Foil wire hybrid coil and transformer

Abstract

A foil wire hybrid coil (10), comprising: a first copper wire section (101), a second copper wire section (103), and a copper foil section (102) located between the first copper wire section and the second copper wire section, wherein the heights and structures of the first copper wire section and the second copper wire section are the same; the first copper wire section is formed by means of winding copper wires; the first copper wire section and the second copper wire section are identical in terms of structure and equal in terms of height; and the first copper wire section is electrically connected to the copper foil section by means of a connecting copper bar, and the first copper wire section is electrically connected to the copper foil section by means of a connecting copper bar. The improved coil reduces eddy current loss caused due to transverse leakage flux at upper and lower ends of the coil, and reduces temperature rise of the upper end of the coil. Wire turns are uniformly distributed at the height of the whole coil, such that the ampere-turn balance between the coil and a high-voltage coil is ensured, and thus an axial electrodynamic force caused by ampere-turn imbalance in a short circuit is avoided, thereby ensuring anti-short circuit ability of the coil.

Description

Foil-wire hybrid coil and transformer Technical Field

[0001] The invention belongs to the technical field of transformer coil winding, and particularly relates to a foil-wire hybrid coil and a transformer. Background Art

[0002] Currently, there are usually two structures for the low-voltage coil of distribution transformers. One is a foil structure, that is, a whole piece of copper foil is continuously wound with a specified number of turns. The other is a wire-wound structure, that is, multiple wires are axially connected in parallel, and a specified number of turns are wound in the axial direction and a specified number of layers are wound in the radial direction.

[0003] Foil structures have the following drawbacks. First, due to the skin effect, the current is not evenly distributed across the width of the copper foil, resulting in high current density at both ends. Second, transverse magnetic flux leakage occurs at the upper and lower ends of the coil, causing significant eddy current losses. These two factors lead to high temperatures at the upper end of the coil and significant additional losses. These drawbacks become significant when the transformer capacity exceeds 2000kVA.

[0004] For the wire-wound structure, there are helix angles at the upper and lower ends of the coil. The number of turns within the helix angle range is 50% less than that in other parts, and it is impossible to achieve ampere-turn balance with the high-voltage coil in the supply area, resulting in increased lateral magnetic leakage. When a short-circuit fault occurs, the end turns will bear greater axial force, and the coil's short-circuit resistance is poor. The larger the transformer capacity, the more axially parallel wires there are, the larger the helix angle, and the worse the short-circuit resistance.

[0005] In summary, the current low-voltage coil structure of the transformer is gradually unable to meet the requirements of use.

[0006] Summary of the Invention

[0007] The present invention provides a foil-wire hybrid coil and a transformer, which are used to solve the problems of large eddy current loss and poor short-circuit resistance of current transformer coils.

[0008] In order to solve the above technical problems, the technical solution of the present invention is as follows: a foil-wire hybrid coil, comprising: a coil and a connecting copper bar, wherein the coil comprises a first copper wire segment, a second copper wire segment, and a copper foil segment located between the first copper wire segment and the second copper wire segment, wherein the first copper wire segment and the second copper wire segment have the same height and structure;

[0009] The first copper wire segment is made of copper wire, and the first copper wire segment and the second copper wire segment have the same structure and height. The first copper wire segment and the copper foil segment are electrically connected via connecting copper bars.

[0010] In a preferred embodiment of the present invention, the first copper wire segment is wound with a plurality of turns of copper flat wire, and the copper flat wire is parallel to the end of the copper foil segment.

[0011] In a preferred embodiment of the present invention, an outer insulating layer is provided on the outside of the copper flat wires to insulate adjacent copper flat wires from each other.

[0012] In a preferred embodiment of the present invention, interlayer insulation is provided inside the coil, and the height of the interlayer insulation is equal to the height of the coil.

[0013] In a preferred embodiment of the present invention, the connecting copper bar includes a first copper bar and a second copper bar, the first copper bar and the second copper bar have the same structure, the first copper bar is arranged on the inner side of the coil, and the first copper bar is welded to the coil; the second copper bar is arranged on the outer side of the coil, and the second copper bar is welded to the coil.

[0014] In a preferred embodiment of the present invention, the first copper bar has a three-section bent structure, comprising a first section, a second section, and a third section connected in sequence, the first section being welded to the first copper wire section, the copper foil section, and the second copper wire section in sequence, and the third section being led out from the bottom of the coil;

[0015] The third section of the second copper bar is led out from the upper part of the coil.

[0016] In a preferred embodiment of the present invention, the height of the first copper wire segment is equal to the height of the second copper wire segment, and the height h is obtained by formula 1: h = 0.1 × B (1)

[0017] Where B is the total height of the coil;

[0018] The number of copper flat coils in the first copper wire segment and the second copper wire segment is equal, and the number of coils n is obtained by formula 2: n=h / 10 (2)

[0019] Where n is rounded to the nearest integer;

[0020] The height E of the copper foil is obtained by Formula 3: E=B-20n (3).

[0021] In a preferred embodiment of the present invention, the interlayer insulation material is obtained according to the heat resistance grade of the coil;

[0022] When the coil heat resistance grade is Class A, the interlayer insulation adopts 0.18mm thick dotted paper;

[0023] When the coil heat resistance grade is F, the interlayer insulation adopts pre-impregnated DMD with a thickness of 0.18mm;

[0024] When the coil heat resistance grade is H grade, the interlayer insulation adopts pre-impregnated NMN with a thickness of 0.18 mm.

[0025] In a preferred embodiment of the present invention, the surfaces of the dispensing paper, the pre-impregnated DMD, and the pre-impregnated NMN are all coated with a semi-cured adhesive layer.

[0026] In a preferred embodiment of the present invention, the material of the outer insulating layer is obtained according to the heat resistance grade of the coil;

[0027] When the coil heat resistance grade is Class A, the outer insulation layer is made of cable paper with a thickness of 0.08 mm;

[0028] When the heat resistance grade of the coil is F, the outer insulation layer is made of two layers of 0.04mm thick polyester film + one layer of 0.08mm thick polyester non-woven fabric half-lapped;

[0029] When the heat resistance grade of the coil is H grade, the outer insulation layer is formed by half-lapping two layers of 0.05mm thick polyimide film and one layer of 0.05mm thick aramid paper.

[0030] In a preferred embodiment of the present invention, the first copper bar and the coil are welded by argon arc welding, and the second copper bar and the coil are welded by argon arc welding.

[0031] The present invention also discloses a transformer, which includes any of the foil-wire hybrid coils described above. The technical solution provided by the present invention has the following advantages over the prior art:

[0032] The improved coil of the present invention reduces eddy current losses caused by lateral magnetic flux leakage at the upper and lower ends of the coil, lowering the temperature rise at the upper end of the coil. Furthermore, the turns are evenly distributed throughout the coil height, ensuring ampere-turn balance with the high-voltage coil. This prevents axial electrodynamic forces caused by ampere-turn imbalance during a short circuit, ensuring the coil's short-circuit resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying any creative work, they can also obtain drawings of other embodiments based on these drawings.

[0034] FIG1 is a schematic diagram of the first copper bar and coil structure of a foil-wire hybrid coil according to one embodiment of the present invention;

[0035] FIG2 is a schematic diagram of the second copper bar and coil structure of a foil-wire hybrid coil according to an embodiment of the present invention;

[0036] FIG3 is a schematic diagram of welding a first copper bar and a coil of a foil-wire hybrid coil according to an embodiment of the present invention;

[0037] FIG4 is a schematic diagram of welding a second copper bar and a coil of a foil-wire hybrid coil according to an embodiment of the present invention;

[0038] FIG5 is a schematic diagram of the coil and interlayer insulation structure of a foil-wire hybrid coil according to an embodiment of the present invention;

[0039] FIG6 is a schematic diagram of coil dimensions of a foil-wire hybrid coil according to an embodiment of the present invention;

[0040] FIG7 is a schematic diagram of an outer insulation layer of a foil-wire hybrid coil according to an embodiment of the present invention;

[0041] FIG8 is a schematic diagram of a connecting copper busbar of a foil-wire hybrid coil according to an embodiment of the present invention.

[0042] As shown in the figure: 10-coil; 101-first copper wire segment; 1011-copper flat wire; 102-copper foil segment; 103-second copper wire segment; 201-first copper busbar; 202-second copper busbar; 301-outer insulation layer; 302-interlayer insulation; 40-argon arc connection. DETAILED DESCRIPTION

[0043] For ease of understanding, the foil-wire hybrid coil and transformer are described below in conjunction with embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0044] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations and positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0045] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention.

[0046] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The accompanying drawings illustrate preferred embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present disclosure.

[0047] As shown in Figures 1 and 2, the present invention discloses a foil-wire hybrid coil, which includes a coil 10 and a connecting copper bar, wherein the coil 10 includes a first copper wire segment 101, a second copper wire segment 103, and a copper foil segment 102 located between the first copper wire segment 101 and the second copper wire segment 103. The first copper wire segment 101 and the second copper wire segment 103 are of equal height and have the same structure. Taking the first copper wire segment 101 as an example, specifically, in conjunction with Figures 1 and 7, the first copper wire segment 101 is wound with a copper flat wire 1011. The copper flat wire 1011 is wound horizontally, that is, multiple turns of the copper flat wire 1011 are wound sequentially around the two ends of the copper foil segment 102.

[0048] Here, referring to Figure 1, the first copper wire segment 101 and the second copper wire segment 103 are both wound horizontally without adopting a spiral structure, thereby achieving an ampere-turn balance with the high-voltage coil 10 in the supply area, reducing lateral magnetic leakage, and reducing the axial force that the end turns will bear when a short circuit fault occurs, thereby improving the short circuit resistance of the coil 10.

[0049] Referring to Figures 1 and 2 , the connecting copper bar includes a first copper bar 201 and a second copper bar 202. The first copper bar 201 and the second copper bar 202 have the same structure. Referring to Figure 8 , the first copper bar 201 is positioned inside the coil 10 and welded to the coil 10; the second copper bar 202 is positioned outside the coil 10. Referring to Figures 1 and 2 , the second copper bar 202 is welded to the coil 10. The first copper bar 201 has a three-section, bent structure and includes a first, second, and third section, which are sequentially connected. The first section is welded to the first copper wire segment 101, the copper foil segment 102, and the second copper wire segment 103. The third section is led out from the bottom of the coil 10; the third section of the second copper bar 202 is led out from the top of the coil 10.

[0050] As shown in Figures 3 and 4, the first copper bar 201 and the coil 10 are welded by argon arc welding. Referring to Figure 3, the argon arc welding point 40 between the first copper bar 201 and the coil 10 is located at the end of the coil 10. Referring to Figure 4, the argon arc welding point 40 between the second copper bar 202 and the coil 10 is also located at the end of the coil 10.

[0051] 5 and 7 , the copper wire in one embodiment of the present invention is a copper flat wire 1011 , and an outer insulating layer 301 is provided on the outer surface of the copper flat wire 1011 . Specifically, the outer insulating layer 301 is coated on the surface of the copper flat wire 1011 to achieve insulation requirements.

[0052] As shown in Figures 1, 6, and 7, specifically, the coil 10 has a height of B, and the conductor within the range of the upper and lower ends having a height h is made of copper flat wire. The height of the first copper wire segment 101 is equal to the height of the second copper wire segment 103, and their heights are obtained by formula 1: h = 0.1 × B (1)

[0053] The number of copper flat coils 10 in the first copper wire segment 101 and the second copper wire segment 103 is equal, and the number of coils is obtained by formula 2: n = h / 10 (2)

[0054] Where n is rounded to the nearest integer;

[0055] The height of the copper foil is obtained by formula 3: E = B-20n (3)

[0056] The width b of the copper rectangular wire is 10 mm, and its thickness a is equal to that of the copper foil. The thickness c of the copper foil segment 102 is 0.35 mm. The dimensions of the outer insulation layer 301 are the same as those of the copper rectangular wire. The material of the outer insulation layer 301 is selected based on the insulation thermal class of the coil 10. When the heat resistance class of the coil 10 is A, 0.08 mm thick cable paper is used. When the heat resistance class of the coil 10 is F, two layers of 0.04 mm thick polyester film and one layer of 0.08 mm polyester non-woven fabric are used as the wrapping. When the heat resistance class of the coil 10 is H, two layers of 0.05 mm thick polyimide film and one layer of 0.05 mm thick YT516 aramid paper are used as the wrapping.

[0057] Among them, the definitions of Class A, Class F and Class H are: when the relative heat resistance index (RTE) of the insulating material is 105℃, it is Class A; when the relative heat resistance index (RTE) of the insulating material is 155℃, it is Class F; when the relative heat resistance index (RTE) of the insulating material is 180℃, it is Class H;

[0058] 5 and 8 , the interior of the coil 10 is provided with interlayer insulation 302, the height of the interlayer insulation 302 being equal to the height of the coil 10. The interlayer insulation 302 is selected according to the different insulation heat resistance grades of the coil 10. When the heat resistance grade of the coil 10 is Class A, 0.18mm dotted paper is used; when the heat resistance grade of the coil 10 is Class F, 0.18mm thick pre-impregnated DMD is used, which is a soft composite insulation material composed of a middle layer of polyester film and two outer layers of polyester fiber non-woven fabric. When the heat resistance grade of the coil 10 is Class H, 0.18mm thick pre-impregnated NMN is used, which is a soft composite insulation material composed of a middle layer of polyester film and two outer layers of NOMEX insulation paper. The surfaces of the dotted paper, pre-impregnated DMD, and pre-impregnated NMN are all coated with a semi-cured adhesive layer. When heated to a specified temperature, the adhesive layer melts, and after cooling, the two layers of conductors can be bonded together to ensure that the coil 10 has sufficient mechanical strength.

[0059] The present invention also discloses a transformer provided with the foil-wire hybrid coil 10 .

[0060] The improved coil 10 of the present invention reduces eddy current losses caused by transverse magnetic flux leakage at the upper and lower ends of the coil 10, thereby lowering the temperature rise at the upper end of the coil 10. Furthermore, the turns are evenly distributed throughout the coil 10, ensuring ampere-turn balance with the high-voltage coil 10. This prevents axial electrodynamic forces caused by ampere-turn imbalance during a short circuit, thus ensuring the coil 10's short-circuit resistance.

[0061] Finally, it should be noted that the above embodiments are intended only to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art will appreciate that the technical solutions described in the above embodiments may be modified or some or all of the technical features thereof may be replaced with equivalents, and that such modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the various embodiments of the present invention.

Claims

1. A foil-wire hybrid coil, characterized in that, it includes: a coil and a connecting copper bar, the coil includes a first copper wire segment, a second copper wire segment and a copper foil segment located between the first copper wire segment and the second copper wire segment, and the height and structure of the first copper wire segment and the second copper wire segment are the same; The first copper wire segment is wound by copper wire, the structure of the first copper wire segment and the second copper wire segment is the same and the height is equal, and the first copper wire segment is electrically connected to the copper foil segment and the first copper wire segment is electrically connected to the copper foil segment through a connecting copper bar.

2. A foil-wire hybrid coil according to claim 1, characterized in that: The first copper wire segment is wound by a plurality of turns of copper flat wire, and the copper flat wire is parallel to the end of the copper foil segment.

3. A foil-wire hybrid coil according to claim 2, characterized in that: An outer insulating layer is provided outside the copper flat wire to insulate adjacent copper flat wires from each other.

4. A foil-wire hybrid coil according to claim 3, characterized in that: The material of the outer insulating layer is obtained according to the heat resistance grade of the coil; When the heat resistance grade of the coil is A grade, the outer insulating layer uses cable paper with a thickness of 0.08 mm; When the heat resistance grade of the coil is F grade, the outer insulating layer uses 2 layers of polyester film with a thickness of 0.04 mm + 1 layer of polyester non-woven fabric with a thickness of 0.08 mm and is semi-overlapped and wound; When the heat resistance grade of the coil is H grade, the outer insulating layer uses 2 layers of polyimide film with a thickness of 0.05 mm + 1 layer of aramid paper with a thickness of 0.05 mm and is semi-overlapped and wound.

5. A foil-wire hybrid coil according to claim 1, characterized in that: Interlayer insulation is provided inside the coil, and the height of the interlayer insulation is equal to the height of the coil.

6. A foil-wire hybrid coil according to claim 5, characterized in that: The material of the interlayer insulation is obtained according to the heat resistance grade of the coil; When the heat resistance grade of the coil is A grade, the interlayer insulation uses spot glue paper with a thickness of 0.18 mm; When the heat resistance grade of the coil is F grade, the interlayer insulation uses pre-impregnated DMD with a thickness of 0.18 mm; When the heat resistance grade of the coil is H grade, the interlayer insulation uses pre-impregnated NMN with a thickness of 0.18 mm.

7. A foil-wire hybrid coil according to claim 6, characterized in that: A semi-cured adhesive layer is coated on the surface of the spot glue paper, the pre-impregnated DMD, and the pre-impregnated NMN.

8. A foil-wire hybrid coil according to claim 1, characterized in that: The connecting copper bar includes a first copper bar and a second copper bar, the structures of the first copper bar and the second copper bar are the same, the first copper bar is arranged inside the coil and is welded to the coil; the second copper bar is arranged outside the coil and is welded to the coil.

9. A foil-wire hybrid coil according to claim 8, characterized in that: The first copper bar is of a three-section bending structure, the first copper bar includes a first section, a second section and a third section connected in sequence, the first section is welded to the first copper wire segment, the copper foil segment and the second copper wire segment in sequence, and the third section is led out from the lower part of the coil; The third section of the second copper bar is led out from the upper part of the coil.

10. A foil-wire hybrid coil according to claim 8, characterized in that: The first copper bar and the coil are welded by argon arc welding, and the second copper bar and the coil are welded by argon arc welding.

11. A foil-wire hybrid coil according to claim 1, characterized in that: The height of the first copper wire segment is equal to the height of the second copper wire segment, and its height h is obtained by Equation 1: h = 0.1×B (1) where B is the total height of the coil; The number of copper flat wire turns in the first copper wire segment is equal to the number of copper flat wire turns in the second copper wire segment, and its number of turns n is obtained by Equation 2: n = h / 10 (2) where n takes the closest integer; The height E of the copper foil is obtained by Equation 3: E = B - 20n (3).

12. A transformer, characterized in that: It includes the foil-wire hybrid coil according to any one of claims 1-11.

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