As a very practical excitation equipment, electromagnets are widely used in magnetic material testing devices, vibrating sample magnetometers, Hall effect research, magnetoresistance effect research and magnetic field orientation. In the process of magnetic circuit design and pole head contraction, the design and processing are generally based on experience. How to choose the cross-sectional area of the magnetic yoke? And what kind of angle is used to shrink the pole head to maximize efficiency? There are few introductions. Often encountered some electromagnets, the design of the yoke is very unreasonable, the efficiency is low, causing a lot of energy waste in the excitation, the pole contraction angle is also varied. In return for users in the magnetic materials industry,
Hunan Yongyi Technology Co., Ltd.The method of designing electromagnets is made public for your reference and sharing.
1, how to choose the cross-sectional area of the yoke design electromagnet yoke iron requirements are: permeability as high as possible, the length as small as possible, the cross-sectional area as large as possible, the general use of yoke cross-sectional area S for the pole head cross-sectional area S 1.2 to 1.4 times. To avoid a decrease in permeability u due to saturation of the yoke. This is due to the fact that, assuming that the yoke and the pole are in good contact and there is no magnetic leakage, all the magnetic flux in the pole head passes through the yoke, I .e. BS = BS. For general soft magnetic materials, the knee bend of the magnetization curve is at 70%-80% of the saturation value. In order to improve efficiency and reduce magnetic flux leakage, we generally design the cross-sectional area of the yoke to be: 1/0.80-1/0.70, that is, S/S>1.2-1.4. When designing the measuring electromagnet, in order to meet the adjustment of the pole head, we generally choose the upper limit of 1.4 times, and the electromagnet with fixed gap is designed to choose 1.2 times.
2. How to Shrink the pole head of the pole head electromagnet is divided into a pillar and a platform. For the pillar pole head, pure Fe(BS is 2.15T) or Fe-Co(BS is 2. 4 T) alloy is used,. The use of circular table pole head (or contraction pole head) is to increase the gap magnetic field in the pole head as much as possible under the same excitation power condition. Some people blindly think that the foreign design is the best according to the contraction angle of some electromagnets measured abroad. It is said that the half angle thinks that the 39 ° circular table pole head is the best, but in fact there is no scientific basis. References, there is an accurate calculation theory for the cone angle of the truncated pole (as shown below),
It can be obtained from Coulomb's law, and the analytical formula used is: ΔHx =(Ms * 2π * r * dr * cos а)/[4r * μ 0 * (r2x2) * cosa] picture, where Ms is the saturation magnetic polarization strength of the pole head. to satisfy that ΔHx is the maximum value, the value of x can be changed to make a change and satisfy: d(ΔHx)/dx = 0, thus: x = SQRT(2)* 2, I .e., tana = r/x = 2. It can be deduced that a = 54 44 '(surprisingly, it is found that this angle is completely consistent with the axis direction of hard magnetization [11 1] of iron single crystal, which can also explain that the contraction of the contraction pole head at this angle facilitates the aggregation of magnetic lines of force). In order to facilitate the processing specification, we generally design the shrinkage half angle to 60 °.
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