Disassembled and transported transformer core

Abstract

To provide a disassembled and transported transformer core capable of suppressing degradation of the performance of a disassembled and transported transformer.SOLUTION: A disassembled and transported transformer core used in a disassembled and transported transformer is a three-phase five-legged core, in which the main legs, side legs, and multiple yokes connecting the upper and lower ends of adjacent main legs or side legs are each constructed by laminating multiple layers of steel plate, the lower yoke connecting the lower ends of adjacent main legs and the lower yoke connecting the lower ends of the main legs and side legs are each divided by two divisions, and in each division, the steel plates are overlapped with the position of the steel plate shifted in the extension direction of the lower yoke in successive layers and overlapped with a predetermined lap length, and the lap length in each division provided on the lower yoke connecting the lower ends of adjacent main legs and the lap length in each division provided on the lower yoke connecting the lower ends of the main legs and side legs are different lengths.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an iron core for a disassembled transport transformer used in a disassembled transport transformer. [Background technology]

[0002] As one type of large-capacity transformer, a disassembled-and-transported transformer is known. After fabrication, assembly, testing, and inspection are completed in a factory, the transformer is disassembled into multiple parts that satisfy transportation constraints, transported to an installation site, and reassembled, tested, and inspected.

[0003] The cores for disassembled and transported transformers are constructed by laminating oriented silicon steel sheets, etc., in order to minimize the need for reassembly at the installation site. In the case of a transformer core for disassembly and transportation, for example, a yoke core that connects a plurality of main leg cores around which windings are wound may need to be divided into a plurality of segments. In this case, the yoke core needs a plurality of joints.

[0004] As such a disassembled transport transformer, for example, one described in Patent Document 1 is known. In the disassembled transport transformer described in Patent Document 1, a lower yoke core that connects three main leg cores of a three-phase three-legged core formed by laminating grain-oriented silicon steel plates is divided, and the main leg core and a part of the divided lower yoke core are transported in an assembled state, and when reassembled, a yoke that connects the divided lower yoke cores is formed by laminating grain-oriented silicon steel plates. At this time, the joints of the divided lower yoke core and the connecting yoke are connected by a lap joint structure in which the grain-oriented silicon steel plates are overlapped while being shifted by a certain distance. Patent Document 1 discloses a setting range for the amount of overlap (lap length) between shifted oriented silicon steel plates in the above-mentioned lap joint structure and the number of layers of oriented silicon steel plates (number of lap stages) that form the repeating unit of the lap joint structure in order to suppress deterioration in the performance of the disassembled transport transformer.

[0005] Patent Document 1 relates to a disassembled transport transformer that uses a three-phase, three-legged core. However, a method for disassembling and reassembling the core of a three-phase, five-legged disassembled transport transformer that is used in larger capacity transformers is known, for example, as described in Patent Document 2.

[0006] Patent Document 2 discloses a method of dividing the three main leg cores of a three-phase five-legged core made by laminating directional silicon steel plates, and of dividing the lower yoke core that connects the main leg cores to the side leg cores at both ends, and of dividing the main leg cores longitudinally. Furthermore, in the method disclosed in Patent Document 2, the divided main leg core and a portion of the divided lower yoke core are transported in an assembled state, and during reassembly, the yoke that connects the divided lower yoke cores together is constructed by laminating oriented silicon steel plates, resulting in a core for a disassembled and transported transformer. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2012-15210 A [Patent Document 2] JP 2010-272786 A Summary of the Invention [Problem to be solved by the invention]

[0008] The technologies disclosed in Patent Documents 1 and 2 relate to methods for disassembling and reassembling three-phase three-legged type and three-phase five-legged type iron cores, and in both cases the lower yoke iron core is divided to enable transportation of the iron cores. At the joints of the divided cores, the magnetic flux flowing inside the core crosses over to the adjacent directional silicon steel plates, which increases iron loss due to eddy currents and also increases the excitation current, resulting in a decrease in the performance of the disassembled transport transformer.

[0009] In addition, Patent Document 1 discloses a setting range for the lap length and number of lap stages between the directional silicon steel sheets at the connection part of the divided core in order to suppress deterioration of transformer performance. However, the structure of the connection part of each divided core is all the same, and the effect of suppressing deterioration of performance is limited.

[0010] In order to solve the above-mentioned problems, the present invention provides an iron core for a disassembled and transported transformer that can suppress deterioration in the performance of the disassembled and transported transformer.

[0011] The above and other objects of the present invention and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0012] The iron core for a disassembled-and-transported transformer of the present invention is an iron core for a disassembled-and-transported transformer used in a disassembled-and-transported transformer, and is a three-phase five-legged core composed of three main legs arranged in parallel, two side legs arranged in parallel to the main legs located on both outside of the three main legs, and a number of yokes connecting the upper and lower ends of adjacent main legs or side legs. In addition, the iron core for a disassembled-transport transformer of the present invention has three main legs, two side legs, and multiple yokes, each constructed by laminating multiple layers of steel plate, and among the multiple yokes, the lower yokes that connect the lower ends of adjacent main legs and the lower yokes that connect the lower ends of the main legs and side legs are each divided by two dividing sections.

[0013] In the first iron core for disassembled transportation transformer of the present invention, the steel plates are overlapped in each divided section with the positions of opposing steel plates in the same layer shifted in the extending direction of the lower yoke in successive layers and overlapped with a predetermined overlap length. The iron core for disassembled transportation transformer of the first invention is configured such that the overlap length in each divided section provided in the lower yoke connecting the lower ends of adjacent main legs is different from the overlap length in each divided section provided in the lower yoke connecting the lower ends of the main legs and the side legs.

[0014] The second iron core for disassembled transport transformers of the present invention further has a lap joint structure in which the steel plates are overlapped in a state in which the positions of opposing steel plates in the same layer are shifted in the extending direction of the lower yoke in successive layers and overlapped with a predetermined lap length, and in the lap joint structure of each divided part, the positions of opposing steel plates in the same layer are repeated with a predetermined number of lap stages as a repeating unit. The second iron core for disassembled transport transformers of the present invention is configured such that the number of lap stages in each divided part provided in the lower yoke connecting the lower ends of adjacent main legs is different from the number of lap stages in each divided part provided in the lower yoke connecting the lower ends of the main legs and the side legs. Effect of the Invention

[0015] According to the configuration of the first present invention's iron core for a disassembled-transport transformer, the wrap lengths in each divided section are different between the lower yoke connecting adjacent main legs of a three-phase five-legged iron core and the lower yoke connecting the main legs and side legs. Since the wrap length of each divided part of the lower yoke is different depending on the part of the lower yoke, the difference in magnetic flux density in each part of the iron core can be adjusted by the wrap length of each part. This reduces the iron loss generated in the iron core, reduces the harmonic components of the excitation current flowing through the windings wound around the main legs, and reduces the excitation noise of the iron core.

[0016] According to the configuration of the second present invention's iron core for a disassembled-transport transformer, the number of lap stages in each divided section is different between the lower yoke connecting adjacent main legs of a three-phase five-legged iron core and the lower yoke connecting the main legs and side legs. Since the number of wrap stages in each divided section of the lower yoke varies depending on the location of the lower yoke, the difference in magnetic flux density in each section within the iron core can be adjusted by adjusting the number of wrap stages for each section. This reduces the iron loss generated in the iron core, reduces the harmonic components of the excitation current flowing through the windings wound around the main legs, and reduces the excitation noise of the iron core.

[0017] Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0018] [Figure 1] FIG. 2 is a front view of the disassembled transportation transformer of the first embodiment. [Diagram 2] FIG. 2 is a bottom view of the disassembled transport transformer of the first embodiment. [Diagram 3] 2 is an enlarged cross-sectional view of parts A, B and C in FIG. 1. [Figure 4] FIG. 2 is a front view showing the definition of dimensions of each part of a three-phase five-legged core used in a three-dimensional electromagnetic field analysis. [Diagram 5] 11 is a diagram comparing calculation results of magnetic flux density distribution in the center of a three-phase five-legged iron core between Example 1 and a conventional configuration. [Figure 6] 1 is a calculation result of the excitation current waveform of a three-phase five-legged disassembled transport transformer with a conventional joint structure. [Figure 7] 1 shows the calculation results of the excitation current waveform of the three-phase five-legged disassembled transport transformer of Example 1. [Figure 8] 1A to 1C are diagrams showing a method for manufacturing the three-phase five-legged disassembled transport transformer of Example 1. [Figure 9] 10 is an enlarged cross-sectional view of parts A, B, and C of the disassembled transport transformer of Example 2. [Figure 10] 11 is an enlarged cross-sectional view of parts A, B, and C of the disassembled transport transformer of Example 3. [Figure 11] 10 is an enlarged cross-sectional view of parts A, B, and C of the disassembled transport transformer of Example 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, the embodiments and examples of the present invention will be described with reference to text and drawings. However, the structures, materials, and other specific configurations shown in the present invention are not limited to the embodiments and examples described here, and can be appropriately combined or improved without changing the gist of the invention. Elements that are not directly related to the present invention are not shown.

[0020] The disassembled and transported transformer iron core of the present invention is an iron core used in a disassembled and transported transformer. The iron core for a disassembled-transport transformer of the present invention is a three-phase five-legged iron core composed of three main legs arranged in parallel, two side legs arranged in parallel to the main legs located on both outside of the three main legs, and a number of yokes connecting the upper and lower ends of adjacent main legs or side legs. In addition, the iron core for disassembled transportation transformer of the present invention has three main legs, two side legs, and multiple yokes of the above-mentioned three-phase five-legged iron core, each constructed by laminating multiple layers of steel plates. Furthermore, among the multiple yokes, the lower yoke connecting the lower ends of adjacent main legs and the lower yoke connecting the lower ends of the main legs and side legs are each divided by two division parts.

[0021] In the first iron core for disassembled transportation transformer of the present invention, the steel plates are overlapped in each divided section with the positions of opposing steel plates in the same layer shifted in the extending direction of the lower yoke in successive layers and overlapped with a predetermined overlap length. The iron core for disassembled transportation transformer of the first invention is configured such that the overlap length in each divided section provided in the lower yoke connecting the lower ends of adjacent main legs is different from the overlap length in each divided section provided in the lower yoke connecting the lower ends of the main legs and the side legs.

[0022] The second iron core for disassembled transport transformers of the present invention further has a lap joint structure in which the steel plates are overlapped in a state in which the positions of opposing steel plates in the same layer are shifted in the extending direction of the lower yoke in successive layers and overlapped with a predetermined lap length, and in the lap joint structure of each divided part, the positions of opposing steel plates in the same layer are repeated with a predetermined number of lap stages as a repeating unit. The second iron core for disassembled transport transformers of the present invention is configured such that the number of lap stages in each divided part provided in the lower yoke connecting the lower ends of adjacent main legs is different from the number of lap stages in each divided part provided in the lower yoke connecting the lower ends of the main legs and the side legs.

[0023] According to the configuration of the first present invention's iron core for a disassembled-transport transformer, the wrap lengths in each divided section are different between the lower yoke connecting adjacent main legs of a three-phase five-legged iron core and the lower yoke connecting the main legs and side legs. Since the wrap length of each divided part of the lower yoke is different depending on the part of the lower yoke, the difference in magnetic flux density in each part of the iron core can be adjusted by the wrap length of each part. This reduces the iron loss generated in the iron core, reduces the harmonic components of the excitation current flowing through the windings wound around the main legs, and reduces the excitation noise of the iron core.

[0024] According to the configuration of the second present invention's iron core for a disassembled-transport transformer, the number of lap stages in each divided section is different between the lower yoke connecting adjacent main legs of a three-phase five-legged iron core and the lower yoke connecting the main legs and side legs. Since the number of wrap stages in each divided section of the lower yoke varies depending on the location of the lower yoke, the difference in magnetic flux density in each section within the iron core can be adjusted by adjusting the number of wrap stages for each section. This reduces the iron loss generated in the iron core, reduces the harmonic components of the excitation current flowing through the windings wound around the main legs, and reduces the excitation noise of the iron core.

[0025] In each of the above-mentioned configurations of the iron core for the disassembly-transport transformer of the present invention, various steel plates used for disassembly-transport transformers, such as grain-oriented silicon steel plates, can be used as the steel plate constituting the iron core.

[0026] In the above-mentioned first present invention of the disassembled transport transformer core, the average magnetic flux density in all main legs under rated excitation conditions can be higher than the average magnetic flux density in all side legs, and the lap length in each split portion provided in the lower yoke connecting the lower ends of adjacent main legs can be shorter than the lap length in each split portion provided in the lower yoke connecting the lower ends of the main legs and side legs. In this configuration, the lap length of the divided part of the lower yoke for the main leg with the higher average magnetic flux density under rated excitation conditions is short, and the shorter the lap length, the greater the magnetic resistance, so the difference in magnetic flux density between the main leg and the side leg can be reduced. This reduces the iron loss generated in the core, reduces the harmonic components of the excitation current flowing through the winding wound around the main leg, and reduces the excitation noise of the core.

[0027] In the above-mentioned first present invention of the disassembled transport transformer core, the average magnetic flux density in all main legs under rated excitation conditions can be lower than the average magnetic flux density in all side legs, and the lap length in each split portion provided in the lower yoke connecting the lower ends of adjacent main legs can be longer than the lap length in each split portion provided in the lower yoke connecting the lower ends of the main legs and side legs. In this configuration, the lap length of the divided part of the lower yoke for the main leg with the lower average magnetic flux density under rated excitation conditions is longer, and the longer the lap length, the smaller the magnetic resistance, so the difference in magnetic flux density between the main leg and the side leg can be reduced. This reduces the iron loss generated in the core, reduces the harmonic components of the excitation current flowing through the winding wound around the main leg, and reduces the excitation noise of the core.

[0028] In the above-mentioned first present invention of the disassembled transport transformer core, in the lap joint structure in which the positions of opposing steel plates of the same layer are shifted in each divided part of the lower yoke, the number of lap stages, which is the number of layers in the unit of repeating the positions of opposing steel plates of the same layer, can be configured to be all the same.

[0029] In the above-mentioned first present invention of the disassembled transport transformer core, in a lap joint structure in which the positions of opposing steel plates of the same layer are shifted in each divided portion of the lower yoke, the number of lap stages, which is the number of layers in the unit of repeating positions of opposing steel plates of the same layer, can be configured to be any different value depending on the part of the lower yoke. In this configuration, in the wrap joint structure, the difference in magnetic flux density from one location to another within the iron core can be adjusted not only by the difference in wrap length but also by the difference in the number of wrap stages, and it becomes possible to reduce the harmonic components of the excitation current flowing through the windings wound around the main legs and to reduce the excitation noise of the iron core.

[0030] In the above-mentioned second present invention of the disassembled transportation transformer core, the average magnetic flux density in all main legs under rated excitation conditions is higher than the average magnetic flux density in all side legs, and the number of wrap stages in each divided section provided in the lower yoke connecting the lower ends of adjacent main legs is less than the number of wrap stages in each divided section provided in the lower yoke connecting the lower ends of the main legs and side legs. In this configuration, the number of wrap stages of the lower yoke division section associated with the main leg with the higher average magnetic flux density under rated excitation conditions is smaller, and the smaller the number of wrap stages, the greater the magnetic resistance, so the difference in magnetic flux density between the main leg and the side leg can be reduced. This reduces the iron loss generated in the core, reduces the harmonic components of the excitation current flowing through the winding wound around the main leg, and reduces the excitation noise of the core.

[0031] In the above-mentioned second present invention of the disassembled transportation transformer core, the average magnetic flux density in all the main legs under rated excitation conditions can be lower than the average magnetic flux density in all the side legs, and the number of wrap stages in each divided section provided in the lower yoke connecting the lower ends of adjacent main legs can be greater than the number of wrap stages in each divided section provided in the lower yoke connecting the lower ends of the main legs and the side legs. In this configuration, the number of wrap stages of the lower yoke division section associated with the main leg with the lower average magnetic flux density under rated excitation conditions is greater, and the greater the number of wrap stages, the smaller the magnetic resistance, so the difference in magnetic flux density between the main leg and the side leg can be reduced. This reduces the iron loss generated in the core, reduces the harmonic components of the excitation current flowing through the winding wound around the main leg, and reduces the excitation noise of the core. EXAMPLES

[0032] Next, a specific example of a disassembled transportation transformer using an iron core for a disassembled transportation transformer will be described.

[0033] Example 1 Hereinafter, the disassembled transport transformer of the first embodiment will be described with reference to FIGS. FIG. 1 is a front view of the disassembled transportation transformer of the first embodiment, and FIG. 2 is a bottom view of the disassembled transportation transformer of the first embodiment. In the following description, the width direction, height direction, and depth direction of the disassembled transport transformer when placed stationary and faced directly are defined as the x direction, the y direction, and the z direction, respectively.

[0034] The disassembled transport transformer 10 shown in FIG. 1 is configured with a three-phase five-legged core in which steel plates are stacked in the z direction, three main legs 1u, 1v, and 1w for three phases, and two side legs 2 provided at both outer ends of the main legs are arranged in parallel with their longitudinal direction in the y direction.

[0035] The main legs 1u, 1v, 1w and the main leg 1u, 1v, 1w-side leg 2 are connected at their upper ends by an upper yoke core 2a and at their lower ends by a lower yoke core 2b. The upper yoke core 2a is made up of an inter-main-leg upper yoke 3 that connects the upper ends of adjacent main legs, and an inter-main-leg-side-leg upper yoke 4 that connects the upper ends of the main leg and side leg. The lower yoke core 2b is composed of the inter-main-leg lower yoke 5a, the inter-main-leg lower connecting yoke 5b, and the main-leg-to-side-leg lower yoke 6a and the main-leg-to-side-leg lower connecting yoke 6b. Specifically, the lower yoke connecting the lower ends of adjacent main legs is divided at two divisions into two inter-main-leg lower yokes 5a and an intermediate inter-main-leg lower connecting yoke 5b. In addition, the lower yoke connecting the lower ends of the main legs and side legs is divided at two divisions into two inter-main-leg lower yokes 6a and an intermediate inter-main-leg lower connecting yoke 6b.

[0036] In this embodiment, the steel plates are laminated with varying widths, so that the cross sections of the main legs 1u, 1v, and 1w are substantially circular, and the cross section of the side leg 2 is substantially elliptical, as shown in FIG. In addition, the yokes 3 and 4 that constitute the upper yoke core 2a and the yokes 5a, 5b, 6a, and 6b that constitute the lower yoke core 2b are also laminated with steel plates of different widths, so that the cross section of each yoke is approximately elliptical.

[0037] Each yoke core 2a, 2b is connected to the main legs 1u, 1v, 1w and the side legs 2 at a connection portion 7 formed by laminating the steel plates of both sides with a predetermined lap length and a predetermined number of lap stages. The inter-main-leg lower yoke 5a and the connection yoke 5b are connected at two divided portions by a connection portion 8a in which steel plates are laminated with a predetermined lap length and a predetermined number of lap stages. The main leg-side leg lower yoke 6a and the connection yoke 6b are connected at two divided portions by a connection portion 8b in which steel plates are laminated with a predetermined lap length and a predetermined number of lap stages. Here, the overlap length is the overlap length of the steel plates when the positions of opposing steel plates in the same layer are shifted in the extending direction of the lower yoke in successive layers and the steel plates are overlapped by a predetermined length. The number of lapped layers is the number of layers in a repeating unit when the positions of opposing steel plates in the same layer are repeated for a predetermined number of layers as a repeating unit.

[0038] As the steel plate constituting the iron core of the three-phase five-leg type disassembled transport transformer 10 of this embodiment, for example, grain-oriented silicon steel plate can be used. The steel plate constituting the core is not limited to the grain-oriented silicon steel plate, and various steel plates used for the core of a disassembled transport transformer can be used.

[0039] Furthermore, three-phase windings 9u, 9v, 9w are wound around the main legs 1u, 1v, 1w. The windings 9u, 9v, 9w are wound with a low-voltage winding on the inside and a high-voltage winding on the outside. Depending on the use of the transformer, medium-voltage windings, tap windings, etc. may be further wound in layers to form a disassembled transport transformer 10. In FIG. 1, these multiple windings are simplified as an integrated unit, and the contours of the outermost windings 9u, 9v, and 9w are drawn by dashed lines.

[0040] Fig. 3 shows enlarged cross-sectional views of parts A, B, and C in the core of the three-phase five-legged disassembled transport transformer 10 shown in Fig. 1. Part A shows the connection part 8a that connects the inter-main leg lower yoke 5a and the connection yoke 5b. Part B shows the connection part 8b that connects the inter-main leg-side leg lower yoke 6a and the connection yoke 6b. Part C shows the connection part 7 that connects the main legs 1u, 1v, and 1w or the side legs 2 and the yoke cores 2a and 2b.

[0041] In this embodiment, as shown in Figure 3, each connection portion 8a, 8b, 7 is formed by a lap joint structure in which the positions of opposing steel plates of the same layer in adjacent layers 11a and 11b are stacked while being shifted by a certain amount. In FIG. 3, the overlapping amounts (lap lengths) of steel plates 11a, 11b at parts A, B, and C are defined as Lm, Ls, and Ln, respectively, and the laminated structure of steel plates 11a, 11b is repeated in the vertical direction of the figure.

[0042] In Fig. 3, in the lap joint structure of each of the connecting parts 8a, 8b, and 7, the positions of the opposing steel plates in the same layer are stacked alternately for each layer. Hereinafter, such a stacked lap joint structure is referred to as "one-stage alternating stacking." In a one-layer alternating stacking lap joint structure, the positions of opposing steel plates in the same layer are repeated with two layers as a repeating unit, so the number of lap layers, which is the repeating unit, is 2 (two layers).

[0043] In each of the joints 8a, 8b, 7, a gap G is provided at the butt joint between the steel plates of the same layer (11a and 11b, respectively) to absorb errors that occur during the manufacturing process of the iron core. However, strictly controlling the length of this gap G is not practical.

[0044] In this embodiment, in particular, the wrap length Lm at the connection portion 8a (part A) in the lower yoke that connects the main legs and the wrap length Ls at the connection portion 8b (part B) in the lower yoke that connects the main legs and the side legs are different lengths.

[0045] Furthermore, it is preferable that the relationship between the long and short wrap lengths Lm, Ls be determined by the high and low relationship between the average magnetic flux densities Bm and Bs generated in the main legs 1u, 1v, 1w and the side leg 2 of the three-phase five-legged core shown in Figure 1 under rated excitation conditions. Specifically, when the wrap lengths Lm and Ls are designed to be the same (Lm = Ls) as in the past, if the average magnetic flux density Bm of the main legs is higher than the average magnetic flux density Bs of the side legs, Lm is made shorter than Ls, and conversely, if the average magnetic flux density Bm of the main legs is lower than the average magnetic flux density Bs of the side legs, Lm is made longer than Ls. FIG. 3 shows one of these configurations in which the lap length Lm at the connection portion 8a (portion A) is shorter than the lap length Ls at the connection portion 8b (portion B). When the average magnetic flux density Bm of the main legs is lower than the average magnetic flux density Bs of the side legs, it is preferable to make the wrap length Lm at the connection portion 8a (part A) longer than the wrap length Ls at the connection portion 8b (part B), contrary to FIG. 3.

[0046] When the wrap length is designed to be the same (Lm = Ls), the average magnetic flux densities Bm and Bs can be calculated from the materials and dimensions of each component of the core (main legs 1u, 1v, 1w, side leg 2, yoke core 2a, 2b) and windings 9u, 9v, 9w, the amount of current flowing through the windings 9u, 9v, 9w, etc.

[0047] In addition, in FIG. 3, the lap length Ln at the connection portion 7 (part C) is set to be equal to the lap length Ls at the connection portion 8b (part B). However, the wrap length Ln at the connection portion 7 (portion C) is not particularly limited as it is not relevant to obtaining the effects of the iron core of the present invention, and may be the same length as either Lm or Ls, or may be a length different from Lm, Ls.

[0048] Next, with reference to Figs. 4 to 7, the effect of applying the configuration of this embodiment to a three-phase five-legged core with a divided lower yoke will be quantified and described using a three-dimensional electromagnetic field analysis. FIG. 4 is a front view showing the definition of the dimensions of each part of the three-phase five-legged core used in the three-dimensional electromagnetic field analysis. Table 1 shows the relative dimensions of each part, based on the diameter D of the main legs, which have a circular cross section. The side legs have an elliptical cross section with a minor diameter Ds, the yoke has an elliptical cross section with a minor diameter Dy, and the thickness of the core in the depth direction is D, the same as the diameter of the main legs.

[0049] [Table 1]

[0050] For the three-phase five-leg core model, the magnetization characteristics and iron loss characteristics of grain-oriented silicon steel sheet 30ZH105 manufactured by Nippon Steel Corporation were defined taking into consideration the magnetization easy axis direction and lamination direction. Then, windings for generating the rated magnetic flux density were set on the three main legs in the electromagnetic field analysis model, and a specified 50Hz sine wave voltage was applied to the windings. An equivalent magnetic resistance equivalent to a specified wrap length was added to the connection between the main leg or side leg and the yoke, and to the connection between the lower split yoke, reproducing the excitation impedance characteristics of a three-phase five-legged core.

[0051] Fig. 5 is a diagram showing a comparison of magnetic flux density distributions along the center (x-axis) of the three-phase five-legged core shown in Fig. 4, calculated under the above conditions. The dashed line 21 corresponds to the conventional configuration and is the calculation result when the wrap lengths Lm, Ls, and Ln of each connection part of the core shown in Fig. 3 are all set to 10 mm. The solid line 22 is the calculation result for one embodiment of this embodiment, where the wrap length Lm is set to 2 mm, and the wrap lengths Ls and Ln are set to 10 mm.

[0052] 5, according to the calculation result 21 of the conventional configuration, the magnetic flux density in the V-phase main leg 1v is higher than the magnetic flux density in the U-phase main leg 1u and the W-phase main leg 1w, and there is a bias in the distribution of the magnetic flux density between the main legs of the three phases. Furthermore, the magnetic flux density in the side legs 2 at both ends is lower than the magnetic flux density in the main legs by 5% or more, and there is a bias in the magnetic flux density for each part of the three-phase five-legged core.

[0053] In contrast, according to calculation result 22 for the configuration of this embodiment, it is recognized that the bias in magnetic flux density between the main legs of the three phases is reduced, the magnetic flux density in the side leg 2 is increased compared to calculation result 21 for the conventional configuration, and the bias in magnetic flux density of the entire iron core is also reduced. It was found that the calculated value of iron loss generated in the three-phase five-legged core in the configuration of this embodiment is 0.5% to 1.0% lower than the calculated value of iron loss generated in a three-phase five-legged core in a conventional configuration.

[0054] Next, a comparison will be made of the calculation results of the excitation current waveforms flowing through the windings wound around the above-mentioned three-phase five-legged core. Figure 6 shows the calculation results of an example current waveform when the lap lengths Lm, Ls, and Ln of each connection part of the iron core shown in Figure 3 are all set to 10 mm in a three-phase five-legged disassembled transport transformer with a conventional joint structure. In Figure 6, 31u, 31v, and 31w represent the excitation current waveforms flowing through the windings of the U phase, V phase, and W phase, respectively. Fig. 7 shows the calculation results of an example current waveform when Lm is 2 mm, Ls and Ln are 10 mm as one embodiment of the three-phase five-legged disassembled transport transformer of this embodiment. In Fig. 7, 32u, 32v, and 32w represent the excitation current waveforms flowing through the windings of the U phase, V phase, and W phase, respectively. These excitation current waveforms were obtained by determining the excitation current waveforms flowing through the high-voltage winding when the terminals of the low-voltage winding were opened and a 50 Hz sine wave voltage of the rated voltage was applied between the terminals of the high-voltage winding in an electromagnetic field analysis model in which the low-voltage winding and high-voltage winding are wound around the main legs of a three-phase five-legged core.

[0055] In the excitation current waveforms 31u, 31v, and 31w of the three-phase five-legged core corresponding to the conventional configuration shown in FIG. 6, distortion was observed in the sine wave, and harmonic components generated due to the nonlinear magnetization characteristics of the core were superimposed. In contrast, the excitation current waveforms 32u, 32v, and 32w of the three-phase five-legged core corresponding to the configuration of this embodiment shown in FIG. 7 have less superimposition of harmonic components than in FIG. 6, and provide waveforms that are closer to sine waves. Due to this effect, in the three-phase five-legged core having the configuration of this embodiment, it is expected that excitation noise will be suppressed.

[0056] The relationship between the average magnetic flux densities Bm and Bs in the main legs 1u, 1v, and 1w and the side leg 2 under rated excitation conditions varies depending on the cross-sectional area in the horizontal plane perpendicular to the direction of the magnetic flux, the distance between the main legs and the distance between the main leg and the side leg, etc. In the configuration of the first embodiment shown in FIGS. 1 and 2, the main legs 1u, 1v, and 1w have a larger cross-sectional area in the horizontal plane than the side leg 2, so that the main legs 1u, 1v, and 1w tend to have a larger average magnetic flux density than the side leg 2. However, even if the main legs 1u, 1v, and 1w have a larger cross-sectional area in the horizontal plane than the side leg 2, depending on other conditions such as the distance between the main legs and the distance between the main legs and the side leg, the average magnetic flux density of the main legs 1u, 1v, and 1w may be smaller than that of the side leg 2.

[0057] The disassembled transport transformer 10 of this embodiment can be manufactured, for example, as described below. 8A to 8C are diagrams showing a method for manufacturing the three-phase five-leg disassembled transport transformer of this embodiment.

[0058] First, in FIG. 8A, a T-shaped core component 40 formed by integrally assembling the main legs 1u, 1v, 1w and the inter-main-leg lower yoke 5a or the main leg-side leg lower yoke 6a, and an L-shaped core component 41 formed by integrally assembling the side leg 2 and the main leg-side leg lower yoke 6a are arranged side by side at a predetermined interval on the bottom tank 12 using a means such as a crane.

[0059] Next, in FIG. 8B, between the T-shaped core parts 40, and between the T-shaped core parts 40 and the L-shaped core parts 41, the main leg lower connection yokes 5b and the main leg-side leg lower connection yokes 6b are constructed by stacking steel plates, respectively, and all the core parts are connected by the lower yokes. Furthermore, the windings 9u, 9v, 9w are inserted into the main legs 1u, 1v, 1w using a means such as a crane.

[0060] Finally, in FIG. 8C, the upper yoke 3 between the main legs and the upper yoke 4 between the main legs and the side legs are formed by laminating steel plates, and all the iron core parts are connected by the upper yoke. Furthermore, after wiring components between the windings and the like are attached, an upper tank 12a that covers the entire three-phase five-legged iron core is installed, completing the manufacture of the disassembled and transported transformer.

[0061] The disassembled and transported transformer core of this embodiment is an iron core used in a disassembled and transported transformer 10. The iron core for disassembled transportation transformer of this embodiment is a three-phase five-legged iron core composed of three main legs 1u, 1v, 1w arranged in parallel, two side legs 2 arranged in parallel on both outsides of the main legs 1u, 1v, 1w, and a plurality of yokes 2a, 2b connecting the upper and lower ends of adjacent main legs 1u, 1v, 1w or side legs 2. The three main legs 1u, 1v, 1w, the two side legs 2, and the plurality of yokes 2a, 2b are each composed of multiple layers of laminated steel plates. Furthermore, among the multiple yokes 2a, 2b, the lower yoke connecting the lower ends of adjacent main legs 1u, 1v, 1w and the lower yoke connecting the lower ends of the main legs 1u, 1v, 1w and the side leg 2 are each divided into three by two division parts. At each division part, two adjacent yokes (5a and 5b, 6a and 6b) of the three divided lower yokes are connected by overlapping steel plates to form connection parts 8a, 8b. In each divided portion, the positions of opposing steel plates 11a, 11b in the same layer are shifted in the extending direction (x direction) of lower yoke core 2b in successive layers, and steel plates 11a, 11b are overlapped with a predetermined overlap length.

[0062] According to the core for the disassembled and transported transformer of this embodiment, in particular, in the connection part formed in the divided part of the lower yoke, which is composed of the lower yoke connecting adjacent main legs 1u, 1v, 1w and the lower yoke connecting the main leg and the side leg 2, the lap lengths are configured to be different lengths. Specifically, the lap length Lm of the connection part 8a (part A) connecting the lower yoke 5a between the main legs and the connection yoke 5b and the lap length Ls of the connection part 8b (part B) connecting the lower yoke 6a between the main leg and the side leg and the connection yoke 6b are different lengths. Since the lap lengths Lm and Ln of the connection parts 8a and 8b in each divided part of the lower yoke are made different according to the part of the lower yoke, the difference in the magnetic flux density for each part in the core can be adjusted by the respective lap lengths Lm and Ln. As a result, it becomes possible to reduce the iron loss generated in the core, reduce the harmonic component of the exciting current flowing through the winding wound around the main leg, and reduce the exciting noise of the core.

[0063] Also, when the average magnetic flux density Bm in the main legs 1u, 1v, 1w is higher than the average magnetic flux density Bs in the side leg 2 (Bm > Bs) under the rated exciting condition, as shown in FIG. 3, the lap length Lm in each divided part provided in the lower yoke connecting the lower end parts of the adjacent main legs can be made shorter (Lm < Ls) than the lap length Ls in each divided part provided in the lower yoke connecting the lower end parts of the main leg and the side leg. When configured in this way, since the magnetic resistance increases as the lap length becomes shorter, the difference in the magnetic flux density between the main leg and the side leg can be reduced. As a result, the iron loss generated in the core can be reduced, the harmonic component of the exciting current flowing through the winding wound around the main leg can be reduced, and the exciting noise of the core can be reduced.

[0064] Also, when the average magnetic flux density Bm in the main legs 1u, 1v, 1w is lower than the average magnetic flux density Bs in the side leg 2 (Bm < Bs) under the rated excitation condition, contrary to that shown in FIG. 3, the lap length Lm in each divided portion provided in the lower yoke connecting the lower ends of adjacent main legs is longer than the lap length Ls in each divided portion provided in the lower yoke connecting the lower ends of the main leg and the side leg (Lm > Ls). In this configuration, since the magnetic resistance decreases as the lap length increases, the difference in magnetic flux density between the main leg and the side leg can be reduced. As a result, the iron loss generated in the iron core can be reduced, the harmonic component of the exciting current flowing through the winding wound around the main leg can be reduced, and the exciting noise of the iron core can be reduced.

[0065] (Example 2) Next, the configuration of the disassembled and transported transformer of Example 2 will be described with reference to FIG. 9. FIG. 9 is an enlarged cross-sectional view of the connection portions A, B, and C between the steel plates in the three-phase five-leg iron core shown in FIG. 1. The same components as those in FIG. 3 of Example 1 are denoted by the same reference numerals, and redundant descriptions are omitted.

[0066] In this embodiment, as shown in FIG. 9, the connection portions 8a, 8b, and 7 are formed by a lap joint structure in which the positions of the opposing steel plates in the same layer of the adjacent steel plates 11a, 11b, and 11c are laminated while being shifted by a certain amount. In FIG. 9, in particular, in the lap joint structure of each connection portion 8a, 8b, and 7, the positions of the opposing steel plates in the same layer are laminated so as to be repeated in units of three layers. Hereinafter, such a laminated lap joint structure is referred to as a "three-step lap joint structure". In the three-step lap joint structure, since the positions of the opposing steel plates in the same layer are repeated in units of three layers, the number of lap steps, which is the repeating unit, is 3 (three steps).

[0067] In this embodiment, as in embodiment 1, the length relationship between the wrap length Lm of connection portion 8a (part A) and the wrap length Ls of connection portion 8b (part B) are made different in accordance with the height relationship between the average magnetic flux densities Bm and Bs in the three-phase five-legged core, thereby obtaining the same effect as in embodiment 1. FIG. 9 shows such a configuration in which the lap length Lm at the connection portion 8a (portion A) is shorter than the lap length Ls at the connection portion 8b (portion B). In FIG. 9 of this embodiment, similarly to FIG. 3 of the first embodiment, the overlap length Ln at the connection portion 7 (part C) is equal to the overlap length Ls at the connection portion 8b (part B).

[0068] Example 3 Next, the configuration of the disassembled transport transformer of the third embodiment will be described with reference to FIG. Fig. 10 is an enlarged cross-sectional view of connection parts A, B, and C between steel plates in the three-phase five-legged core shown in Fig. 1. Note that the same components as those in Fig. 3 of Example 1 and Fig. 9 of Example 2 are given the same reference numerals and redundant explanations will be omitted.

[0069] In this embodiment, as shown in Figure 10, each connection portion 8a, 8b, 7 is formed by a lap joint structure in which the positions of opposing steel plates in the same layer among adjacent steel plates 11a to 11f are stacked while being shifted by a certain amount. 10, in particular, in the lap joint structure of each of the connecting portions 8a, 8b, and 7, the positions of the opposing steel plates of the same layer are stacked so that six layers are repeated as a repeating unit. Hereinafter, the lap joint structure stacked in this way is referred to as a "six-step lap joint structure." In a six-stage step lap joint structure, the positions of opposing steel plates in the same layer are repeated every six layers as a repeating unit, so the number of lap stages, which is the repeating unit, is six (six stages).

[0070] In this embodiment, as in the first and second embodiments, the wrap length Lm of the connection portion 8a (part A) and the wrap length Ls of the connection portion 8b (part B) are set to different lengths in accordance with the high / low relationship between the average magnetic flux densities Bm and Bs in the three-phase five-legged core, thereby obtaining the same effects as in the first and second embodiments. FIG. 10 shows such a configuration in which the lap length Lm at the connection portion 8a (portion A) is shorter than the lap length Ls at the connection portion 8b (portion B). In addition, in Figure 3 of Example 1 and Figure 3 of Example 2, the wrap length Ln at the connection portion 7 (part C) is equal to the wrap length Ls at the connection portion 8b (part B), but in Figure 10 of the present embodiment, the wrap length Ln at the connection portion 7 (part C) is equal to the wrap length Lm at the connection portion 8a (part A).

[0071] Example 4 Next, the configuration of the disassembled transport transformer of the fourth embodiment will be described with reference to FIG. Fig. 11 is an enlarged cross-sectional view of connection parts A, B, and C between steel plates in the three-phase five-legged core shown in Fig. 1. Note that the same components as those in Fig. 3 of Example 1, Fig. 9 of Example 2, and Fig. 10 of Example 3 are given the same reference numerals and redundant explanations will be omitted.

[0072] In this embodiment, as shown in Fig. 11, each of the connections 8a, 8b, and 7 is configured with a lap joint structure in which the positions of opposing steel plates in the same adjacent layers are stacked while being shifted by a certain amount, as in the first to third embodiments.

[0073] However, in this embodiment, as shown in Figure 11, an example is shown in which, instead of making the lap lengths Lm, Ls of the connection parts different between connection parts 8a (part A) and connection parts 8b (part B), the number of lap stages, which is the number of layers of the repeating unit in the lap joint structure, is made different. In this embodiment, the number of wrap stages at connection portion 8a (part A) and the number of wrap stages at connection portion 8b (part B) are made different in accordance with the relationship between the average magnetic flux densities Bm and Bs in the three-phase five-legged core, thereby obtaining the same effects as in embodiments 1 to 3.

[0074] In FIG. 11, among these configurations, the connection portion 8a (portion A) has a one-step alternating stacking with two layers of wrapping, the connection portion 8b (portion B) has a six-step stepped wrap joint structure with six layers of wrapping, and the number of wrapping layers of the connection portion 8a (portion A) is less than that of the connection portion 8b (portion B).

[0075] Furthermore, it is preferable that the relationship between these numbers of wrapping layers is determined by the relationship between the levels of the average magnetic flux densities Bm and Bs generated in the main legs 1u, 1v, 1w and the side leg 2 of the three-phase five-leg core shown in FIG. 1 under the rated excitation condition. Specifically, when the number of wrapping layers is designed to be the same as before, if under the rated excitation condition, the average magnetic flux density Bm of the main leg is higher than the average magnetic flux density Bs of the side leg (Bm > Bs), then as in the configuration shown in FIG. 11, the number of wrapping layers of the connection portion 8a (portion A) related to the main legs is made less than the number of wrapping layers of the connection portion 8b (portion B) related to between the main leg and the side leg. With this configuration, since the magnetic resistance increases as the number of wrapping layers decreases, the difference in magnetic flux density between the main leg and the side leg can be reduced. As a result, the iron loss generated in the core can be reduced, the harmonic component of the exciting current flowing through the winding wound around the main leg can be reduced, and the exciting noise of the core can be reduced.

[0076] When the number of wrapping layers is designed to be the same as before, if conversely, under the rated excitation condition, the average magnetic flux density Bm of the main leg is lower than the average magnetic flux density Bs of the side leg (Bm < Bs), then the number of wrapping layers of the connection portion 8a (portion A) related to the main legs is made more than the number of wrapping layers of the connection portion 8b (portion B) related to between the main leg and the side leg. With this configuration, since the magnetic resistance decreases as the number of wrapping layers increases, the difference in magnetic flux density between the main leg and the side leg can be reduced. As a result, the iron loss generated in the core can be reduced, the harmonic component of the exciting current flowing through the winding wound around the main leg can be reduced, and the exciting noise of the core can be reduced.

[0077] In FIG. 11, the number of lap steps in the connecting portion 8a (part A) and the number of lap steps in the connecting portion 8b (part B) are a combination of a 1-step alternating stack with 2 lap steps and a 6-step step lap joint structure with 6 lap steps. In the configuration with different numbers of wrap stages, other combinations of the numbers of wrap stages may be used. For example, a three-stage step wrap structure with three wrap stages may be used for either of the connecting parts.

[0078] (Modification) In each of the above-described embodiments, only one of the wrap length or the number of wrap stages is different at connection portion 8a (part A) and connection portion 8b (part B), but it is also possible to configure both the wrap length and the number of wrap stages to be different. In particular, when the relationship between the long and short wrap lengths and the number of wrap stages are determined by the high and low average magnetic flux densities Bm and Bs of the main legs 1u, 1v, and 1w and the side leg 2 under rated excitation conditions, the effect of reducing the harmonic components of the excitation current flowing through the windings and the effect of reducing the excitation noise of the iron core can be further enhanced.

[0079] In addition, in the enlarged cross-sectional views shown in Figs. 9 and 10, in a repeating unit of the lap joint structure, the steel plates are shifted in one direction from top to bottom and from left to right in the drawings. In contrast to this, it is also possible to adopt a configuration in which the shift direction is changed alternately, such as a configuration in which the shift direction is changed in one direction from right to left from top to bottom in the figure, or a configuration in which the shift direction is changed from left to right and then from right to left, as in the configuration of parts B to D in Figure 3 of Patent Document 1. In the configuration of parts B to D in FIG. 3 of Patent Document 1, the lap joint structure in which the steel plates are shifted is repeated in the same direction for three layers, so the number of lap stages, which is the layer of the repetition unit, is three. When the configuration of parts B to D in Figure 3 of Patent Document 1 is compared with the configuration of parts B to D in Figure 4 of Patent Document 1, which is shifted in one direction from left to right, the configuration has the same number of wrap stages (3) and the magnitude of magnetic resistance at the connection part is also the same, but the number of repeated layers (period) of the steel plate positions is different.

[0080] The present invention is not limited to the above-described embodiments and examples, and includes various modified examples. For example, the above-described embodiments and examples have been described in detail to easily explain the present invention, and the present invention is not necessarily limited to those having all of the configurations described. [Explanation of symbols]

[0081] 1u, 1v, 1w: main landing gear, 2: side leg, 2a: upper yoke core, 2b: lower yoke core, 3: upper yoke between main legs, 4: upper yoke between main legs and side legs, 5a: lower yoke between main legs, 5b: lower connecting yoke between main legs, 6a: lower yoke between main legs and side legs, 6b: lower connecting yoke between main legs and side legs, 7: connection part between leg core and yoke core, 8a: connection part between main legs and lower yoke, 8b: connection part between main legs and lower yoke, 9u, 9v, 9w: windings, 10: disassembled transport transformer, 11a to 11f: grain-oriented silicon steel plate, 12: bottom tank, 12a: upper tank, 40: T-shaped core part, 41: L-shaped core part

Claims

1. A disassembled and transported transformer core used in a disassembled and transported transformer, a three-phase five-legged core including three main legs arranged in parallel, two side legs arranged in parallel with the main legs arranged on both outer sides of the three main legs, and a plurality of yokes connecting upper and lower ends of the adjacent main legs or side legs, The three main legs, the two side legs, and the plurality of yokes are each formed by laminating a plurality of layers of steel plates, Among the plurality of yokes, a lower yoke connecting lower ends of adjacent main legs and a lower yoke connecting lower ends of the main legs and the side legs are each divided by two dividing portions; In each of the division sections, the steel plates are overlapped in a state in which the positions of the opposing steel plates in the same layer are shifted in the extending direction of the lower yoke in successive layers and overlapped with a predetermined overlap length, The lap length at each of the divisions provided on a lower yoke connecting the lower ends of adjacent main legs is different from the lap length at each of the divisions provided on a lower yoke connecting the lower ends of the main leg and the side leg. Disassembled and transported transformer cores.

2. 2. An iron core for a disassembled transportation transformer according to claim 1, wherein an average magnetic flux density in all of the main legs under rated excitation conditions is higher than an average magnetic flux density in all of the side legs, and the lap length in each of the split portions provided in a lower yoke connecting the lower ends of adjacent main legs is shorter than the lap length in each of the split portions provided in a lower yoke connecting the lower ends of the main legs and the side legs.

3. 2. An iron core for a disassembled transportation transformer according to claim 1, wherein an average magnetic flux density in all of the main legs under rated excitation conditions is lower than an average magnetic flux density in all of the side legs, and the lap length in each of the split portions provided in a lower yoke connecting the lower ends of adjacent main legs is longer than the lap length in each of the split portions provided in a lower yoke connecting the lower ends of the main legs and the side legs.

4. 2. The iron core for a disassembled transport transformer according to claim 1, wherein in a lap joint structure in which the positions of the opposing steel plates of the same layer are shifted in each divided portion of the lower yoke, the number of lap stages, which is the number of layers in a unit of repeating the positions of the opposing steel plates of the same layer, is the same for all of the divided portions.

5. 2. An iron core for a disassembled transportation transformer as described in claim 1, wherein in a lap joint structure in which the positions of the opposing steel plates of the same layer are shifted in each divided portion of the lower yoke, the number of lap stages, which is the number of layers in a unit of repeating positions of the opposing steel plates of the same layer, is set to an arbitrary different value depending on the portion of the lower yoke.

6. A disassembled and transported transformer core used in a disassembled and transported transformer, a three-phase five-legged core including three main legs arranged in parallel, two side legs arranged in parallel with the main legs arranged on both outer sides of the three main legs, and a plurality of yokes connecting upper and lower ends of the adjacent main legs or side legs, The three main legs, the two side legs, and the plurality of yokes are each formed by laminating a plurality of layers of steel plates, Among the plurality of yokes, a lower yoke connecting lower ends of adjacent main legs and a lower yoke connecting lower ends of the main legs and the side legs are each divided by two dividing portions; In each of the divided portions, the positions of the opposing steel plates in the same layer are shifted in the extending direction of the lower yoke in the consecutive layers, and the steel plates are overlapped with a predetermined overlap length, and the steel plates have a lap joint structure, In the lap joint structure of each of the divided parts, the positions of the steel plates facing each other in the same layer are repeated with a predetermined number of lap stages as a repeating unit, The number of lap stages in each of the divisional sections provided on a lower yoke connecting the lower ends of adjacent main legs is different from the number of lap stages in each of the divisional sections provided on a lower yoke connecting the lower ends of the main leg and the side leg. Disassemble and transport transformer cores.

7. 7. A disassembled transportation transformer core according to claim 6, wherein an average magnetic flux density in all of the main legs under rated excitation conditions is higher than an average magnetic flux density in all of the side legs, and the number of wrap stages in each of the split sections provided in a lower yoke connecting the lower ends of adjacent main legs is smaller than the number of wrap stages in each of the split sections provided in a lower yoke connecting the lower ends of the main legs and the side legs.

8. 7. A disassembled transportation transformer core according to claim 6, wherein an average magnetic flux density in all of the main legs under rated excitation conditions is lower than an average magnetic flux density in all of the side legs, and the number of wrap stages in each of the split sections provided in a lower yoke connecting the lower ends of adjacent main legs is greater than the number of wrap stages in each of the split sections provided in a lower yoke connecting the lower ends of the main legs and the side legs.

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