Segmented skeleton flexible current transformer

Abstract

This invention discloses a segmented skeleton-type flexible current transformer, relating to the field of current measurement technology. The invention aims to solve the technical problems of traditional rigid current transformers, such as inconvenient installation, incompatibility with Rogowski coil outputs, low accuracy, and excessive errors at the joints of existing flexible current transformers. The transformer core employs differentiated impregnation treatment; the middle flexible main body section is not impregnated to maintain flexibility, while the rigid connecting sections at both ends are impregnated, cured, and have smooth connecting surfaces. Multiple I-shaped skeletons are fixed at equal intervals on the flexible main body section, with air gaps reserved between adjacent skeletons. Independent secondary windings wound on each skeleton are connected in series to form a single closed loop. Locking docking mechanisms are provided at both ends to form a closed magnetic circuit. An auxiliary compensation winding connected in the same direction is fixed on the rigid connecting section to compensate for measurement errors at the magnetic circuit connection point. This invention allows for uninterrupted winding installation, direct output of standard current signals without auxiliary power, full-circuit measurement accuracy of 0.5%, simple and reliable structure, and is suitable for power distribution upgrades and current measurement in confined spaces.

Description

Technical Field

[0001] This invention relates to the field of current measurement technology, and specifically to a segmented skeleton-type flexible current transformer. Background Technology

[0002] Current transformers are core infrastructure devices in power systems for current measurement, energy metering, and relay protection, and are widely used in industrial power distribution, data centers, building electrical systems, and other fields. With the rapid growth in demand for intelligent power distribution transformation and industrial energy consumption monitoring, there is an increasing number of scenarios involving upgrading old equipment and adding measurement points in confined spaces, which places higher demands on the ease of installation and on-site adaptability of current transformers.

[0003] Current mainstream current measurement solutions have significant technical shortcomings: Traditional rigid switchable current transformers use an integral rigid iron core structure with epoxy resin casting or metal shell, which is large and heavy. Sufficient opening and closing space must be reserved during installation, making them unsuitable for confined environments with dense cables, such as distribution cabinets and cabinets. Moreover, the installation process requires disassembling busbars or disconnecting cables, necessitating power outages and severely impacting production continuity. Although Rogowski coils use a hollow flexible structure that can be directly wound and installed, they lack the magnetic flux amplification effect of an iron core. The output is a millivolt-level voltage signal that is proportional to the rate of change of current. It requires an external integrator, amplifier, and auxiliary power supply to be used, resulting in complex wiring. It cannot be directly compatible with the standard 5A / 1A input interface of existing power equipment. At the same time, the error is significant when measuring low currents, with a ratio error of ±5% for primary currents below 5A, making it difficult to meet the accuracy requirements of industrial-grade measurements.

[0004] In summary, existing technologies present a binary opposition: rigid high precision but inconvenient installation versus flexible easy installation but insufficient performance. There is a lack of a current measurement solution that can simultaneously achieve flexible, wrap-around installation, directly output standard current signals without auxiliary power supply, and meet the accuracy requirements of industrial measurements. This makes it impossible to meet the actual application needs of current power distribution transformation and energy consumption monitoring. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a segmented skeleton flexible current transformer and its manufacturing method, which solves the technical problems of inconvenient installation, incompatibility of Rogowski coil output and large low current error of traditional rigid current transformers, and achieves rapid installation without power outage or wire breakage, while directly outputting standard current signals.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A segmented skeleton flexible current transformer includes an iron core and a secondary winding wound on the iron core. The iron core is a long strip-shaped flexible iron core, including a flexible main body section in the middle and a first rigid connecting section and a second rigid connecting section respectively disposed at both ends of the iron core; wherein, the first rigid connecting section and the second rigid connecting section are impregnated with paint and cured, and the end faces are flat connecting surfaces; Multiple I-shaped frames are fixed at equal intervals on the flexible main body section, and air gaps are reserved between adjacent I-shaped frames for bending the iron core. Each of the I-shaped frames is tightly wound with an independent secondary winding segment, and all the secondary winding segments are electrically connected end to end to form a single closed secondary circuit. The first rigid docking section and the second rigid docking section are provided with locking docking mechanisms to dock the two ends of the flexible iron core to form a closed ring magnetic circuit. The center of the closed ring magnetic circuit forms a through-hole channel for a primary conductor to pass through. The two ends of the closed secondary circuit converge at the locking and docking mechanism, and a secondary output lead is drawn out from one end of the locking and docking mechanism.

[0007] Furthermore, the number of turns in the secondary winding segments on each I-beam frame is equal.

[0008] Furthermore, the secondary winding section is tightly wound with enameled copper wire, and adjacent secondary winding sections are electrically connected by welding or terminals.

[0009] Furthermore, the locking and docking mechanism is a spiral locking joint, with the first rigid docking section and the second rigid docking section respectively fixed to the two docking ends of the joint.

[0010] Furthermore, at least one I-shaped auxiliary frame is fixed inside the locking and docking mechanism. An auxiliary compensation winding is wound on the I-shaped auxiliary frame. The auxiliary compensation winding is connected in series with the secondary winding segment in the same direction to compensate for the measurement error at the magnetic circuit docking point.

[0011] Furthermore, the I-beam frame is made of insulating material, and all I-beam frames and secondary winding sections are entirely covered with a flame-retardant insulating protective layer.

[0012] Furthermore, the two secondary output leads are used to directly output a standard current signal that is proportional to the primary current.

[0013] Furthermore, the inner diameter of the flexible iron core after docking to form a closed annular magnetic circuit is not less than 80mm.

[0014] A method for manufacturing a segmented skeleton-type flexible current transformer, comprising the flexible current transformer described above, includes the following steps: S1. Differentiated treatment is applied to the flexible iron core by impregnating and curing both ends of the iron core with paint to form the first rigid connection section and the second rigid connection section. S2. The first and second rigid joint sections after impregnation and curing are smoothed. S3. Fix multiple insulating frames at equal intervals on the flexible main body section of the iron core, and tightly wind independent secondary winding sections on each insulating frame. S4. Connect all the secondary winding segments end to end in sequence to form a single closed secondary circuit. S5. Fix the outer periphery of the first rigid docking section to the I-shaped auxiliary frame, and wind the auxiliary compensation winding on the I-shaped auxiliary frame. Connect the auxiliary compensation winding and the secondary winding section in series in the same direction to the closed secondary circuit. Then fix the first rigid docking section and the second rigid docking section to the two docking ends of the locking docking mechanism respectively. S6. Lead both ends of the closed secondary circuit out from one end of the locking and docking mechanism to form a secondary output lead.

[0015] S7. The entire exterior of all insulating frames and secondary winding sections is covered with a flame-retardant insulating protective layer.

[0016] Furthermore, the end face flattening process in step S3 specifically involves: first, using a grinding wheel to cut the end face of the rigid mating section until it is smooth and without any light-transmitting gaps; then, using wire cutting to process positioning bayonets at the edge of the end face.

[0017] Compared with the prior art, the present invention has the following advantages: 1. Through a differentiated impregnation process, the main body section in the middle of the iron core remains flexible and bendable, while the connecting sections at both ends remain rigid and flat. Combined with the air gap between the segmented skeletons, the entire transformer can be directly wound onto the cable or busbar without cutting the wire or interrupting the power, greatly shortening the installation time and making it suitable for narrow spaces and old equipment renovation scenarios. 2. It retains the flux amplification characteristics of iron-core current transformers, and forms a complete secondary circuit through multiple windings connected in series. The total number of turns meets the preset transformation ratio requirements, and it can directly output a 5A / 1A standard current signal without the need for an external integrator, amplifier or auxiliary power supply, and is fully compatible with existing power system equipment.

[0018] 3. The design of equally spaced segmented skeleton and windings with equal number of turns ensures the uniform distribution of magnetomotive force along the circumference of the iron core, effectively reducing the leakage magnetic error caused by the segmented structure; combined with high-precision end face processing technology, the air gap of the magnetic circuit is reduced, and the overall accuracy can reach 0.5 level, meeting the application requirements of industrial energy consumption monitoring, relay protection and other applications.

[0019] 4. It adopts a modular design, and the processing technology of each component is mature and easy to assemble; the whole is covered with a flame-retardant insulating protective layer, which has good insulation and mechanical protection performance, and has passed reliability tests such as high and low temperature cycling and lightning strike, and has a long service life. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the flexible current transformer of the present invention; Figure 2 This is a schematic diagram of the internal structure of the flexible current transformer of the present invention; Figure 3 This is a schematic diagram of the iron core structure of the present invention. Figure 4 This is a front cross-sectional view of the flexible current transformer of the present invention; Figure 5 This is a flowchart of the flexible current transformer manufacturing method of the present invention; In the diagram: 1. Flexible iron core; 11. Flexible main body section; 12. First rigid connection section; 13. Second rigid connection section; 2. I-shaped frame; 3. Secondary winding section; 4. Locking connection mechanism; 5. Secondary output lead; 6. Flame-retardant insulation protective layer; 7. I-shaped auxiliary frame; 8. Auxiliary compensation winding. Detailed Implementation

[0021] The present application will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1 As shown, the segmented skeleton flexible current transformer disclosed in this embodiment includes a flexible iron core 1, multiple I-shaped skeletons 2, multiple secondary winding segments 3, a locking and docking mechanism 4, secondary output leads 5, and auxiliary compensation windings 8.

[0023] The flexible iron core 1 is formed by multi-layer winding of high-permeability silicon steel strips into a long strip structure. The overall length is customized according to the required inner diameter, and the inner diameter after closure is not less than 80mm, which can be adapted to most low-voltage cables and busbars. The flexible iron core 1 is divided into a flexible main body section 11 in the middle and a first rigid mating section 12 and a second rigid mating section 13 at both ends. Among them, the flexible main body section 11 is not impregnated and cured, retaining the relative sliding ability between the silicon steel strips, allowing the iron core to bend freely; the first rigid mating section 12 and the second rigid mating section 13 are vacuum impregnated and cured to form a hard rigid structure, which facilitates the processing of flat mating end faces and the installation of locking mating mechanism 4.

[0024] The I-beam frame 2 is injection molded from insulating plastic and has a winding groove in the middle. Multiple I-beam frames 2 are fixed at equal intervals along the length of the flexible main body section 11, and the fixing method can be epoxy resin bonding or snap-fit ​​connection. Uniform air gaps are reserved between adjacent I-beam frames 2. These gaps provide the necessary deformation space for the iron core to bend, avoiding the problem of continuous winding forming a rigid whole that cannot be bent.

[0025] The secondary winding segment 3 is made of high-strength enameled copper wire tightly wound in the winding slots of the I-shaped frame 2. The number of turns of the secondary winding segment 3 on each I-shaped frame 2 is equal. All secondary winding segments 3 are connected end to end by welding enameled wire, and the welding points are insulated with insulating sleeves to form a single closed secondary circuit. The total number of turns of the secondary circuit is designed according to the turns ratio requirements. For example, the total number of turns for the 1000 / 5A specification is 200 turns, and the total number of turns for the 2000 / 5A specification is 400 turns.

[0026] The locking and mating mechanism 4 adopts a spiral locking connector, consisting of a male and a female part, which are respectively fixed to the ends of the first rigid mating section 12 and the second rigid mating section 13. The male and female parts are locked together by threaded engagement, so that the flat end faces of the two rigid mating sections are tightly fitted together, forming a closed annular magnetic circuit. The center of the closed annular magnetic circuit forms a through-hole channel, through which the primary conductor being measured passes to form the primary winding of the current transformer.

[0027] The auxiliary compensation winding 8 is wound on an I-shaped auxiliary frame 7, which is located immediately adjacent to the magnetic circuit mating surface. The winding direction of the auxiliary compensation winding 8 is exactly the same as that of the secondary winding segment 3, and its two ends are connected in series to a closed secondary circuit. The number of turns of the auxiliary compensation winding is precisely calibrated according to the turns ratio and error compensation requirements. In this embodiment, the number of turns of the auxiliary compensation winding is 1%-3% of the total number of turns.

[0028] Secondary output lead 5 consists of two multi-strand copper wires with insulating sheaths, used to connect to external measuring or protection devices. Secondary output lead 5 can directly output a standard 5A or 1A current signal proportional to the primary current, without any auxiliary power supply.

[0029] The flame-retardant insulating protective layer 6 is made of flame-retardant sponge adhesive and is completely wrapped around the outside of all I-shaped skeletons 2 and secondary winding sections 3. It provides additional insulation protection, enhances the product's flexibility and resistance to mechanical impact, and also serves to prevent moisture and dust.

[0030] like Figure 5 As shown, in another embodiment, a method for fabricating the above-mentioned segmented skeleton flexible current transformer is disclosed, the specific steps of which are as follows: S1. The cut high-permeability silicon steel strip is wound in multiple layers into a long strip of iron core of a predetermined length; the main body section in the middle of the iron core is completely wrapped with masking tape, leaving only the straight edge sections at both ends exposed; the iron core is placed in a varnish-impregnating tank for vacuum varnish-impregnation treatment; after varnish-impregnation, it is taken out, the masking tape is removed, and it is placed in an oven for curing; after curing, the straight edge sections at both ends of the iron core form a hard first rigid joint section 12 and a second rigid joint section 13, while the main body section in the middle is not varnished and remains flexible; S2. Clamp the cured rigid butt joint section onto the cutting machine. First, use an abrasive wheel cutting machine to cut the end face until it is flat, requiring the cut surface to be smooth and without any light-transmitting gaps. Then, use a wire cutting machine to process four rectangular positioning slots on the edge of the end face, which are used to cooperate with the positioning groove of the locking and docking mechanism 4 to ensure docking accuracy. S3. Mark the skeleton installation positions at equal intervals on the flexible main body section 11, and use epoxy resin to bond the I-shaped skeleton 2 to the marked positions in sequence; after the glue has cured, use a CNC winding machine to tightly wind the pre-set number of enameled copper wires on each I-shaped skeleton 2 to form an independent secondary winding section. S4. Connect the tail end of the previous secondary winding segment 3 to the beginning end of the next secondary winding segment 3 by soldering, and put a heat-shrinkable insulating sleeve on the solder joint; connect all secondary winding segments 3 in sequence to form the main secondary circuit. S5. In the internal cavity of the female head of the locking docking mechanism 4, the I-shaped auxiliary frame 7 is fixed with epoxy resin; an auxiliary compensation winding 8 with a preset number of turns is wound on the I-shaped auxiliary frame 7, and the two ends of the auxiliary compensation winding 8 are connected in series to the main secondary circuit to form a complete closed secondary circuit; the first rigid docking section 12 and the second rigid docking section 13 are respectively inserted into the mounting holes of the male and female heads of the locking docking mechanism 4, and positioned by the positioning slots in the mounting holes. S6. Solder the two ends of the closed secondary circuit to the inner core of the secondary output lead 5 respectively, and put an insulating sleeve on the solder joint; lead out the secondary output lead 5 and seal the lead hole with sealant.

[0031] S7. Use flame-retardant sponge adhesive to tightly wrap all I-shaped frame 2 and secondary winding section 3, requiring uniform wrapping without air bubbles, to finally form a complete flexible current transformer product.

[0032] The working principle of this invention is based on the law of electromagnetic induction and Ampere's circuital law: when the measured current I1 flows through the primary conductor passing through the center of the closed loop magnetic circuit, an alternating magnetic field is generated around the conductor; the highly permeable flexible iron core 1 concentrates most of the magnetic field inside the iron core, forming a closed main magnetic flux Φ; the main magnetic flux passes through the secondary winding segment 3 wound on the iron core, inducing an alternating electromotive force in each winding segment; since all winding segments are connected in series, the total induced electromotive force is the sum of the electromotive forces of each segment, and when a load is connected to the secondary side to form a closed loop, a secondary current I2 is generated.

[0033] According to the ampere-turn balance principle, ideally I1N1=I2N2, where N1=1 and N2 is the total number of turns in the secondary winding. Therefore, the turns ratio K=I1 / I2=N2 / N1. By designing a suitable total number of turns in the secondary winding, a standard 5A or 1A current signal can be output from the secondary side.

[0034] To address the error issue at the joint, the auxiliary compensation winding 8 operates as follows: Due to the presence of a small air gap and the absence of main winding coverage at the magnetic circuit connection point, the primary magnetomotive force cannot be completely canceled out, resulting in leakage flux. The auxiliary compensation winding 8, positioned close to the connection surface, precisely couples this leakage flux, generating an induced electromotive force and current in the same direction as the main winding. The resulting magnetomotive force precisely cancels out the unbalanced magnetomotive force at the joint, thereby significantly reducing the ratio and angle difference at the joint and achieving a measurement accuracy of 0.5% across the entire circumference.

[0035] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A segmented frame-type flexible current transformer, comprising an iron core and a secondary winding wound on the iron core, characterized in that: The iron core is a long strip-shaped flexible iron core, including a flexible main body section in the middle and a first rigid connecting section and a second rigid connecting section respectively disposed at both ends of the iron core; wherein, the first rigid connecting section and the second rigid connecting section are impregnated with paint and cured, and the end faces are flat connecting surfaces; Multiple I-shaped frames are fixed at equal intervals on the flexible main body section, and air gaps are reserved between adjacent I-shaped frames for bending the iron core. Each of the I-shaped frames is tightly wound with an independent secondary winding segment, and all the secondary winding segments are electrically connected end to end to form a single closed secondary circuit. The first rigid docking section and the second rigid docking section are provided with locking docking mechanisms to dock the two ends of the flexible iron core to form a closed ring magnetic circuit. The center of the closed ring magnetic circuit forms a through-hole channel for a primary conductor to pass through. The two ends of the closed secondary circuit converge at the locking and docking mechanism, and a secondary output lead is drawn out from one end of the locking and docking mechanism.

2. The flexible current transformer according to claim 1, characterized in that, The number of turns in the secondary winding section on each I-beam frame is equal.

3. The flexible current transformer according to claim 1, characterized in that, The secondary winding section is tightly wound with enameled copper wire, and adjacent secondary winding sections are electrically connected by welding or terminals.

4. The flexible current transformer according to claim 1, characterized in that, The locking and docking mechanism is a spiral locking joint, with the first rigid docking section and the second rigid docking section respectively fixed to the two docking ends of the joint.

5. The flexible current transformer according to claim 1, characterized in that, An I-shaped auxiliary frame is fixed on the first or second rigid docking section, within the locking docking mechanism. An auxiliary compensation winding is wound on the I-shaped auxiliary frame. The auxiliary compensation winding is connected in series to the single closed secondary circuit, and its winding direction is the same as that of the secondary winding section.

6. The flexible current transformer according to claim 1, characterized in that, The I-beam frame is made of insulating material, and all I-beam frames and secondary winding sections are completely covered with a flame-retardant insulating protective layer.

7. The flexible current transformer according to claim 1, characterized in that, The two secondary output leads are used to directly output a standard current signal that is proportional to the primary current.

8. The flexible current transformer according to claim 1, characterized in that, The inner diameter of the flexible iron core after docking to form a closed annular magnetic circuit is not less than 80mm.

9. A method for manufacturing a flexible current transformer as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1. Differentiated treatment is applied to the flexible iron core by impregnating and curing both ends of the iron core with paint to form the first rigid connection section and the second rigid connection section. S2. The first and second rigid joint sections after impregnation and curing are smoothed. S3. Fix multiple insulating frames at equal intervals on the flexible main body section of the iron core, and tightly wind independent secondary winding sections on each insulating frame. S4. Connect all the secondary winding segments end to end in sequence to form a single closed secondary circuit. S5. Fix an I-shaped auxiliary frame around the first rigid docking section, and wind an auxiliary compensation winding on the I-shaped auxiliary frame; connect the auxiliary compensation winding in series with the closed secondary circuit in the same winding direction as the secondary winding section; then fix the first rigid docking section and the second rigid docking section to the two docking ends of the locking docking mechanism respectively. S6. Lead both ends of the closed secondary circuit out from one end of the locking and docking mechanism to form a secondary output lead; S7. The entire exterior of all insulating frames and secondary winding sections is covered with a flame-retardant insulating protective layer.

10. The preparation method according to claim 9, characterized in that, The end face flattening process in step S2 specifically involves: first, using a grinding wheel to cut the end face of the rigid butt joint section until it is smooth and without any light-transmitting gaps; then, using wire cutting to process positioning bayonets at the edge of the end face.

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