The Halbach array is a magnet arrangement structure. Before we study this structure, let’s take a look at the distribution of the magnetic field lines of some common permanent magnets.
From these pictures, that is easily to find that the direction and arrangement of the magnet will directly affect the distribution of the magnetic field lines, that is the form of the magnetic field distribution around the magnet.
Halbach Array (Halbach permanent magnet set) is a kind of magnet structure. In 1979, American scientist Klaus Halbach discovered this special permanent magnet structure and gradually improved it during the electron acceleration experiment, and finally formed the so-called “Halbach” magnet It is an approximate ideal structure in engineering. It uses a special arrangement of magnet units to enhance the field strength in the unit direction. The goal is to generate the strongest magnetic field with the least amount of magnets.
This array is completely composed of rare earth permanent magnet materials. According to a certain rule arranging permanent magnets with different magnetization directions. And then the magnetic force lines can be condensed on one side of the magnet and weakened on the other side. So people can obtain an ideal unilateral magnetic field. This has a very important significance in engineering. With excellent magnetic field distribution characteristics, the Halbach array is widely used in industrial fields such as nuclear magnetic resonance, magnetic levitation, and permanent magnet special motors.
The left picture is a single magnet set, all of them are north pole, and the color shows that the strength of the magnetic field is at the bottom and top of the magnet. The right picture is a Halbach array. The magnetic field on the top of the magnet is high, while the bottom is relatively weak. (In the same volume, the strong side surface magnetic field strength of the Halbach array magnet group is about 1.4 times of the traditional single magnet, especially when the thickness of the magnet is 4-16mm
The most common example of the Halbach array is probably the flexible refrigerator sticker. These magnets are thin and soft, usually printed on the refrigerator or behind the car. Although their magnetic properties are relatively weak (only 2% -3% strength) compared to NdFeB. The low price and practicality make it widely used.
THE FORM AND APPLICATION OF HALBACH ARRAY
LINEAR HALBACH ARRAY
The linear type is the most basic form of Halbach array. This array magnet can be regarded as a combination of radial array and tangential array, as shown below.
Linear Halbach arrays are currently mainly used in linear motors. The levitation principle of a maglev train is that the interaction between the moving magnet and the magnetic field generated by the current induced in the conductor generates levitation force, and is accompanied by magnetic resistance. Improving the buoyancy-to-resistance ratio is the key to improving the performance of the levitation system. This requires the weight of the onboard magnet Light, strong magnetic field, uniform magnetic field and high reliability. The Halbach array is installed horizontally in the center of the car body, and generates a propulsive force with the winding in the center of the track. The magnetic field is maximized with a smaller amount of magnets, and the other side has less magnetic field, which can avoid passengers being exposed to strong magnetic fields.
RING HALBACH ARRAY
The ring-shaped Halbach array can be regarded as a ring shape formed by combining linear Halbach arrays end to end.
In the permanent magnet motor, the permanent magnet motor using the Halbach array structure has a more sinusoidal air gap magnetic field than the traditional permanent magnet motor. With the same amount of permanent magnet material, the air gap magnetic density of the Halbach permanent magnet motor is greater. The iron loss is small. In addition, Halbach ring arrays are also widely used in permanent magnetic bearings, magnetic refrigeration equipment and magnetic resonance equipment.
MANUFACTURING AND PRODUCTION METHOD OF HALBACH ARRAY
Method 1: According to the topology of the array, use magnet glue to bond the pre-magnetized magnet segments together. Because the mutual repulsion between the magnet segments is very strong, use a mold to clamp when bonding. The manufacturing efficiency of this method is lower, but it is easier to implement, and it is more suitable for laboratory research.
Method 2: At first, use a mold filling or compression molding method to manufacture a complete magnet, and then magnetize it in a special fixture. The array structure processed by this method is similar to the following figure. This method has high processing efficiency and comparison. It is easy to realize mass production. However, people have to design magnetizing fixtures and formulating magnetizing processing.
Method 3: Use a winding array of a specific shape to achieve the Halbach-type magnetic field distribution, as shown below.
WHERE TO BUY HALBACH ARRAY
The answer is buy it from China.
Buy halbach array is not easy. Because Halbach Array is neodymium magnet + knowledge+experience. Without knowledge and experience hard to make a perfect Halbach Array.There lots of magnet factories in China, they know how to produce neodymium magnet. But just few of them know how to produce Halbach Array. These factories is hard to find.
But if you want to buy Halbach Array, welcome contact us. We have experienec with that. No matter linear array or ring array, we have experience with that. welcom contact us and send us your drawing. We will check your drawing and reply you ASAP with a reasonable price.
Can we get the uniformity with the Halbach?
We understand some customers will ask for the uniformity value. They will ask us, can you make a Halbach with the magnetic field in the void is 10,000 Gauss and with uniformity from 500-600ppm?
Unfourntly, the answer is NO.
But we still have no idea which company can offer exactly uniformity value. That is still a concept to us.