Wound iron core

Abstract

To provide a wound iron core having a structure that suppresses vibration and displacement of the iron core even when thermal deformation occurs due to rated operation, thereby improving no-load characteristics.SOLUTION: The wound iron core includes multiple segmented iron cores divided by the legs of wound steel plates and a band-shaped member that clamps the multiple segmented iron cores. At the butt joint surfaces of the multiple segmented cores, the outer peripheral ends are positioned inward relative to the inner peripheral surface of the band-shaped member. In one embodiment, the legs of the segmented cores are inclined such that they approach the inner side of the wound core as they approach the butt joint surface. In one embodiment, a groove is provided on the outer peripheral side of the butt joint surface of the segmented cores.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] This embodiment of the present invention relates to a wound core. [Background technology]

[0002] For example, one of the iron cores used in transformers is a wound core formed by winding thin silicon steel sheets. One method of assembling an iron core involves winding a roughly rectangular core material around a mandrel, cutting it in the center along the length to create a split core known as a C-cut core, and then incorporating the cut core into the winding. After incorporating the split core into the winding, the outer surface is fastened with a steel band to secure it in place.

[0003] Because magnetic flux passes through this butting surface, it induces vibration and also causes uneven thermal deformation. The gap between the butting surfaces is called the gap, and the distance between the butting surfaces is called the gap length. To ensure that the gap length is the same on the inner and outer peripheries, the cores are not butted together directly, and a gap sheet is generally placed between the gaps.

[0004] For example, Patent Document 1 discloses a reactor device using amorphous material, characterized in that the reactor device is divided into two or more sections by butting together multiple units at butt joints to form wound core units, each of which is made up of multiple layers of laminated amorphous material, each layer being made up of multiple sheets of amorphous ribbon material cut to a predetermined length. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-134448 Summary of the Invention [Problem to be solved by the invention]

[0006] The steel band is required to maintain the core shape without loosening due to the expansion and contraction of the wound core when the transformer is in operation, or resonance caused by electromagnetic vibration. If the steel band is subjected to repeated stress due to excessive vibration or thermal deformation, the steel band may loosen, even if gap material is provided, causing the upper and lower core segments to shift, which may impede the flow of magnetic flux and degrade the no-load characteristics of the core.

[0007] 1 shows a conventional wound core 110 in which core segments 111 are fastened and fixed with steel bands 120. Two core segments 111 are butted together at their butt surfaces 114. A gap material (not shown) is placed in the gap between the butt surfaces 114. Each core segment 111 has two legs 113 and a yoke portion 112 that connects the two legs 113 at one end.

[0008] When the rated voltage is applied to the wound core 110, iron loss occurs in the core and heats up. Iron loss does not occur uniformly throughout the core; rather, loss density is high on the inner periphery of the core and rapidly decreases toward the outer periphery, resulting in a non-uniform distribution of loss. This results in a non-uniform temperature distribution in the wound core 110. Figure 2 shows the results of an analysis of the heat distribution in the wound core 110, and Figure 3 shows the results of an analysis of the thermal deformation of the wound core 110. As shown in Figure 2, it can be seen that the temperature is higher on the inner periphery of the leg 113 than on the outer periphery. Furthermore, as shown in Figure 3(a), significant thermal deformation is observed, particularly near the outer periphery of the butt surface 114. As shown in Figure 3(b), as a result of thermal deformation, the gap length G is larger on the outer periphery of the butt surface 114 than on the inner periphery.

[0009] Due to the thermal deformation of the core segments 111, the steel bands 120 are subjected to a large amount of tension in the longitudinal direction. Figure 4 shows the results of an analysis of the stress acting on the steel bands 120. The analysis revealed that stress is concentrated on the steel bands 120, particularly around the edges of the outer peripheral ends 1141 of the butt surfaces 114, which act as fulcrums. The stress rapidly increases near the butt surfaces 114, exceeding 350 MPa in particular in the gap area. When this condition occurs, the yield strength of the steel bands 120 is exceeded, and the steel bands 120 undergo plastic deformation, causing the clamping of the core segments 111 to loosen. This amplifies the vibration excitation force, causing the wound core 110 itself to shift, and significantly degrading the no-load characteristics.

[0010] A wound core having a structure that suppresses the occurrence of vibration and displacement of the core even if thermal deformation occurs due to rated operation, and improves no-load characteristics. [Means for solving the problem]

[0011] The wound core of this embodiment includes a plurality of core segments separated by the legs of a wound steel plate, and a band-shaped member that fastens the core segments together. At the butt surfaces of the core segments, the outer peripheral ends are positioned inside the inner peripheral surface of the band-shaped member. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing a schematic configuration of a conventional wound core; [Figure 2] Analysis results of heat distribution in conventional wound core during rated operation [Figure 3] 1A and 1B are diagrams visually illustrating the analysis results of thermal deformation (50 times magnified) of a conventional wound core during rated operation, where (a) is a diagram showing the entire wound core, and (b) is an enlarged view of part III in (a). [Figure 4] 1A and 1B are diagrams visually illustrating the analysis results of the equivalent stress acting on the steel band during rated operation of a wound core according to a conventional example, where (a) is a diagram showing the entire steel band, and (b) is an enlarged view of the framed portion IV in (a). [Figure 5]FIG. 1 is a front view showing a schematic configuration of a wound core according to a first embodiment; [Figure 6] Enlarged view of the area within box VI in Figure 5 [Figure 7] 1 is a flowchart showing a manufacturing process for a wound core according to a first embodiment. [Figure 8] A graph showing the temperature distribution of the progress of thermal deformation in a wound core in a comparative example (when θ=0°) [Figure 9] Graph showing the progress of thermal deformation of the wound core according to the first embodiment in terms of temperature distribution (when θ=0.25°) [Figure 10] Graph showing the progress of thermal deformation of the wound core according to the first embodiment in terms of temperature distribution (when θ=0.5°) [Figure 11] A graph showing the temperature distribution of the progress of thermal deformation of a wound core in a comparative example (when θ=1.0°) [Figure 12] FIG. 10 is a front view showing a schematic configuration of a wound core according to a second embodiment. [Figure 13] FIG. 13 is an enlarged view of the area enclosed by the frame XIII in FIG. 12. [Figure 14] An enlarged view of the area within frame XIV in FIG. 13. [Figure 15] FIG. 10 is a front view showing a schematic configuration of a wound core according to a third embodiment. [Figure 16] An enlarged view of the area within box XVI in Figure 15. [Figure 17] FIG. 17 is an exploded perspective view showing an enlarged view of the periphery of the portion shown in FIG. 16; DETAILED DESCRIPTION OF THE INVENTION

[0013] Wound cores according to several embodiments will be described below with reference to the drawings. Elements that are essentially the same in several embodiments will be given the same reference numerals, and descriptions thereof will be omitted. Hereinafter, the wound core may be simply referred to as the iron core.

[0014] (First embodiment) A first embodiment will be described with reference to Figures 5 to 11. The wound core 10 shown in Figure 5 is formed into an overall annular shape. The wound core 10 includes a core segment 11 and a strip-shaped member 20. The core segments 11 are formed by winding a steel plate or the like into an annular shape and dividing it into two pieces, in this case vertically. Each core segment 11 has two legs 13, if there are multiple core segments, and a yoke 12 connecting ends on one side of the legs 13. The other end of the leg 13 is the cut surface of the core segment 11 and forms the butt surface where the core segments 11 are butted together. The strip-shaped member 20 is formed from a thin strip of steel or other material, and is wound around the outer periphery of the core segment 11 formed by butting the butt surfaces 14 of the core segments 11 together to form an annular shape.

[0015] 5 and 6, the legs 13 are inclined slightly toward the inner periphery of the wound core 10 with respect to the vertical direction. That is, the outer peripheral end 141 of the butt surface 14 is located more inward than the inner peripheral surface of the band-shaped member 20. Therefore, in a cooled state where there is no thermal deformation, a horizontal gap is formed between the outer peripheral end 141 and the inner peripheral surface of the band-shaped member 20. As a result, even if the core segments 11 are thermally deformed during rated operation, the outer peripheral end 141 is unlikely to come into contact with the band-shaped member 20, and the outer peripheral end 141 acts as a fulcrum to prevent excessive stress from being generated in the band-shaped member 20.

[0016] The leg portions 13 of the split core 11 are inclined so that the closer they are to the butt surface 14, the closer they are to the inside of the wound core 10. The inclination angle θ of the leg portions 13 shown in FIG. 6 with respect to the vertical direction can be set, for example, within the range of 0.2° to 0.5°.

[0017] With reference to Figure 7, the method for manufacturing wound core 10 will be described. First, in step S1, a worker winds a steel sheet into a ring shape multiple times. In step S2, the worker impregnates the ring-shaped wound steel sheet with resin. In step S3, the worker divides the ring-shaped wound steel sheet into two parts vertically to form core segments 11. In step S4, the worker applies an external force to tilt legs 13 inward. In step S5, the worker incorporates core segments 11 with tilted legs 13 into a winding (not shown). In step S6, the worker tightens a strip-shaped member around the outer peripheries of the two butted core segments 11. In this manner, wound core 10 is manufactured.

[0018] Figures 8 to 11 are graphs showing the thermal distribution analysis results of the progression of thermal deformation during rated operation of wound cores in the example and comparative example. Figure 8 shows the analysis results for a conventional example with an inclination angle of θ = 0°. The operating time increases in the order of t0, t1, t2, and t3. As time passes, the temperature increases closer to the inner circumferential surface of the core, indicating that thermal deformation is progressing. In particular, at t = t3, the temperature exceeds 55°C on the inner circumferential surface side of the core. The analysis results also closely match the measured values ​​for the conventional example, indicated by circles. Figure 9 shows the analysis results for an example with an inclination angle of θ = 0.25°, and Figure 10 shows the analysis results for an example with an inclination angle of θ = 0.5°. For θ = 0.25° and θ = 0.5°, the temperature near the inner circumferential surface of the core does not exceed 55°C over time, indicating that thermal deformation is suppressed. Figure 11 shows the analysis results for a comparative example with an inclination angle of θ = 1.0°. In this case, it was observed that the deformation on the inner peripheral surface side became excessive at t=t2, and the outer peripheral end 141 bit into the gap material, causing damage. The computer analysis was stopped due to an error.

[0019] From the above analysis results, it can be seen that stress concentration on the strip-shaped member 20 in the gap portion due to thermal deformation of the iron core 10 is suppressed within the range of θ=approximately 0.2° to approximately 0.5°.

[0020] The wound core 10 of the present embodiment described above comprises a plurality of core segments 11 separated by leg portions 13 of wound steel plates, and a strip-shaped member 20 that fastens the plurality of core segments 11. At the butt surfaces 14 of the plurality of core segments 11, the outer peripheral end portions 141 are located inside the inner peripheral surface of the strip-shaped member 20.

[0021] According to this, since the outer peripheral end 141 does not contact the band-shaped member 20 in the cooled state, even if the outer peripheral side of the leg 13 expands slightly due to thermal deformation, it is possible to prevent it from coming into contact with the band-shaped member 20 and becoming a fulcrum for stress, and to prevent excessive stress exceeding the strength of the band-shaped member 20 from being applied. This makes it possible to prevent loosening due to deformation of the band-shaped member 20 and the resulting amplification and deviation of the vibration force of the core segments 11. Therefore, a wound core with improved no-load characteristics is provided.

[0022] The legs 13 of the multiple core segments 11 are inclined so that the closer they are to the butting surface 14, the closer they are to the inside of the wound core 10.

[0023] This makes it possible to provide a wound core with improved no-load characteristics through the relatively simple process of inclining the legs 13 inward.

[0024] The inclination angle θ of the leg 13 relative to the vertical direction is set within the range of 0.2° to 0.5°.

[0025] This makes it possible to provide a wound core with improved no-load characteristics within an appropriate range of inclination angle that takes into consideration the concentration of stress on the strip-shaped member 20 due to thermal deformation and damage to the gap material.

[0026] (Second embodiment) A second embodiment will be described with reference to Figures 12 to 14. The wound core 10 of this embodiment includes a backing plate 30 in addition to the configuration of the wound core 10 of the first embodiment. The backing plate 30 is arranged between the core segments 11 and the strip-shaped member 20 so as to cover the outer periphery of the abutment surfaces of the upper and lower core segments 11. This makes it possible to suppress stress acting on the strip-shaped member 20 due to thermal deformation. In this embodiment, two backing plates 30 are provided, one for each of the two abutment surfaces 14 on the left and right.

[0027] The backing plate 30 is made of an insulating material. For example, the backing plate 30 in this embodiment can be made of wood or a heat-resistant resin material. The backing plate 30 is formed in a plate shape with a surface direction perpendicular to the extension direction of the yoke portion 12 (in this case, the left-right direction). The backing plate 30 distributes the concentrated load applied to the fulcrum over the entire outer surface of the backing plate 30, thereby preventing the outer end 141 of the butt surface 14 from acting as a fulcrum and applying stress exceeding its yield strength to the strip-shaped member 20 due to thermal deformation of the core segments 11 during rated operation. Furthermore, the backing plate 30 generates friction between the backing plate 30 and the core segments 11, thereby preventing deformation of the core segments 11.

[0028] The backing plate 30 is formed in a generally rectangular plate shape with the vertical direction as the longitudinal direction and the front-rear direction as the hand direction. For example, the vertical length dimension H of the backing plate 30 can be set within a range of about 1 to about 2.5 times the left-right width dimension W of the leg portion 13.

[0029] 13 and 14, the backing plate 30 has a first surface 31 and a second surface 32. The first surface 31 is the surface on the outer periphery of the backing plate 30. The second surface 32 is the surface opposite to the first surface 31 and is the surface on the inner periphery of the backing plate 30. In this embodiment, the first surface 31 and the second surface 32 form a surface perpendicular to the left-right direction.

[0030] The first surface 31 is set to have a smaller coefficient of friction with respect to the strip-shaped member 20 than the second surface 32. That is, the first surface 31 forms a smooth surface. In contrast, the second surface 32 has a plurality of minute irregularities, forming a surface with a three-dimensional structure. This reduces friction between the strip-shaped member 20 and the backing plate 30 on the first surface 31 side, while promoting friction between the outer circumferential surfaces of the legs 13 and the backing plate 30 on the second surface 32, thereby reducing thermal deformation on the outer circumferential side of the core segments 11.

[0031] The thickness of the backing plate 30, which is the length dimension in the left-right direction, is set to be significantly larger than the thickness of the strip-shaped member 20. This provides the backing plate 30 with sufficient resistance to thermal deformation of the core segments 11. For example, the thickness of the backing plate 30 can be set within a range of about 10 to about 20 times the thickness of the strip-shaped member 20.

[0032] The method for manufacturing the wound core 10 of this embodiment is generally similar to the method for manufacturing the wound core 10 of the first embodiment, but differs in the following respects: when tightening the strip-shaped member 20 in step S6, the worker places a backing plate 30 between the strip-shaped member 20 and the core segments 11, and tightens the core segments 11 together with the backing plate 30. In this manner, the wound core 10 of this embodiment is manufactured.

[0033] The wound core 10 of this embodiment includes a backing plate 30 disposed between the plurality of core segments 11 and the strip-shaped member 20 so as to cover the butting surface 14 from the outer periphery side.

[0034] This allows the end 141 of the butt surface 14 to serve as a fulcrum, preventing excessive stress above the yield stress from being applied to the strip-shaped member 20, and as a result, preventing the strip-shaped member 20 from loosening and causing shifting or vibration in the split iron core 11.

[0035] In this embodiment, the backing plate 30 has a rectangular parallelepiped shape, but is not limited to this. For example, the second surface 32, which is the surface on the inner periphery side, may be inclined to correspond to the inclination of the core segments 11, so that the upper portion is inclined inward as it goes downward, and the lower portion is inclined outward as it goes downward.

[0036] (Third embodiment) A third embodiment will be described with reference to Figures 15 to 17. A wound core 10 of this embodiment has grooves 15 on the outer periphery of the butt surfaces of the core segments 11. The grooves 15 are formed by recessing inward the corners on the outer periphery of the butt surfaces of the core segments 11.

[0037] The wound core 10 further includes an auxiliary member 40. The auxiliary member 40 is fitted vertically across the grooves 15 of the two butted upper and lower core segments 11. That is, the auxiliary member 40 is arranged across the grooves 15 of the upper core segment 11 and the grooves of the lower core segment 11. The auxiliary member 40 distributes the concentrated load acting on the fulcrum across the entire outer circumferential surface of the auxiliary member 40, thereby preventing the outer circumferential end 141 of the butt surface 14 from acting as a fulcrum and applying stress exceeding the yield strength of the strip-shaped member 20 due to thermal deformation of the core segment 11 during rated operation. Furthermore, the auxiliary member 40 generates friction between the auxiliary member 40 and the core segment 11, thereby suppressing deformation of the core segment 11.

[0038] The vertical outer dimension of the auxiliary member 40 is set to be slightly smaller than the vertical inner dimension of the arrangement space S formed by the upper and lower grooves 15, so that the auxiliary member 40 fits snugly into the arrangement space S. The left-right outer dimension of the auxiliary member 40 is set so that, when the auxiliary member 40 is fitted into the groove 15, the outer peripheral surface of the leg 13 and the outer peripheral surface of the auxiliary member 40 are on the same plane, i.e., flush. Furthermore, the front-rear outer dimension of the auxiliary member 40 is set to be the same as the front-rear outer dimension of the leg 13.

[0039] The auxiliary member 40 is made of an insulating material. For example, the auxiliary member 40 can be made of wood or a heat-resistant resin material. The auxiliary member 40 is formed as a generally rectangular, elongated piece whose longitudinal direction is in the front-to-rear direction and whose proximal direction is in the vertical direction.

[0040] The height dimension of the outlet side of the arrangement space S, i.e., the outer periphery, is set smaller than the height dimension of the rear part of the arrangement space S, i.e., the inner periphery. In other words, the vertical length dimension Ho of the outer periphery side of the auxiliary member 40 is set smaller than the vertical length dimension Hi of the inner periphery side. That is, the auxiliary member 40 is formed as a trapezoidal column with a trapezoidal front-to-rear face. Therefore, even if thermal deformation of the core segments 11 causes stress to act in a direction pushing the auxiliary members 40 out of the grooves 15, the outlet side of the grooves 15, i.e., the outer periphery, is narrower, making it difficult for the auxiliary members 40 to come out of the grooves 15 toward the outer periphery. As a result, the core segments 11 receive a reaction force from the auxiliary members 40, suppressing thermal deformation of the core segments 11.

[0041] The manufacturing method for wound core 10 of this embodiment is generally similar to the manufacturing method for wound core 10 of the first embodiment, but differs in the following respects. The worker performs step S14 instead of step S4 on the split core divided in two in step S3. In step S14, the worker cuts out the outer corner of the butt surface to form groove 15. Alternatively, the worker may form groove 15 by carving the outer periphery of the portion of the annular resin-impregnated wound steel sheet that will become the butt surface in step S2, and then divide the wound steel sheet in two in step S3. In this manner, wound core 10 of this embodiment is manufactured.

[0042] The auxiliary member 40 may be configured so that the surface roughness of the inner peripheral surface is greater than the surface roughness of the outer peripheral surface, thereby generating a greater frictional force between the auxiliary member 40 and the core segments 11 .

[0043] The wound core 10 of this embodiment includes grooves 15 provided on the outer periphery of the butt surfaces 14 of the multiple core segments 11 , and auxiliary members 40 fitted into the grooves 15 .

[0044] This also prevents the end 141 of the butting surface 14 from acting as a fulcrum and applying excessive stress exceeding the yield stress to the strip-shaped member 20.

[0045] The vertical length dimension Ho of the auxiliary member 40 on the outer periphery side is set to be shorter than the vertical length dimension Hi of the auxiliary member 40 on the inner periphery side.

[0046] This makes it difficult for the auxiliary members 40 to come out of the grooves 15 toward the outer periphery, and also suppresses thermal deformation of the core segments 11, further suppressing excessive stress from being applied to the strip-shaped members 20.

[0047] In this embodiment, the auxiliary member 40 is formed in a trapezoidal columnar shape, but this is not limiting. For example, in another embodiment, the auxiliary member 40 may be a rectangular parallelepiped in which the vertical length dimension Ho on the outer periphery side and the vertical length dimension Hi on the inner periphery side are set to be the same.

[0048] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims. [Explanation of symbols]

[0049] 10... iron core, 11... divided iron core, 13... leg portion, 14... butt surface, 141... outer peripheral end portion, 20... steel band (strip-shaped member), 30... backing plate member, 40... auxiliary member

Claims

1. A plurality of split cores separated by legs of wound steel plates; a band-shaped member that fastens the plurality of core segments, At the butt surfaces of the plurality of core segments, the outer peripheral end portions are located inside the inner peripheral surface of the strip-shaped member. Wound iron core.

2. The leg portions of the plurality of core segments are inclined so as to approach the inner side of the wound core as they approach the butt surface.

2. The wound core according to claim 1.

3. The inclination angle of the leg with respect to the vertical direction is set within a range of 0.2° to 0.5°.

3. The wound core according to claim 2.

4. a backing plate disposed between the plurality of core segments and the strip-shaped member so as to cover the abutting surfaces from the outer circumferential side; 4. A wound core according to claim 2 or 3.

5. a groove provided on an outer circumferential side of the butt surfaces of the plurality of core segments; an auxiliary member fitted into the groove; 2. The wound core according to claim 1.

6. a vertical length dimension of the outer circumferential side of the auxiliary member is set to be shorter than a vertical length dimension of the inner circumferential side of the auxiliary member; 6. A wound core according to claim 5.

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