Rare-earth Magnets In Wind Turbines

Permanent Magnets play a critical part in some of the world’s largest wind turbines. Rare earth Magnetssuch as Strong neodymium-iron-boron magnets, have been used in some wind-turbine designs to lower costs, work stability, and reduce the need for high price and ongoing maintenance.

What are Wind turbine generators?

In 1831, Michael Faraday created an electromagnetic generator. He discovered that an electric current can be created in a conductor when it’s moved through the magnetic field. In the following 200 yearsmagnets and magnetic fields continue to play an integral part in modern electric power generation. People continue to make upon Faraday’s inventions, with new designs to solve 21st-century problems.

In the beginning, people use a kind of Induction generator to make electric power. The induction generator use electromagnets designed into a rotor assembly to create a magnetic field. The electromagnets need to take a small amount of current from the power system. 

Then the alternate type of wind-turbine generator is a permanent magnet synchronous generator. Different from the induction generators, the new wind turbine generators use the magnetic field of strong rare-earth magnets instead of electromagnets. They don’t require slip rings or an external power source to create a magnetic field. Also, the rare-earth magnets replaced by the electromagnet can make the wind-turbine nacelle light and the towers can be produced at a lower cost.

Why rare-earth magnets?

Rare-earth magnets are strong permanent magnets made from alloys of rare earth elements. They are much stronger than other types such as ferrite or alnico magnets. So the strong magnetic performance is the first and most important reason, that choose rare earth magnets to use in wind turbine generators.

Usually, the wind turbine generators’ magnetic field will be designed at alternate poles, different from ferrite or alnico magnets, the rare earth magnets usually have a high Coercive force, it can reduce the influence of the external magnetic field. That is maybe another reason. And usually, choose a neodymium magnet grade of above N42SH. 

The grade of the Neodymium, the number bigger, the magnet stronger, and the letter, the difference in coercive force. The higher coercive force also can be helpful in temperature performance.

The parameters to choose a magnet for a wind turbine

Usually, the designed magnets for a wind turbine are arc-shaped magnets, they will be ranged to a circular. And usually, the wind turbine generator will be made to a big size cause it can supply more power. But the Rare-earth magnets are produced from a process of Powder metallurgy, they will be pressed to form from the powder mixture.  And then sintered in a sintering furnace. In order to reach the requested density, their size cannot be too big.

Currently, we produced a 250 mm max dimension magnet for similar usage.

The size would be one of the factors that need to think about.

The coercive force would be another parameter, usually, the engineer will choose N42SH or higher neodymium magnet grades to reach the request to work in the environment.

Plating is another important one. It needs to choose a better plating to protect the magnet. The magnet will work in a terrible environment on the outside of the room. The Rare-earth magnets have a fatal weakness, they are easy to be destroyed by corroded and oxidized.

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