What are the types of motor magnets?

What are the types of motor magnets?
With the development of the market, magnetic materials are widely used in industrial equipment. So far, the motor is the most widely used in the industrial field. Permanent magnet is an important core component of permanent magnet motor. Compared with the traditional motor, the permanent magnet motor has the advantages of high efficiency, large torque, constant speed with load, etc. They can consume less current than synchronous motors.
1. Ferrite motor magnet Ferrite permanent magnet is the cheapest magnet in magnetic materials
。 Compared with other magnetic materials, it has relatively low magnetic properties, but has strong anti-demagnetization ability and excellent corrosion resistance. It is usually used for DC motors.
Operating temperature The maximum operating temperature of the ferrite magnet is about 250 ℃ or higher, the Curie temperature
It is about 450 ℃.
Good corrosion
Ferrite magnets have good corrosion resistance and usually do not require coating or electroplating.
2. NdFeB motor magnet NdFeB permanent magnet is the most commonly used magnet in hybrid and electric vehicle traction motors
。 High energy NdFeB magnets make the motor as small, light, compact and efficient as possible.
working temperature
Compared with other permanent magnets, NdFeB magnets have poor temperature resistance. Since neodymium magnets have negative coefficients, their coercivity and magnetic energy density (BHmax) decrease with temperature. The maximum operating temperature range is 60 ° C to 220 ° C and the Curie temperature range is 310-370 ° C. However, they can add dysprosium (Dy) or terbium (Tb) to suppress the performance degradation due to temperature changes. But this makes magnets more expensive.
Traction motors in hybrid and electric vehicles, rail vehicles and industrial equipment operate at relatively high temperatures. Therefore, high temperature resistant neodymium magnets are often used in these applications.
Corrosion problems
If there is no coating protection, the corrosion resistance of neodymium magnet is very poor. At the same time, if the proper pre-treatment process is not followed, they will also corrode from inside to outside. In general, multilayer nickel copper nickel coatings are applied. However, for motor applications, more epoxy and zinc coatings are used. More importantly, everlube, another new surface treatment method, can also be used in high humidity and salt fog resistant environments.
3. SmCo motor magnet
SmCo magnets are rare earth permanent magnets with strong brittleness, easy to crack and break. They have two "series", SmCo5 magnets and Sm2Co17 magnets.
Good temperature stability
At typical operating temperature, the performance of SmCo magnet is superior to the strongest heat-resistant Nd magnet currently used for motors. The maximum operating temperature range is 250 to 350 ° C; The Curie temperature range is 700 to 800 ° C.
Corrosion resistance and oxidation resistance
Strong samarium cobalt magnets have excellent corrosion resistance (not neodymium magnets). Most applications do not require electroplating or surface coating, which makes them beneficial for medical applications as well.
Wide source of supply
Like neodymium magnets, neodymium magnets require a large number of rare dysprosium (Dy) to function at moderate temperatures. SmCo magnets use a wider range of materials and have inherent stability at temperatures much higher than the Curie point of sintered neodymium iron boron magnets. This makes the pricing of SmCo magnets more stable and less vulnerable to market changes.
4. Aluminum nickel cobalt motor magnet
Al Ni Co permanent magnetic material is the earliest permanent magnetic material, and its preparation process and technology are relatively mature. Curie temperature is the highest among permanent magnetic materials at present; Its characteristic is that AlNiCo magnet has the advantages of high remanence rate (up to 1.35T) and low temperature coefficient. When the temperature coefficient is -0.02%/° C, the maximum operating temperature can reach about 520 ° C. The disadvantage is that the coercivity is very low (usually less than 160kA/m), and the demagnetization curve is nonlinear, so the aluminum nickel cobalt magnet is easy to be magnetized and demagnetized.
Strong corrosion resistance and oxidation resistance Aluminum nickel cobalt corrosion resistance
Strong, the surface does not need electroplating.
At present, there are four main types of commercial magnets: NdFeB, SmCo, AlNiCo and Ferrite. Among them, ferrite, rare earth samarium cobalt and neodymium magnets can be used for permanent magnet motors and automotive magnets.
When designing the motor, the selection of magnet has a significant impact on the overall performance and project cost of the motor. Therefore, you need to know how to choose the right magnet for your motor.