Preparation method of composite iron core for current transformer and composite iron core

Abstract

A preparation method and composite core for a current transformer, comprising the following steps: separately preparing a silicon steel core, an SMC molded lining, and an amorphous core; embedding the silicon steel core into the SMC molded lining to form a shell; placing the amorphous core into the shell; placing epoxy resin and a curing agent in a blender and stirring and mixing them to obtain a mixture I; pouring the obtained mixture I into the shell, allowing the mixture I to completely penetrate the amorphous core, covering the amorphous core, and then curing; after curing, placing the epoxy resin, curing agent, and silicon powder in a blender and stirring and mixing them to obtain a mixture II; pouring the mixture II into the shell, filling the shell, and curing it to obtain the composite core. The composite core obtained by the above steps of the present invention has improved mechanical properties, protects the silicon steel core and the amorphous core from stress, effectively reduces the composite core buffer layer, increases the effective distance of the main insulation, and improves the power frequency withstand voltage, partial discharge level, measurement accuracy, and protection multiple of the current transformer.

Description

Technical Field

[0001] The present invention relates to the technical field of electrical industry, and in particular to a preparation method of a composite iron core for a current transformer and the composite iron core. Background Art

[0002] The iron core is a core component in electromagnetic devices. Its function is to achieve energy conversion or signal transmission by concentrating magnetic lines of force and enhancing electromagnetic efficiency. However, existing iron cores use a 304 stainless steel casing structure, with an amorphous iron core placed in a stainless steel shell. This is sealed with 704 silicone rubber, and then a 2mm thick epoxy resin ring with the same inner diameter as the amorphous iron core is placed on top. Finally, it is evenly wrapped with low-voltage electrical insulating tape. The iron core buffer layer is as thick as 10mm, reducing the main insulation distance, affecting the power frequency withstand voltage, and partial discharge does not meet technical requirements. Summary of the Invention

[0003] In view of this, the present application provides a preparation method and a composite iron core for a current transformer, which effectively reduces the buffer layer of the composite iron core, increases the effective distance of the main insulation, and improves the power frequency withstand voltage, partial discharge level, measurement accuracy and protection multiple of the current transformer.

[0004] According to one aspect of the present application, a method for preparing a composite core for a current transformer is provided, wherein the composite core for the current transformer comprises an SMC molded lining, a silicon steel core, and an amorphous core; the method comprises the following steps: S1: separately manufacturing the silicon steel core, the SMC molded lining, and the amorphous core; S2: embedding the silicon steel core into the SMC molded lining, with a preset distance between the inner wall of the silicon steel core and the outer wall of the SMC molded lining to form a shell; S3: installing the amorphous core into the shell, at which time a gap exists between the amorphous core and the inner wall of the silicon steel core, and the amorphous core and the SMC molded lining are spaced apart. There are also gaps between the outer walls; S4: putting the epoxy resin and the curing agent into a blender and stirring and mixing them to obtain a mixture I; S5: pouring the obtained mixture I into the shell, allowing the mixture I to completely penetrate into the gap between the amorphous iron core and the inner wall of the silicon steel core and the gap between the amorphous iron core and the outer wall of the SMC molded liner, and covering the top of the amorphous iron core and then curing; S6: after curing, putting the epoxy resin, the curing agent and the silicon powder into a blender and stirring and mixing them to obtain a mixture II; S7: pouring the mixture II into the shell and filling the shell; S8: curing after filling to obtain a composite iron core.

[0005] In one possible implementation, the mass ratio of the epoxy resin to the curing agent in the mixture I is 100:25, and after the mixture I is poured into the shell, the shell is in a partially filled state.

[0006] In one possible implementation, the curing time is not less than 8 hours.

[0007] In one possible implementation, the mass ratio of the epoxy resin, the curing agent, and the silicon powder in the mixture II is 100:25:300, and the mixture II is poured into the shell and fills the shell.

[0008] In one possible implementation, the SMC molded liner is interference fit with the inner ring of the silicon steel core, and the thickness of the SMC molded liner is 2 mm.

[0009] In one possible implementation, the height of the SMC molded liner is the same as the height of the inner ring of the silicon steel core.

[0010] In a possible implementation, the height of the amorphous core is 5 mm lower than the height of the shell.

[0011] In one possible implementation, the area of ​​the silicon steel core window accounts for 70%, and the area of ​​the amorphous iron core window accounts for 30%.

[0012] A composite iron core for a current transformer, prepared by the above method; comprising: an SMC molded liner, a silicon steel core, and an amorphous iron core; the SMC molded liner is a hollow cylindrical structure with openings at both ends, the SMC molded liner has a preset height, and one end of the SMC molded liner extends outwardly with an extension; the silicon steel core is a hollow cylinder with openings at both ends, the silicon steel core has a preset thickness, and is sleeved on the outer wall of the SMC molded liner, with a preset distance between the inner wall of the silicon steel core and the outer wall of the SMC molded liner, and one end of the silicon steel core is interference fit with the extension; the amorphous iron core is also a hollow cylindrical structure with openings at both ends, and is sleeved on the outer wall of the SMC molded liner, located between the silicon steel core and the SMC molded liner.

[0013] In one possible implementation, the inner diameter of the SMC molded liner is smaller than the inner diameter of the amorphous core, and the inner diameter of the amorphous core is smaller than the inner diameter of the silicon steel core.

[0014] The beneficial effects of the present invention are as follows: an SMC molded lining, a silicon steel core, an amorphous iron core, an epoxy resin, a curing agent and silicon powder are provided, and the following steps are performed: S1: the silicon steel core, the SMC molded lining and the amorphous iron core are prepared respectively; S2: the inner ring of the silicon steel core is embedded in the SMC molded lining to form a shell composed of silicon steel and the SMC molded lining; S3: the amorphous iron core is installed in the shell; S4: the epoxy resin and the curing agent are put into a blender and stirred and mixed to obtain Mixture I; S5: Pour the resulting Mixture I into the housing, allowing Mixture I to completely penetrate the gap between the amorphous core and the inner wall of the silicon steel core, and the gap between the amorphous core and the outer wall of the SMC molded liner, covering the amorphous core before curing; S6: After curing, place the epoxy resin, the curing agent, and the silicon powder in a blender and stir and mix them to obtain Mixture II; S7: Pour Mixture II into the housing until it is completely filled; S8: After it is completely filled, cure to obtain a composite core. The resulting composite core is potted with different mixtures to improve its mechanical properties, protect the silicon steel core and the amorphous core from stress, effectively reduce the composite core's buffer layer, increase the effective distance of the main insulation, and improve the current transformer's power frequency withstand voltage, partial discharge level, measurement accuracy, and protection multiple. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A cross-sectional view showing the specific structure of the composite core of the current transformer according to an embodiment of the present application;

[0016] Figure 2 A top view of a composite core of a current transformer according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0018] Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar symbols throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0019] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention or simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore should not be understood as limiting the present invention.

[0020] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0021] In the present invention, unless otherwise expressly specified or limited, terms such as "mounted," "connected," "connect," "fixed," "joined," and "hinge" should be understood in a broad sense. For example, these terms may refer to fixed or detachable connections, or integration; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0022] like Figures 1 to 2 As shown, the preparation method of the composite iron core for current transformer includes SMC molded lining 100, silicon steel core 200, amorphous iron core 300, epoxy resin, curing agent and silicon powder, and the mass ratio of epoxy resin, curing agent and silicon powder is 100:25:300.

[0023] Specifically, SMC molding is used because SMC, the full name of which is Sheet Molding Compound, is a premix composed of resin, reinforcing materials (such as glass fiber, carbon fiber, etc.), fillers, thickeners, pigments and various additives. The SMC molding process has strong adaptability to molds and can produce various products with complex shapes and precise dimensions according to the design requirements of the product. SMC products have excellent electrical properties, mechanical properties, thermal stability and chemical corrosion resistance. Application areas: electrical industry, transportation, construction industry, as well as home appliances, electronics, communications, aerospace and other fields. As an excellent composite material, SMC has broad application prospects and market demand. With the advancement of science and technology and continuous improvement of technology, the performance and application areas of SMC will be further expanded.

[0024] Silicon steel core 200 is used because of its low initial magnetic permeability and high saturation magnetic density. It meets the requirements of small current measurement and short circuit or ground fault. The composite iron core changes according to the primary current to ensure that the secondary current outputs sufficient power, meeting the measurement and reliable operation of the relay protection device, thereby improving power supply reliability.

[0025] The amorphous core 300 is used because it has the characteristics of high initial magnetic permeability and low saturation magnetic flux density, which meet the measurement accuracy of the instrument.

[0026] The SMC molded lining 100 is used because the function of the SMC molded lining 100 is to increase the strength, protect the amorphous iron core 300 from stress, reduce the deformation of the silicon steel core 200, effectively reduce the composite iron core buffer layer, increase the effective distance of the main insulation, and improve the power frequency withstand voltage and partial discharge level of the current transformer.

[0027] One possible implementation includes the following steps: S1: separately preparing a silicon steel core 200, an SMC molded liner 100, and an amorphous core 300; S2: embedding the inner ring of the silicon steel core 200 into the SMC molded liner 100 to form a shell composed of the silicon steel and SMC molded liner 100; S3: installing the amorphous core 300 into the shell; S4: mixing epoxy resin and a curing agent in a blender to obtain a mixture I; S5: pouring the obtained mixture I into the shell, allowing the mixture I to completely penetrate between the layers of the amorphous core 300 and cover the amorphous core 300, and then curing; S6: after curing, adding the epoxy resin, curing agent, and silicon powder into a blender and mixing to obtain a mixture II; S7: pouring the mixture II into the shell until it is completely filled; S8: curing after it is completely filled to obtain a composite core. After curing, the mixtures I and II form a mixed solid 400.

[0028] The manufacturing of the silicon steel core 200, the SMC molded liner 100 and the amorphous core 300 is prior art and will not be described in detail in this application.

[0029] More specifically, the mass ratio of epoxy resin to curing agent in Mixture I is 100:25, and after Mixture I is poured into the housing, the housing is not completely filled. Mixture I is poured into the housing until it completely penetrates the layers between the amorphous core 300 and covers the entire surface of the amorphous core 300. Curing is then performed for eight hours. This long potting and curing time reduces stress, thus minimizing the impact on the performance of the amorphous core 300.

[0030] Preferably, the mass ratio of epoxy resin, curing agent and silicon powder in the mixture II is 100:25:300, and the mixture II is poured into the shell until the shell is completely filled. The potting height is the same as the silicon steel core 200, thereby increasing the mechanical strength of the core.

[0031] In one possible implementation, the SMC molded liner 100 has an interference fit with the inner ring of the silicon steel core 200, and the SMC molded liner 100 is 2 mm thick. A 2 mm thickness is required for sufficient strength. A larger thickness reduces the window area of ​​the amorphous core, affecting core performance parameters.

[0032] The height of the SMC molded liner 100 is the same as the height of the inner ring of the silicon steel core 200 .

[0033] In one possible implementation, the height of the amorphous core 300 is 5 mm lower than the height of the shell. This setting is because if the height of the amorphous core 300 is 5 mm lower than the height of the shell, the core will be easily subjected to stress. If the height is higher than 5 mm, the window area of ​​the amorphous core will be reduced, affecting the performance parameters of the core.

[0034] In one possible implementation method, the window area of ​​the silicon steel core 200 accounts for 70%, and the window area of ​​the amorphous core 300 accounts for 30%. This technical setting solution takes economic considerations into account and effectively controls costs. The amorphous core mainly meets the detection of small currents, and the silicon steel meets the detection of large currents.

[0035] A composite iron core for a current transformer, comprising the composite iron core for a current transformer prepared as described above; an SMC molded liner having a hollow cylindrical structure with openings at both ends, the SMC molded liner having a preset height, and an extension portion extending outward from one end of the SMC molded liner; a silicon steel core having a hollow cylinder with openings at both ends, the silicon steel core having a preset thickness, and being sleeved on the outer wall of the SMC molded liner, with a preset distance between the inner wall of the silicon steel core and the outer wall of the SMC molded liner, and an interference fit between one end of the silicon steel core and the extension portion; and an amorphous iron core also having a hollow cylindrical structure with openings at both ends, the amorphous iron core being sleeved on the outer wall of the SMC molded liner and located between the silicon steel core and the SMC molded liner.

[0036] Specifically, such as Figure 1 As shown, the SMC molded liner 100, the silicon steel core 200 and the amorphous core 300 are all hollow cylinders with openings at both ends and are hollow cylindrical structures with openings at both ends. In order to connect the SMC molded liner 100 with the silicon steel core 200 to form a shell with a preset space, one end of the SMC molded liner 100 extends outward by a preset distance to form an extension portion. When the silicon steel core 200 is sleeved on the outer wall of the SMC molded liner, one end of the silicon steel core 200 is set on the extension portion, and there is a gap between the silicon steel core 200 and the extension portion. Interference fit, at this time, a space is formed between the inner wall of the silicon steel core 200 and the outer wall of the SMC molded liner 100, and the amorphous core 300 is sleeved on the outer wall of the SMC molded liner 100, that is, it is located in this space. In order to enable the amorphous core 300 to be sleeved on the outer wall of the SMC molded liner 100, the silicon steel core 200 is sleeved on the amorphous core 300, the inner diameter of the SMC molded liner 100 is smaller than the inner diameter of the amorphous core 300, and the inner diameter of the amorphous core 300 is smaller than the inner diameter of the silicon steel core 200.

[0037] The following are examples and comparative examples of the present application:

[0038] Example 1

[0039] The composite core includes: SMC molded lining, silicon steel core, amorphous core, epoxy resin, curing agent and silicon powder, and the mass ratio of epoxy resin and curing agent is 100:25, and the mass ratio of epoxy resin, curing agent and silicon powder is 100:25:300.

[0040] Follow these steps to prepare:

[0041] S1: Make silicon steel core, SMC molded lining and amorphous core respectively;

[0042] S2: The silicon steel core is embedded in the SMC molded liner. There is a preset distance between the inner wall of the silicon steel core and the outer wall of the SMC molded liner to form a shell. The SMC molded liner is 2 mm.

[0043] S3: Install the amorphous core into the shell. At this time, there is a gap between the amorphous core and the inner wall of the silicon steel core, and there is also a gap between the amorphous core and the outer wall of the SMC molded liner. The height of the amorphous core is 5 mm lower than the height of the shell.

[0044] S4: putting the epoxy resin and the curing agent into a blender and stirring and mixing them to obtain a mixture I, wherein the mass ratio of the epoxy resin to the curing agent is 100:25;

[0045] S5: Pour the obtained mixture I into the shell, so that the mixture I completely penetrates into the gap between the amorphous iron core and the inner wall of the silicon steel core and the gap between the amorphous iron core and the outer wall of the SMC molded liner, and covers the amorphous iron core and then cures. The curing time is 8 hours;

[0046] S6: After curing, the epoxy resin, curing agent and silicon powder are placed in a blender and stirred to obtain a mixture II, wherein the mass ratio of the epoxy resin, curing agent and silicon powder in the mixture II is 100:25:300;

[0047] S7: Pour the mixture II into the shell to fill it up;

[0048] S8: After filling, solidify to obtain a composite iron core.

[0049] The test records of finished products using the solution of this invention are shown in Table 1:

[0050]

[0051] As can be seen from Table 1, the composite core prepared by the present application has a ratio difference of -0.14% at a current of 1%, a phase difference of 10, a ratio difference of -0.12% at a current of 5%, a phase difference of 9, a ratio difference of -0.13% at a current of 20%, a phase difference of 9, a ratio difference of -0.14% at a current of 100%, a phase difference of 9, and a ratio difference of -0.14% at a current of 120%, a phase difference of 9.

[0052] Comparative Example 1

[0053] The composite core includes: SMC molded lining, silicon steel core, amorphous core, epoxy resin, curing agent and silicon powder, and the mass ratio of epoxy resin and curing agent is 100:25, and the mass ratio of epoxy resin, curing agent and silicon powder is 100:25:300.

[0054] Follow these steps to prepare:

[0055] S1: Make silicon steel core, SMC molded lining and amorphous core respectively;

[0056] S2: The silicon steel core is embedded in the SMC molded liner. There is a preset distance between the inner wall of the silicon steel core and the outer wall of the SMC molded liner to form a shell. The SMC molded liner is 2 mm.

[0057] S3: Install the amorphous core into the shell. At this time, there is a gap between the amorphous core and the inner wall of the silicon steel core, and there is also a gap between the amorphous core and the outer wall of the SMC molded liner. The height of the amorphous core is 5 mm lower than the height of the shell.

[0058] S4: putting the epoxy resin and the curing agent into a blender and stirring and mixing them to obtain a mixture I, wherein the mass ratio of the epoxy resin to the curing agent is 100:25;

[0059] S5: Pour the obtained mixture I into the shell, so that the mixture I completely penetrates into the gap between the amorphous iron core and the inner wall of the silicon steel core and the gap between the amorphous iron core and the outer wall of the SMC molded liner, and covers the amorphous iron core and then cures. The curing time is 4 hours;

[0060] S6: After curing, the epoxy resin, curing agent and silicon powder are placed in a blender and stirred to obtain a mixture II, wherein the mass ratio of the epoxy resin, curing agent and silicon powder in the mixture II is 100:25:300;

[0061] S7: Pour the mixture II into the shell to fill it up;

[0062] S8: After filling, solidify to obtain a composite iron core.

[0063] The finished product test records using this solution are shown in Table 2:

[0064]

[0065] As can be seen from Table 2, the composite core prepared by the present application has a ratio difference of -3.5% at a current of 1%, a phase difference of 50, a ratio difference of -3.1% at a current of 5%, a phase difference of 40, a ratio difference of -2.5% at a current of 20%, a phase difference of 32, a ratio difference of -2.0% at a current of 100%, a phase difference of 30, and a ratio difference of -2.1% at a current of 120%, with a phase difference of 30.

[0066] Comparative Example 2

[0067] The composite core includes: SMC molded lining, silicon steel core, amorphous core, epoxy resin, curing agent and silicon powder, and the mass ratio of epoxy resin and curing agent is 100:25, and the mass ratio of epoxy resin, curing agent and silicon powder is 100:25:300.

[0068] Follow these steps to prepare:

[0069] S1: Make silicon steel core, SMC molded lining and amorphous core respectively;

[0070] S2: The silicon steel core is embedded in the SMC molded liner. There is a preset distance between the inner wall of the silicon steel core and the outer wall of the SMC molded liner to form a shell. The SMC molded liner is 2 mm.

[0071] S3: Install the amorphous core into the shell. At this time, there is a gap between the amorphous core and the inner wall of the silicon steel core, and there is also a gap between the amorphous core and the outer wall of the SMC molded liner. The height of the amorphous core is 5 mm lower than the height of the shell.

[0072] S4: putting the epoxy resin and the curing agent into a blender and stirring and mixing them to obtain a mixture I, wherein the mass ratio of the epoxy resin to the curing agent is 100:25;

[0073] S5: Pour the obtained mixture I into the shell, so that the mixture I completely penetrates into the gap between the amorphous iron core and the inner wall of the silicon steel core and the gap between the amorphous iron core and the outer wall of the SMC molded liner, and covers the amorphous iron core and then cures. The curing time is 6 hours;

[0074] S6: After curing, the epoxy resin, curing agent and silicon powder are placed in a blender and stirred to obtain a mixture II, wherein the mass ratio of the epoxy resin, curing agent and silicon powder in the mixture II is 100:25:300;

[0075] S7: Pour the mixture II into the shell to fill it up;

[0076] S8: After filling, solidify to obtain a composite iron core.

[0077] The finished product inspection records using this solution are shown in Table 3:

[0078]

[0079] As can be seen from Table 3, the composite core prepared by the present application has a ratio difference of -3.1% at a current of 1%, a phase difference of 38, a ratio difference of -3.0% at a current of 5%, a phase difference of 35, a ratio difference of -2.0% at a current of 20%, a phase difference of 30, a ratio difference of -1.8% at a current of 100%, a phase difference of 29, and a ratio difference of -1.91% at a current of 120%, with a phase difference of 28.

[0080] Comparative Example 3

[0081] The composite core includes: SMC molded lining, silicon steel core, amorphous core, epoxy resin, curing agent and silicon powder, and the mass ratio of epoxy resin and curing agent is 100:25, and the mass ratio of epoxy resin, curing agent and silicon powder is 100:25:300.

[0082] Follow these steps to prepare:

[0083] S1: Make silicon steel core, SMC molded lining and amorphous core respectively;

[0084] S2: The silicon steel core is embedded in the SMC molded liner. There is a preset distance between the inner wall of the silicon steel core and the outer wall of the SMC molded liner to form a shell. The SMC molded liner is 2 mm.

[0085] S3: Install the amorphous core into the shell. At this time, there is a gap between the amorphous core and the inner wall of the silicon steel core, and there is also a gap between the amorphous core and the outer wall of the SMC molded liner. The height of the amorphous core is 3 mm lower than the height of the shell.

[0086] S4: putting the epoxy resin and the curing agent into a blender and stirring and mixing them to obtain a mixture I, wherein the mass ratio of the epoxy resin to the curing agent is 100:25;

[0087] S5: Pour the obtained mixture I into the shell, so that the mixture I completely penetrates into the gap between the amorphous iron core and the inner wall of the silicon steel core and the gap between the amorphous iron core and the outer wall of the SMC molded liner, and covers the amorphous iron core and then cures. The curing time is 8 hours;

[0088] S6: After curing, the epoxy resin, curing agent and silicon powder are placed in a blender and stirred to obtain a mixture II, wherein the mass ratio of the epoxy resin, curing agent and silicon powder in the mixture II is 100:25:300;

[0089] S7: Pour the mixture II into the shell to fill it up;

[0090] S8: After filling, solidify to obtain a composite iron core.

[0091] The finished product inspection records using this scheme are shown in Table 4.

[0092]

[0093] As can be seen from Table 4, the composite core prepared by the present application has a ratio difference of -3.2% at a current of 1%, a phase difference of 60, a ratio difference of -3.1% at a current of 5%, a phase difference of 44, a ratio difference of -3% at a current of 20%, a phase difference of 34, a ratio difference of -2.8% at a current of 100%, a phase difference of 32, and a ratio difference of -2.8% at a current of 120%, a phase difference of 32.

[0094] From the above experimental data, it can be seen that compared with Comparative Examples 1, 2, and 3, the composite core prepared in Example 1 has the best core performance.

[0095] The composite iron core prepared by the above steps in the present application solves the problem that the wire package is subjected to excessive force, generates stress, and affects the output accuracy and protection multiple of the current transformer.

[0096] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solutions and concepts of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a composite core for a current transformer, characterized in that: The composite iron core for current transformer comprises a sheet molding compound molded lining, a silicon steel core and an amorphous iron core; The method comprises the following steps: S1: separately manufacturing the silicon steel core, the sheet molding compound molded lining and the amorphous iron core; S2: Embedding the silicon steel core into the sheet molding compound molded liner, with a preset distance between the inner wall of the silicon steel core and the outer wall of the sheet molding compound molded liner to form a shell; S3: Installing the amorphous iron core into the housing, wherein a gap exists between the amorphous iron core and the inner wall of the silicon steel core, and a gap also exists between the amorphous iron core and the outer wall of the sheet molding compound molded liner; S4: Put the epoxy resin and the curing agent into a blender and mix them to obtain a mixture I; S5: pouring the obtained mixed material I into the shell, allowing the mixed material I to completely penetrate the gap between the amorphous iron core and the inner wall of the silicon steel core and the gap between the amorphous iron core and the outer wall of the sheet molding compound molded liner, and covering the upper surface of the amorphous iron core and then curing; S6: After curing, the epoxy resin, the curing agent and the silicon powder are placed in a blender and stirred to obtain a mixture II; S7: pouring the mixed material II into the shell to fill the shell; S8: After filling, solidify to obtain a composite iron core.

2. The method for preparing a composite iron core for a current transformer according to claim 1, wherein: The mass ratio of the epoxy resin to the curing agent in the mixture I is 100:25, and after the mixture I is poured into the shell, the shell is in a partially filled state.

3. The method for preparing a composite iron core for a current transformer according to claim 2, wherein: In step S5, the curing time is not less than 8 hours.

4. The method for preparing a composite iron core for a current transformer according to claim 3, wherein: The mass ratio of the epoxy resin, the curing agent and the silicon powder in the mixture II is 100:25:300, and the mixture II is poured into the shell and fills the shell.

5. The method for preparing a composite iron core for a current transformer according to claim 3, wherein: The sheet molding compound molded liner is interference fit with the inner ring of the silicon steel core, and the thickness of the sheet molding compound molded liner is 2 mm.

6. The method for preparing a composite iron core for a current transformer according to claim 5, characterized in that: The height of the sheet molding compound molded liner is the same as the height of the inner ring of the silicon steel core.

7. The method for preparing a composite iron core for a current transformer according to claim 6, wherein: The height of the amorphous core is 5 mm lower than the height of the shell.

8. The method for preparing a composite iron core for a current transformer according to claim 7, wherein: The window area of ​​the silicon steel core accounts for 70%, and the window area of ​​the amorphous iron core accounts for 30%.

9. A composite core for a current transformer, characterized in that: A composite iron core for a current transformer prepared by the method for preparing a composite iron core for a current transformer according to any one of claims 1 to 8; comprising: a sheet molding compound molded lining, a silicon steel core, and an amorphous iron core; The sheet molding compound molded liner is a hollow cylindrical structure with two ends open, the sheet molding compound molded liner has a preset height, and one end of the sheet molding compound molded liner extends outward to form an extension portion; The silicon steel core is a hollow cylinder with two ends open. The silicon steel core has a preset thickness and is sleeved on the outer wall of the sheet molding compound molded liner. There is a preset distance between the inner wall of the silicon steel core and the outer wall of the sheet molding compound molded liner. One end of the silicon steel core is interference fit with the extension portion. The amorphous iron core is also a hollow cylindrical structure with two ends open. The amorphous iron core is sleeved on the outer wall of the sheet molding compound molded liner and is located between the silicon steel core and the sheet molding compound molded liner.

10. The composite iron core for current transformer according to claim 9, characterized in that: The inner diameter of the sheet molding compound molded liner is smaller than the inner diameter of the amorphous iron core, and the inner diameter of the amorphous iron core is smaller than the inner diameter of the silicon steel core.

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