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# NdFeB magnetic circuit design method

2018-06-13
Design basis and requirements
Magnetic circuit design roughly has the following several points:
1. Analysis and design requirements
The first to determine the use of the magnetic circuit, the magnetic performance requirements, the security of the use of the environment, structural requirements, price requirements and other requirements. It is also necessary to understand the source and processing of materials, and the relationship between this magnetic circuit and other parts. A more comprehensive understanding also includes the history of the use of similar magnetic circuits, each with its own advantages and disadvantages.
2. Determine the magnetic circuit structure
According to the various requirements for magnetic circuit design, according to the principles and principles of magnetic circuit design described in this book, and with the designer's experience, the structure of the magnetic circuit can be roughly determined. For example, what type of magnets are used, magnetic or magnetic, surface or hidden, etc. Based on the above considerations, the magnetic circuit structure diagram to be designed can be drawn.
3. Design calculation
Design calculations include undetermined geometry, as well as other undetermined magnetic circuit requirements.
We have repeatedly stressed that because there is no magnetically-defective material, magnetic lines of force are ubiquitous, so accurate calculations are difficult.
This has led to a variety of approximations. After the preliminary design is completed, there is also a design calculation verification process. Because each design method has a certain approximation. Often after one design has been designed, use another method to verify. Such as the use of magnetic circuit design and then verified by magnetic conductivity method. If the two are close, it means when designing Chuan Chuanzhu. Otherwise, we must redesign to find out the reasons.
4. Verification test
This is a must for most designs, from the actual composition of Sakazaki, to the correctness of the measurement and inspection sites, and to modify the design.

Equivalent circuit method
Magnetic circuit design methods are numerous, and equivalent circuit method is one of them. This is a long-term method of use. The magnetic circuit is replaced by an equivalent circuit and can be calculated using Ohm's law or the like. Such as flux-current; permeability-conductivity, magnetomotive force-voltage. Magnetic flux is the product of magnetic flux density and cross section. Magnetic permeability is the ratio of the magnetic flux density to the magnetic field strength, which is equal to the product of the magnetic field strength of the operating point and the length of the magnet. But this analog circuit is also different from the usual circuit. Here, the magnetic permeability corresponds to the conductivity, and the magnetic permeability of the voltage, the strength of the magnetic field, or the magnetic flux density are actually very difficult to calculate. Using a small electronic computer can make the calculation easy.
There are usually seven impedance units, each corresponding to the path of each flux. The currents of each path are obtained separately, and the magnetic flux density of each part is obtained after conversion. The determination of this method is that the various characteristics of the magnetic circuit can not be summarized, the details of the magnet magnetization characteristics can not all "and the branches accounted for the right leaf quite Leizun Xuan Yu H out fortunately magnetism of the Niu Yu L Wu a lack of county accountancy The Benefici- ban Phosphorus reactor is present, so its accuracy is limited. The biggest drawback of this approach is that it does not know the distribution of magnetic flux in the air gap (this is sometimes important, it can determine the distortion of the magnetic circuit). Another disadvantage is that it does not know the AC magnetic flux distribution.