Halbach Array Magnets

Explore Halbach Array technology that enhances magnetic field strength on one side while canceling it on the opposing side for efficient use in motors, levitation, and data storage systems. Benefit from increased efficiency and focused magnetic field control with this innovative magnet configuration, providing practical solutions for advanced magnetic applications.

The Halbach Array is a well-known magnetic assembly with significant magnetic strength. Our company has extensive experience in producing Halbach Arrays.

Our Halbach Array Magnets

Flat Halbach Arrays

Halbach Cylinder Arrays

Large Halbach Arrays

Linear Halbach Arrays

What Is Halbach Array?

The Halbach array is a structure that arranges magnets highly efficiently. It consists of multiple high-grade magnets placed on a flat surface in an alternating pattern. The magnetic fields of each magnet point toward the middle of the array, where they combine to create an incredibly powerful magnetic strength.

Before delving into this structure, let’s examine the distribution of magnetic field lines of some common permanent magnets.

From these pictures, it is evident that the direction and arrangement of the magnet directly affect the distribution of the magnetic field lines, which determines the form of the magnetic field distribution around the magnets.

The left picture shows a single magnet set, with all magnets being north poles. The color indicates that the magnetic field strength is higher at the top and bottom of the magnet.
The right picture shows a Halbach array, where the magnetic field is stronger at the top of the magnet and weaker at the bottom.

In the same volume, the Halbach array magnet group has a strong side surface magnetic field strength of about 1.4 times that of a traditional single magnet, especially when the magnet thickness is between 4-16mm.

The most common example of a Halbach array is the flexible refrigerator magnet. These thin and soft magnets are usually placed on refrigerators or cars. Although their magnetic properties are relatively weak (only 2%-3% strength) compared to NdFeB, their low price and practicality make them widely used.

Halbach Array Structure

Halbach has many different structures, but regardless of the shape, the magnetic strength is concentrated on one surface.

Circular Halbach Array/Halbach Array Ring

The Halbach array is a ring-shaped structure that combines linear Halbach arrays end to end.

When used in a permanent magnet motor, the Halbach array structure produces a more sinusoidal air gap magnetic field than traditional permanent magnet motors. This results in a greater air gap magnetic density with the same amount of permanent magnet material and lower iron loss.

Halbach ring arrays are also commonly utilized in permanent magnetic bearings, refrigeration equipment, and magnetic resonance equipment.

Linear Halbach arrays

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

Linear Halbach arrays are mainly used in linear motors. The levitation principle of a maglev train is based on the interaction between the moving magnet and the magnetic field generated by the current induced in the conductor, which generates levitation force and magnetic resistance.

Improving the buoyancy-to-resistance ratio is crucial for enhancing the performance of the levitation system. This necessitates a lightweight onboard magnet with a strong, uniform, and reliable magnetic field. To achieve this, a Halbach array is installed horizontally at the center of the car body, generating a propulsive force with the winding in the center of the track.

The magnetic field is stronger with fewer magnets, while the opposite side has a weaker one. This helps prevent passengers from being exposed to strong magnetic fields.

Arc Halbach

The Halbach arc, named after physicist Klaus Halbach, is a magnetic assembly that arranges permanent magnets to concentrate the magnetic field on one side while canceling it out on the opposite side. This configuration benefits magnetic crawler robots by enhancing their ability to grip and move across vertical or upside-down metallic surfaces firmly without requiring an external power source. One key feature of these robots is their ability to efficiently perform inspection and maintenance tasks in challenging environments, such as ship hulls, storage tanks, and large machinery, by maximizing magnetic force.

Designers can optimize the functionality and flexibility of magnetic crawler robots by tailoring the shape and size of the Halbach arc to specific applications. The Halbach arc is pivotal in advancing robotic technology by contributing to the robots’ energy efficiency. This allows for prolonged operation times in remote or hazardous locations. Its innovative use in concentrating magnetic fields enhances the capability of robots to access and work in areas that are difficult or dangerous for humans. This showcases the significant impact of this magnetic assembly in robotics.

Special Shape

This structure is unique and requires the use of two specific magnet grades: N52 and N48SH. It combines N52 for maximum magnetization and N48SH for thermal stability. N52 grade is used for its high magnetic field strength in sections that don’t face high heat, while the N48SH is utilized in parts susceptible to higher temperatures, protecting against loss of magnetism.

This configuration ensures that the magnetic structure operates efficiently, with N52 magnets providing compact power where it’s safe to do so and N48SH magnets offering resilience to high temperatures. The result is a magnetic system capable of delivering strong performance without the risk of demagnetization, even in variable thermal environments.

The Halbach array structure in a permanent magnet motor produces a more sinusoidal air gap magnetic field than traditional permanent magnet motors. This results in a greater air gap magnetic density with the same amount of permanent magnet material and lower iron loss. Halbach ring arrays are also used in permanent magnetic bearings, refrigeration, and magnetic resonance equipment.

Homogeneity

A ring Halbach array may not be the most suitable option if you require a consistently uniform setup. Scientists often request a Halbach array with a homogeneity level of 300ppm, which is theoretically plausible but challenging to achieve in practice due to magnetic declination and limitations in magnetic assembly capabilities. In these situations, it is recommended to consider a yoke design. This design often creates a uniform magnetic field for NMR (nuclear magnetic resonance) instruments.

Simulation

Simulation and Reality:
When simulating small-sized Halbach arrays, the error between the results and actual values is approximately +5% to -10%. However, the error can reach as much as -25 % or -30 % for larger sizes.

Based on our experience, it is challenging to ensure similar magnetic fields even if the Halbach arrays are produced simultaneously.