In industrial applications, a Halbach Array is most commonly used to produce a magnetic field utilizing permanent magnets arranged in a 90° orientation change between magnetic elements, which amplifies the magnetic force applied. Halbach Arrays, both planar and circular, produce a magnetic field similar to what a powered solenoid (Electromagnet) would create, but without the extra size, cost, and maintenance. Planar Halbach Arrays contain the magnetic field to one side of the array, while a Circular Halbach Array concentrates the magnetic field on the ID or OD. Other iterations exist as well, and although the orientation of “bucking magnets” provides a 45° angle between magnets instead of a 90° iteration, they can be considered “non-traditional” Halbach Arrays.
For Circular Halbach Arrays, the simplest geometry is an arrangement of wedge shape magnets, with various magnetic orientations around a common axis.
Planar Halbach Arrays can be thought of as an unrolled Halbach cylinder. This variation does not necessarily create a uniform field, but it does create a very strong magnetic field on one working-face.
Halbach Array Applications
Planar Halbach Arrays are typically used for:
Linear coupling applications
Circular Halbach Arrays (on the OD iteration) are used in:
Rotors for Brushless DC Motors
Rotors for magnetic couplers
Rotors for power generations
Circular Halbach Arrays (on the ID iteration) are used to:
Steer, sort, and accelerate moving charged particles
Halbach Array Design Considerations
Between the work-piece and magnet array for a Planar design
In the ID of a Halbach Cylinder
Between a Halbach Rotor and the stator
External Demagnetizing Fields
This is important especially in Halbach Arrays used for Rotors.
Required Lifetime in Service
Available Room or Volume that Can Be Allotted to the Array
Size of the Array Assembly
Halbach Arrays depend on the assemblage of magnets, which by their nature attract and repel each other. The size of the array complicates its construction.
Halbach Array Benefits
The most obvious benefit of a Halbach-style Array is that the field produced is very strong when compared to other arrays having the same amount of the magnet alloy. The arrangement essentially increases the efficiency of the magnetic circuit.
The by-product of the design is that there is only one working surface or “working face.” The one working-face, where the magnetic field resides, is very strong; and the non-working face has essentially no field. In essence, the magnetic field, which would normally be present on the non-working face, is rerouted to the working-face. This is true for both Circular and Planar style Arrays.
Disadvantages of Halbach Arrays
The primary disadvantage of the Halbach Array geometry is that it is difficult to put together, resulting in potentially higher manufacturing costs than other potential solutions. This is because all of the magnet elements are repelling each other in a Halbach Array. This can create a variety of assembly issues including: needing to assemble the magnets magnetized, combating the forces during assembly, and ensuring the assembly will “hold together” during its use.
Another disadvantage is that Halbach Arrays may have an issue in high heat applications because the array elements apply a demagnetizing field on each other. As the operating temperature increases, a magnet is more susceptible to demagnetizing, and the neighboring magnet demagnetization is exacerbated.
Not all applications are good candidates for a using a Halbach Array. It has been pointed out that the Halbach Array is a more efficient use of magnet alloy, but it is important to consider the difficulty of design and manufacture before implementing a Halbach Array. There are many opportunities for a Halbach design to improve performance, but the benefit will come with a cost.