Current transformer with internal parallel connection of coils

Abstract

This utility model relates to a current transformer with internally connected parallel coils, including a housing, and a secondary winding comprising first and second amorphous iron cores concentrically wound on the primary winding. The first secondary wire wound on the first amorphous iron core and the second secondary wire wound on the second amorphous iron core are connected in parallel. The current transformer with internally connected parallel coils designed using this utility model solves the problem that conventional transformer design calculates the corresponding iron core size based on the selected ampere-turns and then winds the secondary wires on the iron core. However, to meet the requirements of large thermal stability current and large rated output, transformers typically use a coil series connection method, which allows for a very low selectable ampere-turns, making it difficult to meet the accuracy error requirements of the measuring winding.

Description

Technical Field

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

[0002] In the existing technology, small current ratio current transformers cannot simultaneously meet the requirements of high thermal stability current, large protection multiple, 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, it is difficult to meet the accuracy error requirements of the measurement winding.

[0003] Conventional current transformer design involves calculating the core size based on the selected ampere-turns and then winding secondary windings on the core. However, to meet the requirements of larger thermal stability current and larger rated output, current transformers typically use a series connection of coils. In this case, the selectable ampere-turns are very low, making it difficult to meet the accuracy error requirements of the measurement windings.

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

[0005] The utility model embodiment provides a current transformer with internal coils connected in parallel, which solves the problem that in the conventional design of current transformers, 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, in order to meet the requirements of large thermal stability current and large rated output, the current transformer usually adopts the method of coil series connection. At this time, the ampere-turns that can be selected are very low, which makes it difficult to meet the accuracy error requirements of the measurement winding.

[0006] This utility model provides a current transformer with internally connected parallel coils, including a housing, an epoxy resin-filled interior, and a primary winding and a secondary winding fixed within 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 from the top of the housing. A fixing plate is wrapped around the bottom of the secondary winding with packing straps. The secondary winding includes a first amorphous iron core and a second amorphous iron core concentrically mounted on the primary winding. The first secondary wire is wound around the core, and the first secondary wire includes a starting end S1 and an ending end S2; the second amorphous iron core is wound with a second secondary wire, and the second secondary wire includes a starting end S3 and an ending end S4; the starting end S1 is welded to the starting end S3 and a first parallel end is led out between the starting end S1 and the starting end S3; the ending end S2 is welded to the ending end S4 and a second parallel end is led out between the ending end S2 and the ending end S4; the first parallel end and the second parallel end are respectively welded to the secondary terminals located at the bottom of the housing and corresponding in polarity.

[0007] Furthermore, it also includes a common iron core, which is concentrically mounted on the primary winding along with the second amorphous iron core. The common iron core is located on the side of the second amorphous iron core away from the first amorphous iron core. A third secondary wire is wound on the common iron core. The third secondary wire includes a starting end S5 and an ending end S6. The starting end S5 and the ending end S6 are respectively welded to the secondary terminals located at the bottom of the housing and corresponding in polarity.

[0008] Furthermore, both the first secondary wire and the second secondary wire are composed of two winding wires arranged side by side.

[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 amorphous iron core, the second amorphous iron core, and the ordinary 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 ordinary iron core is a silicon steel core.

[0014] Furthermore, the first amorphous iron core and the second amorphous iron core are permalloy iron cores.

[0015] Beneficial effects:

[0016] As can be seen from the above technical solutions, this utility model provides a current transformer with internal coils connected in parallel. After the first and second secondary windings are connected in parallel, the current is shared, reducing the heat load of a single winding, ensuring stable operation under high-temperature conditions, and improving the thermal stability current. After parallel connection, the equivalent ampere-turns can be increased on the basis of high thermal stability, thereby obtaining a higher accuracy level. After parallel connection, the total cross-sectional area is effectively increased, improving the rated output power. At the same time, the optimization of the core material and structure ensures that the magnetic flux density and saturation characteristics meet the design requirements, improving the rated output capacity. The design of the first and second amorphous cores, and the parallel connection, makes winding operable under existing equipment conditions, improving the feasibility of the equipment.

[0017] 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.

[0018] 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

[0019] 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:

[0020] Figure 1 This is a cross-sectional view of the structure of a current transformer with internal coils connected in parallel, as described in an embodiment of this application.

[0021] Figure 2 This is a side view of the structure of a current transformer with internal coils connected in parallel, as described in an embodiment of this application.

[0022] Figure 3 This is a schematic diagram of the winding of the first and second secondary wires on the first amorphous iron core of a current transformer with internal coils connected in parallel according to an embodiment of this application.

[0023] Figure 4 This is a schematic diagram of the winding of the second secondary wire on the second amorphous iron core of a current transformer with internal coils connected in parallel according to an embodiment of this application.

[0024] Figure 5 This is a schematic diagram of the first amorphous iron core and the second amorphous iron core connected in parallel in a current transformer with internal coils connected in parallel according to an embodiment of this application.

[0025] Explanation of icon numbers:

[0026] 1. Housing; 2. Primary winding; 3. Primary terminal; 4. First amorphous iron core; 401. First secondary winding; 5. Second amorphous iron core; 501. Second secondary winding; 6. Secondary terminal; 7. Ordinary iron core; 8. Fixing plate. Detailed Implementation

[0027] 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.

[0028] 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.

[0029] In the existing technology, conventional current transformer design calculates the core size of the corresponding specification based on the selected ampere-turns, and then winds the secondary wire on the core. However, in order to meet the requirements of larger thermal stability current and larger rated output, current transformers usually use the coil series connection method. At this time, the selectable ampere-turns is very low, which makes it difficult to meet the accuracy error requirements of the measurement winding.

[0030] Therefore, this utility model embodiment provides a current transformer with internal coils connected in parallel, referring to... Figure 1 and Figure 2 The transformer includes a housing 1, which is filled with epoxy resin, and a primary winding 2 and a secondary winding fixed inside 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 of the top of the housing 1. The bottom of the secondary winding is wrapped with a fixing plate 8 by packing straps. If the outer diameter of the ordinary iron core 7 is larger than the outer diameter of the first amorphous iron core 4, an insulating gasket is also fixed on the fixing plate 8. The insulating gasket contacts the outer contour of the first amorphous iron core 4. The housing 1, the epoxy resin filled inside the housing 1, and the primary winding 2 inside the housing 1 use the corresponding design existing in the current design.

[0031] The secondary winding includes a first amorphous iron core 4 and a second amorphous iron core 5 concentrically mounted on the primary winding 2, as shown in the reference. Figure 3 The first amorphous iron core 4 is wound with a first secondary wire 401, which includes a starting end S1 and an ending end S2; refer to Figure 4 The second amorphous iron core 5 is wound with a second secondary wire 501, which includes a beginning S3 and an end S4; refer to Figure 5 The starting end S1 is welded to the starting end S3 and a first parallel end is led out between the starting end S1 and the starting end S3; the ending end S2 is welded to the ending end S4 and a second parallel end is led out between the ending end S2 and the ending end S4; the first parallel end and the second parallel end are respectively welded to the secondary terminal 6 located at the bottom of the housing 1 and corresponding in polarity.

[0032] Reference Figure 2 The secondary terminals 6 corresponding to the first parallel terminal and the second parallel terminal are terminal 1S1 and terminal 1S2, respectively. After the first secondary line 401 and the second secondary line 501 are connected in parallel, the measuring instrument can be connected using 1S1–1S2 to realize the measurement function.

[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: Select the first ampere-turns, and use double the ampere-turns to calculate the required amorphous core specifications;

[0035] Step 2: Take two amorphous iron cores that meet the calculation results of Step 1, namely the first amorphous iron core 4 and the second amorphous iron core 5, and wind the number of secondary wire turns corresponding to double the number of ampere-turns on the two amorphous iron cores respectively.

[0036] Step 3: Connect the secondary wires of the first amorphous iron core 4 and the second amorphous iron core 5 that have been wound in Step 2 in parallel. That is, weld the beginning S1 of the first amorphous iron core 4 and the beginning S2 of the second amorphous iron core 5 together and lead them out. Weld the end S2 of the first amorphous iron core 4 and the end S4 of the second amorphous iron core 5 together and lead them out.

[0037] For example:

[0038] Step 1: ① Determine the rated ampere-turns: Select a primary ampere-turns of 200 for design. The ampere-turns of the first amorphous iron core 4 and the second amorphous iron core 5 are double the primary ampere-turns, which is 400 turns.

[0039] ② Select the rated magnetic flux density: B n =0.6;

[0040] ③ Calculate the cross-sections of the two required amorphous iron cores (the first amorphous iron core 4 and the second amorphous iron core 5 have the same specifications):

[0041] A c =K 2z I 2n Z 2n / (4.44fN 2n B n )×10 4 = 1.1 × 1 × 30 / (4.44 × 50 × 400 × 0.6) ×

[0042] 10 4 =6.19cm 2 ;

[0043] Where K2z, I2n, Z2n, and f are the internal impedance coefficient, secondary current, secondary load, and frequency, respectively, with values ​​of 1.1, 1, 30, and 50.

[0044] ④ Determine the width of the first amorphous iron core 4 and the second amorphous iron core 5 (it is known that the specifications of the first amorphous iron core 4 and the second amorphous iron core 5 are the same, so the inner and outer diameters are the same, the inner diameter value is 110, and the outer diameter value is 160):

[0045] A c = (outer diameter - inner diameter) / 2 × width × 0.0075 = (160 - 110) / 2 × width × 0.0075, where "×0.0075" is the lamination coefficient, and the solved width value is approximately 35;

[0046] Therefore, the first amorphous iron core 4 and the second amorphous iron core 5 should be amorphous iron cores with a width of 35mm.

[0047] Step 2: Select the ampere-turns of the first amorphous iron core 4 and the second amorphous iron core 5 as 400; select the wire diameters of the primary quadrature wire 401 and the secondary quadrature wire 501, wherein the cross-section S of the primary quadrature wire 401 and the secondary quadrature wire 501 is the same, and 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. The third secondary wire uses a single winding wire. However, in some embodiments, due to error compensation, both the first secondary wire 401 and the second secondary wire 501 are composed of two winding wires side-by-side, that is, the two winding wires are wound synchronously in a parallel and close manner. One winding wire has a diameter of 0.8mm, and the other winding wire can be empirically selected to have a diameter of 0.5mm. Then, 400 turns of Φ0.8 wire and 399 turns of Φ0.5 wire are uniformly wound on the first amorphous iron core 4 and the second amorphous iron core 5. The 399 turns of Φ0.5 wire are used to meet national standards, reducing the number of turns in the transformer to achieve error compensation. The number of turns reduced can be obtained based on experience or calculation.

[0048] Step 3: Perform a parallel operation on the secondary wires of the first amorphous iron core 4 and the second amorphous iron core 5 that have been wound in step 1. That is, weld the beginning end S1 of the first amorphous iron core 4 and the beginning end S2 of the second amorphous iron core 5 together and lead them out through the first parallel terminal. Weld the end end S2 of the first amorphous iron core 4 and the end end S4 of the second amorphous iron core 5 together and lead them out through the second parallel terminal. The first parallel terminal and the second parallel terminal are both welded to the secondary terminal 6 located at the bottom of the housing 1 and with corresponding polarities.

[0049] In some embodiments, a conventional iron core 7 is also included. The conventional iron core 7 and the second amorphous iron core 5 are concentrically mounted on the primary winding 2. The conventional iron core 7 is located on the side of the second amorphous iron core 5 away from the first amorphous iron core 4. A third secondary wire is wound on the conventional iron core 7. The third secondary wire includes a starting end S5 and an ending end S6, which are respectively welded to 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 S5 and the ending end S6 are terminals 2S1 and 2S2, respectively. Since current transformers are generally divided into measuring windings and protection windings, and their accuracy levels are different, amorphous cores are generally required to meet the error specified in the national standard for measuring windings, while iron cores are required for protection windings. Therefore, when the first amorphous iron core 4 and the second amorphous iron core 5 are used for measuring windings, an ordinary iron core 7 is added to enable the current transformer to realize the function of the protection winding.

[0050] 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 annularly wound around the first amorphous iron core 4, the second amorphous iron core 5, and the ordinary iron core 7. In some embodiments, the insulating tape is self-adhesive insulating tape. The wire has high voltage resistance, electrical insulation, and heat resistance properties. Together 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.

[0051] 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.

[0052] In some embodiments, the ordinary iron core 7 is a silicon steel core.

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

[0054] In summary, this utility model provides a current transformer with internal coils connected in parallel. By connecting the first secondary winding 401 and the second secondary winding 501 in parallel, the current is shared, reducing the heat load of a single winding, ensuring stable operation under high-temperature conditions, and improving the thermal stability current. After parallel connection, the equivalent ampere-turns can be increased on the basis of high thermal stability, thereby obtaining a higher accuracy level. Parallel connection effectively increases the total cross-sectional area, improving the rated output power. At the same time, the optimization of the core material and structure ensures that the magnetic flux density and saturation characteristics meet the design requirements, improving the rated output capacity. The design of the first amorphous core 4 and the second amorphous core 5, and the parallel connection, makes winding operable under existing equipment conditions, improving the feasibility of the equipment.

[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 current transformer with internally connected parallel coils, 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 amorphous iron core and a second amorphous iron core concentrically wound on the primary winding. A first secondary wire is wound on the first amorphous iron core, and the first secondary wire includes a starting end S1 and an ending end S2. A second secondary wire is wound on the second amorphous iron core, and the second secondary wire includes a starting end S3 and an ending end S4. The starting end S1 is welded to the starting end S3, and a first parallel end is led out between the starting end S1 and the starting end S3. The ending end S2 is welded to the ending end S4, and a second parallel end is led out between the ending end S2 and the ending end S4. The first parallel end and the second parallel end are respectively welded to secondary terminals located at the bottom of the housing and corresponding in polarity.

2. The current transformer with internal shunt coil according to claim 1, characterized in that It also includes a common iron core, which is concentrically mounted on the primary winding along with the second amorphous iron core. The common iron core is located on the side of the second amorphous iron core away from the first amorphous iron core. A third secondary wire is wound on the common iron core. The third secondary wire includes a starting end S5 and an ending end S6. The starting end S5 and the ending end S6 are respectively welded to the secondary terminals located at the bottom of the housing and corresponding in polarity.

3. A current transformer with internal shunt coil according to claim 2, characterized in that Both the first secondary wire and the second secondary wire are composed of two winding wires arranged in parallel.

4. A current transformer with internal shunt coil according to claim 3, characterized in that The first secondary line, the second secondary line, and the third secondary line are enameled wires.

5. A current transformer with internal shunt coil according to claim 3, characterized in that Insulating bandages are wrapped around the first amorphous iron core, the second amorphous iron core, and the ordinary iron core in a ring.

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

8. The current transformer with internal shunt coil according to claim 2, characterized in that, The ordinary iron core is a silicon steel core.

9. A current transformer with internal coils connected in parallel according to claim 1, characterized in that, The first amorphous iron core and the second amorphous iron core are permalloy iron cores.

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