The development of permanent magnet motors and their applications in various fields

The permanent magnet motor uses permanent magnets to generate the magnetic field of the motor. It does not require an excitation coil or an excitation current. It has high efficiency and a 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 widespread.

The development history of permanent magnet motors

The development of permanent magnet motors is closely related to the development of permanent magnet materials. Our country is the country in the world to discover the magnetic properties of permanent magnet materials and apply them in practice. More than 2,000 years ago, our country used the magnetic properties of permanent magnet materials to make compasses, which played a huge role in navigation, military and other fields. It has become one of the four great inventions in ancient my country.

The world's motor that appeared in the 1920s was a permanent magnet motor that produced an excitation magnetic field from permanent magnets. However, the permanent magnet material used at that time was natural magnetite (Fe3O4), which had a very low magnetic energy density. The motors made with it were bulky and were soon replaced by electric excitation motors.

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 (magnetic energy product about 2.7 kJ/m3) , cobalt steel (magnetic energy product about 7.2 kJ/m3) and other permanent magnet materials.

In particular, the AlNiCo permanent magnets that appeared in the 1930s (the magnetic energy product can reach 85 kJ/m3) and the ferrite permanent magnets that appeared in the 1950s (the magnetic energy product can now reach 40 kJ/m3) have greatly improved their magnetic properties. There has been a huge improvement, and various micro and small motors are using permanent magnet excitation. The power of permanent magnet motors ranges from a few milliwatts to tens of kilowatts. They are widely used in military, industrial and agricultural production, and daily life, and their output has increased dramatically. Correspondingly, during this period, breakthrough progress was also made in the design theory, calculation methods, magnetization and manufacturing technology of permanent magnet motors, and a set of analysis and research methods represented by the permanent magnet working diagram diagram method was formed.

However, the coercive force of AlNiCo permanent magnets is low (36-160 kA/m), and the remanence density of ferrite permanent magnets is not high (0.2-0.44 T), which limits their application range in motors. Until the 1960s and 1980s, earth cobalt permanent magnets and neodymium iron boron permanent magnets (both collectively referred to as earth permanent magnets) came out one after another. Their high remanence density, high coercive force, high magnetic energy product and linearity

Characteristics and applications of permanent magnet motors

Compared with traditional electric excitation motors, permanent magnet motors, especially earth permanent magnet motors, have significant advantages such as simple structure, reliable operation, small size and light weight, low loss and high efficiency, and the shape and size of the motor can be flexible and diverse. . Therefore, it has an ly wide range of applications, covering al all fields of aerospace, national defense, industrial and agricultural production, and daily life.

The important role of permanent magnet motors in various application fields

1. Energy-saving earth permanent magnet motors are mainly targeted at consumption, such as earth permanent magnet synchronous motors in the textile and chemical fiber industries, petroleum, mining, and coal mine transportation machinery. Rare earth permanent magnet synchronous motors drive various pumps and fans. .

2. Various earth permanent magnet motors are used by various types of vehicles (cars, motorcycles, trains), and earth permanent magnet motors are the largest market. According to statistics, about 70% of earth permanent magnet motors are used in vehicles. Luxury cars, more than 70 sets of motors for various applications. Since the requirements of various automobile motors are different, the selection of permanent magnet materials is different. Motor magnets are used in air conditioners, fans, and electric windows. From a price perspective, ferrite will continue to have the advantage in the future. Ignition coils, drive devices, and sensors still use Sm-Co sintered magnets. In addition, auto parts cannot be ignored for electric vehicles, as an environmentally friendly vehicle (EV) and a hybrid electric vehicle (HEV).

3. Rare earth permanent magnet motor AC servo system is a set of electronic, high-performance, speed control system mechatronics machinery. The system is a self-controlled permanent magnet synchronous motor body. The system is used in the development of CNC machine tools, flexible manufacturing technology; and is also used in electric vehicles, rather than traditional thermally powered vehicles, to make vehicle emissions free. Rare earth permanent magnet motor is a promising high-tech industry.

4. The new field is mainly to support the frequency conversion speed regulation system of low-power earth permanent magnet synchronous motors for new air conditioners and refrigerators, wireless electric gadgets for various earth permanent magnet DC micromotors, and earth permanent magnet brushless DC motors. They are instruments with different powers. There is also a huge demand for such motors.

5. Rare earth permanent magnet materials have advantages in aerospace applications, making them very suitable for aero-engine applications. Although there are some applications of earth permanent magnet motors in the air (such as generator voltage and short-circuit protection, etc.), experts at home and abroad agree that earth permanent magnet motors are an important development direction for the new generation of aeroengines.