Characteristics of permanent magnet materials
3.5 Corrosion resistance
The problem of easy corrosion of NdFeB materials has a great influence on the quality of the motor. At present, its surface protection problem has not been solved well in China. The plating method used by the method often causes the surface coating to fall off and the motor to malfunction. At the same time, the ability to withstand special environmental conditions (such as humidity, salt spray and special gases) is limited, which affects the ability of the motor to adapt to special environmental conditions. It is hoped that the permanent magnet material will have further improvement in surface protection ability.
3.6 Magnetic performance stability, uniformity, consistency
In order to ensure that the performance of the motor does not change greatly during its life cycle, especially for some military motors with special requirements, the reliable working life requirement is more than 15 years. It is hoped that the magnetic properties of the permanent magnet material will remain stable for a long time.
Motors, especially high-precision motors, require high magnetic properties uniformity and consistency of permanent magnet materials. Uneven magnetic properties will result in uneven magnetic field of the motor, increased torque ripple, increased output voltage ripple of the generator, poor linearity, and reduced accuracy of the control motor. In addition, the magnetic properties of the same grade of permanent magnet material in different batches are inconsistent, sometimes causing the motor to fail in batches. Therefore, the high-precision motor requires that the magnetic properties of the permanent magnet material have consistent performance within 5%, and the uniformity error is within 3%.
3.7 processing technology
There are still more processing problems in the manufacturing process of permanent magnet motors, which are worth studying. For example, how to master the process parameters in the bonding process will affect the magnetic properties. Whether the impact, vibration and processing environment during the machining process have an impact on the magnetic properties, and how to take protective measures with the magnetic components during the process turnover and during the assembly process.
Permanent magnets in permanent magnet motors are mostly supplied with magnetic materials, which reduces the difficulty of magnetization in motor manufacturers, but greatly increases the difficulty of manufacturing processes, such as permanent magnet brushless DC motors and permanent magnet synchronous motors. Multi-pole magnets are directly attached to the surface mount structure of the rotor surface. The use of high-performance sintered NdFeB is complicated and the operation process is difficult. When the rotation speed is high, the bonding reliability is not ideal. If the sintered magnet can be made into a radially crystal-magnetized multi-pole annular structure, the manufacturing process of the motor rotor will be greatly simplified. Bonding magnets can be done at present, but the magnetic properties are not high. Such as sintered magnets can be realized and can be supplied in batches and the price is not high (it is reported that manufacturers have carried out this research), it will have a promising future.
Conclusion
In summary, the development of permanent magnet materials has promoted the development of permanent magnet motors, and the wide application of permanent magnet motors and the requirements for permanent magnet materials have further promoted the further improvement of permanent magnet materials. With permanent magnet motors widely used in aviation, aerospace, defense, industrial and agricultural production and daily life, the application of permanent magnet materials in motors will be quite extensive.
