Iron core for disassembling / transporting transformer

Abstract

The invention provides an iron core for dismounting / transporting a transformer, which can control the performance reduction of the dismounting / transporting transformer. An iron core of a disassembly / transportation transformer for a disassembly / transportation transformer is a three-phase / five-column iron core in which a main column, a side column, and a plurality of yokes connecting an upper end portion and a lower end portion of the main column or the side column are formed by laminating a plurality of steel plates, the lower yoke connecting the lower end portions of the adjacent main columns and the lower yoke connecting each lower end portion of the main columns and the side columns are separated by two separation portions, and the steel plates are laminated at the separation portions by moving the positions of the steel plates at the continuous layers in the extension direction of the lower yokes, and a lap length at each of the partition portions provided at the lower yokes connecting the adjacent main columns is different from a lap length at each of the partition portions provided at each of the lower yokes connecting the main columns and each of the lower end portions of the side columns.

Description

Technical Field

[0001] This invention relates to a core for disassembling / transporting a transformer. Background Technology

[0002] As a type of large-capacity transformer, it is known that disassembled / transported transformers are disassembled into multiple parts to meet transportation restrictions after production, assembly, testing and inspection, reassembly, testing and inspection are completed in the factory.

[0003] The core used for disassembling / transporting transformers is constructed from laminated grain-oriented silicon steel sheets, etc., to minimize reassembly work at the installation location.

[0004] Regarding the core used for disassembling / transporting transformers, the yoke core, which connects the multiple main column cores around which the winding wires are wound, can be disassembled into multiple parts. In this case, the yoke core requires multiple joints.

[0005] As a type of core for dismantling / transporting transformers, the core described in Patent Document 1 is known, for example. In the core for dismantling / transporting the transformer described in Patent Document 1, a lower yoke core separates the three main columns of a three-phase / three-limb core, which is formed by laminating grain-oriented silicon steel sheets; the main column cores and a portion of the separated lower yoke core are assembled together and transported; and then, during reassembly, a yoke connecting the separated lower yoke cores is formed by laminating grain-oriented silicon steel sheets. In this case, the joint between the separated lower yoke cores and the connecting yoke is connected by an lap joint structure, wherein the grain-oriented silicon steel sheets are laminated by moving the silicon steel sheets a given distance.

[0006] Patent document 1 discloses the setting range of the stacking amount (lap length) and the number of layers (lap level) of grain-oriented silicon steel plates in the above-mentioned lap joint structure, so as to control the performance degradation of the transformer during disassembly / transportation.

[0007] Although Patent Document 1 relates to a dismantling / transporting transformer using a three-phase / three-limb core, the dismantling / transporting transformers described in Patent Document 2 are known as a method for separating and reassembling the cores of a three-phase / five-limb dismantling / transporting transformer for a transformer with a larger capacity.

[0008] Patent document 2 discloses a method for separating a lower yoke core, which connects to the three main columns of a three-phase / five-column core formed by laminated grain-oriented silicon steel plates, and also connects the main column cores to the side columns on both sides, and discloses a method for separating the main column cores in the longitudinal direction.

[0009] Furthermore, in the method disclosed in Patent Document 2, a portion of the separated main core and lower yoke core are integrally assembled before transportation, and during reassembly, the yoke connecting the separated lower yoke core is constructed by laminating grain-oriented silicon steel sheets to form a core for disassembling / transporting the transformer.

[0010] Existing technical documents Patent documents Patent Document 1: Japanese Patent Publication No. 2012-15210 Patent Document 2: Japanese Patent Publication No. 2010-272786 Summary of the Invention

[0011] The problem to be solved by the present invention The technology disclosed in Patent Documents 1 and 2 relates to methods for disassembling and reassembling three-phase / three-limb iron cores and three-phase / five-limb iron cores respectively so that the lower yoke iron core can be separated and transported.

[0012] In the connection section of the separated iron core, because the magnetic flux flowing inside the iron core is carried to the adjacent grain-oriented silicon steel plate, the problem is the increase in iron losses caused by eddy currents and excitation current, which leads to a decrease in the performance of the disassembly / transport transformer.

[0013] Patent document 1 discloses a setting range for the overlap length / lap level of grain-oriented silicon steel plates at the connection part of the separator core in order to control the performance degradation of the transformer during disassembly / transportation; however, since the connection parts of the separator core have the same structure, the effect of controlling the performance degradation is limited.

[0014] To address the aforementioned problems, this invention discloses an iron core for disassembling / transporting transformers, which can control the performance degradation of the transformer during disassembly / transportation.

[0015] Furthermore, the above-mentioned and other objectives of the present invention, as well as the novel features of the present invention, will be revealed through the description in this application and the accompanying drawings.

[0016] means for solving problems The core for dismantling / transporting a transformer according to the present invention is a three-phase / five-limb core, which includes three parallel main limbs, two side limbs arranged parallel to the three main limbs on the outside of the three main limbs, and a plurality of yokes connecting the upper and lower portions of adjacent main limbs or side limbs.

[0017] Furthermore, in the core of the transformer for disassembly / transportation according to the present invention, the three main columns, two side columns and multiple yokes are all constructed by laminating multiple steel plates, and from the multiple yokes, the lower yokes connecting the lower ends of adjacent main columns and the lower yokes connecting the lower ends of each main column and side column are separated by two partitions.

[0018] Furthermore, in the core of the transformer for disassembly / transportation according to the first invention, by moving the positions of the facing steel plates of the same layer in a continuous layer along the extension direction of the lower yoke, the steel plates are laminated at the partitions with a given overlap length. Moreover, in the core of the transformer for disassembly / transportation according to the first invention, this configuration ensures that the overlap length at each partition of the partitions provided at the lower yoke connecting the lower ends of adjacent main columns is different from the overlap length at each partition of the partitions provided at each lower yoke connecting the corresponding lower ends of the main columns and side columns.

[0019] Furthermore, the core of the transformer for disassembly / transportation according to the second invention has an overlap joint structure at each partition, wherein the steel plates are laminated at the partition by moving the positions of opposing steel plates of the same layer in a continuous layer along the extension direction of the lower yoke, and at the overlap joint structure of each partition, the positions of opposing steel plates of the same layer are repeated as repeating units with a given number of overlap levels. Moreover, in the core of the transformer for disassembly / transportation according to the second invention, this configuration is such that the number of overlap levels at each partition in the partition provided at the lower yoke connecting adjacent main columns is different from the number of overlap levels at each partition in the partition provided at each lower yoke connecting the corresponding lower ends of the main columns and side columns.

[0020] Effects of the present invention According to the first embodiment of the invention, the lap length at each partition is different between the lower yoke connecting adjacent main columns of the three-phase / five-column core and the lower yoke connecting the main column and the side column.

[0021] Since the overlap length at each section of the lower yoke varies depending on the position of the lower yoke, the difference in magnetic flux density within the core at each location can be adjusted by means of the overlap length. This reduces iron losses occurring in the core, thereby reducing the harmonic components of the excitation current flowing through the winding wires wound around the main post, and lowering the excitation noise of the core.

[0022] According to the second embodiment of the invention, the number of lap stages at each partition is different between the lower yoke that connects adjacent main columns of the three-phase / five-column core and the lower yoke that connects the main column and the side column.

[0023] Since the number of overlap stages at each section of the lower yoke varies depending on the location of the lower yoke, the difference in magnetic flux density within the core at different locations can be adjusted by using the number of overlap stages. This can reduce iron losses occurring in the core, thereby reducing the harmonic components of the excitation current flowing through the winding wires wound around the main post, and reducing excitation noise in the core.

[0024] The problems, configurations, and effects beyond those described above will become clear from the detailed description of the invention shown below. Attached Figure Description

[0025] [ Figure 1 [Front view of the transformer being disassembled / transported according to Example 1.]

[0026] [ Figure 2 [A bottom view of the transformer being disassembled / transported according to Example 1.]

[0027] [ Figure 3 ] Figure 1 Enlarged cross-sectional views of parts A, B, and C in the diagram.

[0028] [ Figure 4 This is a front view showing the definition of the dimensions of each section of a three-phase / five-limb iron core used for three-dimensional electromagnetic field analysis.

[0029] [ Figure 5 A view of the calculated magnetic flux density distribution at the central portion of a three-phase / five-limb core, comparing Example 1 with a conventional construction.

[0030] [ Figure 6 Calculation results of the excitation current waveform in a three-phase / five-column dismantling / transport transformer with a conventional joint structure.

[0031] [ Figure 7 Based on the calculation results of the excitation current waveform in the three-phase / five-limb dismantling / transport transformer in Example 1.

[0032] [ Figure 8 (AC): A view showing a method for producing a three-phase / five-limb dismantling / transporting transformer according to Example 1.

[0033] [ Figure 9 [Enlarged cross-sectional view of sections A, B, and C in the three-phase / five-limb dismantling / transporting transformer according to Example 2.]

[0034] [ Figure 10 [Enlarged cross-sectional views of sections A, B, and C in the three-phase / five-limb dismantling / transporting transformer according to Example 3.]

[0035] [ Figure 11 [Enlarged cross-sectional views of sections A, B, and C in the three-phase / five-limb dismantling / transporting transformer according to Example 4.] Detailed Implementation

[0036] The following detailed description and examples are illustrated with reference to the accompanying drawings. However, the structures, materials, and other various constructions described herein in specific terms are not limited to those described herein, but can be combined and modified in a suitable manner without altering the spirit of the invention.

[0037] The core for disassembling / transporting a transformer according to the present invention is a core for disassembling / transporting a transformer.

[0038] The core of the transformer for disassembly / transportation according to the present invention is a three-phase / five-limb core, which includes three parallel main limbs, two side limbs arranged parallel to the main limbs on the outside of the three main limbs, and a plurality of yokes connecting the upper and lower portions of adjacent main limbs or side limbs.

[0039] Furthermore, the core of the transformer for disassembly / transportation according to the present invention is constructed by laminating multiple steel plates for the three main columns, two side columns, and multiple yokes of the aforementioned three-phase / five-column core. In addition, the lower yokes of the multiple yokes connecting the lower ends of adjacent main columns, and the lower yokes connecting the lower ends of each main column and side column, are separated by two partitions.

[0040] Furthermore, in the core of the transformer for disassembly / transportation according to the first invention, by moving the positions of opposing steel plates of the same layer in a continuous layer along the extension direction of the lower yoke, the steel plates are laminated at the partitions with a given overlap length. Moreover, in the core of the transformer for disassembly / transportation according to the first invention, this configuration ensures that the overlap length at each partition of the partitions provided at the lower yoke connecting the lower ends of adjacent main columns is different from the overlap length at each partition of the partitions provided at each lower yoke connecting the corresponding lower ends of the main columns and side columns.

[0041] Furthermore, the core of the transformer for disassembly / transportation according to the second invention has an overlap joint structure at each partition, wherein the steel plates are laminated at the partition by moving the positions of opposing steel plates of the same layer in a continuous layer along the extension direction of the lower yoke, and at the overlap joint structure of each partition, the positions of opposing steel plates of the same layer are repeated as repeating units with a given number of overlap levels. Moreover, in the core of the transformer for disassembly / transportation according to the second invention, this configuration is such that the number of overlap levels at each partition in the partition provided at the lower yoke connecting adjacent main columns is different from the number of overlap levels at each partition in the partition provided at each lower yoke connecting the corresponding lower ends of the main columns and side columns.

[0042] According to the first embodiment of the invention, the lap length at each partition is different between the lower yoke connecting adjacent main columns of the three-phase / five-column core and the lower yoke connecting the main column and the side column.

[0043] Since the overlap length at each section of the lower yoke varies depending on the position of the lower yoke, the difference in magnetic flux density within the core at each location can be adjusted by means of the overlap length. This reduces iron losses occurring in the core, thereby reducing the harmonic components of the excitation current flowing through the winding wires wound around the main post, and lowering the excitation noise of the core.

[0044] According to the second embodiment of the invention, the number of lap stages at each partition is different between the lower yoke that connects adjacent main columns of the three-phase / five-column core and the lower yoke that connects the main column and the side column.

[0045] Since the number of overlap stages at each section of the lower yoke varies depending on the location of the lower yoke, the difference in magnetic flux density within the core at different locations can be adjusted by using the number of overlap stages. This can reduce iron losses occurring in the core, thereby reducing the harmonic components of the excitation current flowing through the winding wires wound around the main post, and reducing excitation noise in the core.

[0046] In each of the above-described constructions of the core for disassembling / transporting a transformer according to the present invention, various steel plates including grain-oriented silicon steel plates for disassembling / transporting the transformer can be used as the steel plates constituting the core.

[0047] In the core of the transformer for disassembly / transportation according to the first invention, the configuration allows for the following: under rated excitation conditions, the average magnetic flux density in all main columns can be higher than the average magnetic flux density in all side columns, and the overlap length at each partition provided at the lower yoke connecting the lower ends of adjacent main columns can be shorter than the overlap length at each partition provided at the lower yoke connecting the lower ends of each main column and side column.

[0048] In this configuration, the overlap length at the dividing portion of the lower yoke associated with the main column, which has a high average magnetic flux density under rated excitation conditions, is shorter. Since the magnetic reluctance is higher when the overlap length is shorter, the difference in magnetic flux density between the main column and the side columns can be reduced. This reduces iron losses occurring in the core, thereby reducing the harmonic components of the excitation current flowing through the winding wires wound around the main column, and lowering the excitation noise of the core.

[0049] In the core of the transformer for disassembly / transportation according to the first invention, the configuration allows for the following: under rated excitation conditions, the average magnetic flux density in all main columns can be lower than the average magnetic flux density in all side columns, and the overlap length at each partition provided at the lower yoke connecting the lower ends of adjacent main columns can be longer than the overlap length at each partition provided at the lower yoke connecting the lower ends of each main column and side column.

[0050] In this configuration, the overlap length at the dividing portion of the lower yoke associated with the main column, which has a lower average magnetic flux density under rated excitation conditions, is longer. Since the magnetic reluctance is lower with a longer overlap length, the difference in magnetic flux density between the main column and the side columns can be reduced. This reduces iron losses occurring in the core, thereby reducing the harmonic components of the excitation current flowing through the winding wires wound around the main column, and lowering the excitation noise of the core.

[0051] In the above-described core for disassembling / transporting a transformer according to the first invention: in the lap joint structure at each partition in the lower yoke partition, the positions of opposing steel plates of the same layer are moved, and the number of lap levels is made the same, which is the number of layers of repeating units for the positions of opposing steel plates of the same layer.

[0052] In the above-described core for disassembling / transporting a transformer according to the first invention: in the lap joint structure at each partition of the lower yoke, the positions of opposing steel plates of the same layer are moved, and the number of lap levels can be any different value depending on the position of the lower yoke, the number of lap levels being the number of layers of repeating units for the positions of opposing steel plates of the same layer.

[0053] In this configuration, the difference in magnetic flux density within the core at different locations can be adjusted not only by the difference in overlap length but also by the difference in the number of overlap stages in the overlap joint structure. This reduces the harmonic components of the excitation current flowing through the winding wires wound around the main post and lowers the excitation noise of the core.

[0054] In the core of the transformer for disassembly / transportation according to the second invention, the configuration allows for the following: under rated excitation conditions, the average magnetic flux density in all main columns can be higher than the average magnetic flux density in all side columns, and the number of overlap levels at each partition provided at the lower yoke connecting the lower ends of adjacent main columns can be less than the overlap length at each partition provided at the lower yoke connecting the lower ends of each main column and side column.

[0055] In this configuration, the number of overlap stages at the dividing portion of the lower yoke, which is associated with the main column having a high average magnetic flux density under rated excitation conditions, is small. Since a smaller number of overlap stages results in higher magnetic reluctance, the difference in magnetic flux density between the main column and the side columns can be reduced. This reduces iron losses occurring in the core, thereby reducing the harmonic components of the excitation current flowing through the winding wires wound around the main column, and lowering the excitation noise of the core.

[0056] In the core of the transformer for disassembly / transportation according to the second invention, the configuration allows for the following: under rated excitation conditions, the average magnetic flux density in all main columns can be lower than the average magnetic flux density in all side columns, and the number of overlap levels at each partition provided at the lower yoke connecting the lower ends of adjacent main columns can be greater than the overlap length at each partition provided at the lower yoke connecting the lower ends of each main column and side column.

[0057] In this configuration, the number of overlap stages at the dividing section of the lower yoke, associated with the main column which has a lower average magnetic flux density under rated excitation conditions, is large. Since a larger number of overlap stages results in lower magnetic reluctance, the difference in magnetic flux density between the main column and the side columns can be reduced. This reduces iron losses occurring in the core, thereby reducing the harmonic components of the excitation current flowing through the winding wires wound around the main column, and lowering the excitation noise of the core.

[0058] (Example) Next, a specific example of disassembling / transporting a transformer using the core of the disassembled / transported transformer will be described.

[0059] (Example 1) Next, refer to Figures 1 to 8 The description is based on the disassembly / transportation of the transformer according to Example 1.

[0060] Figure 1It is a front view of the disassembled / transported transformer based on Example 1, and Figure 2 This is a bottom view of the transformer being disassembled / transported according to Example 1.

[0061] When dismantling / transporting a transformer upright, the width, height, and depth directions are defined here as the x-direction, y-direction, and z-direction, respectively.

[0062] Figure 1 The disassembly / transport transformer 10 shown includes a three-phase / five-limb core, wherein steel plates are laminated in the z-direction, and three main limbs 1u, 1v and 1w for the three phases and two side limbs 2 disposed on the outside of these main limbs are placed side by side, thus having a longitudinal orientation along the y-direction.

[0063] The main columns 1u, 1v and 1w, as well as the main columns 1u, 1v and 1w and the side column 2, are connected by the upper yoke core 2a on the upper part of the side column and the lower yoke core 2b on the lower part of the side column.

[0064] The upper yoke core 2a includes an upper yoke 3 between the main columns that connect adjacent main columns, and an upper yoke 4 between the main column and the side column.

[0065] The lower yoke core 2b includes lower yokes 5a between main posts, lower connecting yokes 5b between main posts, lower yokes 6a between main posts and side posts, and lower connecting yokes 6b between main posts and side posts. More specifically, the lower yokes connecting the lower ends of adjacent main posts are separated at two dividing sections, thereby forming two lower yokes 5a between the main posts and an intermediate lower connecting yoke 5b between the main posts. Furthermore, the lower yokes connecting the lower ends of the main posts and side posts are separated at two dividing sections, thereby forming two lower yokes 6a between the main posts and side posts and an intermediate lower connecting yoke 6b between the main posts and side posts.

[0066] Since the steel plates are laminated by changing their width in this example, therefore, as Figure 2 As shown, the cross-sections of the main columns 1u, 1v and 1w are approximately circular, and the cross-section of the side column 2 is approximately elliptical.

[0067] Moreover, the corresponding cross sections of the yokes 3 and 4 constituting the upper yoke core 2a and the yokes 5a, 5b, 6a and 6b constituting the lower yoke core 2b are also approximately elliptical, because they are laminated to each other by changing the width of the steel plates.

[0068] Each yoke core 2a, 2b, main posts 1u, 1v and 1w and side posts 2 are connected to each other at the connection portion 7, wherein the corresponding steel plates are laminated to each other with a predetermined overlap length and a predetermined overlap level.

[0069] The lower yoke 5a between the main column and the connecting yoke 5b is connected to each other at the connecting part 8a, wherein the steel plates are laminated to each other with a predetermined overlap length and a predetermined overlap level.

[0070] The lower yoke 6a and the connecting yoke 6b between the main column and the side column are connected to each other at the connecting portion 8b, wherein the steel plates are laminated to each other with a predetermined overlap length and a predetermined overlap level.

[0071] Here, the overlap length refers to the lamination length when steel plates are laminated together, such that the positions of opposing steel plates in the same layer are laminated at a predetermined length in a continuous layer by moving the steel plates along the extension direction of the lower yoke.

[0072] In addition, the overlap level refers to the number of layers that are used as repeating units when the positions of opposite steel plates of the same layer are repeated with a predetermined number of layers as repeating units.

[0073] The steel plate used for the core of the three-phase / five-limb dismantling / transporting transformer 10 that constitutes this example can be, for example, grain-oriented silicon steel plate.

[0074] However, the steel plates that make up the core are not limited to grain-oriented silicon steel plates, but can be various steel plates used for disassembling / transporting transformer cores.

[0075] In addition, the three-phase windings 9u, 9v and 9w are wound around the main posts 1u, 1v and 1w.

[0076] The winding lines 9u, 9v and 9w have a low-voltage winding line on the inner side and a high-voltage winding line on the outer side, which are wound in a laminated manner, and can also have a medium-voltage winding line, a tap winding line, etc., wound in the same manner, depending on the application of the transformer, thereby constituting a disassembly / transmission transformer 10.

[0077] Figure 1 The multiple winding lines are simplified into a single unit, and the outermost contour is shown with dashed lines.

[0078] Figure 3 It shows how to use such Figure 1 The diagram shows enlarged cross-sectional views of sections A, B, and C within the core of the three-phase / five-limb dismantling / transport transformer 10. Section A shows the connection portion connecting the lower yoke 5a between the main limbs to the connecting yoke 5b. Section B shows the connection portion 8b connecting the lower yoke 6a between the main limbs and the side limbs to the connecting yoke 6b. Section C shows the connection portion 7 connecting the main limbs 1u, 1v, 1w or the side limb 2 to the yoke cores 2a, 2b.

[0079] This example constitutes a structure as follows: Figure 3Each connection portion 8a, 8b, 7 of the lap joint structure shown herein is wherein adjacent steel plate layers 11a and 11b are laminated to each other by shifting the position of opposing steel plates of the same layer by a given amount.

[0080] exist Figure 3 In the design, the lamination amount (overlap length) of steel plates 11a and 11b at parts A, B, and C is defined as Lm, Ls, and Ln, respectively, and the lamination structure of steel plates 11a and 11b is along... Figure 3 The vertical direction is repeated.

[0081] In such Figure 3 In the lap joint structure of the connecting parts 8a, 8b, and 7 shown, the steel plates are laminated to each other such that the positions of opposing steel plates in the same layer alternate for each layer. The lap joint structure laminated in this way is referred to below as "alternating lamination".

[0082] In a single-layer alternating laminated lap joint structure, the positions of the opposing steel plates of the same layer are repeated for the two layers as repeating units, and therefore, the number of lap levels as repeating units is two (2 levels).

[0083] Furthermore, in each of the connecting parts 8a, 8b and 7, the butt portion of the steel plates of the same layer (11a, 11b) is provided with a gap G to absorb errors that occur during the production of the iron core.

[0084] However, any strict management of this gap G is practically impractical.

[0085] In this example, the overlap length Lm of the connecting portion 8a (part A) located at the lower yoke connecting the main column is different from the overlap length Ls of the connecting portion 8b (part B) located at the lower yoke connecting the main column and the side column.

[0086] Furthermore, preferably, under the rated excitation conditions occurring in the main columns 1u, 1v, 1w and side columns 2 of the three-phase / five-column core, the relative (longer or shorter) relationship of these overlap lengths Lm and Ls should be determined based on the relative (higher or lower) relationship of the average magnetic flux densities Bm and Bs.

[0087] More specifically, if the overlap lengths Lm and Ls are designed to be the same as in the conventional manner (Lm=Ls), then when the average magnetic flux density Bm of the main column is higher than the average magnetic flux density Bs of the side column, Lm should be shorter than Ls, and conversely, when the average magnetic flux density Bm of the main column is lower than the average magnetic flux density Bs of the side column, Lm should be longer than Ls.

[0088] In these constructions, Figure 3The diagram shows a configuration in which the overlap length Lm at the connecting portion 8a (part A) is made shorter than the overlap length Ls at the connecting portion 8b (part B).

[0089] and Figure 3 Conversely, if the average magnetic flux density Bm of the main column is lower than the average magnetic flux density Bs of the side column, then it is preferable to make the overlap length Lm at the connecting part 8a (part A) longer than the overlap length Ls at the connecting part 8b (part B).

[0090] Here, when the overlap length is designed to be the same (Lm=Ls), the average magnetic flux density Bm and Bs can be obtained by calculation based on the material and size of each part of the core (main post 1u, 1v, 1w, side post 2, yoke core 2a, 2b) and the winding lines 9u, 9v, 9w, the amount of current flowing through the winding lines 9u, 9v, 9w, etc.

[0091] In addition, Figure 3 In the process, the overlap length Ln at the connecting part 7 (part C) is made equal to the overlap length Ls at the connecting part 8b (part B).

[0092] However, the overlap length Ln at the connecting portion 7 (part C) is irrelevant to achieving the effect of the core according to the invention, and therefore, the overlap length is not limited, that is, the overlap length can be the same as either Lm or Ls or a different length from Lm and Ls.

[0093] Next, by using a reference Figures 4 to 7 The quantitative method of three-dimensional electromagnetic field analysis describes the effect of applying the construction of this example to a three-phase / five-limb iron core with a separated lower yoke.

[0094] Figure 4 This is a front view showing the definition of the dimensions of each section of a three-phase / five-limb iron core used for three-dimensional electromagnetic field analysis.

[0095] Using the diameter D of the main column with a circular cross-section as a reference, a list of the relative dimensions of each part is shown in Table 1. The side columns consist of elliptical cross-sections with a short diameter Ds, the yoke consists of elliptical cross-sections with a short diameter Dy, and the core has a thickness D in the depth direction (the same as the diameter of the main column).

[0096] [Table 1] symbol Meaning of symbols Relative size D Diameter of the main column 1.00 Ds Short diameter of side column 0.50 Dy short diameter of the yoke 0.57 Wm Window width between main columns 0.77 Hw Window height between main columns 2.69 Ws Window width between main column and side column 0.38 Pm Length of the connecting yoke between the main columns 0.32 Ps Length of the connecting yoke between the main column and the side column 0.18 W Width of iron core 6.30 H The height of the iron core 3.84 For the three-plate / five-limb core model, the magnetization and iron loss characteristics of grain-oriented silicon steel sheet 30ZH105 manufactured by Nippon Steel Corporation are defined considering the easy magnetization axis direction and the lamination direction. Then, based on the electromagnetic field analysis model, the winding lines are set for generating the rated magnetic flux density, and a predetermined 50Hz sinusoidal voltage is applied to the winding lines.

[0097] Equivalent magnetic reluctance corresponding to a predetermined overlap length is added to the connection between the main column or side column and the yoke, as well as the connection of the separated lower yoke, to reproduce the excitation impedance characteristics of the three-phase / five-column core.

[0098] Figure 5 It shows along such Figure 4 The view shown depicts the magnetic flux density of the central portion (x-axis) of the three-phase / five-limb core. For comparative purposes, this magnetic flux density is calculated based on the conditions described above. Dashed line 21 corresponds to the conventional construction, where, when... Figure 3 The calculation results are shown when all overlap lengths Lm, Ls, and Ln at the connection portion are 10 mm. Solid line 22 shows the calculation results of one embodiment of this example, where the overlap length Lm is 2 mm and the overlap lengths Ls and Ln are 10 mm.

[0099] exist Figure 5 In the calculation results 21 based on the conventional structure, the magnetic flux density in the V-phase main column 1v is higher than that in the U-phase main column 1u and the W-phase main column 1w, which shows the bias magnetic flux density distribution appearing in the three-phase main columns. Furthermore, the magnetic flux density in the side columns 2 at both ends is 5% or more lower than that in the main columns, which shows the bias magnetic flux density at each part of the three-phase / five-column core.

[0100] On the other hand, calculation results 22 based on the construction of this example have shown that the bias flux density distribution in the three-phase main column is reduced, the flux density in the side column 2 is increased compared with the calculation results 21 of the conventional construction, and the bias flux density is reduced for the entire core.

[0101] It is also shown that the calculated iron loss at the three-phase / five-limb core in the construction of this example is reduced by 0.5% to 1.0% compared to the calculated iron loss at the three-phase / five-limb core in a conventional construction.

[0102] The following section presents a comparison of the calculated waveforms of the excitation current flowing through the winding wires wound around the aforementioned three-phase / five-limb iron core.

[0103] Figure 6 The calculation results of exemplary current waveforms in a three-phase / five-limb dismantling / transport transformer with a conventional joint structure are shown, where, as Figure 3 All overlap lengths Lm, Ls, and Ln at the connection points of the iron core shown are set to 10mm. Figure 6 In the figure, 31u, 31v and 31w show the waveforms of the excitation current flowing through the windings of phases U, V and W, respectively.

[0104] Figure 7 The calculation results of an exemplary current waveform are shown in one embodiment of a three-phase / five-limb dismantling / transporting transformer according to this example, where Lm is set to 2 mm and Ls and Ln are set to 10 mm. Figure 7 In the figure, 32u, 32v and 32w show the waveforms of the excitation current flowing through the windings of phases U, V and W, respectively.

[0105] These excitation current waveforms show the waveforms of the excitation current flowing through the high-voltage winding when the terminals of the low-voltage winding are released and a rated current 50Hz sinusoidal voltage is applied between the terminals of the high-voltage winding based on an electromagnetic field analysis model, wherein the low-voltage and high-voltage windings are wound around the main posts of a three-phase / five-limb iron core.

[0106] With Figure 6 The waveforms of the excitation currents 31u, 31v, and 31w for the three-phase / five-limb iron core corresponding to the conventional construction shown in the figure indicate the deformation in the sine wave, illustrating the superposition of harmonic components caused by the nonlinear magnetization characteristics of the iron core.

[0107] On the other hand, in relation to Figure 7 The waveforms of the excitation currents 32u, 32v, and 32w corresponding to the three-phase / five-limb iron core construction shown in this example exhibit the superposition of harmonic components and... Figure 6 The superposition of harmonic components in the waveform is controlled, thus producing a waveform similar to a sine wave.

[0108] This effect allows us to expect excitation noise to be controlled in a three-phase / five-column iron structure with the construction of this example.

[0109] Under rated excitation conditions, the relative (higher or lower) relationship of the average magnetic flux densities Bm and Bs in the main columns 1u, 1v and 1w and the side column 2 varies depending on the cross-sectional area of ​​the horizontal plane perpendicular to the magnetic flux direction, the distance between the main columns, the distance between the main column and the side column, etc.

[0110] In such Figure 1 and Figure 2 In the construction of Example 1 shown, the main columns 1u, 1v and 1w have a larger cross-sectional area in the horizontal plane than the side column 2, and therefore, the average magnetic flux density in the main columns 1u, 1v and 1w tends to be greater than that in the side column 2.

[0111] However, even when the main columns 1u, 1v, and 1w have a larger cross-sectional area on the horizontal plane than the side column 2, the average magnetic flux density of the main columns 1u, 1v, and 1w can be less than the average magnetic flux density of the side column 2, depending on other conditions such as the distance between the main columns and the distance between the main columns and the side columns.

[0112] The disassembly / transportation transformer 10 of this example can be produced by the method described below.

[0113] Figure 8 A to Figure 8 C illustrates a method for producing the three-phase / five-limb dismantling / transporting transformer of this example.

[0114] First of all, Figure 8 In A, T-shaped iron core portions 40 and L-shaped iron core portions 41 are arranged side by side on the bottom tank 12 in a predetermined space by means of a crane or the like. The T-shaped iron core portion 40 is formed by integrally assembling the main columns 1u, 1v, 1w and the lower yoke 5a between the main columns or the lower yoke 6a between the main column and the side column. The L-shaped iron core portion 41 is formed by integrally assembling the side column 2 and the lower yoke 6a between the main column and the side column.

[0115] Next, in Figure 8 In section B, by means of laminated steel plates, lower connecting yokes 5b between the main columns and lower connecting yokes 6b between the main columns and the side columns are provided between the T-shaped iron core sections and between the T-shaped iron core section 40 and the L-shaped iron core section 41, thereby connecting all the iron core sections with the lower yokes.

[0116] In addition, the winding wires 9u, 9v and 9w are inserted into the main posts 1u, 1v and 1w by means of a crane or the like.

[0117] Finally, Figure 8 In section C, the upper yoke 3 between the main columns and the upper yoke 4 between the main columns and the side columns are provided by laminated steel plates, thereby connecting all the iron core parts to the upper yoke.

[0118] Furthermore, after supplying wiring sections between the winding lines, an upper tank that fully covers the three-phase / five-limb core is installed to complete the production of disassembling / transporting the transformer.

[0119] The core of the transformer used for dismantling / transporting in this example is the core of transformer 10 used for dismantling / transporting.

[0120] The transformer core used for disassembly / transportation in this example is a three-phase / five-limb core, comprising three parallel main limbs 1u, 1v, and 1w; two side limbs 2 arranged parallel to the outer sides of the main limbs 1u, 1v, and 1w; and multiple yokes 2a and 2b for connecting the upper and lower portions of adjacent main limbs 1u, 1v, and 1w or side limbs 2. The three main limbs 1u, 1v, and 1w, the two side limbs 2, and the multiple yokes 2a and 2b are constructed by laminating multiple layers of steel plates.

[0121] In the multiple yokes 2a and 2b, the lower yoke connecting the lower ends of adjacent main columns 1u, 1v and 1w, and the lower yoke connecting the lower ends of main columns 1u, 1v and 1w and side column 2, are divided into three lower yokes by two partition sections. At each partition section of the three lower yokes, two adjacent yokes (5a and 5b, 6a and 6b) are connected by laminated steel plates to form connecting sections 8a and 8b.

[0122] At each partition, the opposing steel plates 11a and 11b of the same layer are laminated with a predetermined overlap length by moving their positions in the continuous layer along the extension direction (x direction) of the lower yoke core 2b.

[0123] According to the example of the core for disassembling / transporting a transformer, the construction is specifically such that the lap length is made different at the connection portion between the lower yoke that connects the adjacent main columns 1u, 1v and 1w and the lower yoke that connects the main column and the side column 2, which is formed at the dividing portion of the lower yoke.

[0124] More specifically, the overlap length Lm of the connecting portion 8a (part A) that connects the lower yoke 5a between the main columns to the connecting yoke 5b is different from the overlap length Ls of the connecting portion 8b (part B) that connects the lower yoke 6a between the main columns and the side columns to the connecting yoke 6b.

[0125] Since the overlap length Lm of connecting part 8a and the overlap length Ln of connecting part 8b are different at each dividing section of the lower yoke, the difference in magnetic flux density at various locations within the core can be adjusted using the overlap lengths Lm and Ln. This reduces iron losses occurring in the core, thereby reducing the harmonic components of the excitation current flowing through the winding wires wound around the main post, and lowering the excitation noise of the core.

[0126] Moreover, such as Figure 3As shown, when the average magnetic flux density Bm in the main columns 1u, 1v, 1w is higher than the average magnetic flux density Bs in the side column 2 (Bm > Bs) under rated excitation conditions, the structure can be made such that the lap length Lm at each separating portion provided in the lower yoke connecting the lower end portions of adjacent main columns is shorter than the lap length Ls at each separating portion provided in the lower yoke connecting the lower end portions of the main column and the side column (Lm < Ls).

[0127] In this structure, the magnetic reluctance increases as the lap length shortens, and thus, the difference in magnetic flux density between the main column and the side column can be reduced. This can reduce the iron loss occurring in the iron core, enabling the reduction of harmonic components of the excitation current flowing through the winding wire wound around the main column, and can reduce the excitation noise of the iron core. <00,00352>In addition, contrary to what is shown in Figure 3 when the average magnetic flux density Bm in the main columns 1u, 1v, 1w is lower than the average magnetic flux density Bs in the side column 2 (Bm < Bs) under rated excitation conditions, the structure can be made such that the lap length Lm at each separating portion provided in the lower yoke connecting the lower end portions of adjacent main columns is longer than the lap length Ls at each separating portion provided in the lower yoke connecting the lower end portions of the main column and the side column (Lm > Ls).

[0129] In this structure, the magnetic reluctance decreases as the lap length increases, and thus, the difference in magnetic flux density between the main column and the side column can be reduced. This can reduce the iron loss occurring in the iron core, enabling the reduction of harmonic components of the excitation current flowing through the winding wire wound around the main column, and can reduce the excitation noise of the iron core.

[0130] (Example 2) Next, refer to Figure 9 to describe the structure of the dismountable / transportable transformer according to Example 2.

[0131] Figure 9 shows an enlarged cross-sectional view of the connection portions, i.e., portions A, B, and C, between the steel plates in the three-phase / five-column iron core shown in Figure 1 . The same reference numerals are used for the same structures as in Example 1, and any repeated explanations will be omitted. Figure 3 In the present example, as shown in

[0132] the connection portions 8a, 8b, and 7 are formed of a lap joint structure in which adjacent steel plate layers 11a, 11b, 11c are laminated by shifting the positions of the opposing steel plates in the same layer by a given amount. Figure 9

[0133] Figure 9 ​​In particular, the steel plates are laminated such that the positions of opposing steel plates of the same layer are repeated for the three layers of repeating units in the lap joint structure that serve as connecting parts 8a, 8b and 7. The lap joint structure laminated in this way is referred to below as a "three-stage stepped lap joint structure".

[0134] In a three-tiered stepped lap joint structure, the positions of the opposing steel plates of the same layer are repeated for the three layers as repeating units, and therefore, the number of lap levels as repeating units is three (3 levels).

[0135] Based on the relative (higher or lower) relationship between the average magnetic flux densities Bm and Bs in the three-phase / five-limb core, this example can also achieve a similar effect to Example 1 by making the overlap length Lm of the connecting part 8a (part A) different from the overlap length Ls of the connecting part 8b (part B).

[0136] exist Figure 9 In this configuration, the overlap length Lm at the connecting portion 8a (part A) is made shorter than the overlap length Ls at the connecting portion 8b (part B).

[0137] In such Figure 9 In this example shown, similar to Example 1, Figure 3 In this manner, the overlap length Ln at the connecting part 7 (part C) is equal to the overlap length Ls at the connecting part 8b (part B).

[0138] (Example 3) Next, refer to Figure 10 Describe the construction of the transformer for disassembly / transportation according to Example 3.

[0139] Figure 10 It shows Figure 1 Enlarged cross-sectional view of the connection portions between the steel plates within the three-phase / five-limb iron core shown, namely sections A, B, and C. The same reference numerals are used with respect to Example 1. Figure 3 And Example 2 Figure 9 The same structure will be used, and any repeated explanations will be omitted.

[0140] In this example, such as Figure 10 As shown, the connecting portions 8a, 8b and 7 are composed of an lap joint structure, wherein adjacent steel plate layers 11a to 11f are laminated by shifting the position of opposing steel plates of the same layer by a given amount.

[0141] exist Figure 10 In particular, the steel plates are laminated such that the positions of opposing steel plates of the same layer are repeated for six layers of repeating units in the lap joint structure that serves as connecting parts 8a, 8b, and 7. The lap joint structure laminated in this manner is referred to below as a "six-stage stepped lap joint structure".

[0142] In a six-level stepped lap joint structure, the positions of the opposing steel plates of the same layer are repeated for the six layers as repeating units, and therefore, the number of lap levels as repeating units is six (6 levels).

[0143] Based on the relative (higher or lower) relationship between the average magnetic flux densities Bm and Bs in the three-phase / five-limb core, this example can also achieve a similar effect to that of Examples 1 and 2 by making the overlap length Lm of the connecting part 8a (part A) different from the overlap length Ls of the connecting part 8b (part B).

[0144] exist Figure 10 In this configuration, the overlap length Lm at the connecting portion 8a (part A) is made shorter than the overlap length Ls at the connecting portion 8b (part B).

[0145] In Example 1 Figure 3 And Example 2 Figure 3 In this example, the overlap length Ln at connection portion 7 (part C) is equal to the overlap length Ls at connection portion 8b (part B); however, in this example... Figure 10 In the middle, the overlap length Ln at the connecting part 7 (part C) is equal to the overlap length Lm at the connecting part 8a (part A).

[0146] (Example 4) Next, refer to Figure 11 Describe the construction of the transformer for disassembly / transportation according to Example 4.

[0147] Figure 11 It shows Figure 1 Enlarged cross-sectional view of the connection portions between the steel plates within the three-phase / five-limb iron core shown, namely sections A, B, and C. The same reference numerals are used with respect to Example 1. Figure 3 Example 2 Figure 9 And Example 3 Figure 10 The same structure will be used, and any repeated explanations will be omitted.

[0148] In this example, such as Figure 11 As shown, the connecting portions 8a, 8b, and 7 are constructed of lap joint structures, wherein adjacent steel plate layers are laminated by shifting the positions of opposing steel plates of the same layer by a given amount. In this respect, this example is similar to Examples 1 through 3.

[0149] However, in this example, such as Figure 11 As shown, the number of overlapping levels, which are the repeating units in the overlapping joint structure, are made different, rather than the overlapping lengths Lm and Ls of the connecting parts being made different at the connecting parts 8a (part A) and 8b (part B).

[0150] According to the relative (higher or lower) relationship between the average magnetic flux densities Bm and Bs in the three-phase / five-column iron core, this example can also achieve an effect similar to that of Examples 1 to 3 by making the number of lapping stages at the connecting portion 8a (Part A) different from the number of lapping stages at the connecting portion 8b (Part B).

[0151] In Figure 11 From this configuration, the connecting portion 8a (Part A) has a single-stage alternating lamination with a lapping stage number of two, and the connecting portion 8b (Part B) has a six-stage stepped lapping joint structure with a lapping stage number of six. That is, the lapping stage number at the connecting portion 8a (Part A) is made smaller than the lapping stage number at the connecting portion 8b (Part B).

[0152] In addition, under the rated excitation conditions occurring in the main columns 1u, 1v, and 1w and the side columns 2 of the three-phase / five-column iron core as shown in Figure 1 the relationship of the lapping stage numbers is preferably determined based on the relative (higher or lower) relationship between the average magnetic flux densities Bm and Bs.

[0153] More specifically, when the lapping stage numbers are designed to be the same conventionally, if under the rated excitation conditions, the average magnetic flux density Bm of the main columns is higher than the average magnetic flux density Bs of the side columns (Bm > Bs), the lapping stage number at the connecting portion 8a (Part A) between the main columns should be made smaller than the lapping stage number at the connecting portion 8b (Part B) between the main column and the side column.

[0154] In this configuration, the magnetic reluctance increases as the lapping stage number decreases, and thus, the difference in magnetic flux density between the main column and the side column can be reduced. This can reduce the iron loss occurring in the iron core, enabling the reduction of harmonic components of the excitation current flowing through the winding wire wound around the main column, and can reduce the excitation noise of the iron core.

[0155] Conversely, when the lapping stage numbers are designed to be the same as usual, if under the rated excitation conditions, the average magnetic flux density Bm of the main columns is lower than the average magnetic flux density Bs of the side columns (Bm < Bs), the lapping stage number at the connecting portion 8a (Part A) between the main columns should be made larger than the lapping stage number at the connecting portion 8b (Part B) between the main column and the side column.

[0156] In this configuration, the magnetic reluctance decreases as the lapping stage number increases, and thus, the difference in magnetic flux density between the main column and the side column can be reduced. This can reduce the iron loss occurring in the iron core, enabling the reduction of harmonic components of the excitation current flowing through the winding wire wound around the main column, and can reduce the excitation noise of the iron core.

[0157] In Figure 11The structure combines a single-level alternating lamination with two overlap levels, and a six-level stepped lap joint structure with overlap levels applicable to the overlap levels at connection part 8a (part A) and connection part 8b (part B).

[0158] Regarding the construction of different lap heights, other combinations are also possible. For example, a three-tiered lap structure can be used at any connection point, where the number of tiers is three.

[0159] (Example of variation) In each of the above examples, at the connection portion 8a (part A) and the connection portion 8b (part B), only one of the overlap length and the number of overlap levels is made different; however, both the overlap length and the number of overlap levels can be made different.

[0160] In particular, under rated excitation conditions, if the relative (longer or shorter) relationship of the overlap length and the relative (larger or smaller) relationship of the number of overlaps are determined by the relative (higher or lower) relationship of the average magnetic flux density Bm of the main columns 1u, 1v, and 1w and the average magnetic flux density Bs of the side column 2, the effect of reducing the harmonic components of the excitation current flowing through the winding wires and the effect of reducing the excitation noise of the iron core can be further enhanced.

[0161] In such Figure 9 and Figure 10 In the enlarged cross-sectional view shown, the steel plate moves vertically from left to right in one direction relative to the repeating unit of the lap joint structure.

[0162] However, a structure in which the steel plate moves vertically in one direction from right to left as shown in the drawings, or a structure that alternately changes the direction of movement, can be used, as in Patent Document 1. Figure 3 The construction of sections B to D in the figure, wherein the steel plate moves from left to right and then from left to right.

[0163] In patent document 1 Figure 3 In the construction of sections B to D, the lap joint structure of the moving steel plate is repeated for three layers in the same direction, and therefore, the number of lap levels as the repeating unit is three.

[0164] With Patent Document 1 Figure 4 Compared to the structure of parts B to D in Patent Document 1, in which the steel plate is shifted from left to right in one direction, the structure of parts B to D in Patent Document 1 is different. Figure 3 The construction of sections B to D in the middle has the same number of overlapping levels (three) and the same resistance at the connection part, but differs in the number of layers (cycles) at the position of the repeating steel plate.

[0165] This invention is not limited to the foregoing detailed description and examples, but includes a wide variety of variations. For example, the foregoing detailed description and examples have been provided for the purpose of simply facilitating understanding of the invention, but are not necessarily limited to inventions having all of the foregoing constructions.

[0166] List of reference numerals 1u, 1v, 1w: Main pillars 2: Side pillars 2a: Upper yoke core 2b: Lower yoke core 3: The upper yoke between the main pillars 4: The upper yoke between the main column and the side columns 5a: Lower yoke between main pillars 5b: Lower connecting yoke between main columns 6a: Lower yoke between the main column and the lateral column 6b: Lower connecting yoke between the main column and the side column 7: Connection between the column core and the yoke core 8a: The lower yoke connecting the main columns 8b: The lower yoke connection between the main column and the side columns 9u, 9v, 9w: winding wires 10: Dismantling / Transporting Transformers 11a-11f: Grain-oriented silicon steel sheets 12: Bottom-mounted tank 12a: Upper tank 40: T-shaped iron core section 41: L-shaped iron core section

Claims

1. A core for dismantling / transporting a transformer, the core being a three-phase / five-limb core, the three-phase / five-limb core comprising three parallel main limbs, two side limbs arranged parallel to the three main limbs on the outer side of the three main limbs, and a plurality of yokes connecting the upper and lower portions of adjacent main limbs or side limbs, wherein: The three main columns, the two side columns, and the multiple yokes are all constructed by laminating multiple steel plates. Of the plurality of yokes, the lower yoke connecting the lower ends of the adjacent main columns and the lower yoke connecting each lower end of the main column and the side column are separated by two partition portions. By moving the positions of opposing steel plates of the same layer along the extension direction of the lower yoke at continuous layers, the steel plates are laminated at the dividing portion with a given overlap length, and The overlap length at each of the partitions in the yoke connecting the lower ends of the adjacent main column is different from the overlap length at each of the partitions in the yoke connecting the corresponding lower ends of the main column and the side column.

2. The iron core for disassembling / transporting a transformer according to claim 1, wherein, Under rated excitation conditions, the average magnetic flux density in all main columns is higher than the average magnetic flux density in all side columns, and the overlap length at each partition of the lower yoke connecting the lower ends of the adjacent main columns is shorter than the overlap length at each partition of the lower yoke connecting the lower ends of the main columns and side columns.

3. The iron core for disassembling / transporting a transformer according to claim 1, wherein, Under rated excitation conditions, the average magnetic flux density in all main columns is lower than the average magnetic flux density in all side columns, and the overlap length at each partition of the lower yoke connecting the lower ends of the adjacent main columns is longer than the overlap length at each partition of the lower yoke connecting the lower ends of the main columns and side columns.

4. The iron core for disassembling / transporting a transformer according to claim 1, wherein, In the lap joint structure at each of the partitions in the lower yoke, the positions of the opposing steel plates of the same layer are moved, and the number of lap levels is made the same, which is the number of layers of repeating units for the positions of the opposing steel plates of the same layer.

5. The iron core for disassembling / transporting a transformer according to claim 1, wherein, In the lap joint structure at each of the partitions in the lower yoke, the positions of the opposing steel plates of the same layer are moved, and the number of lap levels is made to any different value according to the position of the lower yoke, the number of lap levels being the number of layers of repeating units for the position of the opposing steel plates of the same layer.

6. A core for dismantling / transporting a transformer, the core being a three-phase / five-limb core, the three-phase / five-limb core comprising three parallel main limbs, two side limbs arranged parallel to the three main limbs on the outer side of the three main limbs, and a plurality of yokes connecting the upper and lower portions of adjacent main limbs or side limbs, wherein: The three main columns, the two side columns, and the multiple yokes are all constructed by laminating multiple steel plates. Of the plurality of yokes, the lower yoke connecting the lower ends of the adjacent main columns and the lower yoke connecting each lower end of the main column and the side column are separated by two partition portions. The core has an lap joint structure at each dividing section, wherein the steel plates are laminated at the dividing section by moving the positions of opposing steel plates of the same layer in a continuous layer along the extension direction of the lower yoke, the steel plates being laminated with a given lap length. At each lap joint structure of the partition section, the positions of the opposing steel plates of the same layer are repeated in layers with a given number of lap levels as repeating units, and The number of overlap levels at each of the partitions in the lower yoke connecting the adjacent main columns is different from the number of overlap levels at each of the partitions in the lower yoke connecting the corresponding lower ends of the main columns and the side columns.

7. The core for disassembling / transporting a transformer according to claim 6, wherein, Under rated excitation conditions, the average magnetic flux density in all main columns is higher than the average magnetic flux density in all side columns, and the number of overlap levels at each partition of the lower yoke connecting the lower ends of the adjacent main columns is less than the number of overlap levels at each partition of the lower yoke connecting the lower ends of the main columns and side columns.

8. The core for disassembling / transporting a transformer according to claim 6, wherein, Under rated excitation conditions, the average magnetic flux density in all main columns is lower than the average magnetic flux density in all side columns, and the number of overlap levels at each partition of the lower yoke connecting the lower ends of the adjacent main columns is greater than the number of overlap levels at each partition of the lower yoke connecting the lower ends of the main columns and side columns.

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