An EMC protection packaging structure for a current transformer

Abstract

This utility model discloses an EMC protection packaging structure for a current transformer, belonging to the field of electromagnetic compatibility technology for power equipment. It includes a permalloy metal shell with a stepped annular groove on its inner wall, combined with a multi-layer composite shielding layer. From the inside out, the layers are a conductive rubber layer, a Monel alloy wire woven metal mesh, and a nanocrystalline magnetic shielding layer, forming a gradient shielding system that achieves interference attenuation >40dB across the entire 30MHz-1GHz frequency band. A conductive sealing layer of silver powder-doped epoxy resin is filled between the shell and the shielding layer, combined with an elastic grounding structure 4 using a beryllium copper conductive spring 2, ensuring a grounding impedance ≤0.05Ω. An annular insulating partition uses polyimide heat dissipation fins for partitioned heat dissipation, reducing the temperature difference between the coil cavity and the signal processing cavity by 12K. An integrated π-type filter module further suppresses secondary-side noise. This structure, through material optimization and modular design, comprehensively solves problems related to electromagnetic interference, temperature rise control, and mechanical stability, significantly improving the measurement accuracy and reliability of the current transformer under complex operating conditions.

Description

Technical Field

[0001] This utility model belongs to the field of electromagnetic compatibility technology of power equipment, specifically relating to an EMC protection packaging structure for a current transformer. Background Technology

[0002] With the rapid development of smart grids and new energy power generation systems, current transformers are facing increasingly complex electromagnetic interference environments. Traditional protection structures suffer from problems such as insufficient shielding effectiveness (≤40dB), unstable grounding impedance (>0.5Ω), and poor heat dissipation performance.

[0003] In existing technologies, patent CN202122478540.9 employs a double-fixed protective cover, but fails to solve the high-frequency interference shielding problem; while CN215933307U adjusts the core alignment accuracy via spring clips, but lacks an overall EMC design. Recent research indicates that a permalloy shell combined with a composite shielding layer can achieve a shielding effectiveness of >60dB, but existing packaging structures still have deficiencies in conductive sealing (volume resistivity >0.5Ω·cm) and corona protection. Furthermore, the conflicting requirements of electronic current transformers regarding the light transmittance of the observation window (<70%) and electromagnetic shielding (surface resistance >30Ω / □) have not been effectively resolved. There is an urgent need in this field for a comprehensive protection solution integrating multi-layer shielding, low-impedance grounding, and visual monitoring to meet the stringent electromagnetic compatibility requirements of IEC 61869-10 for CT equipment.

[0004] Therefore, an EMC protection packaging structure for current transformers is needed to solve the problems existing in the prior art. Utility Model Content

[0005] The purpose of this invention is to provide an EMC protection packaging structure for current transformers to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, this utility model provides the following technical solution: an EMC protection packaging structure for a current transformer, comprising:

[0007] The metal alloy shell has a stepped annular groove on its inner wall.

[0008] The multi-layer composite shielding layer consists of a conductive rubber layer, a metal mesh layer, and a nanocrystalline magnetic shielding layer, from the inside out.

[0009] A conductive sealing layer, filling the gap between the outer shell and the shielding layer, contains an epoxy resin doped with silver powder;

[0010] The grounding connection structure includes an integrally molded grounding terminal located at the bottom of the housing and a built-in conductive spring;

[0011] An annular insulating partition divides the inner cavity of the housing into a signal processing cavity and a coil cavity;

[0012] Electromagnetic shielding observation window, a transparent conductive glass layer embedded in the top of the outer casing.

[0013] It should be noted in the solution that the metal alloy shell is made of permalloy material with a wall thickness of 1.2-2.5mm and an anodized layer on the surface.

[0014] It is worth noting that the metal mesh layer (22) in the multi-layer composite shielding layer is woven from Monel alloy wire with a diameter of 0.1 mm and a mesh density of 80-120 mesh.

[0015] It should be further noted that the silver powder doping amount of the conductive sealing layer is 15-25wt%, and the volume resistivity after curing is less than 0.1Ω·cm.

[0016] In a preferred embodiment, the conductive spring of the grounding connection structure is made of beryllium copper and has a spherical contact head at its end, which maintains an elastic contact pressure ≥5N with the inner wall of the outer shell.

[0017] In a preferred embodiment, the annular insulating partition is made of polyimide composite material, and its surface is provided with equally spaced raised heat dissipation ribs.

[0018] In a preferred embodiment, the system also includes a π-type filter circuit module disposed within the signal processing cavity, the input of which is connected to the secondary winding of the current transformer, and the output is led out through a shielded cable.

[0019] In a preferred embodiment, the transparent conductive glass layer of the electromagnetic shielding observation window is provided with an ITO conductive film, with a surface resistance ≤10Ω / □ and a light transmittance ≥80%.

[0020] In a preferred embodiment, the inner wall of the coil cavity is coated with an anti-corona coating, which is composed of silicon carbide microparticles doped into a silicone rubber matrix.

[0021] Compared with the prior art, the current transformer EMC protection packaging structure provided by this utility model has at least the following beneficial effects:

[0022] (1) In terms of the three-dimensional gradient shielding system, the conductive rubber layer, the Monel alloy metal mesh layer and the nanocrystalline magnetic shielding layer are arranged from the inside to the outside to form a progressive protection. The metal mesh layer achieves reflection attenuation of 30-100MHz high-frequency interference through 80-120 mesh precision weaving. The nanocrystalline layer has a high magnetic permeability characteristic and generates >20dB absorption loss for 50Hz power frequency magnetic field. Combined with the elastic contact compensation of the conductive rubber layer, the overall shielding effectiveness is improved by more than 40% compared with the traditional single-layer structure.

[0023] In terms of dynamic grounding system, a combination design of beryllium copper conductive spring and integrated grounding terminal is adopted. The elastic contact pressure of ≥5N ensures that the contact resistance between the shielding layer and the shell is stable below 0.05Ω. Combined with epoxy resin sealing layer doped with 25wt% silver powder, the system grounding impedance fluctuation rate is controlled within ±3%, effectively eliminating common mode interference caused by poor contact.

[0024] In terms of structural reliability, the permalloy shell achieves a surface hardness of HV400 after anodizing. Combined with the stepped annular slot design, the encapsulation structure maintains an IP67 protection rating under temperature cycling from -40℃ to 125℃, significantly improving long-term stability in harsh environments.

[0025] (2) Through electromagnetic-thermal composite management, the polyimide insulating partition (the equally spaced heat dissipation ribs on the surface reduce the thermal resistance of the coil cavity by 15%, and combined with the local electric field homogenization effect formed by silicon carbide particles in the anti-corona coating, the temperature rise of the equipment under rated load is reduced by 8-12K compared with the conventional design, while suppressing the partial discharge to <5pC.

[0026] In terms of signal processing optimization, the π-type filter circuit module integrated in the signal processing cavity forms a two-stage filtering system with the shielded cable. Actual measurements show that it increases the insertion loss of interference signals in the 10kHz-1GHz frequency band by 12dB. Combined with the ITO conductive film observation window with a transmittance of up to 80% and a surface resistance of ≤10Ω / □, it achieves a non-destructive fusion of visual monitoring of operating status and electromagnetic shielding.

[0027] In terms of assembly process innovation, by combining the stepped grooves of the metal shell with the flow control of the conductive sealing layer, the assembly accuracy of the multi-layer shielding structure reaches ±0.05mm, which shortens the working time by 40% compared with the traditional spot welding process, and avoids the performance degradation caused by mechanical damage to the shielding layer. The first-pass yield rate of the product is increased to over 98.5%. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the front structure of this utility model. Figure 1 ;

[0029] Figure 2 This is a schematic diagram of the front structure of this utility model. Figure 2 ;

[0030] Figure 3 This is a schematic diagram of the multi-layer composite shielding layer structure of this utility model;

[0031] Figure 4 This is a schematic diagram of the conductive sealing layer structure of this utility model.

[0032] In the diagram: 1. Outer shell; 2. Multi-layer composite shielding layer; 21. Conductive rubber layer; 22. Metal mesh layer; 23. Nanocrystalline magnetic shielding layer; 3. Conductive sealing layer; 4. Grounding connection structure; 41. Integrated grounding terminal; 42. Built-in conductive spring; 421. Spherical contact head; 5. Annular insulating partition; 51. Signal processing cavity; 52. Coil cavity; 53. Protruding heat dissipation fins; 6. Electromagnetic shielding observation window; 61. ITO conductive film. Detailed Implementation

[0033] The present invention will be further described below with reference to the embodiments.

[0034] Please see Figure 1-4 This utility model provides an EMC protection packaging structure for a current transformer, comprising:

[0035] The metal alloy shell 1 has a stepped annular groove on its inner wall;

[0036] The multi-layer composite shielding layer 2 comprises, from the inside out, a conductive rubber layer 21, a metal mesh layer 22, and a nanocrystalline magnetic shielding layer 23;

[0037] The conductive sealing layer 3, which fills the gap between the outer shell 1 and the shielding layer 2, contains an epoxy resin doped with silver powder.

[0038] The grounding connection structure 4 includes an integrally formed grounding terminal 41 disposed at the bottom of the housing and a built-in conductive spring 42;

[0039] An annular insulating partition 5 divides the inner cavity of the outer shell into a signal processing cavity 51 and a coil cavity 52.

[0040] Electromagnetic shielding observation window 6 is a transparent conductive glass layer embedded in the top of the outer casing.

[0041] Further as Figure 1 As shown, it is worth noting that the metal alloy shell 1 is made of permalloy material with a wall thickness of 1.2-2.5mm and an anodized layer on the surface. Through the 1.2-2.5mm wall thickness design and the anodized layer 11, the permalloy shell 1 has both high magnetic permeability μ>20,000 and surface hardness HV400. It maintains structural integrity under operating conditions of -40℃ to 125℃, achieving a protection level of IP67 and improving mechanical impact resistance by 30%.

[0042] Further as Figure 3As shown, it is worth noting that the metal mesh layer 22 in the multi-layer composite shielding layer 2 is woven from Monel alloy wire with a diameter of 0.1mm and a mesh density of 80-120 mesh. The 80-120 mesh metal mesh layer 22 woven from 0.1mm Monel alloy wire has a dense weave structure that produces a reflection attenuation of >15dB for high-frequency electromagnetic waves of 30-100MHz. At the same time, the tensile strength of the mesh layer reaches 500MPa, avoiding shielding failure caused by assembly deformation.

[0043] Further as Figure 4 As shown, it is worth noting that the silver powder doping amount of the conductive sealing layer 3 is 15-25wt%, and the volume resistivity after curing is less than 0.1Ω·cm. The epoxy resin sealing layer 3 with a silver powder doping amount of 15-25wt% forms a continuous conductive network with a resistivity of <0.1Ω·cm after curing, which makes the contact resistance fluctuation rate between the shell and the shielding layer ≤±3%, effectively suppressing common-mode interference caused by grounding potential difference.

[0044] This solution operates as follows: The encapsulation structure achieves full-band electromagnetic interference suppression through multi-layer shielding and a coordinated grounding mechanism. When the current transformer operates, the permalloy material and stepped slot design of the metal alloy shell 1 form the first electromagnetic barrier, guiding the magnetic field lines to close using its high permeability. In the multi-layer composite shielding layer 2, the conductive rubber layer 21 compensates for assembly gaps through elastic deformation, the metal mesh layer 22 reflects high-frequency interference through an 80-120 mesh Monel alloy mesh, and the nanocrystalline magnetic shielding layer 23 absorbs low-frequency magnetic field energy. The silver powder-doped epoxy resin in the conductive sealing layer 3 forms a continuous conductive path after curing, which, together with the beryllium copper spring 42 of the grounding connection structure 4, establishes a low-impedance grounding loop (<0.05Ω), rapidly guiding the induced charge to the ground. The heat dissipation fins 53 of the annular insulating partition 5 accelerate the conduction of heat from the coil cavity 52 to the signal processing cavity 51, and, in conjunction with the π-type filter module 7, performs common-mode / differential-mode filtering on the secondary side signal, finally outputting the purified electrical signal through the shielded cable 71. The ITO conductive film 61 of the electromagnetic shielding observation window 6 maintains 80% light transmittance while forming an equivalent electromagnetic shielding layer through surface current, achieving a dynamic balance between visual monitoring of operating status and electromagnetic protection.

[0045] Based on the above working process, it can be seen that: the permalloy shell 1, with a wall thickness of 1.2-2.5mm and an anodized layer 11, has both high magnetic permeability μ>20,000 and surface hardness HV400. It maintains structural integrity under operating conditions of -40℃ to 125℃, achieving an IP67 protection level and improving mechanical shock resistance by 30%. The 80-120 mesh metal mesh layer 22, woven from 0.1mm Monel alloy wire, attenuates the reflection of 30-100MHz high-frequency electromagnetic waves by >15dB through its dense structure. At the same time, the tensile strength of the mesh layer reaches 500MPa, avoiding shielding failure caused by assembly deformation. The epoxy resin sealing layer 3, with a silver powder doping content of 15-25wt%, forms a continuous conductive network with a resistivity of <0.1Ω·cm after curing, making the contact resistance fluctuation rate between the shell and the shielding layer ≤±3%, effectively suppressing common-mode interference caused by grounding potential difference.

[0046] Further as Figure 2 As shown, it is worth noting that the conductive spring 42 of the grounding connection structure 4 is made of beryllium copper, and its end is provided with a spherical contact head 421, which maintains an elastic contact pressure ≥5N with the inner wall of the outer shell. The spherical contact head 421 of the beryllium copper conductive spring 42 cooperates with the ≥5N elastic pressure to ensure that the dynamic resistance of the grounding circuit is ≤0.05Ω, and the contact impedance change rate is <5% after withstanding 2000 thermal cycles, thus eliminating the risk of grounding failure caused by vibration.

[0047] Further as Figure 2 As shown, it is worth noting that the annular insulating partition 5 is made of polyimide composite material, and its surface is provided with equally spaced raised heat dissipation ribs 53. The equally spaced heat dissipation ribs 53 of the polyimide partition 5 reduce the thermal resistance between the coil cavity 52 and the signal cavity 51 by 15%. With the matching material having a temperature resistance rating of 180℃, the temperature rise of the equipment during continuous operation is reduced by 8-12K compared with the traditional design.

[0048] Further as Figure 2 As shown, it is worth noting that the signal processing cavity 51 also includes a π-type filter circuit module, whose input is connected to the secondary winding of the current transformer and whose output is led out through a shielded cable. The π-type filter circuit integrated in the signal processing cavity 51 and the shielded cable form a two-stage filter, which increases the insertion loss of 10kHz-1GHz interference signals by 12dB and improves the signal-to-noise ratio of the output signal by more than 20dB.

[0049] Further as Figure 2 As shown, it is worth noting that the surface of the transparent conductive glass layer of the electromagnetic shielding observation window 6 is provided with an ITO conductive film 61. With a light transmittance of ≥80%, the ITO conductive film 61 forms an equivalent electromagnetic shielding layer through a surface resistance of ≤10Ω / □. While maintaining 80% light transmittance, it enables the shielding effectiveness of the observation window area to reach 40dB@1GHz, achieving non-destructive condition monitoring.

[0050] Further as Figure 2 As shown, it is worth noting that the inner wall of the coil cavity 52 is coated with an anti-corona coating. This coating is composed of silicon carbide microparticles doped into a silicone rubber matrix. The anti-corona coating with silicon carbide microparticles doped into a silicone rubber matrix reduces the local electric field intensity in the coil cavity 52 by 50%, the partial discharge is <5pC, and the insulation life is extended by more than 3 times.

[0051] In summary: The spherical contact head 421 of the beryllium copper conductive spring 42, in conjunction with an elastic pressure of ≥5N, ensures that the dynamic resistance of the grounding circuit is ≤0.05Ω, and the contact impedance change rate is <5% after withstanding 2000 thermal cycles, eliminating the risk of grounding failure caused by vibration. The equidistant heat dissipation fins 53 of the polyimide partition 5 reduce the thermal resistance between the coil cavity 52 and the signal cavity 51 by 15%. The materials used have a temperature resistance rating of 180℃, and the continuous temperature rise of the equipment is 8-12K lower than that of traditional designs.

[0052] The π-type filter circuit 7 integrated in the signal processing cavity 51 and the shielded cable 71 constitute a two-stage filter, which increases the insertion loss of interference signals in the 10kHz-1GHz range by 12dB and improves the signal-to-noise ratio of the output signal by more than 20dB. The ITO conductive film 61 forms an equivalent electromagnetic shielding layer through a surface resistance of ≤10Ω / □, which, while maintaining 80% light transmittance, enables the shielding effectiveness of the observation window area to reach 40dB@1GHz, realizing non-destructive state monitoring. The anti-corona coating 8, which is doped with silicon carbide microparticles in the silicone rubber matrix, reduces the local electric field intensity in the coil cavity 52 by 50%, the partial discharge is <5pC, and the insulation life is extended by more than 3 times.

[0053] The foregoing has shown and described the basic principles, main features, and advantages of this utility model. Those skilled in the art should understand that this utility model is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of this utility model. Various changes and modifications can be made to this utility model without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed utility model. The scope of protection of this utility model is defined by the appended claims and their equivalents.

Claims

1. An EMC protection package structure for a current transformer, characterized by, include: The metal alloy shell (1) has a stepped annular groove on its inner wall; The multilayer composite shielding layer (2) includes, from the inside out, a conductive rubber layer (21), a metal mesh layer (22), and a nanocrystalline magnetic shielding layer (23). A conductive sealing layer (3) fills the gap between the outer shell (1) and the shielding layer (2) and contains an epoxy resin doped with silver powder; The grounding connection structure (4) includes an integrally formed grounding terminal (41) disposed at the bottom of the housing and a built-in conductive spring (42). An annular insulating partition (5) divides the inner cavity of the outer shell into a signal processing cavity (51) and a coil cavity (52). Electromagnetic shielding observation window (6) is a transparent conductive glass layer embedded in the top of the outer shell.

2. The packaging structure according to claim 1, characterized in that: The metal alloy shell (1) is made of permalloy material with a wall thickness of 1.2-2.5 mm and an anodized layer on the surface.

3. The package structure of claim 1, wherein: The metal mesh layer (22) in the multi-layer composite shielding layer (2) is woven from Monel alloy wire with a diameter of 0.1 mm and a mesh density of 80-120 mesh.

4. The package structure of claim 1, wherein: The conductive spring (42) of the grounding connection structure (4) is made of beryllium copper material, and its end is provided with a spherical contact head (421) to maintain an elastic contact pressure ≥5N with the inner wall of the outer shell.

5. The package structure of claim 1, wherein: The annular insulating partition (5) is made of polyimide composite material, and its surface is provided with raised heat dissipation ribs (53) distributed at equal intervals.

6. The package structure of claim 1, wherein: It also includes a π-type filter circuit module installed in the signal processing cavity (51), whose input end is connected to the secondary winding of the current transformer and whose output end is led out through a shielded cable.

7. The package structure of claim 1, wherein: The electromagnetic shielded observation window (6) has an ITO conductive film (61) on the surface of its transparent conductive glass layer, with a surface resistance ≤10Ω / □ and a light transmittance ≥80%.

8. The package structure of claim 1, wherein: The inner wall of the coil cavity (52) is coated with an anti-corona coating, which is composed of silicon carbide microparticles doped into a silicone rubber matrix.

Images