A mutual inductor and a direct current circuit breaker

Abstract

The utility model discloses a mutual inductor and direct current circuit breaker belongs to switch electric appliance technical field, and mutual inductor includes mutual inductor body, and mutual inductor body includes magnetic conduction structure, winding, insulating layer and shielding layer, and winding includes excitation winding and two sampling windings, and excitation winding and sampling winding are all wound on the magnetic conduction structure, and the insulating layer is covered in the magnetic conduction structure, excitation winding and sampling winding, and the shielding layer is covered in the insulating layer. Mutual inductor provided by the utility model, the shielding layer can make the magnetic field formed in the magnetic conduction structure not be influenced by high frequency and alternating electromagnetic field, make sampling winding have stable signal output, and through the comparison of the signal output of two sampling windings, can improve the accuracy of leakage current detection.

Description

Technical Field

[0001] This utility model relates to the field of switching electrical equipment technology, and in particular to a current transformer and a DC circuit breaker. Background Technology

[0002] The rapid development of new energy and photovoltaics has promoted the popularization of DC leakage protection. As an important part of leakage protection, DC leakage protection will occupy a large market share in the future.

[0003] Currently, instrument transformers have poor electromagnetic interference immunity. High-frequency or alternating electromagnetic fields in new energy and photovoltaic products can interfere with the current signal output of instrument transformers. For example, when instrument transformers are used in DC circuit breakers for detecting leakage current in new energy and photovoltaic products, the electromagnetic interference can cause the instrument transformer to generate incorrect tripping signals, affecting the normal use of new energy and photovoltaic products. Therefore, there is an urgent need for an instrument transformer and DC circuit breaker to solve the above-mentioned technical problems. Utility Model Content

[0004] One objective of this invention is to provide a current transformer that effectively improves electromagnetic interference resistance.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] A current transformer is provided, including a current transformer body, the current transformer body comprising:

[0007] Magnetic permeable structure;

[0008] The winding includes one excitation winding and two sampling windings, both of which are wound on the magnetically conductive structure;

[0009] An insulating layer covers the magnetically conductive structure, the excitation winding, and the sampling winding;

[0010] A shielding layer is used to cover the insulating layer.

[0011] Optionally, the ratio of the number of turns of the sampling winding to the number of turns of the excitation winding is in the range of 6 to 30.

[0012] Optionally, the number of turns of the sampling winding is 60 to 90; and / or, the number of turns of the excitation winding is 3 to 10.

[0013] Optionally, the magnetically conductive structure is annular in shape, and the shielding layer includes:

[0014] An inner ring shield is disposed within the inner ring of the magnetically conductive structure and abuts against the insulating layer;

[0015] An outer ring shield is disposed outside the outer ring of the magnetically conductive structure and abuts against the insulating layer;

[0016] Two end shielding plates are located along the axial direction of the magnetically conductive structure. The magnetically conductive structure, the inner ring shielding plate, and the outer ring shielding plate are all located between the two end shielding plates, and the magnetically conductive structure, the inner ring shielding plate, and the outer ring shielding plate all abut against the end shielding plates.

[0017] Optionally, the shielding layer may be made of silicon steel, pure iron, permalloy, or iron-based nanocrystalline alloy.

[0018] Optionally, the magnetically conductive structure includes an inner housing and an iron core disposed within the inner housing, the excitation winding and the sampling winding are both wound on the inner housing, and the insulating layer covers the inner housing, the excitation winding and the sampling winding.

[0019] Optionally, the inner shell is made of PA66 material mixed with glass fiber.

[0020] Optionally, under a signal with a voltage amplitude of U = 5V and an operating frequency of f = 2.5kHz, the inductance L1 of the excitation winding is 0.15±0.1mH, and the inductance L2 of the sampling winding is 6.0±0.5mH.

[0021] Optionally, the current transformer further includes an outer casing, and the current transformer body is fixed and sealed inside the outer casing by sealant.

[0022] Another objective of this utility model is to provide a DC circuit breaker, including a housing, a terminal block, and a current transformer as described in any of the above-mentioned embodiments, wherein the terminal block and the current transformer are both disposed within the housing, and the terminal block passes through the current transformer.

[0023] Beneficial Effects: The current transformer provided by this utility model is suitable for DC leakage protection under high current conditions. The shielding layer can shield high-frequency and alternating electromagnetic fields to improve the electromagnetic interference resistance of the current transformer, making it suitable for switching electrical appliances, such as circuit breakers. Based on the leakage detection principle of a fluxgate sensor, when the current transformer is used to detect leakage current in a DC circuit, a high-frequency excitation signal (e.g., a high-frequency square wave voltage signal) is introduced into the excitation winding. The shielding layer can prevent the magnetic field formed within the magnetic structure from being affected by high-frequency and alternating electromagnetic fields, thus ensuring a stable signal output from the sampling winding. Within one excitation signal cycle, the excitation signal undergoes a vector change, causing a change in the excitation current vector, and the magnetic field formed within the magnetic structure changes accordingly. This leads to a shift in the signal output of the sampling winding. However, when the excitation signal undergoes a vector change, due to the residual magnetism within the magnetic structure, the excitation current exhibits a trend of rapid increase, slow increase, and rapid increase approaching saturation. At this point, the next excitation signal cycle begins, and a stable waveform output is observed on the sampling winding. When a leakage current occurs in the DC circuit being tested, because the excitation frequency is a high-frequency signal, even a very short period of leakage will cause a stable waveform change on the sampling winding. By demodulating the waveform signal for leakage protection, it achieves the effect of inducing type B leakage current, thus realizing leakage current detection in the DC circuit. Furthermore, by comparing the signal outputs of the two sampling windings, the accuracy of leakage current detection can be improved. The insulation layer separates the excitation winding from the shielding layer, and the sampling winding from the shielding layer, ensuring stable signal transmission between the excitation winding and the sampling winding.

[0024] The DC circuit breaker provided by this utility model can improve the electromagnetic interference resistance of leakage current detection by setting up a current transformer, which helps to reduce the risk of false tripping of the DC circuit breaker. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the current transformer provided by this utility model;

[0026] Figure 2 This is a partial cross-sectional view of the current transformer provided by this utility model;

[0027] Figure 3 This is a schematic diagram of the structure of the current transformer provided by this utility model within the shielding layer;

[0028] Figure 4 This is a partial cross-sectional view of the structure of the current transformer provided by this utility model within the shielding layer.

[0029] In the picture:

[0030] 100. Magnetic structure; 110. Inner casing; 120. Iron core;

[0031] 200. Winding;

[0032] 300. Insulation layer;

[0033] 400. Shielding layer; 410. Inner ring shielding plate; 420. Outer ring shielding plate; 430. End shielding plate;

[0034] 500. Terminal blocks;

[0035] 600. Outer casing; 610. Sealant. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, not the entire structure.

[0037] In the description of this utility model, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0038] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0039] In the description of this embodiment, the terms "upper," "lower," "left," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. In addition, the terms "first" and "second" are only used for distinction in description and have no special meaning.

[0040] Reference Figures 1 to 4As shown, this embodiment provides a current transformer, which includes a current transformer body, a magnetic conductive structure 100, a winding 200, an insulating layer 300, and a shielding layer 400.

[0041] The winding 200 includes one excitation winding (not shown) and two sampling windings (not shown). Both the excitation winding and the sampling winding are wound on the magnetically conductive structure 100. The insulating layer 300 covers the magnetically conductive structure 100, the excitation winding and the sampling winding, and the shielding layer 400 covers the insulating layer 300.

[0042] In this embodiment, the current transformer is a type B current transformer, suitable for DC leakage current protection under high current conditions. The shielding layer 400 can shield high-frequency and alternating electromagnetic fields to improve the electromagnetic interference resistance of the current transformer, making it suitable for switching devices, such as circuit breakers. Based on the leakage current detection principle of the fluxgate sensor, when the current transformer is used to detect leakage current in a DC circuit, a high-frequency excitation signal (e.g., a high-frequency square wave voltage signal) is introduced into the excitation winding. The shielding layer 400 can prevent the magnetic field formed within the magnetically conductive structure 100 from being affected by high-frequency and alternating electromagnetic fields, thus ensuring a stable signal output from the sampling winding. Within one excitation signal cycle, the excitation signal undergoes a vector change, causing a change in the excitation current vector, and the magnetic field formed within the magnetically conductive structure 100 changes accordingly. This causes a shift in the signal output of the sampling winding. However, when the excitation signal undergoes a vector change, due to the residual magnetism within the magnetically conductive structure 100, the excitation current exhibits a trend of rapid increase, slow increase, and rapid increase approaching saturation. At this point, the next excitation signal cycle begins, and a stable waveform output is observed on the sampling winding. When a leakage current occurs in the DC circuit being tested, because the excitation frequency is a high-frequency signal, even if the leakage current exists for a very short time, it will cause a stable waveform change on the sampling winding. By demodulating the waveform signal for leakage current protection, it achieves the effect of inducing type B leakage current, realizing leakage current detection of the DC circuit. Furthermore, by comparing the signal outputs of the two sampling windings, the accuracy of leakage current detection can be improved. Specifically, the insulating layer 300 separates the excitation winding and the shielding layer 400, as well as the sampling winding and the shielding layer 400, to ensure stable signal transmission between the excitation winding and the sampling winding.

[0043] Understandably, in addition to detecting type B leakage current, current transformers can also detect type AC and type A leakage current.

[0044] For example, current transformers can be applied to molded case circuit breakers, such as DC molded case circuit breakers.

[0045] It is understandable that when a current transformer is used for leakage current detection in a DC circuit breaker, the DC circuit breaker terminal block, such as the (3P+N) copper busbar, passes directly through the current transformer. When there is no leakage in the DC circuit, the sum of the current vectors of the (3P+N) copper busbar is zero. When there is leakage in the DC circuit, the sum of the current vectors of the (3P+N) copper busbar is not zero.

[0046] For example, the excitation winding is concentrated on the magnetically conductive structure 100.

[0047] For example, the sampling windings are uniformly wound on the magnetic structure 100 to ensure high signal consistency between the two sets of sampling windings and improve the stable detection of leakage current.

[0048] For example, the winding 200 is electrically connected to a terminal block 500 to facilitate wiring of the winding 200. The wire of the terminal block 500 can be made of Teflon wire to give it high temperature resistance.

[0049] For example, winding 200 can be made of enameled wire to ensure insulation between windings 200.

[0050] For example, the insulating layer 300 can be formed by wrapping with insulating tape.

[0051] For example, under a signal with a voltage amplitude of U = 5V and an operating frequency of f = 2.5kHz, the inductance L1 of the excitation winding can be 0.15 ± 0.1mH, and the inductance L2 of the sampling winding can be 6.0 ± 0.5mH, which is beneficial for the leakage current detection of DC circuits.

[0052] For example, the ratio of the number of turns of the sampling winding to the number of turns of the excitation winding can be in the range of 6 to 30. This allows for electromagnetic interference suppression design and spatial design of the magnetic conductor structure 100 for current transformers with different leakage current specifications, which is beneficial for maintaining the electromagnetic balance of the current transformer.

[0053] For example, under a signal with a voltage amplitude of U = 5V and an operating frequency of f of 2.5kHz, in order to achieve an inductance L2 of 6.0 ± 0.5mH in the sampling winding and reduce the size of the transformer, the number of turns of the sampling winding can be 60 to 90, for example, 75 turns.

[0054] For example, in order to achieve a balanced design between the excitation voltage and the excitation winding, the number of turns of the excitation winding can be 3 to 10, such as 5 turns of the excitation winding.

[0055] For example, the magnetic conductive structure 100 is designed to be annular, which helps to reduce the size of the transformer while giving it better electromagnetic interference resistance.

[0056] In this embodiment, reference is made to Figure 1 and Figure 2As shown, the shielding layer 400 includes an inner ring shielding plate 410, an outer ring shielding plate 420, and end shielding plates 430. The inner ring shielding plate 410 is located within the inner ring of the magnetically conductive structure 100 and abuts against the insulating layer 300; the outer ring shielding plate 420 is located outside the outer ring of the magnetically conductive structure 100 and abuts against the insulating layer 300; two end shielding plates 430 are provided, and along the axial direction of the magnetically conductive structure 100, the magnetically conductive structure 100, the inner ring shielding plate 410, and the outer ring shielding plate 420 are all located between the two end shielding plates 430, and all three abut against the end shielding plates 430, facilitating the coverage of the insulating layer 300 by the shielding layer 400, resulting in a compact structure.

[0057] For example, the shielding layer 400 can be made of silicon steel, meaning the inner shielding plate 410, outer shielding plate 420, and end shielding plate 430 can all be made of silicon steel, which has high magnetic permeability and good shielding performance. Furthermore, silicon steel has high resistivity, and using sheet-like silicon steel can effectively suppress eddy current losses, thereby reducing heat generation. In practical applications, the silicon steel shielding layer 400 can ensure electromagnetic interference resistance within a limited volume, which is beneficial for reducing the size of the current transformer. Moreover, silicon steel has low material cost and high material utilization. Specifically, silicon steel with an initial magnetic permeability greater than 2000 and a maximum magnetic permeability greater than 8000 can be selected as the shielding layer 400. Of course, the shielding layer 400 can also be made of magnetically conductive materials such as pure iron, permalloy, or iron-based nanocrystalline alloys.

[0058] For example, the shielding layer 400 made of pure iron can be heat-treated to achieve a high magnetic permeability and improve the electromagnetic shielding effect.

[0059] For example, the permalloy shielding layer 400 has a good electromagnetic shielding effect against minor interference.

[0060] For example, the iron-based nanocrystalline alloy shielding layer 400 has a good shielding effect in medium and high frequency electromagnetic shielding scenarios.

[0061] For example, the shielding layer 400 has at least one layer. When the shielding layer 400 has at least two layers, the materials of the different shielding layers 400 can be the same or different, and this embodiment does not limit this. Among them, the electromagnetic shielding effect of the shielding layers 400 with different materials may be better than that of the shielding layer 400 with a single material.

[0062] For example, the inner ring shield 410, the outer ring shield 420 and the end shield 430 are all stacked structures, that is, the inner ring shield 410, the outer ring shield 420 and the end shield 430 are all formed by stacking multiple silicon steel sheets, which is beneficial to improve electromagnetic interference resistance and can disperse mechanical stress (such as deformation caused by vibration or temperature change), avoid single-layer sheet damage due to stress concentration, and reduce eddy currents.

[0063] In this embodiment, reference is made to Figure 3 and Figure 4 As shown, the magnetically conductive structure 100 includes an inner housing 110 and an iron core 120 disposed within the inner housing 110. Both the excitation winding and the sampling winding are wound on the inner housing 110, and an insulating layer 300 covers the inner housing 110, the excitation winding, and the sampling winding. In this embodiment, the inner housing 110 protects the iron core 120 inside and facilitates the winding of the excitation winding and the sampling winding.

[0064] For example, both the inner casing 110 and the iron core 120 can be annular.

[0065] For example, the diameter of the iron core 120 can be set to 20mm-80mm to facilitate the passage of the circuit breaker's terminal block through the current transformer. The selection of the iron core 120 should at least allow the current transformer to be matched with a circuit breaker of 0-1600A specification.

[0066] For example, the core 120 can be made of an iron-based nanocrystalline alloy, which has a certain resistance to electromagnetic interference. For instance, the core 120 can be made by winding 1K107 strip and then annealing it.

[0067] For example, the inner cover 110 can be made of PA66 material mixed with glass fiber. For instance, the mixing ratio of glass fiber and PA66 material is 3:10, which helps to improve the rigidity of the inner cover 110 and provide good protection for the iron core 120.

[0068] In this embodiment, reference is made to Figure 1 and Figure 2 As shown, the current transformer also includes an outer casing 600. The current transformer body is fixed and sealed inside the outer casing 600 by sealant 610, which can prevent external moisture and corrosive gases from affecting the current transformer body, thereby ensuring the lifespan of the current transformer body. It can be understood that the outer casing 600 has an open annular groove to accommodate the current transformer body, which facilitates the assembly of the current transformer.

[0069] For example, the outer casing 600 may be annular.

[0070] For example, the outer casing 600 can be made of PBT material mixed with glass fiber. For instance, the mixing ratio of glass fiber and PBT material is 1:4, which helps to improve the rigidity of the outer casing 600 and give it better high-temperature resistance.

[0071] For example, the sealant 610 can be an epoxy resin adhesive, which provides a stable and reliable connection between the transformer body and the outer casing 600, and can also create a good sealing effect on the transformer body.

[0072] This embodiment also provides a DC circuit breaker, including a housing (not shown), a terminal block (not shown), and the aforementioned current transformer. Both the terminal block and the current transformer are housed within the housing, with the terminal block passing through the current transformer. It is understood that other structures of the DC circuit breaker are existing technologies and are not the focus of this invention, and will not be described in detail here. In this embodiment, the aforementioned current transformer is applied to the DC circuit breaker, thus achieving all the beneficial effects of the aforementioned current transformer, such as improving the electromagnetic interference immunity of leakage current detection and reducing the risk of false tripping of the DC circuit breaker.

[0073] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating the present utility model, and are not intended to limit the implementation of the present utility model. Those skilled in the art can make various obvious changes, readjustments, and substitutions without departing from the protection scope of this utility model. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the protection scope of the claims of this utility model.

Claims

1. A transformer, characterized by Includes a current transformer body, the current transformer body comprising: Magnetic permeable structure (100); The winding (200) includes an excitation winding and two sampling windings, both of which are wound on the magnetically conductive structure (100); An insulating layer (300) covers the magnetically conductive structure (100), the excitation winding, and the sampling winding; A shielding layer (400) covers the outside of the insulating layer (300).

2. The instrument transformer of claim 1, wherein, The ratio of the number of turns in the sampling winding to the number of turns in the excitation winding is in the range of 6 to 30.

3. The instrument transformer of claim 2, wherein, The number of turns of the sampling winding is 60 to 90; and / or, the number of turns of the excitation winding is 3 to 10.

4. The instrument transformer of claim 1, wherein, The magnetically conductive structure (100) is annular in shape, and the shielding layer (400) includes: The inner ring shield (410) is disposed in the inner ring of the magnetic conductive structure (100) and abuts against the insulating layer (300); An outer ring shield (420) is disposed outside the outer ring of the magnetically conductive structure (100) and abuts against the insulating layer (300); Two end shields (430) are located along the axial direction of the magnetically conductive structure (100). The magnetically conductive structure (100), the inner ring shield (410), and the outer ring shield (420) are all located between the two end shields (430), and the magnetically conductive structure (100), the inner ring shield (410), and the outer ring shield (420) all abut against the end shields (430).

5. The instrument transformer of claim 1, wherein, The shielding layer (400) is made of silicon steel, pure iron, permalloy or iron-based nanocrystalline alloy.

6. The instrument transformer of claim 1, wherein, The magnetic structure (100) includes an inner shell (110) and an iron core (120) disposed inside the inner shell (110). The excitation winding and the sampling winding are both wound on the inner shell (110), and the insulating layer (300) covers the inner shell (110), the excitation winding and the sampling winding.

7. The instrument transformer of claim 6, wherein, The inner cover (110) is made of PA66 material mixed with glass fiber.

8. The instrument transformer according to any of claims 1 - 7, characterized in that, Under a signal with a voltage amplitude of U = 5V and an operating frequency of f = 2.5kHz, the inductance L1 of the excitation winding is 0.15 ± 0.1mH, and the inductance L2 of the sampling winding is 6.0 ± 0.5mH.

9. The instrument transformer according to any of claims 1 - 7, characterized in that, The current transformer also includes an outer casing (600), and the current transformer body is fixed and sealed inside the outer casing (600) by sealant (610).

10. A direct current circuit breaker, characterized by It includes a housing, a terminal block, and a current transformer as described in any one of claims 1-9, wherein the terminal block and the current transformer are both disposed within the housing, and the terminal block passes through the current transformer.

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