What Are The Types Of Motor Magnets?

With the development of the market, magnetic materials are widely used in industrial equipment. So far, motors are the most widely used in the industrial field. Permanent magnets are an important core component of permanent magnet motors. Compared with traditional motors, motors with permanent magnets have the advantages of high efficiency, large torque, and constant speed with load. Compared with synchronous motors, they can consume less current.
1. Ferrite motor magnet
Ferrite permanent magnet is the cheapest magnet among magnetic materials. Compared with other magnetic materials, it has relatively low magnetic performance, but it has strong anti-demagnetization ability and excellent corrosion resistance. It is often used in DC motors.
Operating temperature
The maximum operating temperature of ferrite magnets is about 250 degrees Celsius or higher, and the Curie temperature is about 450 degrees Celsius.
good corrosion
Ferrite magnets have good corrosion resistance and usually do not require coating or plating.
2. NdFeB motor magnet
NdFeB permanent magnets are the most commonly used magnets in traction motors for hybrid and electric vehicles. High energy NdFeB magnets keep the motor as small, light, compact and efficient as possible.
Effect of working temperature
Compared with other permanent magnets, NdFeB magnets have poor temperature resistance. Because neodymium magnets have a negative coefficient, their coercive force and magnetic energy density (BHmax) decrease with temperature. Their maximum service temperature ranges from 60°C to 220°C, and their Curie temperature ranges from 310-370°C. However, they can have dysprosium (Dy) or terbium (Tb) added to suppress performance degradation due to temperature changes. But this makes the 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 problem
Neodymium magnets have poor corrosion resistance if not protected by a coating. At the same time, they also corrode from the inside out if the proper pretreatment process is not followed. Typically, multilayer nickel-copper-nickel plating is applied. But for motor applications, epoxy and zinc coatings are used more. What's more, another new surface treatment, everlube, can also be used in high humidity and salt spray resistant environments.
3. SmCo motor magnet
Samarium cobalt magnets are rare earth permanent magnets that are brittle and prone to cracking and chipping. They come in two "series", SmCo5 magnets and Sm2Co17 magnets.
good temperature stability
At typical operating temperatures, samarium cobalt magnets outperform the strongest heat-resistant neodymium magnets currently used in electric motors. The maximum operating temperature range is 250 to 350 °C; the Curie temperature range is 700 to 800 °C.
Strong anti-corrosion and anti-oxidation ability
Samarium cobalt magnets have excellent corrosion resistance (neodymium magnets do not). Most applications do not require plating or surface coating, which makes them advantageous for medical applications as well.
wide range of supply sources
Unlike neodymium magnets, which require large amounts of the rare dysprosium (Dy) to function at moderate temperatures, samarium cobalt magnets use a wider range of materials and are inherently stable at temperatures well above the Curie point of sintered NdFeB magnets sex. This makes the pricing of SmCo magnets more stable and less susceptible to market changes.
4. Alnico motor magnet
Alnico permanent magnet material is the earliest widely used permanent magnet material, and its preparation process and technology are relatively mature. The Curie temperature is the highest among the current permanent magnet materials; its characteristic is that the advantages of AlNiCo magnets are high remanence (up to 1.35T) and low temperature coefficient. When the temperature coefficient is -0.02%/℃, the maximum operating temperature can reach about 520℃. The disadvantage is that the coercive force is very low (usually less than 160kA/m), and the demagnetization curve is nonlinear, so the alnico magnet is easily magnetized and demagnetized.
Strong anti-corrosion and anti-oxidation ability
Alnico has strong anti-corrosion ability, and the surface does not need to be electroplated.
At present, there are four main types of commercial magnets: neodymium iron boron (NdFeB), samarium cobalt (SmCo), aluminum nickel cobalt (AlNiCo) and ferrite (Ferrite). Among them, ferrite, rare earth samarium cobalt and neodymium magnets can be used in permanent magnet motors and automotive magnet applications.
When designing a motor, the choice of magnet has a significant impact on the overall performance of the motor and the cost of the project. So you need to know how to choose the right magnet for your motor.