A double current ratio current transformer with internal coil series connection

Abstract

This utility model relates to a dual-current-ratio current transformer with internal coils connected in series, including a housing, and a secondary winding including a first core and a second core concentrically wound on the primary winding. The lead-out end of the first secondary wire wound on the first core is connected in series with the second secondary wire wound on the second core. The width values ​​of the first core and the second core are determined by the initial core width value that satisfies the dual current ratio. The dual-current-ratio current transformer with internal coils connected in series designed using this utility model solves the problem that conventional current transformer design calculates the core size according to the selected ampere-turns and then winds the secondary wire on the core. However, when the current transformer needs to meet a large protection ratio and a large rated output, the core width will exceed the operable width of the secondary winding machine, making it difficult to achieve a small current ratio current transformer that simultaneously meets a large protection ratio and a large rated output while satisfying a high thermal stability current.

Description

Technical Field

[0001] This utility model relates to the field of power system technology, specifically to a dual current ratio current transformer with internal coils connected in series. Background Technology

[0002] In the existing technology, small current ratio current transformers cannot simultaneously meet the requirements of high thermal stability current, large protection factor, and large rated output, because these three are mutually restrictive. If a small current ratio current transformer is to meet the requirement of high thermal stability current, then a very low ampere-turns number must be used. If the ampere-turns number is low, the protection factor and rated output that can be met according to conventional design will be relatively small.

[0003] Conventional current transformer design involves calculating the core dimensions based on the selected ampere-turns and then winding secondary wires on the core. However, when the current transformer needs to meet a large protection ratio and a large rated output, the core width will exceed the width that the secondary winding machine can operate, making it difficult to achieve a small current ratio current transformer that meets both a large protection ratio and a large rated output while maintaining a high thermal stability current.

[0004] Therefore, existing technologies have shortcomings and need to be improved and developed. Utility Model Content

[0005] The utility model provides a dual current ratio current transformer with internal coils connected in series, which solves the problem that in the conventional current transformer design of the prior art, the core size of the corresponding specification is calculated according to the selected ampere-turns, and then the secondary wire is wound on the core. However, when the current transformer needs to meet a large protection ratio and a large rated output, the width of the core will exceed the width that the secondary winding machine can operate, thus making it difficult to achieve a small current ratio current transformer that meets the requirements of high thermal stability current while simultaneously meeting the requirements of a large protection ratio and a large rated output.

[0006] This utility model provides a dual current ratio current transformer with internal coils connected in series, including a housing, an epoxy resin poured inside the housing, and a primary winding and a secondary winding fixed inside the housing by the epoxy resin. The primary winding passes through the secondary winding, and each end of the primary winding is welded with a primary terminal. Each primary terminal extends out of the top of the housing. The bottom of the secondary winding is secured with a fixing plate by packing straps. The secondary winding includes a first iron core and a second iron core concentrically mounted on the primary winding. A first secondary wire is wound on the first iron core, and the first secondary wire includes a starting end S1 and an ending end S3, and a winding formed by the starting end S1 and the ending end S3. The lead-out terminal S4 is drawn out between S3; a second secondary wire is wound on the second iron core, the second secondary wire includes a starting end S5 and an ending end S2; the lead-out terminal S4 is connected to the starting end S5 by a wire and a series terminal is drawn out on the wire; the starting end S1, the ending end S2, the ending end S3, and the series terminal are respectively welded to the secondary terminals located at the bottom of the housing and corresponding in polarity; the dual current ratio is defined as divided into a large current ratio and a small current ratio according to the magnitude of the current ratio value, wherein the width value of the first initial iron core that satisfies the large current ratio is H, the width value of the second initial iron core that satisfies the small current ratio is h, the width value of the first iron core is equal to H, and the width value of the second iron core is equal to hH.

[0007] Furthermore, it also includes an amorphous iron core, which is concentrically mounted on the primary winding along with the first iron core. The amorphous iron core is located on the side of the first iron core away from the second iron core. A third secondary wire is wound on the amorphous iron core. The third secondary wire includes a starting end S6, an ending end S7, and a lead-out end S8 drawn from between the starting end S6 and the ending end S7. The starting end S6, the ending end S7, and the lead-out end S8 are respectively welded to secondary terminals located at the bottom of the housing and corresponding in polarity.

[0008] Furthermore, the lead-out position of the lead-out terminal S8 is at 1 / 2 turn of the third and second secondary wire wound on the amorphous iron core.

[0009] Furthermore, the first secondary wire, the second secondary wire, and the third secondary wire are enameled wires.

[0010] Furthermore, insulating bandages are wrapped around the first iron core, the second iron core, and the amorphous iron core in a ring.

[0011] Furthermore, each week's insulating bandage, after being wrapped in a loop, covers at least half the width of the insulating bandage from the previous week.

[0012] Furthermore, the insulating bandage is an insulating self-adhesive tape.

[0013] Furthermore, the first core and the second core are silicon steel cores.

[0014] Beneficial effects:

[0015] As can be seen from the above technical solution, this utility model provides a dual-current-ratio current transformer with internal coils connected in series. By designing the width of the first iron core to be H in the high current-ratio range and the width of the second iron core to be hH in the low current-ratio range, the segmented design allows for separate optimization of both, ensuring both high thermal stability current and a high protection factor, thus balancing thermal stability current and protection factor. The series-connected dual-current-ratio windings achieve a larger equivalent number of turns and cross-section within the same size, meeting the requirements of high-power energy transmission and improving rated output capacity when used for output. The segmented design limits the iron core width to the operable range of the winding machine, and the coaxial layout of multiple iron core segments simplifies the assembly process, improving production efficiency and finished product yield. By introducing an amorphous iron core, which acts as a measuring winding, and combining the design of the first and second iron cores, the functions of both measuring and protection windings are considered, improving the functional expandability of the transformer.

[0016] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below can be considered part of the inventive subject matter of this disclosure, provided that such concepts do not contradict each other.

[0017] The foregoing and other aspects, embodiments, and features of the teachings of the present invention will be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the invention, such as features and / or beneficial effects of exemplary embodiments, will become apparent from the following description or may be learned through practice of specific embodiments according to the teachings of the present invention. Attached Figure Description

[0018] The accompanying drawings are not drawn to scale. In the drawings, each identical or nearly identical component shown in the various figures may be denoted by the same reference numeral. For clarity, not every component is labeled in each figure. Embodiments of various aspects of the invention will now be described by way of example and with reference to the accompanying drawings, wherein:

[0019] Figure 1 This is a cross-sectional view of the structure of a dual current ratio current transformer with internal coils connected in series, according to an embodiment of this application.

[0020] Figure 2 This is a side view of the structure of a dual current ratio current transformer with internal coils connected in series, according to an embodiment of this application.

[0021] Figure 3 This is a schematic diagram of the winding of the first and secondary wires on the first core of a dual current ratio current transformer with internal coils connected in series, according to an embodiment of this application.

[0022] Figure 4 This is a schematic diagram of the winding of the second secondary wire on the second iron core of a dual current ratio current transformer with internal coils connected in series, according to an embodiment of this application.

[0023] Figure 5 This is a schematic diagram showing the first and second cores of a dual current ratio current transformer with internal coils connected in series, according to an embodiment of this application.

[0024] Explanation of icon numbers:

[0025] 1. Housing; 2. Primary winding; 3. Primary terminal; 4. First iron core; 401. First secondary wire; 5. Second iron core; 501. Second secondary wire; 6. Secondary terminal; 7. Amorphous iron core; 8. Fixing plate. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art to which this invention pertains.

[0027] The terms "first," "second," and similar words used in the specification and claims of this patent application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, unless the context clearly indicates otherwise, the singular forms of "an," "a," or "the," etc., do not indicate a quantity limitation, but rather indicate the presence of at least one. Terms such as "comprising" or "including" mean that the element or object preceding "comprising" encompasses the features, integrals, steps, operations, elements, and / or components listed following "comprising" or "including," and do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or collections thereof. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described object changes.

[0028] In the existing technology, conventional current transformer design calculates the core size according to the selected ampere-turns and then winds secondary wires on the core. However, when the current transformer needs to meet a large protection ratio and a large rated output, the width of the core will exceed the width that the secondary winding machine can operate. This makes it difficult to achieve a small current ratio current transformer that meets both a large protection ratio and a large rated output while meeting a high thermal stability current.

[0029] Therefore, this utility model embodiment provides a dual current ratio current transformer with internal coils connected in series, referring to... Figure 1 The transformer includes a housing 1, which is filled with epoxy resin, and a primary winding 2 and a secondary winding fixed within the housing 1 by the epoxy resin. The primary winding 2 passes through the secondary winding, and each end of the primary winding 2 is welded with a primary terminal 3. Each primary terminal 3 extends out from the top of the housing 1. The bottom of the secondary winding is secured with a fixing plate 8 by strapping. The housing 1, the epoxy resin filled within the housing 1, and the primary winding 2 within the housing 1 utilize existing designs.

[0030] The secondary winding includes a first core 4 and a second core 5 concentrically mounted on the primary winding 2, as shown in the reference. Figure 3 The first iron core 4 is wound with a first secondary wire 401, which includes a starting end S1, an ending end S3, and a lead-out end S4 extending from between the starting end S1 and the ending end S3. (Refer to...) Figure 4 The second core 5 is wound with a second secondary wire 501, which includes a starting end S5 and an ending end S2. (See reference...) Figure 5 Terminal S4 is connected to terminal S5 via a wire, and a series terminal is led out from the wire. (Refer to...) Figure 2 The starting end S1, the ending end S2, the ending end S3, and the series end are respectively welded to the secondary terminals 6 located at the bottom of the housing 1 and corresponding to the polarity.

[0031] Reference Figure 2 The secondary terminals 6 corresponding to the starting end S1, the ending end S2, the ending end S3, and the series end are respectively terminal 2S1, terminal 2S2, terminal 2S3, and terminal O. After the first secondary line 401 and the second secondary line 501 are connected in series, the output is segmented according to the large and small current ratios: when using 2S1–2S3 for measurement, the large current ratio is used, and 2S2 needs to be shorted to terminal O; when using 2S1–2S2 for measurement, the small current ratio is used.

[0032] The dual current ratio is defined as large current ratio and small current ratio according to the magnitude of the current ratio. The width of the first initial iron core that satisfies the large current ratio is H, and the width of the second initial iron core that satisfies the small current ratio is h. The width of the first iron core 4 is equal to H, and the width of the second iron core 5 is equal to hH.

[0033] Conventional current transformer design involves calculating the core dimensions based on the selected ampere-turns, and then winding the secondary windings on the core. This application, however, determines the relevant data and winds the secondary windings according to the following steps:

[0034] Step 1: Obtain the required small current ratio and large current ratio, select the rated ampere-turns and rated magnetic flux density according to the actual requirements, and calculate the width of the first iron core 4 and the second iron core 5 using the known inner and outer diameters. The width of the first initial iron core that satisfies the large current ratio is H, and the width of the second initial iron core that satisfies the small current ratio is h. The width of the first iron core 4 is equal to H, and the width of the second iron core 5 is equal to hH.

[0035] Step 2: Evenly wind the first secondary wire 401 on the first iron core 4, and evenly wind the second secondary wire 501 on the second iron core 5;

[0036] Step 3: Connect the first secondary line 401 and the second secondary line 501 in series, that is, weld the lead-out end S4 to the start end S5 and draw a series end between the lead-out end S4 and the start end S5.

[0037] For example:

[0038] Step 1: ① Select rated ampere-turns: Assuming a design with 200 turns and 400 turns, the required initial core ampere-turns N is determined. 2n，1 The value is 400, and the second initial core ampere-turns N 2n，2 The value is 200;

[0039] ② Select the rated magnetic flux density: B n =0.08;

[0040] ③ Calculate the cross-sections of the two required iron cores:

[0041] The cross-sectional area of ​​the second initial core (current ratio 100 / 1): A c1 =K 2z I 2n Z 2n / (4.44fN 2n，1 B n )×10 4 = 1.1 × 1 × 30 / (4.44 × 50 × 200 × 0.08) × 10 4 =92.9cm 2 ;

[0042] The cross-sectional area of ​​the first initial core (current ratio 200 / 1): A c2 =K 2z I 2n Z 2n / (4.44fN 2n，2 Bn )×10 4 = 1.1 × 1 × 30 / (4.44 × 50 × 400 × 0.08) × 10 4 =46.45cm 2 ;

[0043] Where K 2z I 2n Z 2n f and f are the internal impedance coefficient, secondary current, secondary load, and frequency, respectively, with values ​​of 1.1, 1, 30, and 50; the first initial core and the second initial core are independent cores that meet the single current ratio requirement;

[0044] ④ Determine the core width (given that the inner and outer diameters of the first and second initial cores are the same, with an inner diameter of 110 and an outer diameter of 210):

[0045] Width of the second initial core (current ratio 100 / 1): A c1 = (outer diameter - inner diameter) / 2 × width × 0.0095 = (210 - 110) / 2 × width × 0.0095, where "×0.0095" is the lamination coefficient, and the width is approximately 195, i.e., h;

[0046] Width of the first initial core (current ratio 200 / 1): A c2 = (outer diameter - inner diameter) / 2 × width × 0.0095 = (210 - 110) / 2 × width × 0.0095, solving for the width gives an approximate value of 100, which is H;

[0047] Therefore, two new iron cores are taken out. The data of the two newly taken-out iron cores satisfy the above calculation results, that is, the width value of the first iron core 4 is the same as the width value of the first initial iron core, which is 100, and the width value of the second iron core 5 is 95. The width value of the second iron core 5 is the width value h of the second initial iron core minus the width value H of the first initial iron core.

[0048] Step 2: Select the wire diameters of the primary and secondary wires 401 and 501, where the cross-section S of the primary and secondary wires 401 and 501 is the same. The calculation formula is S = I 2n / 2 = 1 / 2 = 0.5mm 2Therefore, using the formula for calculating the area of ​​a circle, the wire diameter of the first secondary wire 401 and the second secondary wire 501 is determined to be 0.8mm. Thus, 399 turns of Φ0.8 wire are wound on the first core 4, with one turn reduced for error compensation; a tap is drawn after 199 turns. Similarly, 199 turns of Φ0.8 wire are wound on the second core 5, with one turn reduced for error compensation. The first secondary wire 401 includes a starting end S1, an ending end S3, and a lead-out end S4; the second secondary wire 501 includes a starting end S5 and an ending end S2. The lead-out end S4 is welded to the starting end S5, and a series connection is established between the lead-out end S4 and the starting end S5. The starting end S1, the ending end S2, the ending end S3, and the series connection end are respectively welded to the secondary terminals 6 located at the bottom of the housing 1 and corresponding in polarity. (Refer to...) Figure 1 The secondary terminals 6 corresponding to the starting end S1, the ending end S2, the ending end S3, and the series end are respectively terminal 2S1, terminal 2S2, terminal 2S3, and terminal O. After the first secondary line 401 and the second secondary line 501 are connected in series, 2S1-2S2 is 100 / 1, and 2S1-2S3 is 200 / 1.

[0049] In some embodiments, reference is made to Figure 1 It also includes an amorphous iron core 7, which is concentrically mounted on the primary winding 2 along with the first iron core 4. The amorphous iron core 7 is located on the side of the first iron core 4 away from the second iron core 5. A third secondary wire is wound on the amorphous iron core 7. The third secondary wire includes a starting end S6, an ending end S7, and a lead-out end S8 drawn from between the starting end S6 and the ending end S7. The starting end S6, the ending end S7, and the lead-out end S8 are respectively welded to the secondary terminals 6 located at the bottom of the housing 1 and corresponding in polarity. (Refer to...) Figure 2 The secondary terminals 6 corresponding to the starting end S6, the ending end S7, and the lead-out end S8 are terminals 1S1, 1S2, and 1S3, respectively. Since current transformers are generally divided into measuring windings and protective windings, and their accuracy levels are different, amorphous cores are generally required to meet the national standard for measuring winding errors. However, protective windings require iron cores. Therefore, when the first iron core 4 and the second iron core 5 are used for the protective winding, an amorphous iron core 7 is added to enable the current transformer to connect to measuring instruments and realize the measuring winding function.

[0050] In some embodiments, the lead-out position of the lead-out terminal S8 is at half the number of turns of the third and second winding wound on the amorphous iron core 7. The half-turn tap corresponds to half the current ratio of the total number of turns of the winding, realizing mid-point current shunting.

[0051] In some embodiments, the first secondary wire 401, the second secondary wire 501, and the third secondary wire are enameled wires. In some embodiments, insulating tape is wound in a ring around the first iron core 4, the second iron core 5, and the amorphous iron core 7. In some embodiments, the insulating tape is self-adhesive insulating tape. The enameled wire possesses high voltage resistance, electrical insulation, and heat resistance properties. Combined with epoxy resin and self-adhesive insulating tape, it forms a multi-layer composite insulation structure, meeting the power system's requirements for moisture protection and short-circuit protection, improving the winding's heat resistance level, and extending its service life.

[0052] In some embodiments, the weekly insulating bandage is wrapped in a loop, covering at least half the width of the previous week's insulating bandage. Sufficient overlap ensures seamless insulation, prevents localized electric field concentration, reduces the risk of breakdown, delays insulation aging, and guarantees long-term safe operation.

[0053] In some embodiments, the first iron core 4 and the second iron core 5 are silicon steel cores.

[0054] In summary, this utility model provides a dual-current-ratio current transformer with internal coils connected in series. By designing the width of the first iron core 4 to be H in the high current-ratio segment and the width of the second iron core 5 to be hH in the low current-ratio segment, the segmented design allows for separate optimization of both, ensuring both high thermal stability current and a high protection factor, thus balancing thermal stability current and protection factor. The series-connected dual-current-ratio windings achieve a larger equivalent number of turns and cross-section within the same size, meeting the requirements of high-power power transmission and improving rated output capacity when used for output. The segmented design limits the core width to the operable range of the winding machine, and the coaxial layout of multiple core segments simplifies the assembly process, improving production efficiency and finished product yield. By introducing an amorphous iron core 7, which acts as a measuring winding, combined with the design of the first iron core 4 and the second iron core 5, the transformer functions as both a measuring winding and a protection winding, improving its functional expandability.

[0055] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A dual-current ratio current transformer with internal coils connected in series, comprising a housing, an epoxy resin filling the housing, and a primary winding and a secondary winding fixed within the housing by the epoxy resin filling, wherein the primary winding passes through the secondary winding and each end of the primary winding is welded with a primary terminal, each primary terminal protruding from the top of the housing, and a fixing plate is wrapped around the bottom of the secondary winding by packing straps, characterized in that... The secondary winding includes a first core and a second core concentrically wound on the primary winding. A first secondary wire is wound around the first core, and the first secondary wire includes a starting end S1, an ending end S3, and a lead-out end S4 extending from between the starting end S1 and the ending end S3. A second secondary wire is wound around the second core, and the second secondary wire includes a starting end S5 and an ending end S2. The lead-out end S4 is connected to the starting end S5 by a wire, and a series connection is established on the wire. The starting end S1, the ending end S2, the ending end S3, and the series connection end are respectively welded to secondary terminals located at the bottom of the housing and corresponding in polarity. The dual current ratio is defined as either a large current ratio or a small current ratio based on the magnitude of the current ratio. The width of the first initial core satisfying the large current ratio is H, and the width of the second initial core satisfying the small current ratio is h. The width of the first core is equal to H, and the width of the second core is equal to hH.

2. A double current ratio current transformer with internal series connected coils according to claim 1, characterized in that, It also includes an amorphous iron core, which is concentrically mounted on the primary winding with the first iron core. The amorphous iron core is located on the side of the first iron core away from the second iron core. A third secondary wire is wound on the amorphous iron core. The third secondary wire includes a starting end S6, an ending end S7, and a lead-out end S8 drawn from between the starting end S6 and the ending end S7. The starting end S6, the ending end S7, and the lead-out end S8 are respectively welded to secondary terminals located at the bottom of the housing and corresponding in polarity.

3. A dual current ratio current transformer with internal series connected coils according to claim 2, characterized in that, The lead-out position of the lead-out terminal S8 is at 1 / 2 turn of the third and second secondary wire wound on the amorphous iron core.

4. A dual current ratio current transformer with internal series connected coils according to claim 2, characterized in that, The first secondary wire, the second secondary wire, and the third secondary wire are enameled wires.

5. A dual current ratio current transformer with internal series connected coils according to claim 2, characterized in that, Insulating bandages are wrapped around the first iron core, the second iron core, and the amorphous iron core in a ring.

6. A dual current ratio current transformer with an internal series coil according to claim 5, characterized in that Each week, the insulating bandage is wrapped in a loop and then covers at least half the width of the insulating bandage from the previous week.

7. A dual current ratio current transformer with an internal series coil according to claim 6, characterized in that The insulating bandage is an insulating self-adhesive tape.

8. A dual current ratio current transformer with internal series connected coils according to claim 1, characterized in that, The first core and the second core are silicon steel cores.

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