Miniature mutual inductor with shielding and anti-interference functions

Abstract

The utility model provides a miniature mutual inductor with shielding and anti-interference functions. Comprising an annular iron core, a first shielding layer wrapping the annular iron core and capable of inhibiting external low-frequency magnetic field interference, a secondary winding annularly wound outside the first shielding layer, an annular shell capable of being packaged and a second shielding layer wrapping the annular shell and capable of inhibiting external high-frequency electric field interference. According to the miniature mutual inductor with the shielding and anti-interference functions, the first shielding layer is arranged between the annular iron core and the secondary winding, magnetic lines are guided, magnetic leakage and external magnetic field penetration are reduced, and low-frequency magnetic field interference is restrained; the second shielding layer arranged outside the annular shell inhibits interference of a high-frequency electric field; therefore, interference of a high-frequency electric field and a low-frequency magnetic field can be suppressed simultaneously.

Description

Technical Field

[0001] This utility model belongs to the field of miniature current transformer technology, specifically relating to a miniature current transformer with shielding and anti-interference function. Background Technology

[0002] A miniature current transformer is a device used to measure current. Based on the principle of electromagnetic induction, it can convert large currents into small current or voltage signals, facilitating measurement and control. Due to their small size, high accuracy, and fast response, miniature current transformers are widely used in power systems, industrial automation, electronic equipment, and other fields.

[0003] In existing technologies, the electrical components in the environments where miniature instrument transformers are used are relatively compact, making them susceptible to electromagnetic interference. For example, external high-frequency electric fields and low-frequency magnetic fields can couple into the transformer, causing measurement errors or signal distortion. The commonly used shielding method is to use a thick metal casing, which increases size and weight, but still fails to simultaneously suppress both high-frequency electric field interference and low-frequency magnetic field interference. Utility Model Content

[0004] This utility model provides a miniature current transformer with shielding and anti-interference function, which aims to solve the problem that the shielding method used in existing miniature current transformers is not practical because it cannot simultaneously suppress the interference of high-frequency electric field and low-frequency magnetic field.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is as follows: a miniature current transformer with shielding and anti-interference function is provided, including a toroidal iron core, a first shielding layer covering the toroidal iron core and used to suppress external low-frequency magnetic field interference, a secondary winding wound in a ring around the first shielding layer, a ring-shaped outer shell for encapsulation, and a second shielding layer covering the outer shell and used to suppress external high-frequency electric field interference.

[0006] In one possible implementation, the first shielding layer is a nanocrystalline ribbon wrapped around it.

[0007] In one possible implementation, the second shielding layer is a copper foil strip wrapped around it.

[0008] In one possible implementation, the second shielding layer is connected to a grounding lead.

[0009] In one possible implementation, the annular shell is filled with epoxy resin.

[0010] In one possible implementation, the second shielding layer is annularly wrapped with high-temperature resistant insulating tape.

[0011] In one possible implementation, the annular housing includes an annular base shell and an annular cover plate; the annular base shell has an annular space with one side open, and the annular base shell also has a through hole for a primary winding to pass through and coaxially arranged with the annular space; the annular cover plate is adapted to the opening of the annular space.

[0012] In one possible implementation, the annular base shell is provided with perforations through which the secondary winding passes.

[0013] In this implementation, a first shielding layer is set between the toroidal core and the secondary winding, which can guide the magnetic lines of force and reduce leakage magnetic field and external magnetic field penetration, thereby suppressing low-frequency magnetic field interference; while the second shielding layer set outside the toroidal shell suppresses high-frequency electric field interference; thus, it can simultaneously suppress the interference of high-frequency electric field and low-frequency magnetic field, which is highly practical. Attached Figure Description

[0014] Figure 1 A schematic diagram of the structure of a miniature current transformer with shielding and anti-interference function provided in this embodiment of the utility model;

[0015] Figure 2 A schematic diagram of the annular shell structure of a miniature current transformer with shielding and anti-interference function provided in this embodiment of the utility model;

[0016] Figure 3 A cross-sectional view of a miniature current transformer with shielding and anti-interference function provided in an embodiment of this utility model;

[0017] Explanation of reference numerals in the attached figures:

[0018] 10. Annular core; 20. First shielding layer; 30. Secondary winding; 40. Annular outer shell; 41. Annular base shell; 42. Annular cover plate; 43. Annular space; 44. Through hole; 45. Via hole; 50. Second shielding layer; 51. Grounding lead; 60. High-temperature resistant insulating tape; 70. Epoxy resin. Detailed Implementation

[0019] To make the technical problems, technical solutions, and beneficial effects of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0020] Please refer to the following: Figure 1 as well as Figure 3The present invention provides a miniature current transformer with shielding and anti-interference function. The miniature current transformer with shielding and anti-interference function includes a toroidal core 10, a first shielding layer 20 covering the toroidal core 10 and capable of suppressing external low-frequency magnetic field interference, a secondary winding 30 wound in a ring around the first shielding layer 20, an encapsulating annular outer shell 40, and a second shielding layer 50 covering the annular outer shell 40 and capable of suppressing external high-frequency electric field interference.

[0021] The miniature current transformer with shielding and anti-interference function provided in this embodiment, compared with the prior art, has a first shielding layer 20 between the toroidal core 10 and the secondary winding 30, which can guide the magnetic lines of force and reduce leakage flux and external magnetic field penetration, thereby suppressing low-frequency magnetic field interference. The second shielding layer 50, which is set outside the toroidal shell 40, suppresses high-frequency electric field interference.

[0022] In some embodiments, the first shielding layer 20 may be as follows: Figure 3 The structure shown. See also Figure 3 The first shielding layer 20 is wrapped with nanocrystalline ribbon.

[0023] The nanocrystalline ribbon is composed of Fe-Si-B-Cu-Nb, etc., which forms an amorphous structure through rapid solidification, and then generates nanocrystals (grain size of about 10-20 nm) after annealing. It has high magnetic permeability and maintains low loss at high frequencies, making it suitable for shielding low- to mid-frequency magnetic fields.

[0024] The high permeability of the nanocrystals causes the magnetic field lines inside the toroidal core 10 to preferentially close through the first shielding layer 20. Magnetic flux (leakage flux) that might otherwise leak from the sides of the toroidal core 10 is forcibly confined within the first shielding layer 20, reducing its diffusion into the surrounding space. When an external low-frequency magnetic field attempts to penetrate, the high permeability of the first shielding layer 20 attracts these magnetic field lines, causing them to bypass the internal toroidal core 10. The external magnetic field energy forms a closed loop through the first shielding layer 20, rather than penetrating into the region where the toroidal core 10 is located.

[0025] In addition, the wrapping method can be adapted to ring structures, making it easy to manufacture.

[0026] The nanocrystalline ribbons can be strips with a width of 5-20mm, making them easy to wind.

[0027] Regarding the specific steps for wrapping the nanocrystalline ribbon, the nanocrystalline ribbon can be tightly wound in a spiral stacked manner around the outer surface of the toroidal iron core 10. When stacking each layer, the overlap area of ​​the ribbon edges can be approximately 30% to 50%, ensuring no gaps. Alternatively, multiple layers (2 to 4 layers) can be wound, with insulating adhesive (such as epoxy resin 70) applied between each layer to prevent eddy current losses. After winding, high-temperature resistant tape can be used for temporary fixation, followed by overall impregnation with insulating varnish (such as polyurethane varnish), which, after curing, forms a rigid protective layer.

[0028] In some embodiments, the second shielding layer 50 may be as follows: Figure 3 The structure shown. See also Figure 3 The second shielding layer 50 is made of copper foil wrapped around it.

[0029] As a good conductor, copper foil allows free electrons inside to redistribute under the influence of external electric fields (such as electromagnetic waves in space or the electric field of nearby high-voltage conductors), forming reverse induced charges. According to Gauss's law, the electric field strength inside the conductor is zero. Therefore, the external electric field cannot penetrate the conductive layer formed by the second shielding layer 50, and the internal secondary winding 30 is completely isolated from the external electric field, thus suppressing the external high-frequency electric field.

[0030] Regarding the specific steps for wrapping the copper foil strip, the copper foil strip can be tightly wrapped around the surface of the transformer housing using a spiral lamination method. The overlap width of each layer must be ≥50% (to avoid electromagnetic leakage caused by gaps). At the same time, a 30mm lead-out hole for the secondary winding must be reserved.

[0031] The width of the copper foil can be 10-20mm and the thickness can be 0.05-0.1mm. This size can balance toughness and conductivity.

[0032] In addition, the wrapping method can be adapted to ring structures, making it easy to manufacture.

[0033] In some embodiments, the second shielding layer 50 may be as follows: Figure 1 The structure shown. See also Figure 1 The second shielding layer 50 is connected to a grounding lead 51. The induced charge on the second shielding layer 50 is quickly conducted to the ground through the grounding lead 51 to avoid charge accumulation that could lead to potential drift or discharge interference.

[0034] In some embodiments, the annular outer shell 40 may be adopted as follows: Figure 3 The structure shown. See also Figure 3 The annular outer shell 40 is filled with epoxy resin 70, which encapsulates the annular iron core 10, secondary winding 30, and first shielding layer 20 within the annular outer shell 40. This protects the internal components, preventing loosening or displacement and providing mechanical support. It also provides moisture and dust protection, improving the reliability of the internal components.

[0035] In some embodiments, the second shielding layer 50 may be as follows: Figure 1 and Figure 3 The structure shown. See also Figure 1 and Figure 3 The second shielding layer 50 is wrapped with high-temperature resistant insulating tape 60 in a ring shape, which can ensure the protection of the second shielding layer 50.

[0036] It should be noted that the high-temperature insulating tape wrapped around the outside of the second shielding layer 50 can be wound in the opposite direction to the winding direction of the second shielding layer 50. For example, if the second shielding layer 50 is wound counterclockwise, then the high-temperature insulating tape 60 is wound clockwise to ensure the tightness of the second shielding layer 50 and to ensure the stability of both.

[0037] In some embodiments, the annular outer shell 40 may be adopted as follows: Figure 2 The structure shown. See also Figure 2 The annular housing 40 includes an annular base shell 41 and an annular cover plate 42. The annular base shell 41 has an annular space 43 with one side open, and the annular base shell 41 also has a through hole 44 that allows a primary winding to pass through and is coaxially arranged with the annular space 43. The annular cover plate 42 is adapted to the opening of the annular space 43.

[0038] The annular space 43 provided by the annular base shell 41 can ensure that the assembly formed by the annular iron core 10, the first shielding layer 20 and the secondary winding 30 can be placed in it and sealed by the annular cover plate 42. This structure can facilitate the filling of epoxy resin 70 inside the annular base shell 41, thereby ensuring the reliability of the internal components.

[0039] In this embodiment, the annular cover plate 42 can be directly fastened to the annular opening after the epoxy resin 70 is filled, and the annular cover plate 42 is directly bonded by the cured epoxy resin 70. Subsequently, the annular cover plate 42 is further wrapped by the second shielding layer 50 for further fixation.

[0040] The annular outer shell 40 can be made of a non-metallic material, such as engineering plastic or PBT.

[0041] In some embodiments, the annular outer shell 40 may be adopted as follows: Figure 2 The structure shown. See also Figure 2 The annular base shell 41 is provided with a through hole for the secondary winding 30 to pass through. The through hole 45 can ensure the passage of the secondary winding 30, thereby ensuring the extraction of the secondary side current.

[0042] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A miniature current transformer with shielding and anti-interference function, characterized in that, It includes a toroidal iron core, a first shielding layer covering the toroidal iron core and used to suppress external low-frequency magnetic field interference, a secondary winding wound in a ring around the first shielding layer, a ring-shaped outer shell for encapsulation, and a second shielding layer covering the outer shell and used to suppress external high-frequency electric field interference.

2. The miniature current transformer with shielding and anti-interference function as described in claim 1, characterized in that, The first shielding layer is wrapped with nanocrystalline ribbon.

3. The miniature current transformer with shielding and anti-interference function as described in claim 1, characterized in that, The second shielding layer is a copper foil strip wrapped around it.

4. The miniature current transformer with shielding and anti-interference function as described in claim 3, characterized in that, The second shielding layer is connected to a grounding lead.

5. The miniature current transformer with shielding and anti-interference function as described in any one of claims 1-4, characterized in that, The annular outer shell is filled with epoxy resin.

6. The miniature current transformer with shielding and anti-interference function as described in any one of claims 1-4, characterized in that, The second shielding layer is annular and wrapped with high-temperature resistant insulating tape.

7. The miniature current transformer with shielding and anti-interference function as described in claim 1, characterized in that, The annular outer shell includes an annular base shell and an annular cover plate; the annular base shell has an annular space with one side open, and the annular base shell also has a through hole for the primary winding to pass through and is coaxially arranged with the annular space; the annular cover plate is adapted to the opening of the annular space.

8. The miniature current transformer with shielding and anti-interference function as described in claim 7, characterized in that, The annular base shell is provided with perforations for the secondary winding to pass through.

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