JP7632411B2 - Three-phase, three-legged wound core and three-phase, three-legged wound core transformer using the same - Google Patents

Description

The present invention relates to a three-phase three-legged wound core and a three-phase three-legged wound core transformer using the same, and in particular to a three-phase three-legged wound core for a transformer manufactured using grain-oriented electromagnetic steel sheets and a three-phase three-legged wound core transformer using the wound core.

Grain-oriented electrical steel sheets, which have a crystal structure in which the <001> orientation, the easy axis of magnetization of iron, is highly aligned in the rolling direction of the steel sheet, are used particularly as iron core materials for power transformers. The first characteristic required of grain-oriented electrical steel sheets is low iron loss, which is the loss caused when excited. Magnetic domain refinement is a technology for reducing iron loss. Magnetic domain refinement is a technology for reducing iron loss by irradiating the surface of a steel sheet with a laser, plasma jet, electron beam, etc. to generate magnetic domains called closure domains on the surface of the steel sheet. The closure domains are generated along the easy magnetization direction of the electrical steel sheet. Normally, the <001> orientation is concentrated in the rolling direction, but the <100> and <010> orientations, which are equivalent to this orientation and perpendicular to it, are also easy magnetization directions. These two orientations are a composite component of the direction perpendicular to the rolling direction and the sheet thickness direction. Since the closure domains are generated along these orientations, they are magnetic domains with components in the direction perpendicular to the rolling direction and the sheet thickness direction.

Transformers are broadly classified into wound core transformers and stacked core transformers based on their core structure. A wound core transformer has a core formed by winding and stacking steel sheets. On the other hand, a stacked core transformer has a core formed by stacking steel sheets cut to a specific shape. There are various characteristics required for a transformer core, but the most important are low iron loss and low noise.

In order to reduce transformer iron loss, it is generally believed that it is necessary to reduce the iron loss (material iron loss) of the grain-oriented electromagnetic steel sheet, which is the core material. Using electromagnetic steel sheet with magnetic domain refinement as the core material also reduces transformer iron loss. However, it is known that in transformer cores, especially wound-core transformers with three-phase excitation and three- or five-legged electromagnetic steel sheets, the iron loss in the transformer is larger than the material iron loss. The value obtained by dividing the iron loss value (transformer iron loss) when electromagnetic steel sheet is used as the transformer core by the iron loss value of the material obtained by the Epstein test or single sheet magnetic measurement test (SST test) is generally called the building factor (BF). In other words, in three-phase excitation wound-core transformers with three or five legs, the BF generally exceeds 1.

It is generally believed that the concentration of magnetic flux in the inner core, which occurs mainly due to differences in magnetic path length, is the reason why transformer iron loss in wound core transformers increases compared to material iron loss. Figure 1 shows a schematic diagram of the magnetic flux flow at the moment when a three-legged wound core transformer is excited in three phases and only the left leg and the center leg are excited. When the inner core 1 and the outer core 2 are both excited, the magnetic path of the inner core 1 is shorter than that of the outer core 2, so the magnetic flux is concentrated in the inner core 1. When the excitation magnetic flux density becomes relatively large, the inner core 1 alone cannot support the excitation, and more magnetic flux also passes through the outer core 2, alleviating the concentration of magnetic flux. However, as shown in Figure 1, the magnetic flux passing through the outer core 2 flows toward the non-excited right leg, and when it tries to return to the excited center leg, the magnetic flux passes through the inner core 1, resulting in an interlayer magnetic flux crossover 3 between the inner core 1 and the outer core 2. Magnetization perpendicular to the surface creates in-plane eddy current loss, which increases the transformer's iron loss.

The noise generated by transformers is generally due to magnetostriction, which is the distortion that occurs when electromagnetic steel sheets are magnetized, the inherent vibration of the iron core, and electromagnetic vibration caused by magnetized steel sheets. Of these, electromagnetic vibration caused by magnetized steel sheets refers to minute vibrations that occur when magnetization changes over time in the case of AC excitation, and the attractive force between stacked steel sheets also changes over time. In-plane magnetization, such as the interlayer magnetic flux transfer 3 that occurs between the inner core 1 and outer core 2, also changes the attractive force between the steel sheets, causing electromagnetic vibration, which is one of the causes of transformer noise.

Based on a qualitative understanding of the factors that increase transformer iron loss and transformer noise, the following have been proposed as measures to reduce transformer iron loss and transformer noise:

Patent Document 1 discloses that transformer iron loss can be effectively reduced by arranging an electromagnetic steel sheet with inferior magnetic properties to the outer periphery side, where the magnetic path length is short and the magnetic resistance is small, and an electromagnetic steel sheet with superior magnetic properties to the inner periphery side, where the magnetic path length is long and the magnetic resistance is large. Patent Document 2 discloses that transformer noise can be effectively reduced by arranging a wound core wound with grain-oriented silicon steel sheet on the inner part and winding a magnetic material with lower magnetostriction than the grain-oriented silicon steel sheet on the outside of this wound core to form a combined core. Patent Document 3 discloses a technology that can reduce iron loss by providing a wrap part and performing a magnetic domain refinement process only on the wrap part of a transformer core that is laminated and wound. In addition, Patent Document 4 discloses a technology related to a wound core called Unicore, in which the distortion of the iron core is reduced by individually bending and assembling the iron core material, and the distortion relief annealing performed after the iron core is formed is unnecessary, and a magnetic domain refinement material with low iron loss due to thermal distortion can be used as the iron core material.

JP 2010-87536 A Japanese Patent Application Publication No. 3-268311 International Publication No. 2020/121691 JP 2021-163943 A JP 2011-75297 A

As disclosed in Patent Documents 1 and 2, by utilizing the concentration of magnetic flux on the inner core and applying different materials to the inner and outer cores, it is possible to efficiently improve the transformer characteristics. However, as disclosed in Patent Document 3, when the excitation magnetic flux density increases, magnetic flux also flows to the outside of the core where loss is large, and the effect of improving the transformer characteristics is reduced. In addition, at this time, the magnetic flux passing through the outer core passes to the inner core, and this interlayer magnetic flux transfer not only increases eddy current loss in the interlayer magnetic flux transfer section, but also increases noise due to electromagnetic vibration between the steel sheets, which are the material, and the transformer characteristics are significantly deteriorated. Even if a low-loss magnetic domain-refined material is used for the core material as in Patent Document 4, the iron loss of the iron core increases due to the above-mentioned interlayer magnetic flux transfer when a three-phase three-legged wound core is used.

The present invention aims to provide a three-phase, three-legged core that uses grain-oriented electromagnetic steel sheet that has been subjected to a magnetic domain refining process by introducing thermal distortion as the core material, and that has excellent iron loss reduction and noise reduction effects.

In three-phase, three-limbed wound core transformers, the transformer iron loss can be reduced by using a low-loss material that has been treated with magnetic domain refinement as the core material, but the complex magnetization state inside the core, typified by the occurrence of magnetic flux transfer, deteriorates the transformer iron loss, and the improvement in transformer iron loss is smaller than the improvement in iron loss of the core material due to magnetic domain refinement. By suppressing magnetic flux transfer from the outer core to the inner core and inhibiting the occurrence of eddy current loss, it is possible to reduce this difference in improvement, further reduce transformer iron loss, and further suppress transformer noise, and methods for achieving this were investigated.

Since magnetic flux transfer is the transfer of magnetic flux in the thickness direction from the outer core to the inner core of a three-phase, three-legged wound core transformer, it was thought that magnetic flux transfer could be suppressed by reducing the amount of magnetic flux flowing in the thickness direction in the area where magnetic flux transfer occurs. Therefore, the inventors attempted to reduce the magnetic flux that passes from the outer core to the inner core of the transformer core.

As mentioned above, in grain-oriented electrical steel sheets that have been subjected to domain refinement by thermal strain, closure domains with components in the direction perpendicular to the rolling direction and in the sheet thickness direction are formed in the thermal strain-introduced areas. The closure domains reduce the iron loss of the steel sheet as a whole, but when considered as a transformer core material, the closure domains promote magnetic flux transfer, which is magnetization in the sheet thickness direction, and there is a problem in that they locally increase transformer iron loss. Therefore, in order to investigate the effect of closure domains on magnetic flux transfer, a three-phase three-legged wound core was manufactured using material that had not been subjected to domain refinement by thermal strain only in the interlayer magnetic flux transfer areas where magnetic flux transfer occurs in the transformer core, and experiments were conducted to investigate the magnetic flux transfer area iron loss, transformer iron loss, and transformer noise. The details of the experiment are explained below.

A three-phase three-legged wound core was produced in the wound core shape shown in FIG. 2 using a grain-oriented electromagnetic steel sheet with a magnetic flux density B8 of 1.92 T at 800 A/m, which was subjected to magnetic domain refinement treatment by thermal strain introduction by irradiating the steel sheet surface with a laser with a steel strip width of 150 mm. This three-phase three-legged wound core is composed of two adjacent inner cores 10 made using the above-mentioned core material and one outer core 12 surrounding the two inner cores 10. It is also a unicore with bent parts (bent parts) at each corner. The magnetic domain refinement treatment by thermal strain introduction was applied to the entire sheet width (full width) of the steel sheet. In addition, in the region (interlayer magnetic flux crossing part) 4 where magnetic flux crossing occurs between the outer core and the inner core between the legs when assembled into a wound core, the magnetic domain refinement treatment by thermal strain introduction was not applied to the region forming the non-processed part 5 described later. As shown in FIG. 2, in the present invention, the interlayer magnetic flux crossing portion 4 is the region between adjacent legs 6 (between adjacent legs 6) when the wound core is viewed from the side. More specifically, the length f of the interlayer magnetic flux crossing portion 4 is defined as the length between adjacent legs 6. The thickness g of the interlayer magnetic flux crossing portion 4 is defined as the sum of the thickness e of the outer core from the adjacent portion 8, which is the point where the inner core 10 and the outer core 12 contact at the center position (center position between legs) 7 between the adjacent legs 6, to the outside, and the thickness e' of the inner core from the adjacent portion 8 to the inside. In this specification, the side view refers to the view of the wound core in a direction perpendicular to the winding direction of the grain-oriented electromagnetic steel sheet, i.e., in the width direction of the long grain-oriented electromagnetic steel sheet that constitutes the wound core.

In the interlayer magnetic flux transfer section 4, a region (also referred to as "non-treated section" in this specification) 5 formed of directional magnetic steel sheet that has not been subjected to magnetic domain refinement treatment by thermal strain introduction was formed. Specifically, the non-treated section 5 is a region having a thickness of L in the outward direction from the adjacent section 8 of the outer core and the inner core, and a region having a thickness of M in the inward direction from the adjacent section 8 (the region shown by hatching in FIG. 2). The thicknesses of L and M of the non-treated section 5 were adjusted by changing the number of stacks in the thickness direction of the wound core of the core material having a region that has not been subjected to magnetic domain refinement treatment by thermal strain introduction. Then, three-phase three-legged wound core transformers with different thicknesses of L and M of the non-treated section 5 were manufactured, and three-phase excitation of 50 Hz and 1.7 T was performed, and iron loss and noise measurements were performed for each three-legged wound core transformer. At the same time as measuring the iron loss, as disclosed in Patent Document 5, an infrared camera was used to measure the average temperature rise of the interlayer magnetic flux transfer section 4 on the end face of the iron core during excitation, and it was confirmed that the iron loss had actually increased locally in the interlayer magnetic flux transfer section 4. Then, the local iron loss of the interlayer magnetic flux transfer section 4 was measured.

The transformer noise was measured for each wound core transformer during excitation at 1/2 the core height d, at a distance of 30 cm from the surface of the wound core transformer, and at eight points surrounding the wound core transformer, and the average value was taken as the transformer noise.

The transformer iron loss was calculated by winding 50 turns on both the primary and secondary sides of each of the three-phase three-legged wound cores, performing three-phase excitation under conditions of a maximum excitation magnetic flux density of 1.7 T and a frequency of 50 Hz, measuring the primary current and secondary voltage with a wattmeter, calculating the no-load loss, and dividing by the weight of the core. Table 1 shows the values of transformer iron loss, transformer noise, and iron loss in the interlayer magnetic flux transfer section 4 (average iron loss in the interlayer magnetic flux transfer section 4) for each wound core transformer manufactured by changing the thickness of L and M of the non-processing section 5.

By providing the interlayer magnetic flux transfer section 4 with a region (non-treated section) 5 formed of directional magnetic steel sheet that has not been subjected to magnetic domain refinement treatment by introducing thermal strain, it was found that the transformer iron loss, transformer noise, and interlayer magnetic flux transfer section iron loss are significantly reduced compared to a wound core transformer (No. 1 in Table 1) in which the entire core is made of directional magnetic steel sheet that has been subjected to magnetic domain refinement treatment by introducing thermal strain. In particular, when the thickness of the non-treated section 5 is 20% or more of the thickness of both the outer core and the inner core, it was found that the effect of suppressing interlayer magnetic flux transfer is further enhanced, and the effect of reducing both transformer iron loss and transformer noise is further enhanced. It is presumed that the decrease in iron loss in the interlayer magnetic flux transfer section 4 is a result of reflecting the decrease in the amount of magnetic flux transfer in the interlayer magnetic flux transfer section 4.

In a three-phase three-legged core, magnetic flux transfer occurs from the inside of the outer core, which has a longer magnetic path, to the outside of the inner core, which has a shorter magnetic path. Grain-oriented electrical steel sheets are materials that increase the magnetic permeability in the rolling direction and are specialized for magnetization only in the rolling direction, so magnetic flux transfer, which is magnetization in the thickness direction, increases iron loss because it is magnetization in the direction of low magnetic permeability in grain-oriented electrical steel sheets. In addition, eddy currents flowing on the rolled surface of grain-oriented electrical steel sheets also lead to an increase in eddy current loss. The return magnetic domains formed by magnetic domain refinement have a component in the thickness direction of grain-oriented electrical steel sheets, so they increase the magnetic permeability in the thickness direction and promote interlayer magnetic flux transfer. The amount of magnetic flux attempting to flow from the outer core to the inner core increases if the magnetic permeability in the thickness direction of the magnetic flux transfer part of the outer core is high, and if the magnetic permeability in the thickness direction of the inner core is high, the amount of transfer magnetic flux that the inner core can accept increases. Therefore, by applying a material that has not been subjected to a magnetic domain refinement treatment by introducing thermal strain to the region where magnetic flux transfer occurs in the outer core, the increase in magnetic permeability is suppressed and the magnetic flux that tries to flow into the inner core is suppressed, and by applying a material that has not been subjected to a magnetic domain refinement treatment by introducing thermal strain to the region where magnetic flux transfer occurs in the inner core, the amount of magnetic flux that the inner core can accept is similarly reduced, and it is considered that interlayer magnetic flux transfer can be suppressed by both of these effects. Therefore, it is presumed that the reduction in transformer iron loss is due to the reduction in iron loss in the interlayer magnetic flux transfer portion by suppressing interlayer magnetic flux transfer, which in turn reduces the transformer iron loss. In addition, under the condition that the thickness of the non-treated portion is 20% or more of the thickness of each of the inner and outer cores, the transformer iron loss is further improved. This is presumed to be because the effect of suppressing magnetic flux transfer is further enhanced by the increase in the thickness of the non-treated portion, and the reduction in iron loss due to the suppression of magnetic flux transfer can greatly exceed the increase in iron loss due to the absence of a magnetic domain refinement treatment by introducing thermal strain to the core material.

A reduction in transformer noise was observed in all wound core transformers with non-treated sections. In particular, a significant improvement in transformer noise was observed when the thickness of the non-treated section L was 20% or more of the thickness of the outer core, and the thickness of the non-treated section M was 20% or more of the thickness of the inner core. It is generally known that when a wound core transformer is made using a magnetic domain refinement material, the transformer noise is greater than that of a wound core transformer made using a core material that has not been subjected to magnetic domain refinement treatment. Therefore, the transformer noise decreases as the non-treated area in the wound core transformer increases. However, the significant reduction in transformer noise when the area is 20% or more of the thickness of the outer core and inner core is presumably due to the suppression of electromagnetic vibration caused by in-plane magnetization due to a reduction in interlayer magnetic flux transfer, in addition to the reasons mentioned above.

Based on the above experimental facts and assumptions, we have found that in order to reduce the transformer iron loss and transformer noise in a three-phase three-legged wound core transformer, it is essential to reduce the magnetic flux transfer at the interlayer magnetic flux transfer section. Furthermore, we have also found that in order to reduce the magnetic flux transfer at the interlayer magnetic flux transfer section, it is effective to provide an area (non-treated area) formed of directional electromagnetic steel sheet that has not been subjected to magnetic domain refinement treatment by introducing thermal strain in the area where the interlayer magnetic flux transfer occurs, and to form the other areas with directional electromagnetic steel sheet that has been subjected to magnetic domain refinement treatment by introducing thermal strain. Furthermore, we have found that if the non-treated area is 20% or more of the thickness of each of the inner core and the outer core, the effect of suppressing the interlayer magnetic flux transfer is large, and both the transformer iron loss and the transformer noise are greatly improved, so it is particularly preferable that the non-treated area is 20% or more (20 to 100%) of the thickness of each of the inner core and the outer core.

Based on the above findings, the present invention has been completed. That is, the present invention has the following features.
[1] A three-phase three-legged wound core including two adjacent inner cores made of grain-oriented electromagnetic steel sheets and one outer core surrounding the two inner cores,
The three-phase three-legged wound core is
The magnetic material has a region formed of a grain-oriented electrical steel sheet that has been subjected to a magnetic domain refinement treatment by introducing thermal strain, and a region formed of a grain-oriented electrical steel sheet that has not been subjected to a magnetic domain refinement treatment by introducing thermal strain,
A three-phase, three-legged wound core, in which, when viewed from the side perpendicular to the winding direction, a region between the legs where magnetic flux transfer occurs between the outer core and the inner core has a region formed of directional electromagnetic steel sheet that has not been subjected to the magnetic domain refining treatment by introducing thermal distortion.
[2] A three-phase, three-legged wound core as described in [1], in which, when viewed from the side in a direction perpendicular to the winding direction, the region formed by the grain-oriented electrical steel sheet that has not been subjected to the magnetic domain refinement treatment by introducing thermal strain is a region between the legs, and a region that is 20 to 100% of the thickness of the outer core from the adjacent portion of the outer core and the inner core in an outward direction, and a region that is 20 to 100% of the thickness of the inner core in an inward direction from the adjacent portion.
[3] A three-phase, three-legged wound core according to [1] or [2], in which the magnetic domain refining treatment by introducing thermal strain is applied to all or part of the sheet width of the steel sheet.
[4] A three-phase, three-legged wound core transformer using the three-phase, three-legged wound core described in [1] or [2] above.
[5] A three-phase, three-legged wound core transformer using the three-phase, three-legged wound core described in [3] above.

According to the present invention, a three-phase three-legged wound core is provided that uses grain-oriented electromagnetic steel sheet that has been subjected to a magnetic domain refining process by introducing thermal strain as the core material, and that has excellent iron loss reduction and noise reduction effects.

According to the present invention, it is possible to provide a three-phase three-limbed wound core and a three-phase three-limbed wound core transformer in which transformer iron loss and transformer noise are reduced by forming an area where non-heat-resistant magnetic domain refinement treatment is not applied in the magnetic flux crossing area where the inner core and outer core contact each other in a three-phase three-limbed wound core that uses grain-oriented electrical steel sheet (non-heat-resistant magnetic domain refinement material) that has been subjected to magnetic domain refinement treatment by introducing thermal strain.
According to the present invention, particularly in a unicore using a non-heat-resistant magnetic domain refinement material, interlayer magnetic flux crossover can be suppressed even when the excitation magnetic flux density is relatively high, thereby achieving excellent iron loss reduction effects and noise reduction effects.

FIG. 1 is a diagram (side view) that shows a schematic diagram of interlayer magnetic flux transfer occurring from an outer core to an inner core in a three-phase, three-legged wound core. FIG. 2 is a side view showing the configuration of a three-phase, three-legged wound core produced in an experiment. FIG. 3 is a side view showing the configuration of a three-phase, three-legged wound core produced in the embodiment.

The present invention will be described in detail below.

The manufacturing method of a three-phase, three-legged wound core according to one embodiment of the present invention will be described using Figure 2.

By irradiating the surface of the grain-oriented electromagnetic steel sheet material with a laser, plasma jet, electron beam, etc., thermal distortion is introduced into the steel sheet, which is subjected to a magnetic domain refinement process, thereby reducing the iron loss of the steel sheet. This magnetic domain refinement process using irradiation with a laser, etc. is not performed over the entire length of the grain-oriented electromagnetic steel sheet that will be the core material, but rather, the irradiation is not performed on the area of the steel sheet that will become the joint between the legs of the core (area where magnetic flux transfer occurs) when assembled into a wound core. The wound core is assembled using the core material produced by the above method, and a suitable wound core to which the present invention can be applied is the Unicore, which is an iron core that undergoes little distortion when assembled.

Unicore is produced by cutting out the grain-oriented electromagnetic steel sheet, which is the core material, to the length of each layer of the core, and then folding and winding it. In the core material produced by the above method, no thermal distortion is introduced into the parts between the legs when the core is assembled, so a three-phase three-legged wound core with a non-processed part 5 as shown in Figure 2 can be produced. From the viewpoint of reducing iron loss, it is most preferable to introduce this thermal distortion into the entire width (steel strip width) of the grain-oriented electromagnetic steel sheet material, but even if the core material has thermal distortion introduced into only a part of the width (steel strip width), the effect of the present invention can be exerted and an iron core with reduced iron loss can be provided. In addition, the present invention is preferably applied to Unicore, but is not limited to Unicore and can be suitably applied to other iron cores. For example, it can be suitably applied to an iron core called a trunco, which is wound with a steel strip.

Next, we will explain the reasons for limiting each component in the present invention.

It was revealed that in the iron loss of a three-phase, three-legged wound core transformer, a flow of magnetic flux occurs that tries to return to the excited leg from the non-excited leg, resulting in magnetic flux transfer from the outer core to the inner core, and that magnetic flux transfer is one of the factors that increases the transformer iron loss.

Therefore, since magnetic flux transfer is a phenomenon that occurs through the part where the outer core and the inner core are in contact, and magnetization occurs in the plate thickness direction, a region (non-treated part) formed of directional electromagnetic steel sheet that has not been subjected to magnetic domain refinement treatment by thermal strain introduction is provided in the region where magnetic flux transfer occurs, in order to suppress magnetic flux transfer, and a lower iron loss has been achieved compared to a transformer core made of directional electromagnetic steel sheet that has been subjected to magnetic domain refinement treatment by thermal strain introduction. In addition, if strain relief annealing is performed on the iron core after the iron core is formed, the magnetic domain refinement effect due to thermal strain introduction is removed from the entire iron core, so the present invention is applicable to transformers and iron cores that do not undergo strain relief annealing after the iron core is formed. In this case, the thickness of the non-treated part is preferably 20% or more of the thickness of the outer core and the inner core, respectively, from the viewpoint of obtaining a particularly excellent iron loss reduction effect. By performing magnetic domain refinement treatment by introducing thermal strain, magnetic domains called closure magnetic domains that are oriented in the plate thickness direction of the steel sheet are formed directly below the irradiation part of the laser or the like. The closure domains are oriented in the thickness direction, so their presence in the flux transfer section promotes flux transfer, leading to increased iron loss in the transformer. In the present invention, a non-processing section is provided in the core to locally remove the closure domains, thereby suppressing flux transfer. Therefore, the method of domain refinement introduced in areas other than the flux transfer section is not particularly limited as long as it is a method that introduces closure domains by thermal distortion.

In addition, although this specification describes the characteristics of a three-phase, three-legged wound core of a specific shape, the present invention is suitable for all three-phase wound cores in which magnetic flux transfer occurs in other three-phase wound core transformers, and the shape and dimensions are not limited.

The core material used in the present invention is not particularly limited, and may be, for example, a heat-resistant magnetic domain refinement treated material with thermal distortion. In addition, any grain-oriented electrical steel sheet can be used as the material, regardless of the degree of orientation of the Goss grains in the base material.

By using the three-phase three-legged wound core of the present invention to create a three-phase three-legged wound core transformer, the transformer's iron loss and transformer noise are reduced. There are no limitations on the shape or characteristics of this transformer, and the present invention can be applied to any wound core transformer.

[Example 1]
Grain-oriented electrical steel sheets with different magnetic flux densities B8 at 800 A/m shown in Table 2 were used as materials, and were subjected to laser irradiation (magnetic domain refinement treatment by thermal distortion introduction) to obtain iron core materials. Then, using the iron core materials, a unicore having the iron core shape shown in FIG. 3 was produced, and a 50-turn winding coil was attached to both the primary and secondary to produce a three-phase three-leg wound core transformer. Excitation was performed under conditions of an excitation magnetic flux density of 1.7 T and a frequency of 50 Hz, and the transformer iron loss and transformer noise were measured by the above-mentioned method. The laser irradiation was performed over the entire width (full width) of the steel sheet. In addition, the iron core materials were not subjected to laser irradiation in the areas corresponding to the areas (interlayer magnetic flux crossing areas) where magnetic flux crossing occurs between the legs and the inner core when assembled into a wound core, and non-treated areas were provided in the areas where the magnetic flux crossing occurs. Furthermore, wound cores were produced in which the thickness of the untreated areas, L and M, were changed by changing the number of stacks of core materials having areas not irradiated with laser in the thickness direction of the wound core. However, for some wound cores, the entire wound core was not made using core materials having areas that had not been subjected to magnetic domain refinement treatment by introducing thermal strain, i.e., the wound core was composed only of core materials that had been subjected to magnetic domain refinement treatment by introducing thermal strain, and no untreated areas were provided in the wound core (wound cores in which the thickness of L and the thickness of M are both 0% in Table 2).

The measurement results of the transformer iron loss and transformer noise are shown in Table 2. In the compatible example (invention example) of the present invention, by providing a non-processing section in the interlayer magnetic flux crossing section, it was found that both the transformer iron loss and the transformer noise were better than in a transformer wound core that did not have a non-processing section, and that the transformer exhibited excellent transformer characteristics.

1, 10 Inner core 2, 12 Outer core 3 Inter-layer magnetic flux transfer 4 Inter-layer magnetic flux transfer portion 5 Non-processing portion 6 Leg 7 Center position between legs 8 Adjacent portion

Claims (5)

A three-phase three-legged core including two adjacent inner cores and one outer core surrounding the two inner cores, the inner cores being made of grain-oriented electromagnetic steel sheets,
The three-phase three-legged wound core is
The magnetic material has a region formed of a grain-oriented electrical steel sheet that has been subjected to a magnetic domain refinement treatment by introducing thermal strain, and a region formed of a grain-oriented electrical steel sheet that has not been subjected to a magnetic domain refinement treatment by introducing thermal strain,
a region between legs where magnetic flux transfer occurs between the outer core and the inner core when viewed from the side perpendicular to the winding direction, the region being formed of a grain-oriented electrical steel sheet that has not been subjected to the magnetic domain refining treatment by introducing thermal strain ,
A three-phase, three-legged wound core, wherein areas other than an area formed from grain-oriented electromagnetic steel sheet that has not been subjected to the magnetic domain refinement treatment by introducing thermal strain are formed from grain-oriented electromagnetic steel sheet that has been subjected to the magnetic domain refinement treatment by introducing thermal strain. The three-phase three-legged wound core according to claim 1, in which, in a side view perpendicular to the winding direction, the region formed by the grain-oriented electromagnetic steel sheet that has not been subjected to the magnetic domain refinement treatment by the thermal strain introduction is a region between the legs, and a region that is 20 to 100% of the thickness of the outer core from the adjacent part of the outer core and the inner core in the outward direction, and a region that is 20 to 100% of the thickness of the inner core from the adjacent part in the inward direction. A three-phase three-legged wound core according to claim 1 or 2, in which the magnetic domain refining process by introducing thermal strain is applied to all or part of the width of the steel plate. A three-phase three-legged wound core transformer using the three-phase three-legged wound core according to claim 1 or 2. A three-phase three-legged wound core transformer using the three-phase three-legged wound core described in claim 3.

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