Why Do Wind Turbines Use High-performance Sintered NdFeB Magnets?

Due to the poor working conditions of wind turbines in the open air, such as the seaside, air vents, etc., there are many requirements for magnets.

1. High remanence: The principle of wind turbine power generation is to use the blades driven by wind to drive the rotor with permanent magnet array to generate electricity through the electromagnetic induction effect in the stator winding (conductor).

The magnitude of the induced electromotive force generated at both ends of the winding is proportional to the magnetic flux density (magnetic induction intensity) Bg generated by the large-sized sintered NdFeB magnet array in the air gap, and this Bg is proportional to the square root of the maximum magnetic energy product of the permanent magnet. Therefore, the high magnetic energy product of the material is one of the parameters pursued by the generator.

2.High coercivity: When the wind turbine is running, the permanent magnet will be demagnetized by the alternating reverse magnetic field generated by the winding, so the wind turbine requires the permanent magnet to have enough coercivity to resist strong reverse demagnetization.

Why Do Wind Turbines Use High-performance Sintered NdFeB Magnets

Why Do Wind Turbines Use High-performance Sintered NdFeB Magnets

3.High working temperature: The wind turbine should work in the range of 120-40, and the magnet is required to have low irreversible loss within this working temperature range to ensure the normal operation of the wind turbine.

4.Other physical properties:

Corrosion resistance:
The atmospheric environment of wind turbines also varies greatly. Some places are wet; the sea is not only wet but salty; sometimes the atmosphere may contain some alkali or acid.

All of the above will have a certain corrosion effect on the large-size sintered NdFeB magnets, thereby reducing the magnetic properties, and even completely destroying the magnets in severe cases.

In order to ensure the normal operation of the wind turbine within 20 years, it is required that the magnets do not undergo significant demagnetization within 20 years.

One of the factors of demagnetization is that the magnet can undergo various corrosion. Therefore, magnets require high corrosion resistance and proper surface treatment for corrosion protection.

Shock resistance:
During the operation of wind turbines, vibration will inevitably occur, especially under strong wind, the motor itself will generate strong vibration, which requires the magnet to maintain its integrity and stable magnetic performance under long-term vibration.

Thermal conductivity:
During the operation of the wind turbine, the magnet will heat up due to eddy currents in the metal magnet material.

In order to reduce the temperature of the magnet, the thermal conductivity of the magnet material should be as high as possible. The reduction of eddy current mainly depends on the reduction of surface resistance.

How to test the reliability of NdFeB magnets?

The design life of the wind turbine generator is 20 years, that is, the magnetic steel is required to be used for 20 years without obvious attenuation of its magnetic properties and no obvious corrosion of the magnetic steel.

The following test and testing methods can be used as a method for manufacturers and users of wind magnetic steel to evaluate and inspect magnets.

Weight loss test:
Use 10mm × 10mm × 12mm cuboid black sheet as the sample (12mm height is the magnetization direction), place it in an environment of 2 standard atmospheric pressure, 100% humidity, 120 ℃, take it out after 48 hours and remove the oxide layer removed, the weight loss is less than 0.2 mg/cm2.

Thermal demagnetization test:
120℃×4hr, open-circuit magnetic flux loss is less than 3%.

Thermal shock test:
After 3 cycles of high and low temperature from -40℃ to 120℃, the open-circuit magnetic flux loss is less than 3%.

Salt spray test and temperature and humidity test are methods for evaluating electroplating and other anti-corrosion coatings.

Other physical properties, such as thermal expansion coefficient, thermal conductivity, resistivity, and mechanical strength, all have varying degrees of influence on the usability and reliability of magnetic steel.

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