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Knowledge of motor magnets

There are many kinds of magnets, which are generally divided into permanent magnets and soft magnets. The so-called magnets generally refer to permanent magnets.

Permanent magnets can be classified into two categories:

The first category is: metal alloy magnets including Nd2Fe14B, SmCo and ALNiCO.

The second category is: ferrite permanent magnets (Ferrite)

1. Nd-Fe-B magnet: It is the most commercialized magnet found at present. It is called the King of Magnets. It has extremely high magnetic properties and its maximum magnetic energy product (BHmax) is more than 10 times higher than that of Ferrite. Its machinability is also quite good. The highest working temperature can be up to 200 C. Moreover, it has a hard texture, stable performance and good cost performance, so it is widely used. However, because of its strong chemical activity, it is necessary to treat its surface layer. (e.g. zinc, nickel, electrophoresis, passivation, etc.).

2. Ferrite magnet: Its main raw materials include BaFe12O19 and SrFe12O19. Made by ceramic process, it is a brittle material with hard texture. Ferrite magnet has become the most widely used permanent magnet because of its good temperature resistance, low price and moderate performance.

3. Aluminum-nickel-cobalt magnet: An alloy consisting of aluminium, nickel, cobalt, iron and other trace metal elements. Casting process can be processed into different sizes and shapes, and it has good machinability. Cast Al-Ni-Co permanent magnet has the lowest reversible temperature coefficient, and its working temperature can be as high as 600 C. Aluminum-nickel-cobalt permanent magnet products are widely used in various instruments and other applications.

4. SmCo can be divided into SmCo5 and Sm2Co17 according to their composition. Because of the high price of its materials, its development is limited. SmCo, as a rare earth permanent magnet, has high magnetic energy product (14-28MGOe), reliable coercivity and good temperature characteristics. Compared with NdFeB magnet, SmCo magnet is more suitable for working in high temperature environment.