Iron core for transformer and manufacturing method thereof

Abstract

The present invention relates to an iron core for a transformer having low no-load loss and a manufacturing method thereof. The iron core for a transformer according to an embodiment of the present invention includes a core subpart in which multiple steel sheets are stacked and which includes a through-hole penetrating in a stacking direction, wherein a direction intersecting the stacking direction is defined as a first direction and a direction intersecting the stacking direction and the first direction is defined as a second direction, and a ratio (D / W) of a diameter (D) to a width (W) of the through-hole is 0.02 to 0.20 under the assumption that a shorter length is defined as a width (W) when comparing a length in the first direction and a length in the second direction in the core subpart.

Description

Transformer iron core and method of manufacturing the same

[0001] The present invention relates to a transformer core with low no-load loss and a method for manufacturing the same.

[0002] A transformer is a device that changes alternating current and voltage values ​​using the phenomenon of electromagnetic induction, and it is one of the essential components of electronic products. Transformers are manufactured by winding electrically conductive coils around a magnetic iron core. Electrical steel sheets with low magnetic loss are used as the core, and these cores are classified into striped cores and wound cores.

[0003] The main characteristics of transformers include losses and noise; in particular, no-load losses and no-load noise—power losses that occur at every moment regardless of whether the transformer is in operation—are subject to institutional regulations. Accordingly, various measures have been proposed to reduce no-load losses and no-load noise.

[0004] As a measure to reduce no-load losses, oriented electrical steel sheets with excellent iron loss are used as the core. Since iron loss increases as the thickness of the oriented electrical steel sheet increases, the thinnest possible material can be selected. Although various technologies to reduce iron loss in electrical steel sheets have existed in the past and improved materials have been developed every year, there is currently a need for technologies to reduce the transformer's no-load losses in addition to iron loss reduction based on the material.

[0005] According to one embodiment of the present invention, a transformer core with improved no-load loss may be provided. Additionally, a transformer core with improved transformer performance relative to the same weight may be provided.

[0006] The problems of the present invention are not limited to those described above. A person skilled in the art to which the present invention pertains will have no difficulty understanding additional problems of the present invention from the overall contents of this specification.

[0007] A transformer core according to one embodiment of the present invention comprises a core subpart having a plurality of steel plates stacked and a through hole penetrating in the stacking direction, a first direction intersecting the stacking direction and a second direction intersecting the stacking direction and the first direction are defined as the first direction, and when the shorter length is compared with the length of the first direction and the length of the second direction in the core subpart and is called the width (w), the ratio (D / w) of the diameter (D) and the width (w) of the through hole is 0.02 to 0.20.

[0008] Additionally, a plurality of the core subparts may have a width parallel to the first direction or the second direction and may be arranged to form a closed cross-section on a plane parallel to the first direction and the second direction when combined.

[0009] In addition, the joint portion where the plurality of core subparts are joined can be joined by stacking in a step-lap manner.

[0010] Additionally, the plurality of core subparts may include a first yoke arranged parallel to the first direction, a second yoke arranged parallel to the first yoke and spaced apart from the first yoke, a first leg arranged parallel to the second direction and connected to the first yoke and the second yoke, a third leg arranged parallel to the first leg and spaced apart from the first leg, and a third leg arranged between the first leg and the second leg.

[0011] In addition, the number of steps in the above step can be 4 to 7.

[0012] In addition, a fastening member may be coupled to the above-mentioned through hole.

[0013] In addition, the pressure applied by the fastening member to the steel plate may be 0.005 to 0.11 MPa.

[0014] In addition, when comparing the length in the first direction and the length in the second direction of the core subpart, the longer length is called the total length. The number of through holes in the core subpart and the second length, which is the distance from the through hole to the end of the core subpart along an arbitrary line extending the center of the plurality of through holes, can satisfy Equation 1 as L / (Nh+4) < Lh < L / (Nh+1). Here, L is the total length, Lh is the length from the through hole to the end of the core subpart, and Nh is the number of through holes.

[0015] A method for manufacturing a transformer core according to one embodiment of the present invention may include a cutting and punching step of cutting a strip into a desired shape, forming through holes in a plurality of the cut strips, and processing the diameter (D) of the through holes to satisfy 0.02 to 0.2 when compared (D / w) with the width (w), which is the shorter length among the first direction of the cut strips and the second direction intersecting the first direction, and a stacking step of stacking the strips.

[0016] In addition, it may include a fixing step of attaching a frame to both outer surfaces of the laminated steel plate strip and fixing it by binding a fastening member to the through hole.

[0017] In addition, the above frame may be a non-ferromagnetic material.

[0018] In addition, the pressure for binding in the above fixing step may be 0.005 to 0.11 MPa.

[0019] According to the present invention, the effect of reducing no-load loss and no-load noise and improving the performance of the transformer is provided.

[0020] FIG. 1 is a perspective view of a transformer iron core according to an embodiment of the present invention.

[0021] FIG. 2 is a first cross-sectional view along A-A' of the perspective view shown in FIG. 1.

[0022] FIG. 3 is a second cross-sectional view along A-A' of the perspective view shown in FIG. 1.

[0023] Figure 4 is an enlarged view of part B shown in Figure 1.

[0024] FIG. 5 is a view of a core subpart according to an embodiment of the present invention, seen from one side.

[0025] FIG. 6 illustrates the manufacturing process of a transformer iron core according to an embodiment of the present invention.

[0026] Preferred embodiments of the present invention will be described below with reference to the attached drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0027] In addition, embodiments of the present invention are provided to more completely explain the present invention to those with average knowledge in the relevant technical field.

[0028] In drawings, the shapes and sizes of elements may be exaggerated for clearer explanation.

[0029] In describing the embodiments of the present invention, if it is determined that a detailed description of known technology related to the present invention may unnecessarily obscure the essence of the present invention, such detailed description will be omitted. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or conventions of the user or operator. Therefore, such definitions should be based on the content throughout this specification. The terms used in the detailed description are merely for describing the embodiments of the present invention and should not be limited in any way. Unless explicitly stated otherwise, expressions in the singular form include the meaning of the plural form.

[0030] In this description, expressions such as “include” or “equipped” are intended to refer to certain characteristics, numbers, steps, actions, elements, parts or combinations thereof, and should not be interpreted to exclude the existence or possibility of one or more other characteristics, numbers, steps, actions, elements, parts or combinations thereof other than those described.

[0031] Unless otherwise specifically defined in the specification of the present invention, % units mean weight %.

[0032] In this specification, terms such as 'top', 'upper', 'upper surface', 'lower', 'lower surface', 'lower surface', and 'side surface' are based on the drawings and may actually vary depending on the direction in which the elements or components are arranged.

[0033] Additionally, throughout the specification, when it is said that one part is 'connected' to another part, this includes not only cases where they are 'directly connected,' but also cases where they are 'indirectly connected' with other elements in between.

[0034] The present invention will be described in detail below through each embodiment or example of the invention. It should be noted that each embodiment or example described in this specification is not limited to a single embodiment or example, but may also be combined with other embodiments or examples. Accordingly, the citation of claims in the patent claims is merely an example of an embodiment, and the technical concept of the present invention should not be interpreted as being limited only to a combination with the cited claims; rather, combinations with various claims are also included within the scope of the technical concept of the present invention.

[0035] The present invention will be described in detail below through examples. However, it should be noted that the examples described below are intended merely to illustrate and embody the present invention and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the patent claims and matters reasonably inferred therefrom.

[0036] In the drawings and description below, based on the stacking direction (DR3), a first direction (DR1) intersecting the stacking direction (DR3) and a second direction (DR2) intersecting the stacking direction (DR3) and the first direction (DR1) are defined.

[0037] FIG. 1 shows a perspective view of a transformer iron core according to an embodiment of the present invention.

[0038] A transformer core according to one embodiment of the present invention comprises a plurality of core subparts (100, 200, 300, 400, 500) in which a plurality of steel plates (S) are stacked and a through hole (H) penetrates in the stacking direction (DR3), and a plurality of core subparts (100, 200, 300, 400, 500) are arranged in a direction intersecting the stacking direction (DR3). At this time, if the lengths of the first direction (DR1) and the second direction (DR2) of the core subparts (100, 200, 300, 400, 500) are compared and the shorter length is defined as the width (w, see FIG. 2), the ratio (D / w) of the diameter (D) and the width (w) of the through hole (H) satisfies 0.02 to 0.20.

[0039] Among the coils of a transformer, the primary coil is connected to the input circuit that requires voltage conversion, while the secondary coil is connected to the output circuit where the converted voltage is used. Here, magnetic energy is used for the electrical energy conversion between the primary and secondary coils. Depending on whether a power load connected to the secondary coil is in use, it is classified into no-load characteristics and load characteristics. No-load characteristics refer to the case where there is no load; they occur constantly regardless of whether the transformer is operating, and the power loss consumed in the iron core is called no-load loss, while the noise generated at this time is called no-load noise. On the other hand, load characteristics occur when power is used by the load connected to the secondary coil; load loss is determined by the Joule loss dissipated in the coil, and load noise appears due to the electromagnetic force between the coil and the iron core. As a method to reduce no-load loss, electrical steel sheets with low iron loss can be used as the iron core. Since iron loss increases as the thickness of the electrical steel sheet increases, it is desirable to select the thinnest possible electrical steel sheet. In addition, since iron loss decreases when components with high resistivity, such as silicon or aluminum, are contained in large quantities, it is desirable to select electrical steel sheets with high resistivity characteristics. Even if an iron core is manufactured with a constant weight using the same electrical steel sheet, the no-load characteristics of the transformer vary. Since this depends on the width and length of the upper and lower yokes of the iron core, the size of multiple racks, and the stacking height of each part, most transformer manufacturers manage their design drawings optimally through experience.

[0040] The through hole (H) can perform various roles in the transformer core. For example, to facilitate lamination when stacking multiple electrical steel sheets, the through hole (H) can be inserted into a long rod to align and stack the cut steel sheets. For other uses, fastening members (not shown), such as bolts, can be attached to the through hole (H) to maintain the joined state during fixing. However, the through hole (H) has a problem in that it affects iron loss. The increased magnetic flux density or harmonic waveforms caused by the through hole (H) are factors that worsen iron loss and noise.

[0041] When electrical steel sheets of the same material and weight are used as single sheets, the difference in iron loss is approximately 5 to 25% depending on the size of the through hole (H). Since the through hole (H) acts as a magnetic resistance, it causes a bottleneck in the magnetic field flowing evenly across the cross-section of the electrical steel sheet, which can affect the iron loss.

[0042] If the ratio (D / w) of the diameter (D) and width (w) of the through hole (H) is less than 0.02, the size of the fastening member fastened to the through hole (H) is also limited, which may result in insufficient rigidity and cause a problem where the transformer core is prone to separation. In addition, if the ratio (D / w) of the diameter (D) and width (w) of the through hole (H) is greater than 0.20, the rate of increase in no-load loss increases rapidly, which may lead to excessive heat generation and worsening noise. Magnetic fields generally tend to gather in areas with relatively low magnetic resistance; however, as the through hole (H) becomes larger, the area with low magnetic resistance becomes smaller, causing the local magnetic flux density to increase and potentially resulting in the generation of harmonic waveforms.

[0043] For example, the core subpart (100, 200, 300, 400, 500) may be a laminated steel plate body forming a yoke portion (100, 200) or a leg portion (300, 400, 500). The yoke portion (100, 200) may include a first yoke (100) arranged parallel to a first direction (DR1) that intersects the stacking direction (DR3) of the steel plates (S) and a second yoke (200) arranged parallel to and spaced apart from the first yoke (100).

[0044] The leg portion (300, 400, 500) may include a plurality of steel plates (S) stacked thereon, a first leg (300) connected to a first yoke (100) and a second yoke (200) and arranged in a second direction (DR2), and a second leg (400) spaced apart from and arranged parallel to the first leg (300). Additionally, the leg portion (300, 400, 500) may include a third leg (500) positioned within a closed rectangular section parallel to the first leg (300) and the second leg (400).

[0045] For example, a connecting portion (600, see FIG. 4) to which core subparts (100, 200, 300, 400, 500) are connected may be formed. For example, the connecting portion (600) may be stacked in a step-lap manner. If the connecting portion (600; see FIG. 4) is formed according to the step-lap method, the iron loss that rises rapidly in the connecting portion (600) can be minimized. However, the connecting portion (600) is not limited to being formed in a step-lap manner.

[0046] FIG. 2 illustrates a cross-section marked A-A' in FIG. 1, and FIG. 3 illustrates another cross-section of the portion marked A-A' in FIG. 1.

[0047] Referring to FIG. 2, for example, the width of the laminated steel plate can be constant. In this case, the width (w) can be defined as a single numerical value.

[0048] Referring to FIG. 3, for example, the width of the laminated steel plates within the core subpart (100, 200, 300, 400, 500) may vary. In this case, the core subpart (100, 200, 300, 400, 500) may include steel plates having a wide width (wwd) and steel plates having a narrow width (w). In this case, in the present invention, it is preferable that the narrow width (w) satisfies the relationship between the diameter (D) and the width (w) of the through hole (H).

[0049] Generally, the ratio (wwd / w) of the widest width (wwd) to the narrowest width (w) can be 1.8 to 2.9. Even if only the widest width (wwd) is specified on the design drawing, it is sufficient if the diameter (D), which is the size of the through hole (H), is located within the range of the ratio (D / w) of the diameter (D) to the width (w) of the through hole (H) using the above ratio of the widest width to the narrowest width.

[0050] Figure 4 illustrates a joint portion when stacked by the step-lap method.

[0051] According to the step-lap method, the length of the portion of the steel plate protruding outward from the joint (600) is significantly increased, and the spacing between the step-laps is also widened. The joint (600) acts as a path for leakage of the magnetic field within the iron core, and when the magnetic flux density is high, it causes vibration and noise due to the shaking phenomenon. In addition, if the iron core fastening spacing by the step-laps widens, there is a counterproductive effect in which harmonic generation increases in the waveform of the magnetic field passing from the yoke (100, 200) to the leg (300, 400, 500) or from the leg (300, 400, 500) to the yoke (100, 200). As a result, if the number of step-laps exceeds 8, the load loss and noise worsen. On the other hand, if the number of step-laps is small, the spacing of the joint (600) is narrow, so the magnetic field flow is not smooth, magnetic field saturation occurs easily, and harmonic generation increases. When the step lap is 3 stages, it can be seen that no-load loss and noise worsen.

[0052] Figure 5 is a diagram illustrating the location of a through hole in a core subpart in relation to the shape of the core subpart.

[0053] In the core subparts (100, 200, 300, 400, 500), when comparing the length of the first direction (DR1) with the length of the second direction (DR2), the shorter length is defined as the width (w). The length in a direction other than the width direction can be defined as the total length (L). If the lengths measured in the length direction vary, the average is used.

[0054] The following description is based on the first leg (300), but the same applies to other core subparts (100, 200, 300, 400, 500).

[0055] For example, in a core subpart (100, 200, 300, 400, 500), the total length (L) and the number of through holes (H) are defined as the number of through holes (Nh), and an arbitrary length connecting the centers of the through holes (H) can be defined as the first length (Lhh). At this time, if an extension line is drawn from the line connecting the centers of the through holes (H) to the corner of the core subpart (100, 200, 300, 400, 500), the second length (Lh) can be defined as the smaller value between the distance from the through hole (H) to the corner of the core subpart (100, 200, 300, 400, 500). At this time, the second length (Lh) must be greater than the value obtained by dividing the total length (L) by the number of through holes (Nh) plus 4, and smaller than the value obtained by dividing the number of through holes (Nh) plus 1. More preferably, the second length (Lh) should be greater than the value obtained by dividing the number of through holes (Nh) by the sum of 3, and smaller than the value obtained by dividing the number of through holes (Nh) by the sum of 2.

[0056] That is, L / (Nh+4) < Lh < L / (Nh+1). More preferably, L / (Nh+3) < Lh < L / (Nh+2).

[0057] If the second length (Lh) is smaller than L / (Nh+4), the through hole (H) obstructs the magnetic field flow and distorts the magnetic field, thereby inducing high-frequency iron loss. The joint core region of the surrounding part, which includes the connecting part (600) where the core subparts (100, 200, 300, 400, 500) are connected, is a section that gradually prepares for a 45-degree rotation in the rolling direction and the length direction to allow the magnetic field to pass over to the iron core facing it, but a problem may occur if this section becomes narrow. In this case, if the frequency of the magnetic field increases or becomes distorted, iron loss and noise increase.

[0058] If the second length (Lh) is greater than L / (Nh+1), a problem arises where the first length (Lhh) narrows. This also forms an asymmetric magnetic field, resulting in increased iron loss and worsening noise due to a bottleneck phenomenon, and causes misalignment at both ends of the iron core, which can lead to fastening failures during the final iron core assembly process.

[0059] This phenomenon may be more desirable when L / (Nh+3) < Lh < L / (Nh+2), as a magnetic field can be formed within a relatively stable range between the coupling part (600) and the through hole (H), and between the through hole (H) and the through hole (H).

[0060] Table 1 below summarizes the test data obtained to determine the change in transformer characteristics according to the size of the through hole (H) in the iron core. The ratio (D / w) and the corresponding test results for no-load loss and noise are presented according to the definition of the diameter (D) of the through hole (H) relative to the smallest width (w) among the laminated steel plates.

[0061] In Example 1, the transformer has a shape as shown in FIG. 1 by combining the rack section (300, 400, 500) with the second yoke (200) and then fitting the first yoke (100) to attach a frame, and then fastening it with a fastening member such as a bolt in the through hole (H), and then applying a rated voltage to measure the rated no-load loss and noise. In Example 1, the step wrap is 5 stages and the width (w) is 120 mm. In addition, considering the voltage fluctuation rate of power transmission and distribution, a voltage exceeding 10% was applied and the no-load loss was measured. Furthermore, Example 1 in Table 1 is defined as 100%, and the no-load loss is expressed as a relative ratio (%). Meanwhile, the no-load noise is expressed in dBA units on a logarithmic scale and is represented as an actual measured value rather than a proportional value, and if the no-load noise is 60 dBA or higher, it is classified as a noise defect.

[0062] Ratio of through hole (H) to width (w) (D / w) (%) Rated no-load loss (%) No-load loss at 10% overvoltage (%) Rated no-load noise (dBA) Remarks Comparative Example 1 25 103.5 105.2 62.4 Comparative Example 2 21 101.9 103.6 61.6 Example 1 19 100 100 59.2 Example 2 109 9.1 98.5 58.8 Comparative Example 3 1.5 -- Defective

[0063]

[0064] Based on Example 1, it can be seen that Comparative Examples 1 and 2 have higher rated no-load losses and 10% no-load losses. Additionally, the rated no-load noise is also higher. The reason the difference between the no-load loss at voltages exceeding 10% and the no-load loss at rated voltage is greater is that the magnetic flux density increases proportionally to the applied voltage, and leakage flux is generated due to local magnetic field saturation within the iron core. Furthermore, due to magnetic flux density saturation, the generation rate of harmonic waveforms in the magnetic field also increases rapidly. Therefore, depending on the size of the through-hole (H), the rate of increase in no-load loss was found to be higher as the applied voltage increased. Although a smaller size of the through-hole (H) was advantageous for transformer characteristics, in cases where it was too small, such as in Comparative Example 3, the rigidity of the fastening member secured to the through-hole (H) was insufficient, making it difficult to fix the transformer iron core in a laminated state; consequently, the test itself became impossible due to iron core misalignment.

[0065] Table 2 below shows the results of a test conducted under the same conditions as Example 1, with only the number of steps changed.

[0066] Classification Step Wrap Number of Stages Rated No-load Loss (%) Over 10% Voltage No-load Loss (%) Rated No-load Noise (dBA) Example 15 100 100 59.2 Comparative Example 48 102.5 104.5 61.8 Example 37 100.5 101.1 59.5 Example 44 100.9 101.4 59.9 Comparative Example 53 101.6 103.8 61.3

[0067]

[0068] As in Comparative Example 4, when stacked in a step-lap fashion, the protruding length of the steel plate outward from the joint (600) stacked in the step-lap fashion is significantly increased, and the spacing between the step-laps is also widened. The joint (600) becomes a path for leakage of the magnetic field within the iron core. In addition, the joint (600) causes vibration and noise due to a shaking phenomenon when the magnetic flux density is high.

[0069] If the gap between the iron cores is widened by the step wrap, there is a counterproductive effect in which harmonic generation increases in the waveform of the magnetic field passing from the yoke portion (100, 200) to the leg portion (300, 400, 500) or the magnetic field passing from the leg portion (300, 400, 500) to the yoke portion (100, 200). As a result, as in Comparative Example 4, if the step wrap is 8 stages or more, no-load loss and noise worsen.

[0070] On the other hand, if the number of step wrap stages is small, the gap between the connecting parts (600) is narrow, so the magnetic field flow is not smooth, so magnetic field saturation occurs easily and harmonic generation increases. As in Comparative Example 5, when the step wrap is 3 stages, it can be seen that no-load loss and noise worsen.

[0071] Table 3 below measures no-load loss and noise by applying the size of the through hole (H) and the number of step wraps of the conditions of Example 1 of Table 1, attaching a frame to both outer surfaces of the laminated steel plate body, and adjusting the pressure applied by binding after fastening with bolts, which are fastening members. At this time, the pressure is measured by attaching a piezoelectric sensor to the surface of the core. The piezoelectric sensor used was a thin-film pressure sensor (FSR-402) from Interlink, and it was attached to each of the core subparts (100, 200, 300, 400, 500). The sensor position of the first yoke (100) was placed in the center between the through hole (H) located on the left and the fastening part (600) on the left, and the sensor of the second yoke (200) was attached in the center between the through hole (H) on the right and the coupling part (600) on the right. In addition, the first leg (300) and the second leg (400) were positioned at the point 1 / 3 of the length of the first leg and the point 1 / 3 of the length of the second leg, based on the connecting part (600) facing the second yoke (200). Also, they were attached to the central part of the width (w).

[0072] Classification Clamping Pressure (MPa) No-load Loss (%) No-load Noise (dBA) Remarks Example 10.078 10059.2 Comparative Example 60.118 100.762.2 Example 50.109 100.359.8 Example 60.056 100.458.2 Example 70.014 100.557.6 Comparative Example 70.004 102.3 - Defective

[0073]

[0074] According to Table 3, it can be seen that no-load loss does not show significant change depending on the clamping pressure. However, no-load noise showed different results depending on the pressure.

[0075] As shown in Examples 5 to 7, the noise was maintained at 60 dBA or less within 0.11 MPa, but as shown in Comparative Example 6, it can be seen that the noise deteriorates rapidly when the pressure exceeds 0.11 MPa. Furthermore, if pressure is applied to exceed 0.11 MPa, magnetic domain movement is not facilitated by the pressure applied to the electrical steel sheet, and unnecessary magnetic domains are formed in the thickness direction, which adversely affects the noise.

[0076] On the other hand, as in Comparative Example 7, if a pressure lower than 0.005 MPa is applied, the iron core is hardly pressurized, so the bolt gradually loosens due to vibrations generated in the iron core during transformer operation. Consequently, a problem arises where the iron core assembly is poor. In addition, due to the low fastening force, the step-lap alignment of the coupling part (600) becomes incomplete. As a result, the no-load loss of the transformer gradually increases, and the noise becomes rapidly severe, making it difficult to measure.

[0077] In addition, the material of the frame is usually inexpensive steel that has magnetic properties. Although it is not superior to the magnetic properties of the oriented electrical steel sheet used as the core, the magnetic properties of the frame are significant and cannot be ignored. This is because the magnetic field flowing through the electrical steel sheet is easily leaked into the frame, and especially at the joint (600), the amount of leakage is significant, so there may be cases where the noise is very high during high-voltage testing. Therefore, using a non-magnetic steel material, such as austenitic stainless steel, as the material of the frame is effective in reducing no-load loss and noise. For example, under the same conditions as Example 1, if the frame is changed from magnetic steel to non-magnetic steel, the no-load loss at voltage exceeding 10% of the rated voltage is 98.2% and the rated no-load noise is 58.6 dBA, resulting in a much better effect.

[0078] According to Table 4 below, embodiments and comparative examples of the present invention are shown regarding rated no-load loss and rated no-load noise according to the range of the second length (Lh). Two through holes (H) were applied to each of the core subparts (100, 200, 300, 400, 500), and the experiment was conducted with a total length (L) of 1340 mm. Classification 2nd Length (Lh) Rated No-Load Loss (%) Rated No-Load Noise (dBA) Remarks: Formula for 2nd Length Comparative Example 8 216.2 103.5 62.6 L / (Nh+4.2) Example 8 231 100.8 59.8 L / (Nh+3.8) Example 1 285.1 100 59.2 L / (Nh+2.7) Example 9 418.7 100.6 59.6 L / (Nh+1.2) Comparative Example 9 478.6 101.9 61.3 L / (Nh+0.8)

[0079]

[0080] As shown in Table 4 above, according to Example 1 and Examples 8 and 9, it can be seen that the rated no-load loss and no-load noise are superior compared to Comparative Examples 8 and 9.

[0081] In the case of Comparative Example 8, problems such as magnetic field rotation interference and waveform distortion in the joint core region occurred, resulting in poor no-load loss and no-load noise. In addition, in the case of Comparative Example 7, the first length (Lhh), which is the distance between the through holes, narrowed, causing the magnetic field bottleneck phenomenon to intensify and become distorted, and problems requiring reassembly due to faulty core assembly also occurred.

[0082] In the following method for manufacturing a transformer core, the contents described in the above transformer core are to be cited as is, unless otherwise noted. Also, Figures 1 to 4 are to be cited.

[0083] FIG. 6 illustrates a method for manufacturing a transformer core according to an embodiment of the present invention. FIG. 6 shows a slitting step, (b) a cutting and punching step, (c) a lamination step, and (d) a fixing step.

[0084] A transformer core according to one embodiment of the present invention is formed by undergoing a slitting step, a cutting and punching step, a lamination step, and a fixing step.

[0085] The slitting step is a step of dividing electrical steel sheets wound in a coil form into appropriate widths. It is a step for dividing them into several parallel material strips of a specific width.

[0086] The cutting and punching step is a step of cutting the material strip, which has been slit and divided into appropriate widths, into a desired shape. Then, a through hole (H) is formed for stacking the multiple cut strips.

[0087] The lamination step is a step of laminating the cut material strips according to their shape, in which the lamination is performed with the positions of the through holes (H) aligned. In the lamination step, lamination may also be performed using a step-lap method. The step-lap method is a lamination method in which layers are formed by giving a certain spacing between each sheet. For example, one electrical steel sheet constituting a yoke is laminated to another electrical steel sheet constituting a yoke using the step-lap method, and one electrical steel sheet constituting a leg is laminated to another electrical steel sheet constituting a leg using the step-lap method. It is preferable that the step-lap method be formed with 4 to 7 layers.

[0088] The fixing step involves attaching a frame to both outer surfaces of the steel plate laminate, fastening a fastening member (e.g., a bolt) into the through hole (H), and fixing it by binding it tightly around the core. At this time, it is preferable to use a non-magnetic steel frame so as not to affect the electrical steel plate material. Additionally, the pressure applied for binding may be 0.005 to 0.11 MPa. If the pressure is less than 0.005 MPa, there is a higher possibility that the problem of improper fixing will occur, and if the pressure is greater than 0.11 MPa, the pressure may be too high, causing the electrical steel plate to be damaged.

[0089] In particular, according to one embodiment of the present invention, in the cutting and punching step, the diameter of the through hole (H) can be cut and punched to satisfy 0.02 to 0.2 when compared to the width (D / w), which is the shorter length between the first direction (DR1) and the second direction (DR2) that intersects the stacking direction (DR3) in the cut shape.

Claims

1. A plurality of steel plates are laminated, and the core subpart includes a through hole penetrating in the lamination direction, and A first direction intersecting the stacking direction and a direction intersecting the stacking direction and the first direction are defined as a second direction, and When comparing the length in the first direction and the length in the second direction in the above core subpart, and the shorter length is denoted as the width (w), A transformer core having a ratio (D / w) of the diameter (D) and width (w) of the through hole of 0.02 to 0.

20.

2. In Paragraph 1, A transformer core in which a plurality of the above-mentioned core subparts have a width parallel to the first direction or the second direction and are arranged to form a closed cross-section on a plane parallel to the first direction and the second direction when combined.

3. In Paragraph 2, A transformer core in which the joint portion where the above-mentioned plurality of core subparts are joined is joined by stacking in a step-lap manner.

4. In Paragraph 3, A transformer core comprising 4 to 7 stages of the above-mentioned step laps.

5. In Paragraph 4, A plurality of the above-mentioned core subparts are, A plurality of steel plates are stacked, a first yoke arranged parallel to the first direction, and a second yoke arranged parallel to and spaced apart from the first yoke, A transformer core comprising a plurality of steel plates stacked, a first leg connected to the first yoke and the second yoke and arranged in the second direction, a second leg spaced apart from and arranged parallel to the first leg, and a third leg arranged between the first leg and the second leg.

6. In Paragraph 1, A transformer core in which a fastening member is coupled to the above-mentioned through hole.

7. In Paragraph 6, A transformer core in which the pressure applied by the fastening member to the steel plate is 0.005 to 0.11 MPa.

8. In Paragraph 1, When comparing the length of the first direction and the length of the second direction in the above core subpart, and the longer length is referred to as the total length, A transformer core in which the number of through holes of the core subpart and a second length, which is the distance from the through hole to the end of the core subpart along an arbitrary line extending the center of the plurality of through holes, satisfy the following formula. Equation 1: L / (Nh+4) < Lh < L / (Nh+1) (Here, L is the total length, Lh is the second length, and Nh is the number of through holes) 9. A cutting and punching step of cutting a strip into a desired shape, forming a through hole in the cut strip, and processing the diameter (D) of the through hole to satisfy 0.02 to 0.2 when compared (D / w) with the width (w), which is the shorter length between the first direction of the cut strip and the second direction intersecting the first direction; and A method for manufacturing a transformer core, comprising a lamination step of laminating the above strips.

10. In Paragraph 9, A method for manufacturing a transformer core, comprising a fixing step of attaching a frame to both outer surfaces of a laminated steel plate strip and fixing it by binding a fastening member to a through hole.

11. In Paragraph 10, The above frame is a method for manufacturing a transformer core made of a non-ferromagnetic material.

12. In Paragraph 10, A method for manufacturing a transformer core, wherein the pressing force for binding in the above fixing step is 0.005 to 0.11 MPa.

Images