A metering low-voltage current transformer

Abstract

This utility model discloses a metering low-voltage current transformer, including a base plate and a housing disposed on the base plate. The housing is made of insulating material and contains an iron core. A secondary winding is uniformly wound around the outer periphery of the iron core. An integrated conductive unit is disposed on the housing, the integrated conductive unit including a primary conductive rod that passes through the central hole of the iron core. Wiring mechanisms are symmetrically arranged on both sides of the housing, and clamping mechanisms are connected to the wiring mechanisms. This utility model belongs to the field of current transformer technology, specifically referring to a metering low-voltage current transformer.

Description

Technical Field

[0001] This utility model belongs to the field of instrument transformer technology, specifically referring to a metering low-voltage current transformer. Background Technology

[0002] Current transformers are key devices for current measurement and energy metering in power systems. Currently, the "through-hole" structure is commonly used in low-voltage metering, where the primary circuit cable is directly passed through the center hole of the iron core. While this traditional structure is simple, it has revealed two major technical drawbacks in long-term practice: 1. Insufficient measurement accuracy and stability: The position (bending degree, eccentricity) of the flexible cable as the primary conductor in the iron core hole cannot be fixed, resulting in magnetic circuit asymmetry and leakage magnetic flux, introducing additional errors that are difficult to predict and compensate for, and failing to meet the requirements of high-precision measurement.

[0003] 2. Poor installation convenience and connection reliability: First, for large-section cables, bending them and passing them through the narrow center hole of the iron core during on-site construction is extremely difficult, resulting in low installation efficiency. Second, the connection quality between the cable and the outgoing terminal depends on the skill of the construction personnel, and poor contact can easily lead to increased resistance and abnormal heating at the connection point, affecting the stability and safety of long-term operation. In addition, flexible cables are prone to vibration under short-circuit electrodynamic forces, posing a risk of friction damage to the iron core and insulation breakdown. Utility Model Content

[0004] To address the aforementioned problems of insufficient measurement accuracy due to the non-fixed position of the primary conductor in traditional through-type current transformers, as well as the difficulties in installing large-section cables and poor connection reliability, this utility model provides a metering low-voltage current transformer.

[0005] To achieve the above functions, the technical solution adopted by this utility model is as follows: A metering low-voltage current transformer includes a base plate and a housing disposed on the base plate. The housing is made of insulating material and has an iron core inside. A secondary winding is uniformly wound on the outer periphery of the iron core. An integrated conductive unit is provided on the housing, the integrated conductive unit including a primary conductive rod that passes through the central hole of the iron core; The housing is symmetrically provided with wiring mechanisms on both sides, and clamping mechanisms are connected to the wiring mechanisms.

[0006] Furthermore, the integrated conductive unit also includes an electrically insulating material, which is sealed to the outer periphery of the primary conductive rod by a vacuum casting process, and the outer peripheral wall of the electrically insulating material is tightly fitted to the inner wall of the central hole of the iron core.

[0007] Furthermore, the primary conductive rod is fixedly connected to the iron core through the electrical insulating material, and the electrical insulating material forms a fixed fit with the shell.

[0008] Furthermore, the wiring mechanism includes support plates symmetrically fixed to the outer side of the housing, a horizontal plate fixed between the two sets of support plates, a movable plate connected to the support plates, and symmetrically arranged connecting bolts; The plug end of the connecting bolt is rotatably connected to the horizontal plate, and the other end is threadedly adapted to the movable plate. The movable plate and the horizontal plate are arranged parallel to each other, and the primary conductive rod is arranged to pass through the middle of the horizontal plate and the middle of the movable plate in sequence.

[0009] Furthermore, limit plates are symmetrically fixed at both ends of the movable plate; The support plate has a slot, and the limiting plate is movably inserted into the slot.

[0010] Furthermore, a fixing frame is fixed to the outside of the movable plate; A circular channel is provided in the middle of the fixed frame corresponding to the movable plate; The fixed frame is symmetrically provided with two sets of limiting grooves that communicate with the circular channel.

[0011] Furthermore, the clamping mechanisms are symmetrically arranged at the top and bottom of the fixed frame; The clamping mechanism includes a vertical fixing bolt threaded onto the fixed frame and an arc-shaped clamping plate movable within a circular channel; The end of the fixing bolt is positioned to contact the outer wall of the arc-shaped clamping plate.

[0012] Furthermore, the internal cross-section of the arc-shaped clamping plate is trapezoidal, and symmetrically arranged on both sides are limiting blocks that are movable within the limiting groove.

[0013] Furthermore, both the limiting block and the limiting plate are L-shaped.

[0014] Furthermore, the housing is provided with a first terminal and a second terminal.

[0015] Compared with the prior art, the present invention achieves the following beneficial effects by adopting the above structure: 1. By using an integrated conductive unit, a rigidly sealed primary conductive rod replaces the traditional flexible through-core cable, creating a primary-side conductive path that is permanently aligned with the center hole of the iron core. This fundamental improvement structurally eliminates the magnetic circuit asymmetry problem caused by random bending or eccentricity of the cable, significantly reducing additional errors and ensuring the long-term accuracy and stability of current sensing. Simultaneously, the vacuum-cast insulation layer greatly enhances the insulation strength between the primary and secondary windings, and the overall rigid structure strengthens the product's vibration resistance and overload capacity.

[0016] 2. By coordinating the wiring and clamping mechanisms, the traditional time-consuming and labor-intensive "through-the-core" connection is transformed into a highly efficient "terminated" connection. The wiring mechanism uses mechanical transmission to achieve rapid and precise alignment and crimping of the external cable with the built-in primary conductive rod, solving the problem of through-the-core connection for large-diameter cables. The clamping mechanism utilizes the "wedge effect" of the trapezoidal arc-shaped clamping plate to achieve concentric clamping and large-area contact of the cable, forming a low-resistance, highly reliable electrical connection with anti-loosening capabilities. The combination of these two mechanisms fundamentally avoids contact resistance fluctuations and overheating caused by poor manual wiring, greatly improving installation efficiency and long-term electrical stability. Attached Figure Description

[0017] Figure 1 This utility model provides a schematic diagram of the overall structure of a metering low-voltage current transformer. Figure 1 ; Figure 2 This utility model provides a schematic diagram of the overall structure of a metering low-voltage current transformer. Figure 2 ; Figure 3 This utility model provides a schematic diagram of the overall structure of a metering low-voltage current transformer. Figure 3 ; Figure 4 A cross-sectional view of a metering low-voltage current transformer proposed in this utility model. Figure 1 ; Figure 5 A cross-sectional view of a metering low-voltage current transformer proposed in this utility model. Figure 2 ; Figure 6 for Figure 5 Enlarged view of a portion of point A in the middle.

[0018] Among them, 1. base plate, 2. shell, 21. first terminal, 22. second terminal, 23. iron core, 24. secondary winding, 25. integrated conductive unit, 251. primary conductive rod, 252. electrical insulation material, 3. wiring mechanism, 31. support plate, 32. horizontal plate, 33. movable plate, 331. limiting plate, 34. connecting bolt, 4. fixed frame, 41. circular channel, 42. limiting groove, 5. clamping mechanism, 51. fixing bolt, 52. arc-shaped clamping plate, 521. limiting block. Detailed Implementation

[0019] The technical solution of this utility model will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0020] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this utility model and simplifying the description, 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. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0021] Unless otherwise expressly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; 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; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances. The present invention will be further described in detail below with reference to the accompanying drawings.

[0022] like Figure 1-6 As shown, the present invention provides a metering low-voltage current transformer, comprising a base plate 1 and a housing 2 disposed on the base plate 1. The base plate 1 is used to install the device in the working position. The housing 2 is made of insulating material and has an iron core 23 inside. A secondary winding 24 is uniformly wound on the outer periphery of the iron core 23. Based on the law of electromagnetic induction, when the measured current flows through the primary conductive rod 251, an alternating magnetic flux is generated in the iron core 23, thereby inducing a current signal that is reduced to a precise ratio in the secondary winding 24. The insulating housing 2 directly provides basic safety protection to prevent the internal charged body from contacting the outside. The iron core 23 and the uniformly wound secondary winding 24 are the core to realize high-precision electromagnetic induction and current ratio transformation, ensuring the accuracy and stability of the current transformer ratio. The housing 2 is provided with a first terminal 21 and a second terminal 22. The first and second terminals 22 provide a standard and convenient lead-out interface for the induced secondary small current, which facilitates safe and standardized connection with downstream metering instruments (such as electricity meters) or protection devices, and completes the final output of the current sensing signal. The housing 2 is provided with an integrated conductive unit 25, which includes a primary conductive rod 251 that passes through the center hole of the iron core 23. This design replaces the traditional flexible through cable with a rigid primary conductive rod 251. Its core advantage is that it constructs a fixed and centered primary side conductive path, which fundamentally eliminates the magnetic circuit asymmetry and additional error problems caused by random bending or eccentricity of the cable in the traditional method, and provides structural guarantee for high-precision measurement. The housing 2 is symmetrically equipped with wiring mechanisms 3 on both sides. A clamping mechanism 5 is connected to the wiring mechanism 3. The clamping mechanism 5 is used to clamp the external cable, and the wiring mechanism 3 is used to align the end of the clamped external cable with the end of the primary conductive rod 251. This innovative design of the wiring and clamping mechanism 5 changes the primary side connection method of the traditional "through-type" current transformer to "terminal connection". Through mechanical guidance and transmission mechanism, the external cable and the built-in primary conductive rod 251 are accurately and reliably connected, which effectively solves the on-site installation problems of difficulty in through-type large cross-section cables and poor connection consistency. The symmetrical wiring mechanism 3 and clamping mechanism 5 facilitate the access and fixation of the external main circuit conductor, thereby forming a complete current measurement circuit. During operation, the main circuit current is connected from the P1 side connection mechanism 3 of the current transformer, flows through the clamped cable end, enters the primary conductive rod 251, passes through the central hole of the iron core, and flows out from the P2 side connection mechanism 3, returning to the main circuit. The current forms a single-turn through-core path. This complete conductive circuit is based on electromagnetic induction for current measurement.

[0023] like Figure 1-5As shown, the integrated conductive unit 25 also includes an electrically insulating material 252, which is sealed to the outer periphery of the primary conductive rod 251 by a vacuum casting process, and the outer peripheral wall of the electrically insulating material 252 is tightly fitted to the inner wall of the central hole of the iron core 23. The fixed arrangement of the primary conductive rod 251 and the iron core 23 ensures a constant relative position between the primary conductive circuit and the magnetic circuit of the iron core 23, providing a stable structural foundation for accurate current sensing. The vacuum casting process ensures that the electrical insulation material 252 is bubble-free, dense, and uniform, greatly improving the insulation strength between the primary and secondary sides and effectively preventing internal creepage and breakdown. The tightly fitted structure enhances mechanical strength, fixes the relative position of the iron core 23 and the conductive rod, reduces errors caused by vibration or thermal expansion and contraction, and improves the reliability and lifespan of the product. In addition, compared with the traditional flexible cable that passes through the central hole, the rigid primary conductive rod 251 can avoid the problem of uneven electromagnetic coupling gap caused by cable bending and displacement, ensuring uniform magnetic flux distribution. It reduces the transformation ratio error caused by changes in the shape of the primary conductor from the structural source. At the same time, its rigid structure can withstand a larger rated current, improving the overload capacity of the product. The primary conductive rod 251 is fixedly connected to the iron core 23 through the electrical insulation material 252, and the electrical insulation material 252 forms a fixed fit with the shell 2. The integrated solid-sealing design makes the primary conductive rod 251, the electrical insulation material 252, the iron core 23, and the shell 2 form an inseparable whole structure. Compared with the movable fit between the traditional cable and the iron core 23, it completely eliminates the relative displacement between the conductor and the iron core 23 during long-term operation, ensures the consistency of electromagnetic induction, and avoids the risk of insulation damage caused by friction between the cable and the inner wall of the iron core 23.

[0024] like Figure 1-5 As shown, the wiring mechanism 3 includes a support plate 31 symmetrically fixed to the outer side of the housing 2, a horizontal plate 32 fixed between the two sets of support plates 31, a movable plate 33 connected to the support plate 31, and symmetrically arranged connecting bolts 34; the plug end of the connecting bolt 34 is rotatably connected to the horizontal plate 32, and the other end is threadedly adapted to the movable plate 33. By rotating the connecting bolt 34, the movable plate 33 can be driven to move closer to or away from the horizontal plate 32. This structure converts the rotational movement of the connecting bolt 34 into the precise linear displacement of the movable plate 33, realizing the continuous adjustment of the connection spacing; the movable plate 33 and the horizontal plate 32 are arranged parallel to each other, and the primary conductive rod 251 is arranged to pass through the middle of the horizontal plate 32 and the middle of the movable plate 33 in sequence; By rotating the connecting bolt 34, the cable end held by the clamping mechanism 5 is aligned and clamped with the primary conductive rod 251, ensuring tight contact. This establishes a low-resistance, high-reliability electrical connection, ensuring that the measured main circuit current flows stably and with low loss through the primary conductive rod 251, thereby guaranteeing the accuracy of subsequent current sensing. Compared to the traditional method of directly threading and winding cables, this mechanism achieves precise docking between the cable and the primary conductive rod 251 through mechanical transmission, avoiding problems such as contact misalignment and uneven pressure caused by manual wiring. At the same time, the spacing can be adjusted to accommodate cable connectors of different lengths, eliminating the need for cable cutting and improving the versatility and consistency of wiring. The linear movement of the movable plate 33 ensures that the external cable is aligned when connecting to the built-in primary conductive rod 251, thus guaranteeing the concentricity of the connection and the integrity of the contact surface at the structural level. The movable plate 33 has symmetrically fixed limiting plates 331 at both ends; the support plate 31 has a slot, and the limiting plate 331 is movably inserted into the slot. The cooperation between the slot and the limiting plate 331 provides precise guidance for the movement of the movable plate 33, ensuring that the movable plate 33 always maintains a parallel relationship with the horizontal plate 32 during the movement, preventing it from deflecting or getting stuck, making the adjustment process smooth and stable, and at the same time enhancing the rigidity of the entire wiring mechanism 3.

[0025] like Figure 1-6 As shown, a fixed frame 4 is fixed to the outside of the movable plate 33; a circular channel 41 is opened inside the fixed frame 4 corresponding to the central channel of the movable plate 33; two sets of limiting grooves 42 communicating with the circular channel 41 are symmetrically arranged on the fixed frame 4. The fixed frame 4, as an integrated platform, provides a unified installation base and operating space for the symmetrical clamping mechanism 5. The circular channel 41 provides space to accommodate cables and clamping plates, while the limiting grooves 42 are used to constrain the movement trajectory of the clamping plates. The clamping mechanisms 5 are symmetrically arranged at the top and bottom of the fixed frame 4. Each clamping mechanism 5 includes a vertically threaded fixing bolt 51 connected to the fixed frame 4 and an arc-shaped clamping plate 52 movably disposed within the circular channel 41. The end of the fixing bolt 51 contacts the outer wall of the arc-shaped clamping plate 52. By tightening the fixing bolt 51, the arc-shaped clamping plate 52 is pushed towards the center, thereby clamping the cable passing through the circular channel 41 from both top and bottom directions. The symmetrical clamping mechanisms 5 generate a uniform clamping force, achieving concentric clamping of the cable and avoiding poor contact caused by unilateral force. This design provides a larger contact area and a more reliable mechanical connection, effectively reducing contact resistance and heat generation.

[0026] like Figure 1-6As shown, the internal cross-section of the arc-shaped clamping plate 52 is trapezoidal, and symmetrically arranged on both sides are limiting blocks 521 that are movable within the limiting groove 42. The trapezoidal internal cross-section of the arc-shaped clamping plate 52 enables the transformation from line contact to surface contact, thereby significantly increasing the effective contact area with the cable. When the clamping plate moves towards the center, the inclined surface of its trapezoidal cross-section will first or simultaneously contact the cable surface, thus forming at least two main contact areas, changing the situation where the inner wall of the traditional cylindrical surface only forms a single narrow strip of contact. During this process, a "wedge effect" is generated between the inclined plane and the cable. Under the action of clamping force, the cable surface undergoes microscopic deformation, making it more tightly filled into the various contact parts formed by the inclined plane. This makes the arc-shaped clamping plate 52 and the cable clamped in the arc-shaped clamping plate 52 more tightly connected. The trapezoidal cross-section design not only adapts to cables of different diameters, but also forms an interlocking fixation between the cable and the clamping plate through the "wedge effect". Compared with traditional flat or arc-shaped clamping, it can effectively prevent slight slippage of the cable due to heat expansion during current transmission, ensuring long-term stable contact resistance. Both the limiting block 521 and the limiting plate 331 are L-shaped. The cooperation between the L-shaped limiting block 521 and the limiting groove 42 precisely restricts the arc-shaped clamping plate 52 to move only along a predetermined path, preventing it from rotating or falling off.

[0027] In practical use 1. Installation and Cable Pre-treatment: First, use bolts to reliably fix the transformer base plate 1 to the preset mounting base. Then, strip the ends of the main circuit cable to be connected, removing an appropriate amount of insulation to expose the conductor. Insert the treated cable conductor into the circular channel 41 of the fixing frame 4, preparing for subsequent clamping operations.

[0028] 2. Reliable cable clamping: The fixing bolts 51 on the upper and lower sides of the fixing frame 4 are tightened evenly using tools. During the bolt advancement, the arc-shaped clamping plate 52 with the internal trapezoidal cross section moves synchronously towards the center, using a unique wedge effect to clamp the cable evenly from both the upper and lower directions, ensuring that the cable is stably fixed in the center position of the channel, forming an excellent mechanical connection and electrical contact.

[0029] 3. Primary Circuit Connection: The connecting bolt 34 in the rotating wiring mechanism 3 drives the movable plate 33 to move smoothly towards the horizontal plate 32 via threaded transmission, thereby ensuring precise alignment and tight fit between the clamped cable end and the corresponding end of the primary conductive rod 251 penetrating the iron core 23. Simultaneously, the other end of the primary conductive rod 251 is connected to the corresponding power distribution circuit, completing a reliable connection of the primary side main current channel.

[0030] 4. Secondary Circuit Connection and Operation: Accurately connect the signal lines of the metering instrument or protection device to the first and second terminals 22 on the transformer housing 2 to establish a complete signal transmission circuit. After verifying that all connections are correct, the transformer can be put into normal operation to realize current measurement and signal conversion functions.

[0031] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the inventive spirit of the present invention, such designs should fall within the protection scope of the present invention.

Claims

1. A metering low-voltage current transformer, comprising a base plate (1) and a housing (2) disposed on the base plate (1), the housing (2) being made of insulating material and having an iron core (23) disposed inside, wherein a secondary winding (24) is uniformly wound on the outer periphery of the iron core (23), characterized in that: An integrated conductive unit (25) is provided on the housing (2). The integrated conductive unit (25) includes a primary conductive rod (251) that passes through the central hole of the iron core (23). Wiring mechanisms (3) are symmetrically arranged on both sides of the housing (2), and clamping mechanisms (5) are connected to the wiring mechanisms (3).

2. A metering low voltage current transformer according to claim 1, characterized in that: The integrated conductive unit (25) also includes an electrical insulating material (252), which is fixed to the outer periphery of the primary conductive rod (251) by a vacuum casting process, and the outer periphery of the electrical insulating material (252) is tightly attached to the inner wall of the central hole of the iron core (23).

3. A metering low voltage current transformer according to claim 2, characterized in that: The primary conductive rod (251) is fixedly connected to the iron core (23) through the electrical insulating material (252), and the electrical insulating material (252) forms a fixed fit with the shell (2).

4. A metering low voltage current transformer according to claim 1, characterized in that: The wiring mechanism (3) includes a support plate (31) symmetrically fixed to the outer side of the housing (2), a cross plate (32) fixed between the two sets of support plates (31), a movable plate (33) connected to the support plate (31), and symmetrically arranged connecting bolts (34). The plug end of the connecting bolt (34) is rotatably connected to the horizontal plate (32), and the other end is threadedly adapted to the movable plate (33); The movable plate (33) and the horizontal plate (32) are arranged parallel to each other, and the primary conductive rod (251) is arranged to pass through the middle of the horizontal plate (32) and the middle of the movable plate (33) in sequence.

5. A metering low voltage current transformer according to claim 4, characterized in that: Limiting plates (331) are symmetrically fixed at both ends of the movable plate (33); The support plate (31) has a slot, and the limiting plate (331) is movably inserted into the slot.

6. A metering low voltage current transformer according to claim 4, characterized in that: The movable plate (33) is fixed with a fixed frame (4); A circular channel (41) is provided inside the fixed frame (4) corresponding to the central channel of the movable plate (33). The fixed frame (4) is symmetrically provided with two sets of limiting grooves (42) that communicate with the circular channel (41).

7. A metering low voltage current transformer according to claim 6, characterized in that: The clamping mechanism (5) is symmetrically arranged on the upper and lower parts of the fixed frame (4); The clamping mechanism (5) includes a vertical fixing bolt (51) threaded onto the fixed frame (4) and an arc-shaped clamping plate (52) movable in the circular channel (41). The end of the fixing bolt (51) is in contact with the outer wall of the arc-shaped clamping plate (52).

8. A metering low voltage current transformer according to claim 7, characterized in that: The internal cross section of the arc-shaped clamping plate (52) is trapezoidal, and there are symmetrically arranged limiting blocks (521) on both sides that are movable in the limiting groove (42).

9. A metering low voltage current transformer according to claim 8, characterized in that: Both the limiting block (521) and the limiting plate (331) are L-shaped.

10. A metering low voltage current transformer according to claim 1, characterized in that: The housing (2) is provided with a first terminal (21) and a second terminal (22).

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