The design and structure of popular magnetic circuit

The use scenarios of NdFeB permanent magnets are roughly divided into adsorption, repulsion, induction, electromagnetic conversion, etc. In different applications, the demand for magnetic field is different.

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1, The space structure of 3C products is extremely limited, and at the same time, high adsorption strength is required. The space structure does not allow the magnet size to increase, and the magnetic field strength needs to be enhanced through magnetic circuit design;

2, In occasions where magnetic field sensing is required, overly dispersed magnetic lines of force can cause Hall elements to miscontact, requiring control of the magnetic field range through magnetic circuit design;

3, occasions where high adsorption strength is required on one side of the magnet and the other side needs to be shielded from the magnetic field, too high a magnetic field strength on the shielded side will affect the use of electronic components, and problems in this area also need to be solved by magnetic circuit design;

4, The need for accurate positioning effect of the occasion, the need for uniform magnetic field occasions ...... and so on!

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As in all the above cases, it is difficult to use a single magnet to achieve the use of requirements, and when the price of rare earths is high, the volume and dosage of the magnet will seriously affect the cost of the product price, so we can meet the adsorption conditions or normal use of the situation, modify the magnetic circuit structure of the magnet to meet the different use of the scenario, and at the same time, reduce the amount of magnets in order to reduce costs.

Common magnetic circuits are roughly divided into HALBACH ARRAY, multipole magnetic circuit, focusing magnetic circuit, adding magnetically conductive materials, flexible transmission, single-sided magnetic, Magnetic focusing structure and so on. The following is an introduction to each of them:

HALBACH ARRAY

This is an approximately ideal structure in engineering, with the goal of generating the strongest magnetic field with the minimum amount of magnets. Due to the special magnetic circuit structure of the HALBACH?array, most of the magnetic field circuit can circulate inside the magnet?product, thereby reducing magnetic leakage and achieving self shielding effect in the non working area. After optimization of the circular HALBACH?magnetic circuit design, the non working area can achieve a minimum of 100% shielding. As shown in the figure, the magnetic field lines of the conventional magnetic circuit are symmetrically divergent, while the magnetic field lines of the HALBACH?array are mostly concentrated in the working area, Therefore, magnetic attraction can be increased.

Multipole magnetic circuit

The multipole magnetic circuit mainly utilizes the feature of preferentially selecting the nearest opposite pole to form a magnetic circuit. Compared to ordinary monopole magnets, the magnetic field lines of the multipole magnetic circuit are more concentrated on the surface, especially with more poles being more pronounced. There are two types of multipole magnetic circuits, one is the method of multipole magnetization with one magnet, and the other is the method of multiple monopole magnets adsorption. The difference between these two methods lies in their cost, and their actual functions are the same. The advantage of multipole magnetic circuit in small spacing adsorption is very obvious.

Focusing magnetic circuit

Focusing magnetic circuit utilizes a special magnetic circuit direction to concentrate the magnetic field in a small area, making the magnetic field in that area very strong, even reaching 1T, which is very helpful for accurate positioning and local induction.

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Magnetically conductive materials

Magnetically conductive materials use the magnetic field circuit to preferentially choose the path with the lowest magnetic resistance. Using highly conductive materials (SUS430, SPCC, DT4, etc.) in the magnetic circuit can well guide the direction of the magnetic field, thus achieving the effect of localised magnetic aggregation and isolation.

Flexible transmission

The characteristic of flexible transmission is to achieve non-contact flexible transmission through the attraction and repulsion formed by magnets, with small volume, simple structure, and torque that can vary according to the volume of the magnet and the size of the air gap. The adjustable space is big.

Single Sided Magnets

The characteristic of single sided magnetic field is to shield the polarity of one side of the magnet while retaining the polarity of the other side. The direct adsorption force is relatively large, but the magnetic attenuation amplitude increases with distance.

Magnetic focusing structure

The characteristic of this design?is that the magnets and iron yokes are arranged in relative polarity. As the ratio of the thickness of the magnets to the thickness of the iron yokes increases, the thicker the iron yokes, the smaller the divergence of the magnetic field lines. The magnetic focusing structure can be flexibly designed according to the size of the air gap, achieving the optimal effect and effectively saving magnets. The magnetic field is evenly distributed along the iron yoke, but the disadvantage is that the assembly cost is high.