Application of Rare Earth Permanent Magnet in Motor

- Nov 17, 2017 -

Rare earth permanent magnet material is a high performance functional material, this material is the basis of many high-tech industries. In the motor with permanent magnet motor products can be lightweight, high performance, combined with power electronics technology, made of speed, torque adjustable machine integration products.


The rare earth permanent magnet motor is the largest application field of NdFeB magnets, accounting for about 70% of the total magnet, computer hard disk supporting ring motor (VCM) accounted for 40% to 50%, so the computer industry is the largest user of permanent magnet motor. The use of rare earth permanent magnet motor can significantly reduce the weight of the motor, such as 10kW ordinary generator, weight 220kg, and dilute permanent magnet generator 92k8. The 1095kW, 230rpm six-stage permanent magnet synchronous motor developed by Siemens of Germany is used for ship's entry. Compared with the DC motor used in the past, the volume is reduced by 60% and the total loss is reduced by 20%.


Rare earth permanent magnet motor energy efficient, the average saving rate of up to 10%, some special motor saving rate as high as 15% to 20%, and the price is reasonable. Efficient energy-saving rare earth permanent magnet motor developed in China, in the energy index and price, foreign high-efficiency motor can not be compared with it, in the international market has a very strong competitiveness. All countries in the world have made every effort to improve the efficiency and conserve electricity of electric motors, especially the United States. In 1992, the former U.S. President Bush signed the Energy Policy Law. According to the decree, most of the U.S. general efficiency Motors will no longer be produced, only high-efficiency motors will be allowed. More efficient motors will be produced after October 2002 and technically maximally economically viable motors will be economically viable after October 2007.


Rare earth permanent magnet motor is a kind of ideal electric motor from energy conservation aspect, the market prospect is good. In our country, there are 36 million kilowatts of all kinds of electric motors each year, among which 50% of the small electric motors below 18.5kW account for about 50%. The energy-saving effect of rare earth permanent magnet high-efficiency energy-saving motor in the electric motor is the most obvious. Rare earth permanent magnet motor in the information industry, mechanical and electrical integration, automobiles, motorcycles, metallurgical equipment, fans, pumps, oil field equipment, textile machinery, household appliances and other fields has a wide range of applications, including self-starting dilute permanent magnetic energy-efficient motor is oil field Pumping units, fans, pumps and gradually promote the use of, and has formed a series of products.


China's motor holdings of about 400 million kW more than 36 million kWh, annual consumption of electricity accounted for 60% of the total electricity. Fans, pumps supporting motor 55% of the total, the annual electricity consumption accounted for 40% of the total generating capacity, and the current fan, pump power utilization is very low. According to the statistics of the National Bureau of Statistics in 1989, there are more than 3700 sets of pumps and fans in our country with an installed capacity of 1.1 × 105MW. The actual operating efficiency is less than 50%, the system operating efficiency is less than 30% and the annual waste of electricity is about 20 billion kW · h. According to the electricity sector estimates, the coal industry fans, pumps, 50s and 60s. Equipment accounts for about 1/3, its own operating efficiency is only 30% to 40%, the system operating efficiency is about 20%, such as large amount of 5kW pump, often with 7.5kW motor, but often run under 3kW load, measured The efficiency is only 38%, resulting in a huge waste of energy, if the kind of motor rare earth permanent magnet motor, motor cost increased by only 30% to 50%, operating efficiency can be increased to 50% to 55%, fundamentally change the energy waste, If the annual output of 3 million kW rare earth permanent magnet motor, annual savings of 600 million yuan for the country to save electricity and save electricity 300 million yuan.


The development of rare earth permanent magnet motors, in reducing imports, increase export earnings, also has a very important significance, for example, China's annual production of 10 million computers, disk drives for its complete reliance on imports, or the purchase of spare parts in the domestic assembly Once the Western countries led by the United States put restrictions on China's import of disk drives, the computer production in China will be seriously affected. For example, CNC machine tools, due to motor and transmission control system requirements and annual import cost more than 2.2 billion US dollars.

 

The significance of the export trade is even more prominent. As we all know, each mechanical product should be equipped with a motor. In 1997, the United States stopped using legislation to stop the production of motors of general efficiency (equivalent to the Y series motors mass-produced in China). Canada, Britain and Japan all follow the example of the United States to stop producing general efficiency motors. If no measures are taken to speed up the motor, The development of energy-efficient motor, we will soon lose the international market for mechanical products. Rare earth permanent magnet motor developed by our country price, performance is very competitive on the international market, there are already some products exported.


Throughout the development of rare earth permanent magnet motor, appeared in 1821 the world's first motor is a permanent magnet motor, but then the permanent magnet used in the product of very low magnetic energy, the resulting motor bulky and small capacity, soon to be electric Motor replaced. Up to the 1960s, Shanzhu and NdFeB rare earth permanent magnetic materials have emerged one after another, with excellent properties of high remanence, high coercivity and high magnetic energy product, and have the advantages of high efficiency and energy saving after being made into a motor. As early as in 1978, CEM made a highly efficient energy-saving motor below 18.5kW. However, due to the high cost of using SmCo permanent magnets at the time, it was not promoted.

Prior to 1983, due to the high cost of rare earth permanent magnets, research and development focused on aerospace, aerospace motors and high-tech areas that required high performance where price was not a major factor. Typical foreign products are 150kVAl2000 ~ 21000rpm rare earth cobalt permanent magnet starter / generator manufactured by General Electric Company of the United States, and 3kW2000rpm permanent magnet motor developed by Shenyang University of Technology and the 60 developed jointly by the school and Dongfang Electrical Machinery Factory and Harbin Electrical Machinery Factory ~ 75kVA (after extension to 160kVA) dilute cobalt permanent magnet secondary exciter and neodymium iron boron deputy exciter.


In 1983, after the advent of the NdFeB permanent magnets with higher magnetic properties and relatively lower prices, research and development at home and abroad shifted their focus to industrial and civil motors. Foreign mainly computer hard disk drive motor, which drives the read-write magnetic head reciprocating linear motor winding voice coil motor (VCM), CNC machine tools and robots for brushless DC motors and limousine starting motor. The main domestic is a variety of high efficiency permanent magnet synchronous motor, especially the Northwestern Polytechnical University developed 0.8kW textile permanent magnet synchronous motor.


In recent years, with the continuous improvement of properties of rare earth permanent magnetic materials, especially the thermal stability of NdFeB permanent magnetic materials, corrosion resistance and the gradual reduction of the price of power electronics technology and the further development of rare earth permanent magnet motor On the one hand, the achievements of the original development have been widely used in national defense, industry, agriculture and daily life; on the other hand, the positive development toward high power (high speed and high torque) , High-functional and miniaturization development, expansion of new varieties and applications. Currently, the single capacity of rare earth permanent magnet motor has exceeded 1000kW, the maximum speed has exceeded 300000rpm, low speed less than 0.01rplh, the minimum motor diameter is only 0.8mm, length 1.2mm. In the stepper motor, switched reluctance motor, synchronous motor and other special motor to increase NdFeB permanent magnet excitation, its technical and economic performance, dynamic response characteristics have significantly improved and improved.


The national conditions of different countries, rare earth permanent magnet materials in the application of the motor is not the same. Japan's application in VCM accounts for about 50% of the total amount of rare earth permanent magnets. The United States has a large amount of use in the fields of aerospace, aerospace, military, automobile and machine tools, and Europe has the most applications in numerical control machine tools. However, the total amount of rare earth magnets in various motors accounted for rare earth permanent magnet total output of the case is not much difference, usually 60% to 80%.


Rare earth resources in our country, rare earth permanent magnet output ranks first in the world. However, 2/3 of the output of rare earth permanent magnet materials is used for export, and 1/3 of the domestic sales is very low for motors. In the future should be efficient and high performance permanent magnet motor as the focus of development, and quickly industrialization.


Article from NdFeB Industry Network

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