8 Factors to Affect the Magnetic Force of Permanent Magnet

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The magnetic force for permanent magnet can stay for a long time but it is not really permanent. There are 8 factors which will affect magnetic force.
1. The material formulation
Material formulation limits magnetic properties fundamentally. Sintered ndfeb magnet is the strongest and alnico is the weakest. There is also difference for the same material based on formulation. The magnetic force for grade N45 is higher than grade N35 for the same size magnet.
2. Magnet size and shape
3. The magnetization saturability
Only when full charged, magnetic force can be achieved completely.
4. Design of magnetic circuit
Different magnetized direction, the magnetic force is different. For a cylinder magnet, magnetic force by axial-magnetized is stronger than diameter-magnetized.
5. Working temperature
Magnet is very sensitive to working temperature, especially for sintered ndfeb magnet. The momentary and continuous highest temperature of environment may cause certain demagnetization including recoverable and unrecoverable, reversible and irreversible. According to working temperature range 80-200 celsius, sintered ndfeb magnet is divided into several grade series (N, M, H, SH, UH, AH etc.). The cost will be expensive for high working temperature grade. So you need to consider your working temperature and choose the right grade. The loss of magnetic force can be ignored under working temperature permitted range. But magnetic force will decrease rapidly while working under a limit working temperature for a long time.
6. Working humidity
Sintered ndfeb magnet is easy to be oxidized and then loss its magnetic force. We use coating to avoid this problem. But this is not a permanent solution. So the dryer, the better.
7. External magnetic field
Magnetic force will reduce while placing opposite poles around magnet, only when the magnetic field of opposite poles is several times larger than magnet itself, the reduction will be evident.
8. Strong shock
It will reduce magnetic force, but needs long time.

Hast Neodymium Magnets

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With the development of scientific research, requirement on the NdFeB application technology becomes higher and higher. China Magnets Source Material Limited adopts the most advanced technology and equipment to manufacture Hast Neodymium Magnets, which are different from traditional Sintered Neodymium Magnets. Hast Neodymium Magnets have the advantage of low weight loss, high consistency, high temperature resistance, excellent bonding strength, good adhesive affinity etc.

Hast Neodymium Magnets are mainly used in motors, magnetic coupling etc. As per IEC HAST standard, after 168 hours’ test in the high temperature, high pressure and high humidity cooker, the weight loss of the Hast Neodymium Magnets manufactured by China Magnets Source Material Limited is less than 2mg/cm2. That is to say, lifetime of Hast NdFeB in motors will be more than 10 years.

Depending on unique technology, Hast Neodymium Magnets of China Magnets Source Material Limited have very high corrosion resistance and reach the international leading level.

The Special Manufacturing Technique For Hast Neodymium Magnets

Weight loss of Hast NdFeB of China Magnets Source Material Limited in a HAST test (130°C, humidity 95%, vapor pressure 2.7bar)

Generally speaking, we make HAST Neodymium magnets with customer’s different HAST requirements.You are welcome to contact us for more information. Our engineers also are ready to provide technical assistance.

Permanent Magnet for Motor

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Permanent magnet for motor is one of important and high-end applications. In order to achieve optimal performance of PM motor, motor designers need to continually change their design and find best material for motor. Several factors will affect the choice of motor magnet.

1. Magnetic Material: Sintered NdFeB, Bonded NdFeB, Ferrite, SmCo, AlNiCo

• Sintered NdFeB magnet has high magnetic performance (including high magnetic flux, remanence, coercive force, resistance to magnetic demagnetization, and low temperature coefficient, loss of irreversible). It can improve motor performance and reduce the volume as well. It is main magnet material for PM motor.
• Bonded NdFeB magnet is well known for good plasticity. It suits for complex shape magnet or magnet with multipole magnetization direction. Usually, mould is needed for its production.
• Ferrite is an old magnet material which used on PM motor. It’s heavy weight but cheap price.
• SmCo can work under high working temperature. The magnetic force is weaker than Sintered NdFeB magnet, but also very powerful.
• AlNiCo with very high working temperature 450-550℃ is the oldest magnet material for motor and replace by ferrite later.

2. Magnet Max. Working Temperature: Sintered NdFeB magnet 150℃ (N35SH, N38SH, N42SH, N45SH), 180℃ (N35UH, N38UH, N40UH) , 200℃ (N35EH, N38EH); Sm2Co17 300℃

 

3. Magnet Working Environment: low weight loss (high corrosion resistance)

 

4. Magnet Coating: NiCuNi, Zn, Black epoxy, Grey epoxy etc. To make full use of magnet performance and control tolerance well, sometimes the plating of magnet uses phosphorization or passivated for temporary protection

 

5. Magnet Shape: segment (arc), wedge, bread, block, ring, or special shape

 

6. Magnetized direction: it depends on magnet design. In order to get best performance, magnetic declination can’t be ignored.

 

7. Magnet tolerance: a lot of motor magnets are made of segment magnets, and small tolerance is very important to reduce air gap and assemble a ring.



Segment NdFeB Magnet For Motor

China Magnets Soure Material Limited is rich in experience of motor magnet manufacture, such as magnet for flat brushless motor, DC Motor, AC motor, stepper motor , servo motor, synchronous motor; magnet for mini motor or special motor; magnet for high temperature to high humidity; magnet for regular shape or irregular shape.

You are welcome to contact us for more information. Our engineers also are ready to provide technical assistance.