Performance characteristics of permanent magnet materials and permanent magnet motors
1. Main performance of common permanent magnet materials for motors
1.1 Permanent magnet materials commonly used in motors
Permanent magnet materials commonly used in motors include sintered magnets and bonded magnets. The main types are aluminum nickel cobalt, ferrite, samarium cobalt and neodymium iron boron.
AlNiCo materials were used more before the 1980s. It has excellent temperature stability, time stability and the application of ultra-high temperature environment. It is used in some special applications such as motors for special use environments such as military or instrumentation with high temperature requirements and good magnetic stability. .
Ferrite materials are non-metallic permanent magnet materials and are inexpensive. It is mainly used in economical series of micro-motor products with low performance and volume requirements. Such as toy motors, household electrical motors, audio and video motors, office equipment and general-purpose instrument motors, automobile and motorcycle motors, and industrial small-power drive motors.
Samarium-cobalt material is a permanent magnet material with excellent magnetic properties that was developed in the mid-1960s and its performance is very stable. Samarium cobalt is particularly suitable for the manufacture of electric motors in terms of magnetic properties, but because of its high price, it is mainly used in the research and development of military, aerospace, military and other military motors and high-tech motors with high performance and not the main price. NdFeB material is known as the third-generation high-performance permanent magnet material in the 1980s. Its magnetic properties are higher than that of samarium cobalt, its thermal stability is poor, and it is easy to rust. It must be surface-protected, but it is cheap. So quickly get promoted and applied. With the continuous updating of NdFeB materials, the temperature performance has been continuously improved. Especially since the 1990s, low temperature coefficient and high temperature resistant NdFeB materials have been successfully developed. The high temperature heat resistant NdFeB can reach the working temperature. At 200 ° C, and the price is also decreasing, most of the industrial and civil motors use NdFeB materials, and will replace most of the original ferrite materials for low-cost economical motors.
The bonded permanent magnetic material is a composite permanent magnetic material prepared by mixing, compressing, injecting or extruding a binder with a permanent magnetic material, including bonded ferrite, bonded AlNiCo, and viscous. Cobalt and cobalt-bonded NdFeB. Among them, bonded NdFeB is currently the best bonded permanent magnet material. Compared with the sintered permanent magnet material, it has good mechanical processing performance, easy molding, can be made into various complicated shapes, has good uniformity of magnetic properties, and is easy to perform multi-pole magnetization. However, the magnetic properties of the bonded permanent magnetic material are lower than those of the same type of sintered magnet, and the magnetic energy product is about 40% to 70% of the sintered magnet of the same material. Among the bonded permanent magnet materials, the prospect of bonding NdFeB is the best, and if the NdFeB is bonded, the solution is the most promising permanent magnet material if it solves the process problem and improves the quality. It is currently mainly used in precision micro-motors such as small brushless DC motors and stepper motors.
