnetic energy product is about 7.2 kJ/m3) and many other permanent magnet materials. Especially the AlNiCo permanent magnets that appeared in the 1930s (maximum magnetic energy product can reach 85 kJ/m3) and ferrite permanent magnets that appeared in the 1950s (maximum magnetic energy product can reach 40 kJ/m3), the magnetic properties are With great improvement, various micro and small motors have used permanent magnets for excitation. The power of permanent magnet motors is as small as several milliwatts and as large as tens of kilowatts. They are widely used in military, industrial and agricultural production and daily life. The output has increased sharply. Now the appearance of injection molded magnets such as injection molded ferrite and injection molded NdFeB provides a newer and more convenient material for small and micro motors and high-speed motors.