1、Different performance parameters of magnet materials and their application characteristics
Their performance is incremental, as is their price, which determines their respective applications. Injection molding magnets are divided into injection molding ferrite and injection molding NdFeB. The bonded bodies include nylon 6, 12 and PPS. Nylon is slightly cheaper than PPS, but the surface finish, strength and temperature resistance of the magnetic parts composed of it are worse than PPS. Their common feature is that they can be injected together with various parts or shafts to ensure the quality of the product. Injection molded ferrite magnets are divided into isotropic (isotropic) and anisotropic (anisotropic). The isotropic magnetic energy product is relatively low, around 1.5 MGOe, and the anisotropic magnetic energy product is around 2.1 MGOe. It is mainly used for products with a large quantity and a wide range, such as toy motors, stepping motors for air conditioners, fans, etc. The highest magnetic energy product of injection-molded NdFeB is around 6.0MGOe, and it can reach 6.5MGOe if imported raw materials are used, but the price is higher. At present, the application of injection molding NdFeB is not widespread, mainly because it is not well known to everyone. In fact, it can replace more low energy product bonded NdFeB magnetic parts, especially in stepper motors and rotors with shaft injection molding.
Bonded NdFeB is the most widely used in high-performance products. The upper part can enter the sintered NdFeB product, and the lower part can enter the ferrite product. This is mainly because its performance is between the two, and it is isotropic. Suitable for various magnetization methods. Its disadvantage is poor temperature resistance, the highest temperature is 150°C, which determines that it is suitable for small motors and control motors, and it depends on the specific situation for drive motors.
Sintered NdFeB has been widely used because of its high performance, but it is mainly used for driving motors at present. Among the motors we are talking about, they are mainly brushless motors and AC servo motors, and they are mainly tile-shaped, because the current sintered NdFeB is mainly unidirectional, that is, the magnetic parts can only be magnetized in one direction, so it's It cannot be made into a magnetic ring for magnetization with more than 2 poles. The radial orientation sintered NdFeB developed now can do this. The difference between the two is that the orientation direction during pressing is different, but the mold for radial products is more complicated, and there is a mold fee for magnetic parts. Radial orientation sintered NdFeB magnetic ring will first be applied in brushless motor and AC servo motor, which is determined by the price of both. The use of radial orientation is very beneficial even for magnetic tiles, and its magnetized waveform is close to a rectangular wave rather than a saddle shape.
2、Possibilities and Consequences of Magnet Material Interchange
Generally speaking, in the same material, it is easier to replace the high and low performance, and the replacement of different materials, although the performance is also different, but there is a huge difference, the structure of the motor must be changed, otherwise, even if the high-performance motor is used Replacement of low-performance materials with high-quality materials cannot get good performance. Generally, high replaces low, the structure becomes smaller, low replaces high, and vice versa.
3、How to judge the quality of magnetic materials from the running results of the motor
The torque of the motor
Generally speaking, the torque of the motor is large, and the performance of the magnetic steel is high, and the small is low. In small motors, the positioning torque is expected to be small, that is, the momentary torque of the motor from standstill to rotation is mainly determined by the magnetization waveform and the shape of the iron core.
The speed of the motor
The speed of the motor has no-load speed and load speed. When discussing the relationship between the speed and the performance of the magnetic steel, the influence of other resistance torques of the motor should be excluded. High no-load speed, low magnetic performance, otherwise, high magnetic performance; high load speed, high magnetic performance, otherwise, low magnetic performance.
The current size of the motor
The current of the motor also has no-load current and load current. When discussing the relationship between the current and the performance of the magnetic steel, the influence of other resistance torques of the motor should also be excluded. The no-load current is large, the magnetic performance is low, on the contrary, the magnetic performance is high, but this is not obvious in the motor, the size of the no-load current has a greater relationship with the resistance of the winding; the load current is large, the magnetic performance is low, conversely, the magnetic performance high.
In fact, the three are interrelated, and the change of magnetic properties should be considered comprehensively.