JP2025018338A - Disassembled and transported transformer cores - Google Patents

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

The present invention relates to an iron core for a disassembled transport transformer.

One type of large-capacity transformer is known as a disassembled and transported transformer, which is manufactured, assembled, tested, and inspected in a factory, then disassembled into multiple parts that meet transportation constraints, transported to the installation site, and reassembled, tested, and inspected.

The iron core for disassembled and transported transformers is constructed by laminating oriented silicon steel sheets, etc., in order to minimize the reassembly work required 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.

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 cores 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 are the repeating unit of the lap joint structure, in order to suppress deterioration in the performance of the disassembled transport transformer.

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

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 to each other is constructed by laminating directional silicon steel plates, resulting in a core for a transformer that is disassembled and transported.

JP 2012-15210 A JP 2010-272786 A

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.

In addition, in order to prevent a decrease in the performance of the transformer, Patent Document 1 discloses a range for setting the lap length and number of lap stages between the directional silicon steel sheets at the connection part of the divided core, but the structure of the connection part of each divided core is all the same, so the effect of preventing a decrease in performance is limited.

To solve the above problems, the present invention provides an iron core for a disassembled and transported transformer that can prevent the performance of the disassembled and transported transformer from deteriorating.

The above and other objects of the present invention, as well as the novel features of the present invention, will become apparent from the description in this specification and the accompanying drawings.

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 connecting the lower ends of adjacent main legs and the lower yokes connecting the lower ends of the main legs and side legs are each divided by two dividing sections.

The first iron core for disassembled transport transformers of the present invention further has steel plates overlapped in each division such that the positions of opposing steel plates in the same layer are shifted in the extension direction of the lower yoke in successive layers, overlapping with a predetermined lap length. The first iron core for disassembled transport transformers of the present invention is configured such that the lap length in each division provided on the lower yoke connecting the lower ends of adjacent main legs is different from the lap length in each division provided on the lower yoke connecting the lower ends of the main legs and side legs.

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 the opposing steel plates in the same layer are shifted in the extension direction of the lower yoke in successive layers and overlapped with a predetermined lap length, and in the lap joint structure of each divided section, the positions of the 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 section provided in the lower yoke connecting the lower ends of adjacent main legs is different from the number of lap stages in each divided section provided in the lower yoke connecting the lower ends of the main legs and the side legs.

According to the configuration of the first present invention, the three-phase five-legged core for a transformer for disassembled transportation has a lower yoke that connects adjacent main legs and a lower yoke that connects the main legs and side legs, with different lap lengths in each divided section.
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.

According to the configuration of the second present invention of the 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.

Note that issues, configurations, and advantages other than those described above will become clear from the explanation of the embodiments below.

FIG. 2 is a front view of the disassembled transport transformer of the first embodiment. FIG. 2 is a bottom view of the disassembled transport transformer of the first embodiment. 2 is an enlarged cross-sectional view of a portion A, a portion B, and a portion C in FIG. 1. 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. 11 is a diagram comparing calculation results of magnetic flux density distribution in the center portion of a three-phase five-legged iron core between Example 1 and a conventional configuration. 1 is a calculation result of the excitation current waveform of a three-phase five-legged disassembled transport transformer with a conventional joint structure. 1 is a calculation result of an excitation current waveform of a three-phase five-leg type disassembled transport transformer of Example 1. 1A to 1C are diagrams showing a method for manufacturing a three-phase five-legged disassembled transport transformer of Example 1. 10 is an enlarged cross-sectional view of parts A, B, and C of the disassembled transport transformer of Example 2. 11 is an enlarged cross-sectional view of parts A, B, and C of the disassembled transport transformer of Example 3. 10 is an enlarged cross-sectional view of parts A, B, and C of the disassembled transport transformer of Example 4.

The following describes the embodiments and examples of the present invention using text and drawings. However, the structures, materials, and various other specific configurations shown in the present invention are not limited to the embodiments and examples discussed here, and can be combined or improved as appropriate without changing the gist of the invention. In addition, elements that are not directly related to the present invention are not shown in the figures.

The disassembled transport transformer iron core of the present invention is an iron core used in a disassembled transport transformer.
The iron core for a disassembled and transported 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 plate. 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.

The first iron core for disassembled transport transformers of the present invention further has steel plates overlapped in each division such that the positions of opposing steel plates in the same layer are shifted in the extension direction of the lower yoke in successive layers, overlapping with a predetermined lap length. The first iron core for disassembled transport transformers of the present invention is configured such that the lap length in each division provided on the lower yoke connecting the lower ends of adjacent main legs is different from the lap length in each division provided on the lower yoke connecting the lower ends of the main legs and side legs.

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 the opposing steel plates in the same layer are shifted in the extension direction of the lower yoke in successive layers and overlapped with a predetermined lap length, and in the lap joint structure of each divided section, the positions of the 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 section provided in the lower yoke connecting the lower ends of adjacent main legs is different from the number of lap stages in each divided section provided in the lower yoke connecting the lower ends of the main legs and the side legs.

According to the configuration of the first present invention, the three-phase five-legged core for a transformer for disassembled transportation has a lower yoke that connects adjacent main legs and a lower yoke that connects the main legs and side legs, with different lap lengths in each divided section.
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.

According to the configuration of the second present invention of the 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.

In each of the above-mentioned configurations of the iron core for the disassembled transport transformer of the present invention, the steel plate constituting the iron core can be, for example, any of the various steel plates used in disassembled transport transformers, such as oriented silicon steel plate.

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 is higher than the average magnetic flux density in all side legs, and the lap length in each split portion provided on the lower yoke connecting the lower ends of adjacent main legs is shorter than the lap length in each split portion provided on 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.

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 divided portion provided on the lower yoke connecting the lower ends of adjacent main legs can be longer than the lap length in each divided portion provided on 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.

In the first present invention of the disassembled transport transformer core, in the lap joint structure in which the positions of opposing steel plates in 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 the repeating positions of opposing steel plates in the same layer, can all be configured to be the same.

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 the positions of opposing steel plates of the same layer, can be configured to be any different value depending on the portion 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.

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 is higher 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 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 the 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.

In the above-mentioned second present invention of the disassembled transport 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 on 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 on 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.

Next, we will explain a specific example of a disassembled transport transformer using a disassembled transport transformer core.

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 a 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.

The disassembled transport transformer 10 shown in Figure 1 is constructed 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 the ends of both outer sides of the main legs are arranged in parallel with their longitudinal direction in the y direction.

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 which connects the upper ends of adjacent main legs, and an inter-main-leg-to-side-leg upper yoke 4 which 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 dividing portions 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 the side legs is divided at two dividing portions into two inter-main-leg lower yokes 6a and an intermediate inter-main-leg lower connecting yoke 6b.

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, 4 that constitute the upper yoke core 2a, and the yokes 5a, 5b, 6a, 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.

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 stacking the steel plates of both with a predetermined lap length and a predetermined number of lap stages.
The lower yoke between the main legs 5a and the connecting yoke 5b are connected at two divided portions by a connecting portion 8a formed by laminating steel plates with a predetermined lap length and a predetermined number of lap stages.
The main leg-side leg lower yoke 6a and the connecting yoke 6b are connected at two divided portions by connecting portions 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.

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.

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, and depending on the use of the transformer, medium-voltage windings, tap windings, etc. may be further wound in layers to form the 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.

Figure 3 shows an enlarged cross-sectional view of parts A, B, and C in the core of the three-phase five-legged disassembled transport transformer 10 shown in Figure 1. Part A shows the connection part 8a that connects the lower yoke 5a between the main legs and the connecting yoke 5b. Part B shows the connection part 8b that connects the lower yoke 6a between the main legs and the side legs and the connecting yoke 6b. Part C shows the connection part 7 that connects the main legs 1u, 1v, 1w or the side legs 2 to the yoke cores 2a, 2b.

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

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 alternated for each layer. Hereinafter, such a lap joint structure is referred to as "one-stage alternating stacking."
In a one-stage alternating-stack 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 stages, which is the repeating unit, is two (two stages).

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.

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

Furthermore, it is preferable that the relationship between the long and short overlap lengths Lm, Ls be determined by the high and low 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 iron 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 overlap length Lm at the connection portion 8a (portion A) is shorter than the overlap length Ls at the connection portion 8b (portion B).
When the average magnetic flux density Bm of the main leg is lower than the average magnetic flux density Bs of the side leg, 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.

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

In addition, in FIG. 3, the overlap length Ln at the connection portion 7 (part C) is set to be equal to the overlap 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 effect 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.

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 explained using 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.
The relative dimensional values of each part, based on the diameter D of the main legs, which have a circular cross section, are listed in Table 1. 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, which is the same as the diameter of the main legs.

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 on the electromagnetic field analysis model, and a predetermined 50 Hz 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.

Figure 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 Figure 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 Figure 3 are all 10 mm. The solid line 22 is the calculation result when, as one embodiment of this embodiment, the wrap length Lm is 2 mm, and the wrap lengths Ls and Ln are 10 mm.

From Figure 5, calculation results 21 for the conventional configuration show that 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 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 5% or more lower than the magnetic flux density in the main legs, and there is a bias in the magnetic flux density for each part of the three-phase five-legged core.

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

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.
Fig. 6 shows the calculation results of an example current waveform when all of the overlap lengths Lm, Ls, and Ln of each connection part of the iron core shown in Fig. 3 are set to 10 mm in a three-phase five-legged disassembled transport transformer with a conventional joint structure. In Fig. 6, 31u, 31v, and 31w represent the excitation current waveforms flowing through each winding of the U phase, V phase, and W phase, respectively.
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 the high-voltage winding are wound around the main legs of a three-phase five-legged core.

In the excitation current waveforms 31u, 31v, and 31w of the three-phase five-legged iron 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 iron 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 a waveform closer to a sine wave is obtained.
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.

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, it is possible that the average magnetic flux density of the main legs 1u, 1v, and 1w will be smaller than that of the side leg 2.

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-legged disassembled transport transformer of this embodiment.

First, in FIG. 8A, a T-shaped core part 40 in which the main legs 1u, 1v, 1w and the lower yoke between the main legs 5a or the lower yoke between the main legs and the side legs 6a are assembled together, and an L-shaped core part 41 in which the side legs 2 and the lower yoke between the main legs and the side legs 6a are assembled together are arranged side by side at a specified interval on the bottom tank 12 using a crane or other means.

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 yoke 5b and the main leg-side leg lower connection yoke 6b are constructed by stacking steel plates, respectively, and all the core parts are connected by the lower yokes.
Furthermore, the windings 9u, 9v, and 9w are inserted into the main legs 1u, 1v, and 1w using a means such as a crane.

Finally, in FIG. 8C, the main leg upper yoke 3 and the main leg-side leg upper yoke 4 are constructed 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.

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 made up 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 made up 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. In 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 the opposing steel plates 11a, 11b in the same layer are shifted in the extending direction (x direction) of the lower yoke core 2b in successive layers, and the steel plates 11a, 11b are overlapped with a predetermined overlap length.

According to the disassembled-transport transformer core of this embodiment, in particular, the lower yoke connecting adjacent main legs 1u, 1v, 1w and the lower yoke connecting the main legs and side leg 2 are configured to have different wrap lengths at the connection portions formed in the divided parts of the lower yoke.
Specifically, the lap length Lm of the connection portion 8a (part A) connecting the inter-main leg lower yoke 5a and the connecting yoke 5b and the lap length Ls of the connection portion 8b (part B) connecting the inter-main leg-side leg lower yoke 6a and the connecting yoke 6b are different lengths.
Since the overlap lengths Lm, Ln of the connecting parts 8a, 8b in each divided part of the lower yoke are different depending on the part of the lower yoke, the difference in magnetic flux density in each part inside the iron core can be adjusted by the overlap lengths Lm, Ln. This reduces the iron loss generated in the iron core, and makes it 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.

Furthermore, under rated excitation conditions, 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 legs 2 (Bm>Bs), as shown in Figure 3, the overlap length Lm at each divided portion provided in the lower yoke connecting the lower ends of adjacent main legs can be shorter than the overlap length Ls at each divided portion provided in the lower yoke connecting the lower ends of the main legs and side legs (Lm<Ls).
With this configuration, the shorter the wrap length, the greater the magnetic resistance, so the difference in magnetic flux density between the main leg and the side leg can be reduced, thereby reducing the iron loss generated in the core and the harmonic components of the excitation current flowing through the winding wound around the main leg, thereby reducing the excitation noise of the core.

Furthermore, under rated excitation conditions, 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 legs 2 (Bm<Bs), the configuration can be such that, contrary to what is shown in FIG. 3, the overlap length Lm at each divided portion provided in the lower yoke connecting the lower ends of adjacent main legs is longer than the overlap length Ls at each divided portion provided in the lower yoke connecting the lower ends of the main legs and side legs (Lm>Ls).
With this configuration, the longer the wrap length, the smaller the magnetic resistance, so the difference in magnetic flux density between the main leg and the side leg can be reduced, which 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.

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

In this embodiment, as shown in Figure 9, 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 of adjacent steel plates 11a, 11b, 11c are stacked while being shifted by a certain amount.
9, 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 three layers are repeated as a repeating unit. Hereinafter, the lap joint structure stacked in this way is referred to as a "three-step lap joint structure."
In a three-stage step lap joint structure, the positions of opposing steel plates in the same layer are repeated with three layers as a repeating unit, so the number of lap stages, which is the repeating unit, is three (three stages).

In this embodiment, as in the first embodiment, the overlap length Lm of connection portion 8a (portion A) and the overlap length Ls of connection portion 8b (portion 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 effect as in the first embodiment.
FIG. 9 shows such a configuration in which the overlap length Lm at the connection portion 8a (portion A) is shorter than the overlap 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).

Example 3
Next, the configuration of the disassembly 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 iron core shown in Fig. 1. Note that the same components as those in Fig. 3 of the first embodiment and Fig. 9 of the second embodiment are given the same reference numerals, and duplicated explanations will be omitted.

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 of 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 the 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).

In this embodiment, as in the first and second embodiments, the overlap length Lm of connection portion 8a (portion A) and the overlap length Ls of connection portion 8b (portion 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 overlap length Lm at the connection portion 8a (portion A) is shorter than the overlap length Ls at the connection portion 8b (portion B).
In FIG. 3 of Example 1 and FIG. 3 of Example 2, the lap length Ln at the connection portion 7 (part C) is equal to the lap length Ls at the connection portion 8b (part B), but in FIG. 10 of the present embodiment, the lap length Ln at the connection portion 7 (part C) is equal to the lap length Lm at the connection portion 8a (part A).

Example 4
Next, the configuration of the disassembly 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 the first embodiment, Fig. 9 of the second embodiment, and Fig. 10 of the third embodiment are given the same reference numerals, and duplicated explanations will be omitted.

In this embodiment, as shown in FIG. 11, each connection portion 8a, 8b, 7 is formed by a lap joint structure in which the positions of the opposing steel plates of the same adjacent layers are stacked while being shifted by a certain amount. This is the same as in embodiments 1 to 3.

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 (portion A) and the number of wrap stages at connection portion 8b (portion 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 achieving the same effects as in embodiments 1 to 3.

Figure 11 shows a configuration in which the connection part 8a (part A) has a single alternating layer with two lap stages, and the connection part 8b (part B) has a six-stage step lap joint structure with six lap stages, with the number of lap stages in the connection part 8a (part A) being less than the number of lap stages in the connection part 8b (part B).

Furthermore, it is preferable that the relationship between these numbers of wrap stages be determined by the relationship between the levels of average magnetic flux densities Bm and Bs under rated excitation conditions, which are generated in the main legs 1u, 1v, and 1w and the side leg 2 of the three-phase five-legged core shown in FIG. 1.
Specifically, when the number of wrap stages is designed to be the same 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 (Bm>Bs) under rated excitation conditions, the number of wrap stages of the connection part 8a (part A) between the main legs is made smaller than the number of wrap stages of the connection part 8b (part B) between the main legs and the side legs, as in the configuration shown in Figure 11.
With this configuration, the fewer 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, thereby reducing the iron loss generated in the core and the harmonic components of the excitation current flowing through the winding wound around the main leg, thereby reducing the excitation noise of the core.

When the number of wrap stages is designed to be the same as before, if, conversely, the average magnetic flux density Bm of the main legs becomes lower than the average magnetic flux density Bs of the side legs (Bm<Bs) under rated excitation conditions, the number of wrap stages of the connection part 8a (part A) between the main legs is made greater than the number of wrap stages of the connection part 8b (part B) between the main leg and the side leg.
With this configuration, 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, thereby reducing the iron loss generated in the core and the harmonic components of the excitation current flowing through the winding wound around the main leg, thereby reducing the excitation noise of the core.

In Figure 11, a combination of a one-stage alternating stack with two lap stages and a six-stage step lap joint structure with six lap stages is adopted for the number of lap stages of the connection portion 8a (part A) and the number of lap stages of the connection portion 8b (part B).
In the configuration with different numbers of wrap stages, other combinations of the numbers of wrap stages may be adopted. For example, a three-stage step wrap structure with three wrap stages may be adopted for either of the connecting portions.

(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.

In addition, in the enlarged cross-sectional views shown in Figs. 9 and 10, in the 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 the 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 Figure 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 repeating 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.

The present invention is not limited to the above-described embodiments and examples, but includes various modifications. For example, the above-described embodiments and examples have been described in detail to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all of the configurations described.

1u, 1v, 1w: main legs, 2: side legs, 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 between leg core and yoke core, 8a: connection between lower yoke between main legs, 8b: connection between lower yoke between main legs and side legs, 9u, 9v, 9w: windings, 10: disassembled transport transformer, 11a-11f: directional silicon steel plate, 12: bottom tank, 12a: upper tank, 40: T-shaped core part, 41: L-shaped core part

Claims (8)

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,
An iron core for a disassembled and transported transformer, in which the overlap length at each of the divided portions provided on a lower yoke connecting the lower ends of adjacent main legs and the overlap length at each of the divided portions provided on a lower yoke connecting the lower ends of the main legs and the side legs are different lengths. The iron core for a disassembled transport transformer according to claim 1, wherein the average magnetic flux density in all of the main legs under rated excitation conditions is higher than the average magnetic flux density in all of the side legs, and the lap length in each of the split sections provided on the lower yoke connecting the lower ends of adjacent main legs is shorter than the lap length in each of the split sections provided on the lower yoke connecting the lower ends of the main legs and the side legs. The iron core for a disassembled transport transformer according to claim 1, wherein the average magnetic flux density in all of the main legs under rated excitation conditions is lower than the average magnetic flux density in all of the side legs, and the lap length in each of the split sections provided on the lower yoke connecting the lower ends of adjacent main legs is longer than the lap length in each of the split sections provided on the lower yoke connecting the lower ends of the main legs and the side legs. The iron core for disassembled transport transformer according to claim 1, in which the number of lap stages, which is the number of layers in the unit of the repeating positions of the opposing steel plates of the same layer, is the same in the lap joint structure in which the positions of the opposing steel plates of the same layer are shifted in each of the divided parts of the lower yoke. The iron core for disassembled transport transformer according to claim 1, in which the number of lap stages, which is the number of layers in the unit of the repeating positions of the opposing steel plates of the same layer in the lap joint structure in which the positions of the opposing steel plates of the same layer are shifted in each of the divided parts of the lower yoke, is set to an arbitrary different value depending on the part of the lower yoke. 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,
A core for a disassembled and transported transformer, in which the number of lap stages in each of the divided 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 divided sections provided on a lower yoke connecting the lower ends of the main legs and each of the side legs. The iron core for a disassembled transport transformer according to claim 6, wherein the average magnetic flux density in all of the main legs under rated excitation conditions is higher than the average magnetic flux density in all of the side legs, and the number of wrap stages in each of the divisions provided on the lower yoke connecting the lower ends of the adjacent main legs is less than the number of wrap stages in each of the divisions provided on the lower yoke connecting the lower ends of the main legs and the side legs. The iron core for disassembled transport transformer according to claim 6, wherein the average magnetic flux density in all of the main legs under rated excitation conditions is lower than the average magnetic flux density in all of the side legs, and the number of wrap stages in each of the divisions provided on the lower yoke connecting the lower ends of adjacent main legs is greater than the number of wrap stages in each of the divisions provided on the lower yoke connecting the lower ends of the main legs and the side legs.

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