Application of NdFeB permanent magnet in motor

- Mar 19, 2019-

Rare earth permanent magnet material is a kind of high - performance functional material. Permanent magnets can make motor products lighter and smaller in size. Permanent magnet material technology and power electronics technology can be combined to make the motor speed, torque adjustable products.
Rare earth permanent magnet motor is the largest application of NdFeB magnets, it takes about 70% of the total NdFeB magnet, computer hard disk matching coil motor (VCM) accounted for 40% ~ 50%, so the computer industry is the largest user of permanent magnet motor.

Rare earth permanent magnet motor can significantly reduce the weight of the motor, such as the weight of 10kW ordinary generator is 220kg, but the rare earth permanent magnet generator is 92kg.. The 1095kW and 230rpm six-stage permanent magnet synchronous motor developed by Siemens of Germany is used for the advancement of ships. Compared with the DC motor used in the past, the volume is reduced by about 60% and the total loss is reduced by 20%.


Rare earth permanent magnet motors are highly efficient and energy saving, with the average power saving rate up to 10%, and some special motors up to 15% ~ 20%, with reasonable price. In 1992, former US President George w. bush signed and approved the energy policy act. According to this act, since October 24, 1997, most of the general efficiency electric motors in the us will no longer be produced, and only high-efficiency electric motors will be allowed to be produced.


Considering the energy saving, rare earth permanent magnet motor is an ideal kind of motor and has a promising market prospect. Each year, China produces 36 million kW of various types of electric motors, of which about 50% are small motors below 18.5kW. The rare earth permanent magnet high efficiency energy - saving motor has the most remarkable effect. Rare earth permanent magnet motors are widely used in information industry, electromechanical integration, automobile, motorcycle, metallurgical equipment, fan, water pump, oilfield equipment, textile machinery, household appliances and other fields. Among them, self-starting high efficiency and energy-saving rare permanent magnet motors are being gradually promoted and applied in oil field pumping units, fans and pumps.


Throughout the development of rare earth permanent magnet motor, the first permanent magnet motor appeared in the world in 1821. However, at that time, the magnetic energy of the permanent magnet was very low, and the motor made of it was huge in volume and small in capacity, which was soon replaced by electric excited motor. Until the 1960s, have emerged undressed drill and ndfeb rare earth permanent magnetic materials, with high remanence, high coercivity and high magnetic energy product excellent performance, after the motor has the superior performance of high efficiency and energy saving. As early as 1978, the French CEM company made high-efficiency and energy-saving motors below 18.5kw, but the use of samarium cobalt permanent magnets was not popularized due to the high cost.


In recent years, with the constant improvement of the rare earth permanent magnet material performance, especially the thermal stability of the ndfeb permanent magnet materials, the improvement of the corrosion resistance and gradually reduce the price and the further development of power electronics technology, the development of rare earth permanent magnet motor and should be entered a new stage, on the one hand, the results of original development in such aspects as national defense, industry and agriculture and daily life widely used; On the other hand, high power (high speed, high torque), high function and miniaturization are being developed, and new electric varieties and application fields are being expanded. At present, the single capacity of rare earth permanent magnet motor has exceeded 1000kW, the maximum speed has exceeded 300000rpm, the low speed is lower than 0.01 RPLH, the minimum outer diameter of the motor is only 0.8mm, 1.2mm long. After adding nd-fe-b permanent magnet excitation to stepping motor, switched reluctance motor, speed synchronous motor and other special motors, its technical and economic performance, dynamic response characteristics have been significantly improved and improved.


The application amount of Japan in VCM accounts for about 50% of the total amount of rare earth permanent magnet, the United States in aviation, aerospace, military industry, automobile and machine tools and other fields in the use of large motor, Europe in the application of CNC machine tools. However, the total amount of rare earth magnetic steel in all kinds of motors accounted for the total output of rare earth permanent magnetic example is not different, generally 60% ~ 80%.


China is rich in rare earth resources, and its output of rare earth permanent magnet ranks first in the world. But two-thirds of the output of rare-earth permanent-magnet materials is for export, and one-third of domestic sales are for motors. In the future, high efficiency and high performance permanent magnet motors should be the focus of development and industrialization.