A Halbach Array is a magnet structure that is an engineering approximation of the ideal, with the goal of generating the strongest magnetic field with the least amount of magnets. In 1979, American scholar Klaus Halbach discovered this special permanent magnet structure while doing electron acceleration experiments, and gradually perfected this structure, finally forming the so-called “Halbach” magnet.
The Halbach magnet structure is an approximation of the ideal structure in engineering, and the goal is to generate the strongest magnetic field with the least amount of magnets.
Using a special arrangement of magnet units, the field strength in a unit direction is enhanced. It is very important for engineering.
Of course, the specific application is extremely complicated, so it is not covered here.
In 1973, American scholar Mallianson discovered a peculiar permanent magnet structure while conducting assembling experiments on the permanent magnet structure, and called it “Magnetic Curiosity”. He didn’t see the usefulness of this structure at the time. In 1979, American scholar Klaus Halbach discovered this special permanent magnet structure when he used the magnetic field generated by various permanent magnet structures for electron acceleration experiments, and gradually perfected this structure, finally forming the so-called “Halbach” magnet. Halbach magnetic ring is a combination of radial and parallel arrangements of magnets. If the end effect is ignored, and the permeability of the surrounding magnetic conductive material is regarded as infinite, then the above permanent magnet structure will eventually form a unilateral magnetic field (one- sided field), which is a distinctive feature of Halbach. This feature indicates that Halbach magnets have good application value in linear motors. Compared with traditional motors, Halbach motors have the following advantages
Compared with the traditional permanent magnet motor structure, due to the superposition of the parallel magnetic field and the radial magnetic field after the decomposition of the Halbach magnetic ring, the magnetic field strength on the other side is greatly increased, which can effectively reduce the size of the motor and increase the power of the motor. density.
Folding stator and rotor
In the traditional permanent magnet motor, due to the inevitable existence of harmonics in the air gap magnetic field, inclined slots are generally used in the stator and rotor structure to weaken its influence. In the Halbach motor, due to the high degree of sinusoidal distribution of the air-gap magnetic field and the small harmonic content, the stator and rotor do not need inclined slots.
Due to the unilateral magnetic field distribution generated by the self-shielding effect of the Halbach magnet, it is no longer necessary for the rotor to use magnetic materials to provide passages for it, which not only provides a larger selection space for the rotor material selection, but also enables the system to have a lower moment of inertia and a higher Good fast attach performance.
Folding Permanent Magnets
Due to the directional magnetization of the Halbach magnet, the working point of the permanent magnet is relatively high, generally exceeding 0.9, which improves the utilization rate of the permanent magnet.
Folded Concentrated Winding
Distributed windings are often used in traditional permanent magnet motors to weaken the influence of harmonic magnetomotive force. In the Halbach motor, due to the high degree of sinusoidal distribution of the magnetic field, the influence of the harmonic magnetic field is small, so the centralized winding can be used.
The use of the Halbach motor magnet arrangement can reduce the torque ripple of the motor, thus greatly reducing the bearing requirements of the motor.
(a) Magnetic field distribution of radial magnet arrangement
(b) Magnetic field distribution of parallel magnet arrangement
(c) Magnetic field distribution of Halbach arrangement