Halbach Array

Halbach Array, Halbach permanent magnet is a magnet structure. In 1979, American scholar Klaus Halbach discovered this special permanent magnet structure when he was doing electron acceleration experiments and gradually improved it, eventually forming the “Halbach” magnet. It is an almost ideal structure in engineering. It uses special magnet arrangement to enhance the field strength in a 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. By arranging permanent magnets with different magnetization directions according to certain rules, the magnetic force lines can be gathered on one side of the magnet and weakened on the other side, thereby obtaining an ideal unilateral magnetic field. This is of great significance in engineering. With its excellent magnetic field distribution characteristics, the Haier Buick array is widely used in industrial fields such as nuclear magnetic resonance, magnetic levitation, and permanent magnet special motors.

Halbach Array, Halbach permanent magnet

On the left is a single magnet with north poles all up and the strength of the field can be seen from the colors at the bottom and top of the magnet. On the right is a Halbach array with a stronger magnetic field at the top of the magnets and a weaker one at the bottom. (Under the same volume, the strong-side surface magnetic field strength of the Halbach array magnet group is about √2 times (1.4 times) that of a traditional single magnet, especially when the thickness of the magnet in the direction of magnetization is 4-16mm)

Form and Application of Halbach Array

Linear Halbach Array

The linear type is the most basic form of Halbach array. This kind of array magnet can be regarded as a combination of radial array and tangential array, as shown in the figure below.

Linear Array

Linear Halbach arrays are currently mainly used in linear motors. The levitation principle of the maglev train is that the moving magnet interacts with the magnetic field generated by the induced current in the conductor to generate levitation force, accompanied by magnetic resistance. Improving the buoyancy-to-resistance ratio is the key to improving the performance of the levitation system, which requires the weight of the on-board magnet Lightweight, strong magnetic field, uniform magnetic field, high reliability. The Halbach array is installed horizontally in the center of the car body, and it interacts with the winding in the center of the track to generate propulsion. It uses less magnets to maximize the magnetic field, while the other side has less magnetic field, which can prevent passengers from being exposed to strong magnetic fields.

Circular Halbach Array

The circular Halbach array can be regarded as a ring shape formed by combining the linear Halbach array end to end.

Circular Array

The permanent magnet motor using the Halbach array structure has a more sinusoidal distribution of the air gap magnetic field than the traditional permanent magnet motor. Under the condition of the same amount of permanent magnet material, the air gap magnetic density of the Halbach permanent magnet motor is higher and the iron loss is smaller. In addition, the Halbach ring array is also widely used in permanent magnetic bearings, magnetic refrigeration equipment, and magnetic resonance equipment.

Fabrication and production method of Halbach array

Method 1: According to the topological structure of the array, use magnet glue to stick the pre-magnetized magnet segments together. Because the mutual repulsion between the magnet segments is very strong, it is necessary to use a mold for clamping when bonding. The manufacturing efficiency of this method is relatively low, but it is relatively easy to implement, and is more suitable for use in the laboratory research stage.

Method 2: Firstly, a complete magnet is manufactured by mold filling or compression molding, and then magnetized in a special fixture. The array structure processed by this method is similar to the figure below. This method has high processing efficiency and is relatively Easy to achieve mass production. However, it is necessary to specially design the magnetization fixture and formulate the magnetization process.