Dry-type transformer

Abstract

The utility model provides a dry-type transformer, which comprises an iron core, a plurality of iron cores, a plurality of iron cores, a plurality of iron cores, a plurality of iron cores, a plurality of iron cores, a plurality of iron cores and a plurality of iron cores, each core column is sleeved with a set of low-voltage windings, each set of low-voltage windings comprises two pieces of foil wound on the periphery of the core column, each piece of foil forms at least one foil layer completely wrapping the core column, a first included angle is formed by three orthographic projection points, on the bottom face of the transformer, of the two pieces of foil relative to the winding initial end of the core column and the axis of the core column, and the first included angle is formed by three orthographic projection points, on the bottom face of the transformer, of the two pieces of foil; a second included angle is formed by three orthographic projection points of the winding tail ends of the two foils relative to the core column and the axis of the core column on the bottom surface of the transformer, the angle value M of the first included angle is larger than or equal to 175 degrees and smaller than or equal to 185 degrees, and the angle value N of the second included angle is larger than or equal to 175 degrees and smaller than or equal to 185 degrees; and the high-voltage windings are respectively wound on each group of low-voltage windings. The utility model has low circulating current loss and eddy current loss.

Description

Technical Field

[0001] The embodiment of the utility model relates to the technical field of transformer manufacturing, and in particular to a dry-type transformer. Background Art

[0002] In order to meet the requirements of high current use, the low-voltage winding of the existing large-capacity wind turbine cabin (dry type) transformer adopts thickened and increased foil, and has a double-layer foil radially wound side by side structure. Figure 1a As shown, the winding start ends of the two foils relative to the core column overlap, the two foils are wound side by side, and after the winding is completed, the winding end ends of the two foils relative to the core column overlap.

[0003] Based on the structure of double-layer foil radially wound side by side, the existing dry-type transformer has the problems of large circulating current loss and large eddy current loss. Utility Model Content

[0004] The embodiment of the utility model provides a dry-type transformer to solve the problem that the existing dry-type transformer has large circulating current loss and large eddy current loss based on the structure of radially winding double-layer foil.

[0005] In order to solve the above technical problems, the utility model is achieved as follows:

[0006] In a first aspect, an embodiment of the utility model provides a dry-type transformer, comprising:

[0007] The iron core has three core columns, which are arranged in parallel and the axes of the three core columns are perpendicular to the bottom surface of the transformer;

[0008] A low-voltage winding, wherein a group of the low-voltage windings is sleeved on each core column, and each group of the low-voltage windings comprises: two pieces of foil wound around the outer periphery of the core column, each piece of the foil forms at least one foil layer that completely covers the core column, and the winding start end of the two pieces of foil relative to the core column and the axis of the core column form a first angle at three orthographic projection points on the bottom surface of the transformer, and the winding end end of the two pieces of foil relative to the core column and the axis of the core column form a second angle at three orthographic projection points on the bottom surface of the transformer, wherein the angle value M of the first angle satisfies: 175°≤M≤185°, and the angle value N of the second angle satisfies: 175°≤N≤185°;

[0009] The high voltage winding is respectively wound on each group of the low voltage windings.

[0010] Optionally,

[0011] The foil material comprises: an extension area, and a first connection area and a second connection area respectively located at two ends of the extension direction of the extension area;

[0012] The extension area covers the core column to form the foil layer, the winding start end is located in the first connection area, and the winding end end is located in the second connection area.

[0013] Optionally, it further comprises: a plurality of conductive bars; for any one piece of the foil material, the first connection area is coupled to at least one of the conductive bars, and the second connection area is coupled to at least one of the conductive bars.

[0014] Optionally,

[0015] The conductive busbar comprises a copper busbar.

[0016] Optionally, it also includes:

[0017] The first filling layer is arranged in the gap between any two adjacent foil layers.

[0018] Optionally,

[0019] The first filling layer includes: air gaps and airway strips;

[0020] There are a plurality of airway strips arranged at intervals, and a plurality of the airway strips are supported in the gap to form a plurality of the air gaps, and each of the air gaps passes through the low-voltage winding along the axial direction of the core column.

[0021] Optionally,

[0022] The material of the airway strip is resin, and the thermal conductivity L of the resin satisfies: 1W / mK≤L≤1.2W / mK.

[0023] Optionally,

[0024] The gap between the low voltage winding and the high voltage winding is filled with a second filling layer;

[0025] Optionally,

[0026] The second filling layer comprises:

[0027] A plurality of insulating cylinders sleeved on the low voltage winding;

[0028] And, a heat dissipation air gap is provided between each of the insulating tubes.

[0029] In a second aspect, an embodiment of the present utility model provides a method for manufacturing a dry-type transformer, comprising:

[0030] Arrange an iron core, wherein the iron core has three core columns, and the three core columns are arranged in parallel, and the three iron cores are arranged so that the axes of the three iron cores are perpendicular to the bottom surface of the transformer;

[0031] A low-voltage winding is provided, and a group of the low-voltage winding is sleeved on each core column, and each group of the low-voltage winding comprises: two pieces of foil wound around the outer periphery of the core column, each piece of the foil forms at least one foil layer that completely covers the core column, and the winding start end of the two pieces of foil relative to the core column and the axis of the core column form a first angle at three orthographic projection points on the bottom surface of the transformer, and the winding end end of the two pieces of foil relative to the core column and the axis of the core column form a second angle at three orthographic projection points on the bottom surface of the transformer, wherein the angle value M of the first angle satisfies: 175°≤M≤185°, and the angle value N of the second angle satisfies: 175°≤N≤185°;

[0032] A high voltage winding is provided, and the high voltage winding is respectively wound on each group of the low voltage windings.

[0033] In the embodiment of the utility model, the low-voltage winding is a radially staggered winding structure: each piece of foil forms at least one foil layer that completely covers the core column, and the winding start of the two foils relative to the core column and the axis of the core column form a first angle at three orthographic projection points on the bottom surface of the transformer, and the winding end of the two foils relative to the core column and the axis of the core column form a second angle at three orthographic projection points on the bottom surface of the transformer, wherein the angle value M of the first angle satisfies: 175°≤M≤185°, and the angle value N of the second angle satisfies: 175°≤N≤185°. With the radially staggered winding structure, the circulating current loss and eddy current loss of the dry-type transformer of the utility model embodiment are low, the current density of the low-voltage winding in the axial direction of the core column is uniform, and the loss density distribution is more uniform, which is conducive to ensuring the safe and reliable operation of the dry-type transformer. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] By reading the detailed description of the preferred embodiment below, various other advantages and benefits will become clear to those of ordinary skill in the art. The accompanying drawings are only used for the purpose of illustrating the preferred embodiment and are not considered to be limiting of the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0035] Figure 1a It is a structural schematic diagram of the existing low-voltage winding when it is wound;

[0036] Figure 1b It is a schematic diagram of the simulation (temperature cloud diagram) of the additional loss caused by the existing low-voltage winding to the surrounding structural parts;

[0037] Figure 2 It is a front view schematic diagram of a dry-type transformer according to an embodiment of the utility model;

[0038] Figure 3 For the corresponding Figure 2 A partial enlarged schematic diagram of the D position in the middle;

[0039] Figure 4 It is a side view schematic diagram of a dry-type transformer according to an embodiment of the utility model;

[0040] Figure 5 It is a top view schematic diagram of a dry-type transformer according to an embodiment of the utility model;

[0041] Figure 6 This is a schematic diagram of the structure of the low-voltage winding of the dry-type transformer according to an embodiment of the utility model;

[0042] Figure 7 It is a structural schematic diagram of the low-voltage winding of the dry-type transformer of the utility model embodiment when winding;

[0043] Figure 8 It is a top view schematic diagram of the core column and low voltage winding of the dry-type transformer in the embodiment of the utility model;

[0044] Fig. 9 It is a top view schematic diagram of a core column, a low voltage winding and a high voltage winding in a dry-type transformer according to an embodiment of the utility model;

[0045] Fig.10 This is a flowchart of a method for manufacturing a dry-type transformer according to an embodiment of the utility model.

[0046] in:

[0047] 1. Iron core; 2. Core column;

[0048] 3. low voltage winding; 30. foil; 31. foil layer; 311. extension area; 312. second connection area;

[0049] 4. High voltage winding; 41. Insulation tube; 42. Heat dissipation gap;

[0050] 5. Conductive bar;

[0051] 6. first filling layer; 61. air gap; 62. airway strip;

[0052] 9. Clamp; 10. Pull plate;

[0053] α, first angle; β, second angle; b, axis of core column. DETAILED DESCRIPTION

[0054] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0055] The terms "first", "second", etc. in this application are used to distinguish similar objects, and are not used to describe a specific order or sequence. It should be understood that the terms used in this way are interchangeable where appropriate, so that the embodiments of the present application can be implemented in an order other than those illustrated or described herein, and the objects distinguished by "first" and "second" are generally of one type, and the number of objects is not limited, for example, the first object can be one or more. In addition, "or" in this application represents at least one of the connected objects. For example, "A or B" covers three schemes, namely, Scheme 1: including A but not including B; Scheme 2: including B but not including A; Scheme 3: including both A and B. The character " / " generally indicates that the objects associated with each other are in an "or" relationship.

[0056] In the technical solution of the present disclosure, words such as “connect”, “couple” or “connected” are not limited to physical or mechanical connections, but may include electrical connections.

[0057] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0058] In order to meet the requirements of high current use, the low-voltage winding of the existing large-capacity wind turbine cabin (dry type) transformer adopts thickened and increased foil, and has a double-layer foil radially wound side by side structure. Figure 1a As shown, the winding start ends of the two foils 30 relative to the core column 2 overlap, that is, the overlapping winding start end a0. The two foils 30 are wound side by side, and after the winding is completed, the winding ends of the two foils 30 relative to the core column 2 (not shown in the figure) also overlap.

[0059] Based on the structure of double-layer foil radially wound side by side, the existing dry-type transformer has the problems of large circulating current loss and large eddy current loss.

[0060] In addition, based on the structure of radially winding double-layer foils side by side, the leakage magnetic field caused by the large current passing through can easily lead to large additional losses in the peripheral structural parts of the low-voltage winding (structural parts arranged around the low-voltage winding on the dry-type transformer, such as: clamps 9, pull plates 10), which will bring potential safety hazards to the operation of the dry-type transformer. Figure 1b As shown, the leakage magnetic field effect of simulating the low-voltage winding (based on the structure of radially winding double-layer foil in parallel) when a large current passes through it, the upper and lower lateral peripheral structural members (clamps 9) and the three longitudinal peripheral structural members (pull plates 10) arranged between the lateral peripheral structural members all have the problem of additional losses causing local excessive temperature. Figure 1b The temperature scale is shown on the middle right side, with temperatures ranging from low to high from bottom to top.

[0061] The utility model embodiment provides a dry-type transformer, see Figures 2 to 8 As shown, including:

[0062] The iron core 1 has three core columns 2, which are arranged in parallel and the axes of the three core columns 2 are perpendicular to the bottom surface of the transformer;

[0063] Low voltage winding 3, each core column 2 is provided with a set of low voltage winding 3;

[0064] Each group of low-voltage windings 3 includes: two foils 30 wound around the outer periphery of the core column 2, each foil 30 forms at least one foil layer 31 that completely covers the core column, the winding start end of the two foils 30 relative to the core column 2 and the axis b of the core column 2 form a first angle α at three orthographic projection points on the bottom surface of the transformer, and the winding end end of the two foils 30 relative to the core column and the axis b of the core column 2 form a second angle β at three orthographic projection points on the bottom surface of the transformer, wherein the angle value M of the first angle α satisfies: 175°≤M≤185°, and the angle value N of the second angle β satisfies: 175°≤N≤185°; see Figure 6 As shown, one piece of foil material 30 has a winding start end a1 and a winding end b1 relative to the core 2; and another piece of foil material 30 has a winding start end a2 and a winding end b2 relative to the core 2.

[0065] The high voltage winding 4 is respectively wound on each group of low voltage windings 3 .

[0066] See also Figure 2 As shown, from left to right, there are three phases A, B and C of the dry-type transformer, each phase includes a core column 2, and there are three core columns 2 in total for the three phases. The three core columns 2 are arranged in parallel and the axes of the three core columns 2 are perpendicular to the bottom surface of the transformer. Taking the C phase of the dry-type transformer as an example, Figure 3 , Figures 6 to 8 The structural features of the dry-type transformer in the embodiment of the utility model are illustrated by showing the structure of the C phase.

[0067] See Figure 3 As shown, a group of low-voltage windings 3 are sleeved on each core column 2, and a high-voltage winding 4 is respectively wound on each group of low-voltage windings 3.

[0068] See Figures 6 to 8As shown, the winding start end a1 of a piece of foil 30 relative to the core column 2, the winding start end a2 of another piece of foil 30 relative to the core column 2, and the axis b of the core column 2 form a first angle α at three orthographic projection points on the bottom surface of the transformer, and the angle value M of the first angle α satisfies: 175°≤M≤185°. The winding end b1 of a piece of foil 30 relative to the core column 2, the winding end b2 of another piece of foil 30 relative to the core column 2, and the axis b of the core column 2 form a second angle β at three orthographic projection points on the bottom surface of the transformer, and the angle value N of the second angle β satisfies: 175°≤N≤185°. The above arrangement can make the wound parallel wires (turns) have the same length and equal resistance, and the potentials caused by leakage magnetic field offset each other, thereby reducing the circulating current between the wires.

[0069] In some embodiments of the present invention, optionally, see Figure 8 As shown, the winding start a1, the winding start a2, the winding end b1, and the winding end b2 are located on the radial extension line of the same core column 2, so that the wound parallel wires have the same length and equal resistance, and the potentials caused by leakage magnetic field offset each other, reducing the circulating current between the wires.

[0070] It should be noted that each foil 30 forms at least one foil layer 31 that completely covers the core column, which means that the foil 30 is wound at least once. In practical applications, the number of turns is determined by the transformer process requirements, which cannot be listed here, and the inability to list should not be regarded as unclear.

[0071] In the embodiment of the utility model, the low-voltage winding is a radially staggered winding structure: each foil 30 forms at least one foil layer 31 that completely covers the core column, and the winding start of the two foils 30 relative to the core column 2 and the axis b of the core column 2 form a first angle α at three orthographic projection points on the bottom surface of the transformer, and the winding end of the two foils 30 relative to the core column and the axis b of the core column 2 form a second angle β at three orthographic projection points on the bottom surface of the transformer, wherein the angle value M of the first angle α satisfies: 175°≤M≤185°, and the angle value N of the second angle β satisfies: 175°≤N≤185°. With the radially staggered winding structure, the circulating current loss and eddy current loss of the dry-type transformer of the utility model embodiment are low, the current density uniformity of the low-voltage winding 3 in the direction of the axis b of the core column 2 is good, and the loss density distribution is more uniform, which is conducive to ensuring the safe and reliable operation of the dry-type transformer.

[0072] In some embodiments of the present invention, optionally, see Figures 6 to 8 As shown, the foil 30 includes: an extension area 311, and a first connection area (not shown in the figure) and a second connection area 312 respectively located at two ends of the extension direction of the extension area 311;

[0073] The extension area wraps around the core column to form a foil layer. The winding start end is located at the first connection area (not shown in the figure), and the winding end end is located at the second connection area 312.

[0074] In some embodiments of the present invention, the dry-type transformer may further include: a plurality of conductive bars 5 ; for any foil 30 , the first connection area (not shown) is coupled to at least one conductive bar 5 , and the second connection area 312 is coupled to at least one conductive bar 5 .

[0075] In the embodiment of the utility model, for any piece of foil 30, the conductive bar 5 coupled to the first connection area (not shown in the figure) and the conductive bar 5 coupled to the second connection area 312 each bear half of the total current, which can effectively reduce the additional loss in the surrounding structural parts (for example: clamp 9, pull plate 10) caused by leakage magnetic field.

[0076] In addition, by adopting a radially staggered winding structure, the double-layer foil 30 of the low-voltage winding 3 forms an electrically independent insulation structure, and by coupling the conductive bar 5 from the first connection area (not shown in the figure) where the winding starting ends (a1, a2) of the double-layer foil 30 are located and the second connection area 312 where the winding ends (b1, b2) are located, respectively, the conductive bar 5 is relatively led out, which effectively reduces the increase in power loss caused by the "skin effect" of the current-cutting conductor and the "squeeze effect" of the foil winding end, thereby improving the efficiency of large-capacity (for example: 66kV level) wind turbine cabin transformer.

[0077] In some embodiments of the present invention, optionally, the conductive bar 5 includes a copper bar.

[0078] Copper busbars have good electrical conductivity and corrosion resistance, so they are widely used in electrical equipment, power systems, and building grounding systems. In practical applications, the use of copper busbars to achieve electrical conduction in dry-type transformers deployed in wind turbines can improve the operating safety of dry-type transformers, reduce the frequency of repairs for electrical conduction faults, and ensure long-term stable operation of dry-type transformers.

[0079] In some embodiments of the present invention, optionally, see Figure 6 and Figure 8 As shown, the dry-type transformer also includes:

[0080] The first filling layer 6 is disposed in the gap between any two adjacent foil layers 31 .

[0081] In the embodiment of the utility model, the first filling layer 6 is provided to help maintain the insulation distance between any two adjacent foil layers 31, thereby reducing the safety risk caused by the reduction of the insulation distance due to occasional failures.

[0082] In some embodiments of the present invention, optionally, see Figure 6 and Figure 8 As shown, the first filling layer 6 includes: air gaps 61 and air channel strips 62;

[0083] There are multiple airway bars 62 arranged at intervals, and the multiple airway bars 62 are supported in the gap to form multiple air gaps 61 . Each air gap 61 passes through the low-voltage winding 3 along the axis b direction of the core column 2 .

[0084] In the low voltage winding of the existing dry-type transformer, see Figure 1a As shown, the winding start ends of the two foils 30 relative to the core column 2 overlap, which is the overlapping winding start end a0; the two foils 30 are wound side by side, and after the winding is completed, the winding ends of the two foils 30 relative to the core column 2 (not shown in the figure) also overlap. A conductive bar 5 is set at the overlapping winding start end a0 to couple with the two foils 30, and a conductive bar 5 is set at the overlapping winding end (not shown in the figure) to couple with the two foils 30. The current connected to the conductive bar 5 is large, and the conductive bar 5 needs to be a conductive bar 5 with a large cross section. In the case of a large cross section, in order to ensure the insulation size, a cooling air duct cannot be set between the two conductive bars 5, resulting in low heat dissipation efficiency of the existing dry-type transformer, which is prone to transformer failure due to overheating.

[0085] In the embodiment of the utility model, since the conductive bar 5 coupled to the first connection area (not shown in the figure) and the conductive bar 5 coupled to the second connection area 312 each bear half of the total current, the cross-section of the conductive bar 5 can be reduced compared with the conductive bar in the prior art, and an axial cooling air channel (i.e., air gap 61) can be set between the conductive bars 5.

[0086] The first filling layer 6 of the embodiment of the utility model includes: air gaps 61 and airway strips 62; the airway strips 62 have multiple spaced-apart arrangements, and the multiple airway strips 62 are supported in the gaps to form multiple air gaps 61, and each air gap 61 passes through the low-voltage winding 3 along the axis b direction of the core column 2, which can accelerate the discharge rate of heat generated by the low-voltage winding 3 during the operation of the dry-type transformer, that is, the heat is taken out through the air flow.

[0087] In some embodiments of the utility model, the material of the air channel strip 62 is resin, and the thermal conductivity L of the resin satisfies: 1W / mK≤L≤1.2W / mK. The use of a high thermal conductivity resin with a thermal conductivity L satisfying 1W / mK≤L≤1.2W / mK, combined with the above-mentioned scheme of setting the air gap 61, can further accelerate the discharge rate of heat generated by the winding during the operation of the dry-type transformer and avoid heat accumulation.

[0088] In some embodiments of the present invention, optionally, see Fig. 9 As shown, the gap between the low voltage winding 3 and the high voltage winding 4 is filled with a second filling layer;

[0089] In some embodiments of the present invention, optionally, see Fig. 9As shown, the second filling layer includes:

[0090] A plurality of insulating cylinders 41 sleeved on the low voltage winding;

[0091] And, heat dissipation gaps 42 are provided between the insulating tubes 41 .

[0092] The above-mentioned scheme of setting up the second filling layer can improve the insulation performance between the high-voltage winding 4 and the second winding 32, and the setting of the heat dissipation air gap 42 can accelerate the discharge rate of heat generated by the winding during the operation of the dry-type transformer, that is, the heat is taken out through the air flow.

[0093] The present invention provides a method for manufacturing a dry-type transformer. Fig.10 As shown, Fig.10 The flowchart of the manufacturing method of the dry-type transformer of the utility model embodiment is as follows:

[0094] Step S1: Arrange an iron core, wherein the iron core has three core columns, and the three core columns are arranged in parallel, and the axes of the three iron cores are arranged to be perpendicular to the bottom surface of the transformer;

[0095] Step S2: setting a low-voltage winding, a group of low-voltage windings is sleeved on each core column, each group of low-voltage windings includes: two pieces of foil wound around the outer periphery of the core column, each piece of foil forms at least one foil layer that completely covers the core column, the winding start end of the two pieces of foil relative to the core column and the axis of the core column form a first angle at three orthographic projection points on the bottom surface of the transformer, and the winding end end of the two pieces of foil relative to the core column and the axis of the core column form a second angle at three orthographic projection points on the bottom surface of the transformer, wherein the angle value M of the first angle satisfies: 175°≤M≤185°, and the angle value N of the second angle satisfies: 175°≤N≤185°;

[0096] Step S3: setting a high voltage winding, and winding the high voltage winding on each set of low voltage windings respectively.

[0097] In an embodiment of the utility model, radial staggered winding of the low-voltage winding is achieved through step S2, thereby improving the uniformity of the current density of the low-voltage winding in the axial direction of the core column, making the loss density distribution more uniform, and obtaining a dry-type transformer with low circulating current loss and low eddy current loss.

[0098] In some embodiments of the present invention, optionally, the foil material comprises: an extension region, and a first connection region and a second connection region respectively located at two ends of the extension direction of the extension region;

[0099] The manufacturing method also includes:

[0100] The core column is covered with the extension area to form the foil layer, the winding start end is located in the first connection area, and the winding end end is located in the second connection area.

[0101] In some embodiments of the present invention, optionally, the manufacturing method further comprises:

[0102] A plurality of conductive rows are provided; for any one of the foil materials, the first connection area is coupled to at least one of the conductive rows, and the second connection area is coupled to at least one of the conductive rows.

[0103] In some embodiments of the present invention, optionally, the conductive bar comprises a copper bar.

[0104] In some embodiments of the present invention, optionally, the manufacturing method further comprises:

[0105] A first filling layer is provided, and the first filling layer is provided in the gap between any two adjacent foil layers.

[0106] In some embodiments of the utility model, optionally, the first filling layer includes: air gaps and airway strips;

[0107] There are a plurality of airway strips arranged at intervals, and a plurality of the airway strips are supported in the gap to form a plurality of the air gaps, and each of the air gaps passes through the low-voltage winding along the axial direction of the core column.

[0108] In some embodiments of the present invention, optionally, the material of the airway strip is resin, and the thermal conductivity L of the resin satisfies: 1W / mK≤L≤1.2W / mK.

[0109] In some embodiments of the present invention, optionally, the manufacturing method further comprises:

[0110] Filling a second filling layer in the gap between the low voltage winding and the high voltage winding;

[0111] In some embodiments of the present invention, optionally, the second filling layer includes:

[0112] A plurality of insulating cylinders sleeved on the low voltage winding;

[0113] And, a heat dissipation air gap is provided between each of the insulating tubes.

[0114] The embodiments of the utility model are described above in conjunction with the accompanying drawings, but the utility model is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the utility model, ordinary technicians in this field can also make many forms without departing from the scope of protection of the utility model and the claims, all of which are within the protection of the utility model.

Claims

1. A dry-type transformer, characterized in that: include: The iron core has three core columns, which are arranged in parallel and the axes of the three core columns are perpendicular to the bottom surface of the transformer; A low-voltage winding, wherein a group of the low-voltage windings is sleeved on each core column, and each group of the low-voltage windings comprises: two pieces of foil wound around the outer periphery of the core column, each piece of the foil forms at least one foil layer that completely covers the core column, and the winding start end of the two pieces of foil relative to the core column and the axis of the core column form a first angle at three orthographic projection points on the bottom surface of the transformer, and the winding end end of the two pieces of foil relative to the core column and the axis of the core column form a second angle at three orthographic projection points on the bottom surface of the transformer, wherein the angle value M of the first angle satisfies: 175°≤M≤185°, and the angle value N of the second angle satisfies: 175°≤N≤185°; The high voltage winding is respectively wound on each group of the low voltage windings.

2. The dry-type transformer according to claim 1, characterized in that: The foil material comprises: an extension area, and a first connection area and a second connection area respectively located at two ends of the extension direction of the extension area; The extension area covers the core column to form the foil layer, the winding start end is located in the first connection area, and the winding end end is located in the second connection area.

3. The dry-type transformer according to claim 2, characterized in that: Also includes: A plurality of conductive bars; For any one piece of the foil, the first connection area is coupled to at least one of the conductive bars, and the second connection area is coupled to at least one of the conductive bars.

4. The dry-type transformer according to claim 3, characterized in that: The conductive busbar comprises a copper busbar.

5. The dry-type transformer according to claim 3, characterized in that: Also includes: The first filling layer is arranged in the gap between any two adjacent foil layers.

6. The dry-type transformer according to claim 5, characterized in that: The first filling layer includes: air gaps and airway strips; There are a plurality of airway strips arranged at intervals, and a plurality of the airway strips are supported in the gap to form a plurality of the air gaps, and each of the air gaps passes through the low-voltage winding along the axial direction of the core column.

7. The dry-type transformer according to claim 6, characterized in that: The material of the airway strip is resin, and the thermal conductivity L of the resin satisfies: 1W / mK≤L≤1.2W / mK.

8. The dry-type transformer according to claim 1, characterized in that: The gap between the low voltage winding and the high voltage winding is filled with a second filling layer.

9. The dry-type transformer according to claim 8, characterized in that: The second filling layer comprises: A plurality of insulating cylinders sleeved on the low voltage winding; And, a heat dissipation air gap is provided between each of the insulating tubes.

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