Magnetic Core Considering Skin Effect of Magnetic Flux and Design Method

Abstract

The present invention proposes a magnetic core and a design method considering the flux skin effect, which belongs to the application field of magnetic circuit theory, and particularly relates to the design of magnetic cores. Taking the cross-section of the magnetic core through which the magnetic flux flows as the reference plane, combining the electromagnetic characteristics, temperature characteristics, magnetic flux amplitude and operating frequency of the magnetic core, the shape of the cross-section of the magnetic core is designed. By stretching the reference plane along the magnetic flux path, a closed or discontinuous air path is formed inside the magnetic core to constitute a magnetic core with a pipe structure. When high-frequency magnetic flux is passed through the magnetic core, the magnetic core and the design method considering the flux skin effect proposed by the present invention can reduce the weight of the magnetic core, reduce the loss and temperature rise of the magnetic core, and have the effect of suppressing the skin effect of the magnetic core.

Description

Technical Field

[0001] The present invention belongs to the field of application of magnetic circuit theory, and particularly relates to magnetic core design. Background Art

[0002] Similar to the way a conductor conducts current in an electric circuit, the purpose of using a magnetic core in a magnetic circuit is to provide a predictable and well-defined path for magnetic flux and concentrate magnetic field energy in the magnetic core. When the magnetomotive force is constant, the magnetic circuit constructed by the magnetic core can reduce the magnetic resistance of the magnetic circuit and increase the magnetic flux of the magnetic circuit. The presence of the magnetic core not only improves the magnetic energy density of electromagnetic devices but also reduces the size and weight of electromagnetic devices.

[0003] According to the "Transformer and Inductor Design Handbook" (Fourth Edition) translated by Zhou Jinghua and Gong Shaowen, the structure of the magnetic core is divided into a core type and a shell type according to the positional relationship between the magnetic core and the coil. Currently, many domestic and foreign magnetic core manufacturers, such as TDK Corporation in Japan, Ferroxcube Corporation in the United States, and Xinkangda Corporation in China, further divide the magnetic core into toroidal, CC or UU type, pot type, PQ type, RM type, EE type, etc. The shapes of magnetic cores are diverse, and each has its corresponding selection according to different applications. Various magnetic cores can be combined to form a closed or non-closed magnetic circuit.

[0004] When an alternating current is passed through a conductor, the equivalent inductance inside the conductor causes the current distribution in the conductor to be uneven, and the current is concentrated in the "skin" part of the conductor, that is, the current is concentrated in a thin layer on the outer surface of the conductor. The closer to the surface of the conductor, the greater the current density, and the actual current inside the conductor is smaller. As a result, the resistance of the conductor increases, and its power loss also increases. This phenomenon is called the skin effect of current. According to Chinese Patent CN202011350276.4, there are not only magnetic resistance parameters but also magnetic induction parameters in a magnetic circuit. When an alternating magnetic flux is passed through a magnetic core, due to the presence of magnetic induction parameters in the magnetic circuit, the magnetic flux in the magnetic core will exhibit the skin effect, that is, the high-frequency magnetic flux is unevenly distributed in the magnetic core, and the magnetic flux tends to flow from the surface of the magnetic core, and the magnetic induction intensity gradually decreases from the surface to the center. The skin effect of the magnetic core not only brings losses but also limits the ability of the magnetic core to conduct high-frequency magnetic flux. However, the existing magnetic core products and design methods do not consider the magnetic flux skin effect, resulting in more materials used, greater weight, and higher losses. Summary of the Invention

[0005] The technical problem to be solved by the present invention is, in view of the defects of the background art, to propose a magnetic core and a design method considering the magnetic flux skin effect. Taking the cross-section of the magnetic core through which the magnetic flux flows as the reference plane, combining the electromagnetic characteristics, temperature characteristics, magnetic flux amplitude, and operating frequency of the magnetic core, to design the shape of the cross-section of the magnetic core, and by stretching the reference plane along the magnetic flux path, a closed or discontinuous air path is formed inside the magnetic core to constitute a magnetic core with a pipe structure.

[0006] The present invention adopts the following technical solutions to solve the above technical problems:

[0007] The present invention first proposes a magnetic core considering the flux skin effect. Among them, the magnetic core considering the flux skin effect has a closed or discontinuous pipe structure, and through this pipe structure, the weight of the magnetic core can be reduced, and the loss and temperature rise of the magnetic core can be reduced. When high-frequency magnetic flux is passed through the magnetic core, it has the effect of suppressing the skin effect of the magnetic core.

[0008] For the magnetic core considering the flux skin effect, on the premise of determining the outer contour of the magnetic core, the cross-section of the magnetic core through which the magnetic flux flows is designed according to the electromagnetic characteristics, temperature coefficient, magnetic flux amplitude and operating frequency of the magnetic core material, and a magnetic core cross-section with the characteristics of a multi-connected region can be formed. The magnetic core cross-section can be either centrosymmetric or non-centrosymmetric.

[0009] Furthermore, for the magnetic core considering the flux skin effect, its cross-section can be designed as a hollow ring structure, a radial notch structure, etc., to reduce or block the path of induced eddy currents, that is, to reduce the equivalent magnetic induction of the magnetic circuit.

[0010] Furthermore, for the magnetic core considering the flux skin effect, the shape of its internal closed or discontinuous pipe can be obtained by stretching the magnetic core cross-section along the path of the magnetic flux flow.

[0011] Furthermore, for the magnetic core considering the flux skin effect, the thickness of its internal closed or discontinuous pipe is determined by the electromagnetic characteristics, temperature coefficient, magnetic flux amplitude and operating frequency of the magnetic core material, that is, related to the skin depth of the magnetic flux. In the formula, f is the operating frequency of the magnetic flux in the magnetic core, μ is the magnetic permeability of the magnetic core related to temperature, and σ is the electrical conductivity of the magnetic core related to temperature.

[0012] Furthermore, for the magnetic core considering the flux skin effect, its internal closed or discontinuous pipe can be filled with air or other non-magnetic materials. In particular, for a magnetic core with a continuous pipe structure inside, this pipe structure can be used as a circulation path for the cooling medium, thereby improving the cooling effect of the magnetic core.

[0013] Furthermore, for the magnetic core considering the flux skin effect, the closed or discontinuous pipe structure of the magnetic core reduces the equivalent magnetic induction value of the magnetic circuit. According to the magnetic circuit power law it can be known that under the same magnetic flux condition, this magnetic core can generate less magnetic core loss and reduce the temperature rise of the magnetic core.

[0014] Furthermore, for the magnetic core considering the flux skin effect, its material is a magnetic material that can form a magnetic circuit, such as silicon steel, nickel iron (Mumetal), cobalt iron (Permendur), amorphous metal alloy, and ferrite, etc.

[0015] Furthermore, to adapt to different application requirements, the magnetic core considering the flux skin effect has a closed or discontinuous pipe structure inside, and its outer shape can be the same as common magnetic core shapes such as toroidal, CC or UU type, pot type, PQ type, RM type, and EE type.

[0016] The present invention also proposes a design method for a magnetic core considering the flux skin effect, which is as follows:

[0017] S1. Select the outer shape, size, and material of the magnetic core according to actual application requirements;

[0018] S2. Combine the electromagnetic characteristics, temperature characteristics, magnetic flux amplitude, and operating frequency of the magnetic core to design the cross-section of the magnetic core through which the magnetic flux flows, forming a multi-connected region;

[0019] S3. Stretch the cross-section of the magnetic core along the path surface of the magnetic flux flowing through the magnetic core to form a continuous or discontinuous tubular structure inside the magnetic core;

[0020] S4. Form a closed magnetic circuit composed of the magnetic core or the magnetic core and other media to constitute a magnetic core considering the flux skin effect.

[0021] Furthermore, in the design method for a magnetic core considering the flux skin effect proposed by the present invention, in step S1, the outer shape of the magnetic core includes, but is not limited to, toroidal, CC or UU type, pot type, PQ type, RM type, and EE type. The materials of the magnetic core include, but are not limited to, silicon steel, nickel iron (Mumetal), cobalt iron (Permendur), amorphous metal alloy, and ferrite.

[0022] Furthermore, in the design method for a magnetic core considering the flux skin effect proposed by the present invention, in step S4, since a single magnetic core cannot form a closed magnetic circuit and needs to form a closed magnetic circuit together with other magnetic cores or other media, and since the magnetic core in the magnetic circuit considers the flux skin effect, this closed magnetic circuit has the effect of suppressing the flux skin effect.

[0023] The present invention adopts the above technical solutions, and compared with the prior art, its beneficial effects are as follows:

[0024] 1. The proposed magnetic core considering the flux skin effect has a closed or discontinuous pipe structure, which saves the material for making the magnetic core and reduces the weight of the magnetic core.

[0025] 2. Under the condition of generating the same alternating magnetic flux, the magnetic core considering the flux skin effect requires a smaller magnetomotive force at high frequencies.

[0026] 3. The closed or discontinuous pipe structure of the magnetic core can effectively reduce the equivalent magnetic induction value of the closed magnetic circuit formed by the magnetic core. Under the condition of the same alternating magnetic flux, it effectively reduces the loss of the magnetic core and the resulting temperature rise.

[0027] 4. The closed or discontinuous pipe structure of the magnetic core provides a circulation path for the cooling medium of the magnetic core, facilitating the design of the magnetic core cooling system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the principle for generating the flux skin effect of the present invention.

[0029] Figure 2 It is a schematic diagram of different magnetic cores of the magnetic core and design method considering the flux skin effect of the present invention.

[0030] Figure 3 It is a flowchart of the magnetic core and design method considering the flux skin effect of the present invention.

[0031] Figure 4 It is an assembly diagram of the magnetic core of the magnetic core and design method considering the flux skin effect of the present invention.

[0032] Figure 5 It is a verification device of the magnetic core and design method considering the flux skin effect of the present invention.

[0033] Figure 6 It is the experimental result of the magnetic core and design method considering the flux skin effect of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following further elaborates on the technical solutions of the present invention with reference to the accompanying drawings. Obviously, the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] Those skilled in the art of this technology can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of those of ordinary skill in the art in the field to which the present invention belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless defined as such herein.

[0036] When an alternating magnetic flux is applied to the magnetic circuit, the magnetic induction in the magnetic circuit will generate an induced magnetomotive force (induced current) to hinder the change of the magnetic flux in the magnetic core, as shown in (a) of Figure 1 . As the frequency of the alternating magnetic flux in the magnetic circuit increases, the magnetic flux will also exhibit a skin effect similar to the alternating current in a conductor. Here, a cylindrical magnetic core is used to analyze the cause of the generation of the flux skin effect. As shown in Figure 1As shown in (a) of the figure, for simplicity, the circular magnetic core in the figure is divided into four rings: 1, 2, 3, and 4. According to Faraday's law of electromagnetic induction and Lenz's law, induced magnetomotive forces are generated on all four cross-sections. For the induced magnetomotive force on magnetic core 1, the reverse magnetic flux generated not only hinders the change in magnetic flux on magnetic core 1 but also has an obstructive effect on the magnetic fluxes on magnetic cores 2, 3, and 4. That is, the magnetic induction of magnetic core 1 also affects the magnetic fluxes of magnetic cores 2, 3, and 4. Based on the relationship between parts of the magnetic core, an equivalent magnetic circuit diagram can be drawn as shown in Figure 1 (b) of the figure. It can be seen that the closer to the center of the magnetic core, the larger the equivalent magnetic induction value on the branch path and the smaller the corresponding magnetic flux, while the closer to the surface of the branch path, the smaller the equivalent magnetic induction value and the larger the corresponding magnetic flux, that is, the skin effect of the magnetic flux appears. As the frequency of the magnetic core further increases, the magnetic flux density distribution on the magnetic core is as shown in Figure 1 (c) of the figure. It can be seen that all magnetic fluxes only flow in a thin layer on the surface of the magnetic core, which not only brings more losses but also exacerbates magnetic core saturation and limits the ability of the magnetic core to conduct high-frequency magnetic fluxes.

[0037] To solve the problem of the skin effect of the magnetic flux, the present invention proposes a magnetic core and design method considering the skin effect of the magnetic flux. The core content is to use the cross-section of the magnetic core through which the magnetic flux flows as a reference surface, and combine the electromagnetic characteristics, temperature characteristics, magnetic flux amplitude, and operating frequency of the magnetic core to design the shape of the cross-section of the magnetic core. By stretching the reference surface along the magnetic flux path, a closed or discontinuous air path is formed inside the magnetic core to constitute a hollow magnetic core with a pipe structure.

[0038] The magnetic core considering the skin effect of the magnetic flux has a closed or discontinuous pipe structure. The closed pipe structure is as shown in Figure 2 (a) of the figure and Figure 2 (b) of the figure, and the discontinuous pipe structure is as shown in Figure 2 (c) of the figure and Figure 2 (d) of the figure. When high-frequency magnetic flux is passed through the magnetic core, the pipe structure can reduce the weight of the magnetic core, reduce the loss and temperature rise of the magnetic core, and has the effect of suppressing the skin effect of the magnetic core.

[0039] For the magnetic core considering the skin effect of the magnetic flux, on the premise that the outer contour of the magnetic core is determined, the cross-section of the magnetic core through which the magnetic flux flows is designed according to the electromagnetic characteristics, temperature coefficient, magnetic flux amplitude, and operating frequency of the magnetic core material, and a cross-section of the magnetic core with the characteristics of a multi-connected region can be formed. The cross-section of the magnetic core can be centrosymmetric, as shown in Figure 2 (c) of the figure, or it can be non-centrosymmetric, as shown in Figure 2 (d) of the figure. The thickness of the closed or discontinuous pipe inside it is determined by the electromagnetic characteristics, temperature coefficient, magnetic flux amplitude, and operating frequency of the magnetic core material, that is, related to the skin depth of the magnetic flux It is related. In the formula, f is the working frequency of the magnetic flux in the magnetic core, μ is the magnetic permeability of the magnetic core related to temperature, and σ is the electrical conductivity of the magnetic core related to temperature. For example, when the magnetic flux frequency in the magnetic circuit is larger, the skin depth of the magnetic flux is smaller. At this time, the pipe thickness can be appropriately reduced.

[0040] Furthermore, for the magnetic core considering the skin effect of magnetic flux, its cross-section can be designed as a hollow ring structure, a radial notch structure, etc., as shown in Figure 2 (c) and (d) in [reference], so as to reduce or block the induced eddy current path, that is, reduce the equivalent magnetic induction of the magnetic circuit.

[0041] Furthermore, for the magnetic core considering the skin effect of magnetic flux, the shape of the internal closed or discontinuous hollow pipe can be obtained by stretching the cross-section of the magnetic core along the path of the magnetic flux flow. When continuously stretching along the closed magnetic circuit, a magnetic core with a continuous pipe structure can be obtained, as shown in Figure 2 (a) of [reference] and Figure 2 (b) of [reference]. When stretching intermittently along the closed magnetic circuit, a magnetic core with a discontinuous pipe structure can be obtained. For example, in Figure 2 (c) of [reference] and Figure 2 (d) of [reference], the discontinuous pipe structure is obtained by stretching the cross-section of the magnetic core along the path of the middle column magnetic circuit.

[0042] Furthermore, for the magnetic core considering the skin effect of magnetic flux, its internal closed or discontinuous pipe can be filled with air or other non-magnetic conductive materials. In particular, for a magnetic core with a continuous pipe structure inside, this pipe structure can be used as a circulation path for the cooling medium, thereby improving the cooling effect of the magnetic core.

[0043] Furthermore, for the magnetic core considering the skin effect of magnetic flux, the closed or discontinuous pipe structure of the magnetic core reduces the equivalent magnetic induction value of the magnetic circuit. According to the magnetic circuit power law it can be known that under the same magnetic flux condition, this magnetic core can generate less magnetic core loss and reduce the temperature rise of the magnetic core.

[0044] Furthermore, for the magnetic core considering the skin effect of magnetic flux, its material is a magnetic material that can form a magnetic circuit, such as silicon steel, nickel iron (Mumetal), cobalt iron (Permendur), amorphous metal alloy, and ferrite, etc.

[0045] Furthermore, for the magnetic core considering the skin effect of magnetic flux, to meet different application requirements, the magnetic core has a closed or discontinuous pipe structure inside, and its shape can be the same as common magnetic core shapes such as ring type, CC or UU type, can type, PQ type, RM type, and EE type, as shown in Figure 2 (a)-(d) in [reference].

[0046] Furthermore, for a magnetic core considering the flux skin effect proposed by the present invention, since a single magnetic core cannot form a closed magnetic circuit, it is necessary to jointly form a closed magnetic circuit with other magnetic cores or other media, such as Figure 3 shown, which includes windings and a bobbin, a pair of EC-shaped magnetic cores, and clamps provided at both ends for fixing the magnetic cores. A pair of EC-shaped magnetic cores are connected through a matching bobbin to form a closed magnetic circuit. The windings on the bobbin provide magnetomotive force for the closed magnetic circuit to form magnetic flux. The clamps are used to fix the magnetic cores, reduce the air gap between the magnetic cores, and reduce the vibration generated when the magnetic cores work. Since the magnetic cores in the magnetic circuit consider the flux skin effect, this closed magnetic circuit has the effect of suppressing the flux skin effect.

[0047] Based on the above-mentioned magnetic core considering the flux skin effect, the specific process of the magnetic core design method considering the flux skin effect proposed by the present invention is as follows:

[0048] S1. Select the shape, size and material of the magnetic core according to the actual application requirements;

[0049] S2. Combine the electromagnetic characteristics, temperature characteristics, magnetic flux amplitude and operating frequency of the magnetic core to design the cross-section of the magnetic core through which the magnetic flux flows, forming a multi-connected region;

[0050] S3. Stretch the cross-section of the magnetic core along the path surface of the magnetic flux flowing through the magnetic core to form a continuous or discontinuous tubular structure inside the magnetic core;

[0051] S4. The magnetic core or the magnetic core and other media (such as air) form a closed magnetic circuit to constitute a magnetic core considering the flux skin effect.

[0052] Such as Figure 4 shown, the figure is the corresponding flowchart of the magnetic core design method considering the flux skin effect. Next, the magnetic core and design method considering the flux skin effect proposed by the present invention are verified.

[0053] The verification device for the magnetic core and design method considering the flux skin effect is as Figure 5 shown. This verification device is composed of a signal generator, a power amplifier, three groups of magnetic cores to be measured, a power analyzer, a voltage differential probe, a high-frequency current probe and an oscillograph. Three groups of magnetic cores to be measured are EC90 magnetic cores, and the material of the magnetic cores is HP3. Its structure is as Figure 2As shown in (c). The diameters of the central column openings of the three groups of cores tested are 0 mm, 5 mm, and 10 mm respectively, and their weights are 740 g, 723 g, and 680 g respectively. For the primary side of the core winding, Litz wire with a specification of 0.1 mm / 100 is selected, with 25 turns, and the measured DC resistance is 0.0717 Ω. For the secondary side of the core winding, polyester enameled round copper wire with a diameter of 0.47 mm is selected, also with 25 turns, and the measured DC resistance is 0.275 Ω. The windings on the primary and secondary sides of the three groups of cores remain unchanged during measurement.

[0054] Under the condition that the initial core temperature is 25 °C, keeping the magnetic flux in the core at 0.00018 Wb, continuously test the magnetomotive force, core loss, and the highest core temperature of the three groups of cores. According to Ampere's law, the magnetomotive force of the core is obtained by multiplying the current measured by the high-frequency current probe by the number of turns. The core loss power is the input active power measured by power analysis minus the resistance loss of the primary side winding. The highest core temperature is directly measured by three thermocouple sensors on the core.

[0055] The test results of the three groups of cores are as Figure 6 shown. As Figure 6 shown in (a), when the frequency is relatively low, due to the opening causing an increase in the magnetic resistance of the core and the magnetic induction of the core not playing a major role, therefore, for generating the same magnetic flux, the magnetomotive force required for the 15-mm hole core > the magnetomotive force required for the 10-mm hole core > the magnetomotive force of the non-hole core. As the magnetic flux frequency increases, the skin effect of the magnetic flux occurs, and the magnetic resistance values of the three groups of cores are almost the same, and the magnetic induction plays a major role in the magnetic circuit. Therefore, at high-frequency magnetic fluxes, the magnetomotive force required for the 15-mm hole core < the magnetomotive force required for the 10-mm hole core < the magnetomotive force of the non-hole core. This result shows that the proposed core considering the skin effect of the magnetic flux has a smaller magnetic induction value at high-frequency magnetic fluxes and can suppress the skin effect of the magnetic flux.

[0056] Since the closed magnetic circuit composed of the open-core has a closed or discontinuous pipe structure, therefore, the core with a tubular structure has a smaller magnetic induction value. Under the same magnetic flux, according to the magnetic circuit power law it can be known that the core loss generated by the 15-mm hole core is the smallest, the core loss generated by the 5-mm hole core is relatively large, and the core loss generated by the non-hole core is the largest. As Figure 6 shown in (b), the experimental results verify the correctness of the theoretical analysis.

[0057] During the experiment, no heat dissipation or cooling equipment was used. Therefore, the loss value generated by the core can also be reflected by the core temperature rise, as Figure 6As shown in (c) therein, the temperature rise corresponding to the 15-mm hole core is the smallest, the temperature rise of the 5-mm hole core is the second, and the temperature rise of the core without holes is the highest, which verifies again the effectiveness and feasibility of the core considering the flux skin effect proposed by the present invention.

[0058] In summary, the present invention proposes a core and a design method considering the flux skin effect. The above description is only the preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiment. The core is not limited to ferrite, but any material that can form a magnetic circuit and equivalent modifications or changes made by those of ordinary skill in the art according to the content disclosed by the present invention should be included in the protection scope recorded in the claims.

[0059] The above description is only part of the embodiments of the present invention. It should be noted that for those of ordinary skill in the art in the technical field, without departing from the principle of the present invention, several improvements and retouches can be made, and these improvements and retouches should also be regarded as the protection scope of the present invention.

Claims

1. A magnetic core considering the flux skin effect, characterized in that, the magnetic core has a closed or discontinuous hollow pipe structure. When the outer contour of the magnetic core is determined, the thickness of the hollow pipe of the cross-section of the magnetic core through which the magnetic flux flows is designed according to the electromagnetic characteristics, temperature coefficient, magnetic flux amplitude and operating frequency of the magnetic core material, so as to form a cross-section of the magnetic core with the characteristics of a multi-connected region; Among them, the thickness of the closed or discontinuous pipeline inside the magnetic core is determined by the electromagnetic characteristics, temperature coefficient, magnetic flux amplitude, and operating frequency of the magnetic core material, that is, related to the skin depth of the magnetic flux is relevant, where f is the operating frequency of the magnetic flux in the magnetic core, μ is the magnetic core permeability related to temperature, σ is the magnetic core conductivity related to temperature.

2. The magnetic core considering the flux skin effect according to claim 1, characterized in that, the cross-section of the magnetic core is designed as a hollow ring structure or a radial notch structure to reduce or block the path of induced eddy currents, that is, to reduce the equivalent magnetic induction of the magnetic circuit.

3. The magnetic core considering the flux skin effect according to claim 1, characterized in that, the shape of the closed or discontinuous pipe inside the magnetic core is obtained by stretching the cross-section of the magnetic core along the path of the magnetic flux flow.

4. The magnetic core considering the flux skin effect according to claim 1, characterized in that, the closed or discontinuous hollow pipe inside the magnetic core is filled with air or other non-magnetic materials.

5. The magnetic core considering the flux skin effect according to claim 1, characterized in that, for a magnetic core with a continuous pipe structure inside, the pipe structure is used as a circulation path for the cooling medium.

6. The magnetic core considering the flux skin effect according to claim 1, characterized in that, the material of the magnetic core is a magnetic material that can form a magnetic circuit, including silicon steel, nickel iron, cobalt iron, amorphous metal alloy and ferrite.

7. The magnetic core considering the flux skin effect according to claim 1, characterized in that, the magnetic core has a closed or discontinuous pipe structure inside, and its outer shape includes: ring type, CC or UU type, can type, PQ type, RM type and EE type.

8. A closed magnetic circuit with the suppression of the flux skin effect, characterized in that, the magnetic core described in claim 1 is used together with other magnetic cores or other media to form a closed magnetic circuit.

9. A method for designing a magnetic core considering the flux skin effect, characterized in that, specifically as follows: S1. Select the outer shape, size and material of the magnetic core according to the actual application requirements; S2. Combine the electromagnetic characteristics, temperature characteristics, magnetic flux amplitude and operating frequency of the magnetic core to design the cross-section of the magnetic core through which the magnetic flux flows to form a multi-connected region; S3. Stretch the cross-section of the magnetic core along the path surface of the magnetic flux flowing through the magnetic core to form a continuous or discontinuous tubular structure inside the magnetic core; S4. Form a closed magnetic circuit by the magnetic core or the magnetic core and other media to constitute a magnetic core considering the flux skin effect; Among them, the thickness of the closed or discontinuous pipeline inside the magnetic core is determined by the electromagnetic characteristics, temperature coefficient, magnetic flux amplitude, and operating frequency of the magnetic core material, that is, related to the skin depth of the magnetic flux is relevant. In the formula, f is the operating frequency of the magnetic flux in the magnetic core, μ is the magnetic permeability of the magnetic core related to temperature, σ is the electrical conductivity of the magnetic core related to temperature.

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