Iron core for transformer and method for manufacturing same

Abstract

The present invention relates to an iron core for a transformer having low no-load loss and a method for manufacturing same. According to an embodiment of the present invention, the iron core for a transformer comprises: a first stacking unit formed by stacking a plurality of electrical steel sheets in a first direction and positioned to form a continuous surface in a second direction intersecting the first direction; and a second stacking unit formed by stacking a plurality of electrical steel sheets in the first direction and positioned to form a continuous surface in a third direction intersecting the first direction and the second direction, wherein a coupling unit in which the first stacking unit and the second stacking unit are connected includes a stepped portion formed at a first end, which is an end of the electrical steel sheet included in the first stacking unit, and an accommodation unit in which a second end, which is an end of the electrical steel sheet included in the second stacking unit, is shape-coupled to the stepped portion, and the electrical steel sheets included in the first stacking unit and the second stacking unit are stacked in a step lap manner in the first direction.

Description

Transformer 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 use—are subject to institutional regulations. Accordingly, various measures are being proposed to reduce no-load losses and no-load noise.

[0004] In addition, a core coupling part is formed, and it is necessary to improve the quality of the transformer core by facilitating the coupling and secure fixation of multiple cores and preventing them from easily separating during movement.

[0005] According to one embodiment of the present invention, a transformer core with low no-load loss can be provided.

[0006] According to another embodiment of the present invention, a transformer core that is easy to manufacture and easy to disassemble and reassemble can be provided.

[0007] 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.

[0008] A transformer core according to one embodiment of the present invention comprises a first laminated portion formed by stacking a plurality of electrical steel plates in a first direction and positioned so as to form a continuous surface in a second direction intersecting the first direction, and a second laminated portion formed by stacking a plurality of electrical steel plates in the first direction and positioned so as to form a continuous surface in a third direction intersecting the first direction and the second direction, wherein a connecting portion connecting the first laminated portion and the second laminated portion comprises a step portion formed at a first end portion of an electrical steel plate included in the first laminated portion, and a receiving portion formed at a second end portion of an electrical steel plate included in the second laminated portion that is shaped-coupled to the step portion, and the electrical steel plates forming the first laminated portion and the second laminated portion are stacked in a step-lap manner in the first direction.

[0009] According to another embodiment of the present invention, the transformer core may include inclined surfaces corresponding to each other at the first end and the second end.

[0010] In a transformer core according to another embodiment of the present invention, the stepped portion may include a plurality of steps extending in the first direction. The stepped portion may include one or more steps extending in the first direction, and the receiving portion may include one or more inlet grooves extending in the first direction.

[0011] In a transformer core according to another embodiment of the present invention, the step difference may be 10 to 90% based on the height in the first direction of the electrical steel sheet.

[0012] In a transformer core according to another embodiment of the present invention, when there are multiple steps, the sum of the steps may be 10 to 90% based on the height in the first direction of the electrical steel sheet.

[0013] In a transformer core according to another embodiment of the present invention, the first end may have a different number of steps formed on a plane cut in a direction perpendicular to the first direction.

[0014] In a transformer core according to another embodiment of the present invention, the electrical steel sheets may be laminated such that the length of the contact area where the first end and the second end come into contact and overlap is at least longer than the length of the inclined surface projected in the first direction.

[0015] In addition, the electrical steel sheet may have a thickness of 0.05 to 5.0 mm in the first direction.

[0016] A method for manufacturing a transformer core according to one embodiment of the present invention comprises a processing step of forming a shape of a stepped portion or an inlet groove at the end of a cut electrical steel sheet, a lamination step of laminating the electrical steel sheet in a step-lap manner, and a fixing step of fixing a first laminate and a second laminate, which are a plurality of laminated electrical steel sheets, by combining them in shape.

[0017] In addition, the processing step may include the step of forming an inclined surface by obliquely cutting or slicing the end of the electrical steel sheet.

[0018] According to the present invention, the iron core of the transformer is easy to form and no-load losses are reduced, thereby enabling the effect of improving the performance of the transformer.

[0019] FIG. 1 is a perspective view illustrating a transformer core according to one embodiment of the present invention.

[0020] FIG. 2 is a view of the joint portion of a transformer core stacked in step-laps from direction A of FIG. 1, where (a) is a first comparative example, (b) is a part of a transformer core according to the first embodiment of the present invention, and (c) is another comparative example to explain the stacking method of step-laps.

[0021] FIG. 3 is a cross-sectional view illustrating the shape of a transformer core coupling portion according to a first embodiment of the present invention.

[0022] FIG. 4 is a perspective view and an enlarged view of a part of the coupling portion of the transformer core portion according to the first embodiment of the present invention.

[0023] FIG. 5 is a cross-sectional view illustrating the shape of a connecting portion of a transformer core according to a second embodiment of the present invention.

[0024] FIG. 6 is a cross-sectional view illustrating the shape of a connecting portion of a transformer core according to a third embodiment of the present invention.

[0025] FIG. 7 is a perspective view and an enlarged view of a part of the coupling portion of the transformer core portion according to the third embodiment of the present invention.

[0026] FIG. 8 is a perspective view and an enlarged view of a part of the coupling portion of the transformer core portion according to the fourth embodiment of the present invention.

[0027] FIG. 9 is a perspective view and an enlarged view of a part of the coupling portion of the transformer core of Comparative Example 1.

[0028] FIG. 10 is a flowchart of a method for manufacturing a transformer core according to an embodiment of the present invention.

[0029] 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.

[0030] In addition, embodiments of the present invention are provided to more fully explain the present invention to those with average knowledge in the relevant technical field.

[0031] In drawings, the shapes and sizes of elements may be exaggerated for clearer explanation.

[0032] 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.

[0033] 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.

[0034] Unless otherwise specifically defined in the specification of the present invention, % units mean weight %.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] FIG. 1 is a perspective view illustrating a transformer core according to one embodiment of the present invention.

[0040] A transformer core according to one embodiment of the present invention includes a first stacked portion (1), a second stacked portion (2), and a connecting portion (4).

[0041] A transformer core may include a first stacking section (1) in which a plurality of electrical steel plates (S) are stacked in a first direction (DR1) and a surface continuous in a second direction (DR2) intersecting the first direction (DR1) is formed in a stacked state of electrical steel plates (S), a second stacking section (2) in which a surface continuous in a third direction (DR3) intersecting the first direction (DR1) and the second direction (DR2) is formed, and a connecting section (4) in which the first stacking section (1) and the second stacking section (2) are connected.

[0042] For example, the first stacking part (1) may be a yoke and the second stacking part (2) may be a leg. Alternatively, the first stacking part (1) may be a leg and the second stacking part (2) may be a yoke. This is not limited, but the following description will be given in the case where the first stacking part (1) is a yoke and the second stacking part (2) is a leg.

[0043] For example, the electrical steel sheets (S) forming the first laminated section (1) and the second laminated section (2) can be laminated in a step-lap manner in the first direction (DR1).

[0044] As an example of the step lap method, individual electrical steel sheets (S) forming the first laminated section (1) or the second laminated section (2) are cut in a direction perpendicular to the first direction (DR1) and then laminated, and the ends of the electrical steel sheets (S) are laminated so that they are formed in a stepped manner along the first direction (DR1). Accordingly, the spacing shape formed in the joint section (4) formed by the ends of the first laminated section (1) or the second laminated section (2) can also be formed in a stepped manner, and the structural rigidity of the transformer core can be increased. As another example of the step lap method, individual electrical steel sheets (S) are cut obliquely to intersect with the first direction (DR1) to form an inclined surface at the ends, and the electrical steel sheets (S) are laminated so that the ends are formed in a stepped manner along the first direction (DR1). The spacing shape formed in the joint section (4) can also be formed in a stepped manner, and the structural rigidity of the transformer core can be increased.

[0045] For example, a portion of the first laminated section (1) and the second laminated section (2) may be formed integrally. The first laminated section (1) and the second laminated section (2) are each formed by laminating a plurality of electrical steel sheets (S). To do this, two or more electrical steel sheets (S) are prepared first, and each electrical steel sheet (S) can be processed into a cross-sectional shape perpendicular to the first direction (DR1), which is the thickness (t) direction of the electrical steel sheet (S) of the first laminated section (1) or the second laminated section (2). For example, the electrical steel sheet (S) can be slit to the width of the transformer core, and then the electrical steel sheet (S) slit to an appropriate width can be cut and punched to match the shape of the connecting section (4) of the core, thereby forming the shape of the first laminated section (1) and the second laminated section (2). In this way, the electrical steel sheet (S) can be formed to have the same cross-sectional shape as the first laminate (1) and the second laminate (2).

[0046] For example, the electrical steel sheet (S) may be a oriented electrical steel sheet or a non-oriented electrical steel sheet having a thickness (t, see FIG. 3) of 0.05 to 5.0 mm in the first direction (DR1). The end of the second laminated section (2) facing the first laminated section (1) in the joint section (4) may be fitted by creating a step-like step on an inclined surface formed obliquely so as to intersect with the first direction (DR1). The type of electrical steel sheet (S) is not particularly limited, but may be selected from an oriented electrical steel sheet (S) or a non-oriented electrical steel sheet (S) having a thickness (t) of 0.05 to 5.0 mm.

[0047] If the thickness (t) of the electrical steel sheet (S) is thinner than 0.05 mm, the iron loss decreases, but the shape stability decreases. On the other hand, if the thickness (t) of the electrical steel sheet (S) is thicker than 5.0 mm, the iron loss may increase rapidly, so considering these factors, the thickness (t) of the electrical steel sheet (S) may be 0.05 to 5.0 mm.

[0048] FIG. 2 is a view of the joint portion from direction A of FIG. 1, where (a) shows the case of the first comparative example, (b) shows the case of the first embodiment of the present invention, and (c) shows the case of the second comparative example.

[0049] And, in a situation where multiple electrical steel sheets are laminated, it can be examined based on individual electrical steel sheets of each first laminate (1) (11, 12, 13, 14, 15, 16, see FIG. 5, 6 and 8 below) and individual electrical steel sheets of the second laminate (2) (21, 22, 23, 24, 25, 26, see FIG. 5, 6 and 8 below).

[0050] Magnetic fields have the property of flowing to the place with the least magnetic resistance. Magnetic resistance is inversely proportional to permeability, which is an indicator of how smoothly a magnetic field flows. Since permeability is hundreds to tens of thousands times that of electrical steel (S) when air is assumed to be 1, magnetic resistance becomes very high when moving away from electrical steel (S).

[0051] The gap between electrical steel sheets (S) stacked in the first direction (DR1), i.e., the air layer (L), is much wider than the air gap (G) where the electrical steel sheets (S) face each other laterally. Accordingly, magnetic resistance is greater in the air gap (G) than in the air layer (L). According to FIG. 2, the air gap (G) and the air layer (L) are depicted as being almost similar, but the air layer (L) is formed narrower than the air gap (G) in all cases, and the air gap (G) can be formed relatively wider in case (a) of FIG. 2 than in cases (b) and (c).

[0052] As a result, when the magnetic field flowing within a single electrical steel sheet (S) reaches the air gap (G), the magnetic field is dispersed and moves through the air layer (L), which has lower magnetic resistance than the air gap (G), to the electrical steel sheet (S) stacked adjacent to the electrical steel sheet (S).

[0053] Referring to (a), an air gap (G) of about 2 to 6 mm occurs, which increases the harmonics of the magnetic field significantly and increases magnetic resistance. In the case of (b), the air gap (G) becomes smaller than in (a), so the magnetic field flows relatively stably. In the case of (c), the interlayer air gap (G) becomes concentrated, causing the magnetic flux density to rise rapidly and increase iron loss.

[0054] For example, the first end (11a, 12a, 13a, 14a, 15a) and the second end (21a, 22a, 23a, 24a, 25a) may include corresponding inclined surfaces. The angle (θ) of the inclined surface is not specified.

[0055] Referring to FIG. 2(a), the cross-section of each electrical steel sheet (S) at the joint (4) extends in the first direction (DR1), which is the stacking direction of the electrical steel sheet (S), and a stepped spacing shape is formed at a right angle to the adjacent electrical steel sheet (S). Since there is an air medium in the spacing and the magnetic resistance is very high, in this case, a bottleneck phenomenon occurs in which the magnetic field is concentrated in the iron core region where there is no spacing. As a result, a high magnetic flux density is formed locally, and iron loss increases rapidly due to the characteristics of the electrical steel sheet (S). That is, the magnetic field is concentrated in the contact region (Lct1) where the first steel sheet (11) and the second steel sheet (21) are not adjacent to each other in the same layer through the air gap (G), but are adjacent to each other in the air layer (L) in different layers, and the magnetic flux density increases rapidly. In addition, due to the bottleneck phenomenon of the magnetic field, a complex magnetic field containing various harmonics is generated from the magnetic field to a sinusoidal wave. The iron loss of electrical steel sheets (S) increases as the magnetic flux density increases, and furthermore, if harmonics are included, the increase in iron loss increases rapidly.

[0056] In general, it can be assumed that the magnetic field flows from left to right in the drawing. If an air gap is formed, the magnetic field may move by passing through an adjacent steel plate while avoiding the air gap (G). Here, the contact area (Lct1) can be defined as the area where the first end (11a) of the first laminated part (1) and the second end (21a) of the second laminated part (2) overlap when viewed from the first direction, in the path where the magnetic field flows from the middle steel plate and moves to the upper steel plate while avoiding the air gap. In this case, since it is the path where the magnetic field flows, it can be defined on the first steel plate (11) and the second steel plate (21) that form different layers. In (b), the contact area (Lct2) is between the middle in the first direction and the uppermost steel plate in the first direction in the drawing, and the magnetic field avoids the air gap between the end of the upper steel plate and the adjacent steel plate, and the path of movement of the magnetic field is equal to the length indicated in the drawing. In (c), the contact area (Lct3) is likewise equal to the length indicated in the drawing when moving from the upper steel plate in the first direction to the steel plate in the vicinity. However, in this case, it can be understood as the path when the magnetic field moving through the uppermost part moves to the intermediate steel plate. The definition of the contact areas (Lct1, Lct2, Lct3) is the same in the following description and embodiments.

[0057] To resolve this, the length of the contact area (Lct1) in Fig. 2 (a) can be extended, but in this case, the portion exposed from the joint part (4) of the iron core to the outer edge of the iron core is increased by the length of the non-overlapping area (Lov1).

[0058] Here, the non-overlapping area (Lov1) can be defined as an area where the position of either the electrical steel plate (S) of the first laminated section (1) or the electrical steel plate (S) of the second laminated section (2) is changed based on the gap (G). Figure 2(a) shows the area where the second steel plate (21) formed on the bottom layer has moved based on the end (21a) of the second steel plate (21) formed in the middle. The non-overlapping area (Lov1) may include the gap (G). In the case of (b), the non-overlapping area (Lov2) is indicated as the length moved to the left based on the steel plate located in the middle being arranged together with the steel plate located below. In the case of (c), the non-overlapping area (Lov3) is indicated as the length moved to the left based on the steel plate located in the middle being arranged together with the steel plate located below, similar to (b). In the following description and examples, the definition of the non-overlapping regions (Lov1, Lov2, Lov3) is the same.

[0059] The increase in the exposed portion due to the non-overlapping area (Lov1) becomes another factor that increases iron loss by generating a leakage magnetic field where the magnetic field flows out of the iron core, and also results in worsening noise due to vibration of the exposed electrical steel sheet (S). For this reason, there are limitations to the application of methods to increase the length of the non-overlapping area (Lov1). For example, in the iron core of a transformer, the length of the non-overlapping area (Lov1) is typically managed to be within 2 to 6 mm.

[0060] Accordingly, in a transformer core according to one embodiment of the present invention, when cutting an electrical steel sheet (S) as shown in (b) of FIG. 2, the end corresponding to the joining portion (4) of the core in each electrical steel sheet (S) is cut or trimmed at an angle with respect to the first direction (DR1) so that the first end (12a) and the second end (22a) include an inclined surface.

[0061] These inclined surfaces can be formed by grinding the ends. The first end (12a) and the second end (22a) of the first laminated part (1) and the second laminated part (2) can be formed as inclined surfaces symmetrically to each other and arranged correspondingly to match the shape.

[0062] In this way, by forming the first end (12a) and the second end (22a) at an angle, the gap (G) is minimized, so that even if the same non-overlapping area (Lov2) as Comparative Example 1 is applied, the magnetic field distribution within the iron core flows more smoothly, thereby reducing iron loss and noise.

[0063] For example, the electrical steel sheet (S) can be laminated such that the length of the contact area (Lct2) where the first end (12a) and the second end (22a) come into contact and overlap is at least longer than the length (Lp2) of the inclined surface projected in the first direction (DR1).

[0064] When cutting the electrical steel sheets (S) at an angle with an inclined surface in the first direction (DR1) and stacking them in a step-lap manner, it is preferable to stack them in a direction in which the contact area (Lct2) is expanded as shown in (b) of FIG. 2. To do this, the electrical steel sheets (S) can be stacked such that the length of the contact area (Lct2) is at least longer than the length (Lp2) projected by the inclined surface in the first direction (DR1).

[0065] Referring to FIG. 2(c), the length of the contact area (Lct3) is at least shorter than the length (Lp3) projected in the first direction (DR1) of the inclined surface. This is because, even though the first end (13a) and the second end (23a) are formed symmetrically with respect to each other as inclined surfaces and arranged correspondingly to be shaped, the non-overlapping area (Lov3) is very large and the contact area (Lct3) is too small, which would cause the iron loss to be very large and noise to be generated, so this can be prevented.

[0066] For example, an adhesive may be applied between the first end (11a, 12a, 13a, 14a, 15a; see FIGS. 5 and 6 below) and the second end (21a, 22a, 23a, 24a, 25a; see FIGS. 5 and 6 below) to secure them. In this case, they can be secured stably, and there is an advantage that there is no need to drill additional holes or mechanically secure them with screws. However, there are disadvantages, such as the alignment of the iron cores becoming disrupted while securing them with an adhesive between the inclined cross-sections, and the number of iron cores produced being limited due to the heat treatment process. Furthermore, if the transformer iron core does not meet the required characteristics after manufacturing, it is necessary to dismantle the iron core, recycle it, and reassemble it. However, when dismantling the iron core, if adhesive is present, it is difficult to remove the bonded parts, and there may be problems where the shape of the iron core is frequently damaged and iron loss increases significantly, making recycling difficult.

[0067] Accordingly, in order to easily interlock and fix the coupling portion (4), the first end portion (11a, 12a, 13a, 14a, 15a) may further include a stepped portion (120, 140, see FIG. 3 and 5 below), and the second end portion (21a, 22a, 23a, 24a, 25a) may further include a receiving portion (220, 240, see FIG. 3 and 5 below) that is shaped and coupled with the stepped portion (120, 140). The stepped portion (120, 140) and the receiving portion (220, 240) will be described in detail below.

[0068] FIGS. 3 and FIGS. 4 illustrate a joint portion of a transformer core according to a first embodiment of the present invention. FIG. 3 illustrates a portion of a single layer of electrical steel sheet forming a first laminate and a second laminate according to the first embodiment of the present invention, and illustrates a cross-section of the joint portion. FIG. 4 illustrates a perspective view, in which a portion of the steel sheet forming the joint portion has been moved to better show its features, and an enlarged cross-sectional view is added to illustrate a portion of the joint portion in detail.

[0069] For example, the coupling portion (4) may include a step portion (120) formed on a first end portion (12a) on an electrical steel sheet (12) constituting the first laminated portion (1), and a second end portion (22a) constituting the electrical steel sheet (S) constituting the second laminated portion (2) may include a receiving portion (220) that is shaped-coupled with the step portion (120).

[0070] The step portion (120) may be a protruding part forming one or more steps having a step (ts) extending from the first end portion (12a) in the first direction (DR1).

[0071] For example, the step portion (120) may include a first edge (121) extended in a first direction (DR1) and a second edge (122) extended in a direction perpendicular to the first direction (DR1). If an inclined surface is formed at the first end (12a), the step portion (120) may have the shape of a right triangle protruding from the inclined surface in cross-section. If an inclined surface is not formed at the first end (12a), the step portion (120) may have the shape of a rectangle protruding from the end in cross-section. In this case, it may have a shape similar to a step. At this time, the length (ta) of the second edge (122) is not separately set.

[0072] The receiving portion (220) may include one or more inlet grooves that extend from the second end into the first direction (DR1). The receiving portion (220) may be a part that forms a shape with the stepped portion (120) at the second end (22a).

[0073] For example, the receiving portion (220) may include an inlet groove comprising a first wall (221) extending from the second end (22a) in the first direction (DR1) and a second wall (222) extending in a direction perpendicular to the first direction (DR1). If an inclined surface is formed at the second end (22a), the inlet groove may have a right-angled triangle formed from the inclined surface in cross-section. If an inclined surface is not formed at the second end (22a), the inlet groove may have a rectangular shape formed from the inlet surface in cross-section. In this case, it may have the shape of an inverted staircase.

[0074] However, the stepped portion (120) and the receiving portion (220) described above are examples, and may have various shapes in addition to the shape described above.

[0075] For example, the step (ts) may be 10 to 90% based on the material thickness (t), which is the height in the first direction (DR1) of the electrical steel sheet (S).

[0076] Steps (ts) can be formed as one or multiple steps, and the section of the core cutting surface is divided to combine one step and multiple steps (ts) to improve the fastening and assembly of the cores.

[0077] The reason for leaving a non-stepping area within a range not exceeding 10% in the direction of the iron core thickness (t) is to facilitate the movement of magnetic domains within the electrical steel sheet (S).

[0078] Magnetic domains that are invisible to the naked eye are clusters of identical magnetic moments, and when an external magnetic field is applied, they form a regular arrangement within the electrical steel sheet (S) and contribute to aligning the direction of the external magnetic field with the magnetic field within the electrical steel sheet (S). Smooth movement and rotation of the magnetic domains have the characteristic of lowering iron loss. Therefore, the step (ts) can be formed such that it is 10 to 90% of the thickness (t) in the first direction (DR1).

[0079] For example, when a first height (h1) and a second height (h2) are formed with a step difference (ts) in between based on the material thickness (t), there is no limit to these first height (h1) and second height (h2), and they may be zero. However, it is sufficient for the step difference (ts) based on the material thickness (t) to be formed at 10 to 90% as described above.

[0080] FIG. 5 illustrates a joint portion of a transformer core according to a second embodiment of the present invention. It shows a portion of a single layer of electrical steel sheet forming a first laminate and a second laminate, and illustrates a cross-section of the joint portion.

[0081] For example, the first end (14a) and the second end (24a) may be composed of a first end (14a) and a second end (24a) that do not include corresponding inclined surfaces and include a surface parallel to the first direction (DR1).

[0082] In this case, as mentioned above, the stepped portion (240) in cross-section may have a rectangular shape surrounded by a first corner (141) and a second corner (142) protruding from the first end (14a). In this case, it may have a shape similar to a step. The receiving portion (240) may also include an inlet groove surrounded by a first wall (241) parallel to the first direction (DR1) and a second wall (242) perpendicular thereto, so that it can be combined in a shape corresponding to the stepped portion (140). Furthermore, the step (ts) may be formed identically to the first embodiment having an inclined surface, and the length (ta) of the second corner (142) is irrelevant.

[0083] FIGS. 6 and FIGS. 7 illustrate a joint portion of a transformer core according to a third embodiment of the present invention. FIG. 6 illustrates a portion of a single layer of electrical steel sheet forming a first laminate and a second laminate, showing a cross-section of the joint portion, and FIG. 7 is a perspective view and a partial cross-sectional view.

[0084] A stepped portion having a plurality of steps (ts1, ts2) may be formed on the first end (15a) included in the coupling portion (4) of the transformer core according to the third embodiment. And a receiving portion that is shaped and coupled thereto may be formed on the second end (25a).

[0085] An example can be given in which a stepped portion having two steps is formed on the first end (15a). For other explanations, refer to the contents of FIG. 3 above.

[0086] For example, if there are multiple steps (ts1, ts2), the sum of the steps (ts1, ts2) may be 10 to 90% based on the thickness (t), which is the height in the first direction (DR1) of the electrical steel sheet (S).

[0087] When a first step (ts1) and a second step (ts2) are formed and a height of an inclined surface is provided between the first step (ts1) and the second step (ts2), the sum of the first step (ts1) and the second step (ts2) should be within 10 to 90% of the material thickness (t). In such cases, the height (h1, h2, h3) of the part where the steps (ts1, ts2) are not formed is irrelevant, and multiple steps (ts1, ts2) may be formed continuously. In this case as well, the length (ta1, ta2) in the direction perpendicular to the first direction (DR1) of the step portion is irrelevant.

[0088] FIG. 8 shows a perspective view of a coupling portion of a transformer core according to a fourth embodiment of the present invention, and a cross-sectional view cut along the cross-sections BB' and C-C' shown in the drawing.

[0089] The coupling portion (4) of the transformer core according to one embodiment of the present invention may have a different number of steps at the first end on a single sheet of electrical steel (16) of the first laminated portion (1). For example, the number of steps at the first end may be formed differently on a plane cut in a direction perpendicular to the first direction (DR1).

[0090] A plurality of cross-sections perpendicular to the first direction (DR1) at the first end of a single sheet of electrical steel (16) of the same layer may have different steps. On one cross-section, one step may be formed (161), and on another cross-section, two steps may be formed (162).

[0091] When different steps are formed on individual electrical steel sheets (S) in this way, they can be combined with a receiving portion corresponding to the shape and provide the effect of not being easily separated. The number of such steps is not limited to a specific number.

[0092] A plurality of inlet grooves may be formed in a single sheet of electrical steel (26) of the same layer of the receiving portion, and on one cross-section, one inlet groove may be formed (261), and on another cross-section, two inlet grooves may be formed (262).

[0093] In addition, the adhesion of the joint part (4) is superior to that of the first embodiment or the third embodiment having two steps, so the effect of further reducing the gap (G) may occur.

[0094] FIG. 9 is a perspective view and a partial cross-sectional view illustrating the coupling portion of a conventional transformer core.

[0095] In the case where the step portion (120, 140; see FIG. 5) and the receiving portion (220, 240; see FIG. 5) are not formed in the connecting portion (4), a punching hole (not shown) for fixing may be additionally provided for assembly.

[0096] In contrast, the transformer core according to one embodiment of the present invention may omit the hole penetrating the core and the hole punching process for forming such a hole to fix the assembled state of the core. Thus, since the electrical steel sheet (S) is fastened by fitting it into the shape of the end without forming a hole in it, the transformer core according to one embodiment of the present invention can prevent damage to the magnetic properties of the electrical steel sheet (S) caused by the hole. However, the formation of a hole is not excluded from the scope of the present invention because forming a hole has the advantage of making the lamination of the electrical steel sheet (S) easier.

[0097] Due to the above configuration, the transformer core according to one embodiment of the present invention has excellent characteristics, such as excellent coupling with no-load noise and low no-load loss.

[0098] Among the coils of a transformer, the primary coil is connected to an input circuit that requires voltage change, and the secondary coil is connected to an output circuit where the changed voltage is used. Here, magnetic energy is used for the conversion of electrical energy between the primary and secondary coils. Depending on whether a power load connected to the secondary coil is in use, it is divided into no-load characteristics and load characteristics. The no-load characteristic refers to the case where there is no load; it occurs 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.

[0099] On the other hand, load characteristics occur when power is used from a load connected to a secondary coil, and load loss is determined by the Joule loss dissipated in the coil, and load noise appears due to the electromagnetic force of the coil and iron core.

[0100] As a method to reduce no-load loss, an electrical steel sheet (S) with low iron loss can be used as the core. Since iron loss increases as the thickness (t) of the electrical steel sheet (S) increases, it is desirable to select an electrical steel sheet (S) with the thinnest possible thickness (t). In addition, since iron loss decreases when a large amount of components such as silicon or aluminum with high resistivity is contained, it is desirable to select an electrical steel sheet (S) with high resistivity characteristics.

[0101] Even if the iron core is manufactured with a constant weight using the same electrical steel sheet (S), the no-load characteristics of the transformer vary. Since this varies depending on the shape of the first laminated section (1) and the second laminated section (2) of the iron core—namely, the width, length, size, and the laminated height of each part—most transformer manufacturers manage the design drawings optimally through experience.

[0102] And, since the iron loss in the rolling direction of the electrical steel sheet (S) is about 0.2 to 3 times lower than in the rolling direction perpendicular to it, the first laminated section (1) and the second laminated section (2) are arranged so that the direction in which the magnetic field flows within the transformer core matches the rolling direction of the electrical steel sheet (S).

[0103] Meanwhile, the magnetic field flowing in the rolling direction of the electrical steel sheet (S) changes shape when it encounters another medium, such as an air layer (L), or deviates from the rolling direction. As a characteristic, the magnetic field gathers toward the side with lower magnetic resistance, increasing the magnetic flux density, and contains a component in which the frequency of the magnetic field waveform increases by several to tens of times, appearing as a harmonic waveform. This phenomenon generally always occurs at the coupling part (4) of the transformer core. Since the iron loss of the electrical steel sheet (S) increases rapidly when the magnetic flux density is high or a high-frequency magnetic field flows, it becomes a factor that increases the no-load loss of the transformer. To minimize this effect, a step wrap can be used at the coupling part (4).

[0104] As a result of various experiments on cases where step wrap is not used and cases where it is used in the joint (4), when electrical steel sheets (S) of the same material and weight are used, the difference in no-load loss of the transformer is about 5 to 15%, and the transformer with the applied step wrap was found to be superior.

[0105] The cutting method of the step wrap used at this time is as shown in Fig. 2 (a) and Fig. 9.

[0106] However, even with the application of step-lap, the transformer loss is 8 to 15% higher than the theoretical no-load loss (iron core weight [kg] X iron loss per unit iron core weight [watt / kg]). This indicates that the transformer core having a coupling part (4) as in FIG. 2 (a) and FIG. 9 does not have excellent transformer loss. This is because if the iron loss generated in the second stacking part (2) is assumed to be 1, the iron loss of the coupling part (4) increases by 1.7 to 3.2 times.

[0107] Furthermore, the method of cutting electrical steel sheets (S) at an angle, applying an adhesive to fix them, and curing them through a heat treatment process may result in problems such as difficulty in aligning the iron cores and limitations on the number of iron cores produced due to the heat treatment process. Additionally, when disassembling the iron cores, it is difficult to detach the adhesive parts, and especially during the forced separation process, the shape of the iron cores is frequently damaged and iron loss increases significantly, making recycling difficult. According to one embodiment of the present invention, the aforementioned problems can be solved, and holes penetrating the iron cores can be eliminated. At the same time, the gap (G) between the iron cores is minimized, and the magnetic field flow in the joint part (4) is smooth, thereby reducing no-load loss. Therefore, the transformer performance can be significantly improved. Moreover, when stacking the iron cores, alignment is easy without disruption, which causes the magnetic field within the iron cores to flow uniformly. In the event that the iron cores need to be remanufactured due to defects, separation between the iron cores is easy, making disassembly convenient and offering significant advantages in manufacturing.

[0108] Table 1 below compares the no-load loss by using Comparative Example 1, where the transformer core has a coupling part (4) as shown in (a) of FIG. 2 and a through hole for fastening within the core, and Example 1, where the transformer core has a coupling part (4) as shown in (b) of FIG. 2 and a through hole for fastening within the core. Then, the no-load loss is compared by considering a transformer core formed with a coupling part (4) as shown in Example 1, but with the through hole for fastening within the core removed, as Example 2. All conditions were kept the same except for the shape of the coupling part (4).

[0109] Classification No-load Loss Comparison Example 1108.6% Example 1104.7% Example 2100%

[0110]

[0111] Therefore, it can be seen that the magnetic field bottleneck is alleviated and harmonic generation is reduced, so Example 1 has superior no-load loss compared to Comparative Example 1.

[0112] Table 2 below shows a case where a transformer core is manufactured without forming a through hole for fastening inside the core or fastening with bolts, and is compared by varying only the shape of the fastening part. Comparative Example 2 is a case where the transformer core has a coupling part (4) as in (a) of FIG. 2, Example 2 is identical to Example 2 in Table 1, Example 3 is a case where the transformer core has a coupling part (4) as in FIG. 5, and Example 4 is a case where the transformer core has a coupling part (4) as in FIG. 6. Example 5 is a case where the transformer core has a coupling part (4) of the shape shown in FIG. 8, and is a case where the case with one step and the case with two steps are combined in equal proportions. Comparative Example 3 is a case where the end of Comparative Example 2 has an inclined surface, and a thin adhesive is applied thereto and then cured at a constant high temperature.

[0113] No-load Loss No-load Loss upon reassembly after disassembly Remarks Comparison Example 2105.5% 106.3% Insufficient core alignment, excellent core disassembly and reassembly Example 2100% 100.9% Excellent core alignment, excellent core disassembly and reassembly Example 3100.2% 100.9% Excellent core alignment, excellent core disassembly and reassembly Example 499.4% 100.5% Excellent core alignment, excellent core disassembly and reassembly Comparison Example 3102.8% 122.8% Insufficient core alignment, poor core disassembly and reassembly

[0114]

[0115] Comparative Example 2 is a case where the through hole in the iron core is removed from Comparative Example 1. The fastening part with the through hole formed is simply cut perpendicular to the cross-section, so the gap (G) with the opposing iron core is not maintained uniformly, and consequently, the alignment of the stacked iron cores is insufficient. In addition, workability is poor, so a problem arises in that an additional process of aligning the iron cores by hammering the side of the iron core is unavoidable in order to align the stacked iron cores uniformly. Specifically, in Comparative Example 2, the hole penetrating the iron core is removed and the cut surface of the iron core fastening part is processed vertically. When stacking, the assembly performance is inferior, resulting in an uneven gap (G) spacing and insufficient alignment of the iron cores, and consequently, the no-load loss was 5.5% worse than that of Example 2. On the other hand, although it was easy to disassemble and reassemble the iron core, the no-load loss at this time was 6.3%. This is due to the tendency for the no-load loss to worsen somewhat as external stress is applied during the process of handling individual iron cores during disassembly and reassembly.

[0116] Example 2 forms an inclined surface and places a step (ts) in the center of the thickness (t) of the electrical steel sheet (S) to improve assembly with the facing iron core. In Example 2, the iron core alignment is excellent due to the step on the inclined cut surface, and the gap (G) is significantly improved compared to Comparative Example 2, making disassembly and reassembly of the iron core easy to handle. It can be confirmed that the gap (G) is reduced and the change in the magnetic field of the iron core connection part is not large, resulting in excellent no-load loss.

[0117] In Example 3, a coupling part (4) is formed that includes a first end having two steps (ts1, ts2) and forming an inclined surface. In Example 3, the iron core alignment and assembly properties were excellent, the no-load loss was low, and reassembly was easy.

[0118] Example 4 has a better seal of the fastening part than Example 2, resulting in a further reduction in the gap (G). Example 4 is a combination of the methods of Example 2 and Example 3, and the assembly and fastening properties were the best, making alignment easy. As a result, the gap (G) was significantly reduced, and consequently, the no-load loss was the lowest.

[0119] Comparative Example 3 has the disadvantage that the manufacturing time increases by 3 to 4 hours due to the process of applying and curing adhesive on the inclined surface, resulting in a reduced amount of iron core produced. Additionally, the no-load loss tended to be higher than that of the example because the adhesive had to be applied and the iron core aligned with a hammer. Above all, when the iron core is disassembled and reassembled due to dissatisfaction with the transformer characteristics, the adhesive part is not easy to separate and must be forcibly separated, causing damage to accumulate in the iron core and resulting in a rapid increase in no-load loss after reassembly.

[0120] Hereinafter, regarding the method for manufacturing a transformer core, the contents described in the above transformer core shall be cited unless otherwise specified.

[0121] FIG. 10 is a flowchart of a method for manufacturing a transformer core according to an embodiment of the present invention.

[0122] According to one embodiment of the present invention, a method for manufacturing a transformer core comprises a processing step (S100) for forming a shape of a step portion or an inlet groove at the end of a cut electrical steel sheet (S), a lamination step (S200) for laminating the electrical steel sheet (S) in a step-lap manner, and a fixing step (S300) for fixing a first laminate and a second laminate, which are laminates of a plurality of laminated electrical steel sheets (S), by combining them in shape.

[0123] In addition, the processing step (S100) may include a step of forming an inclined surface by obliquely cutting or slicing the end of the electrical steel sheet (S).

[0124] The first laminate and the second laminate may be the yoke or leg of the transformer core, and may mean a case where the first laminate (1) and the second laminate (2) mentioned above are separated into distinct configurations without being combined.

[0125] The term "cut electrical steel sheet (S)" may refer to an electrical steel sheet (S) that has been processed first according to the shape of the first laminate or the second laminate. In addition, the electrical steel sheet (S) can be processed into a suitable shape through processing processes such as a cutting process, a slitting process, or a grinding process.

[0126] In the fixing step (S300), a plurality of first and second laminates may be fitted together and formed into a shape, or the first and second laminates may be alternately placed and formed into a shape. In this case, a part rather than the entirety of the first laminate (1) or the second laminate (2) may become the first laminate or the second laminate.

[0127] When formed in the manner described above, assembly is easy, and processing is facilitated as there is no need to perform separate processes such as pressurization or heat treatment; furthermore, the transformer exhibits excellent no-load losses, and disassembly is advantageous in the event of a defect.

Claims

1. A first laminated portion formed by stacking multiple electrical steel sheets in a first direction and positioned so as to form a continuous surface in a second direction intersecting the first direction; A plurality of electrical steel sheets are laminated in the first direction to form a second laminated portion positioned to form a continuous surface in a third direction intersecting the first direction and the second direction; comprising The connecting part connecting the first stacked part and the second stacked part is A stepped portion formed at the first end of the electrical steel sheet included in the first laminated portion, and a second end of the electrical steel sheet included in the second laminated portion, which is shaped and coupled with the stepped portion, are included. The electrical steel sheets forming the first laminated section and the second laminated section are a transformer core that is laminated in a step-lap manner in the first direction.

2. In Paragraph 1, The transformer core comprising the first end and the second end having mutually corresponding inclined surfaces.

3. In Paragraph 1, The above-mentioned stepped portion is a transformer core comprising a plurality of steps extending in the first direction.

4. In Paragraph 3, The above step is a transformer core that is 10 to 90% based on the height of the first direction of the electrical steel sheet.

5. In Paragraph 3, A transformer core in which, when there are multiple steps, the sum of the steps is 10 to 90% based on the height of the first direction of the electrical steel sheet.

6. In Paragraph 1, The above-mentioned first end is, A transformer core formed with a different number of steps on a plane cut in a direction perpendicular to the first direction above.

7. In Paragraph 2, The above electrical steel sheet is a transformer core laminated such that the length of the contact area where the first end and the second end contact and overlap is at least longer than the length of the inclined surface projected in the first direction.

8. In Paragraph 1, The above electrical steel sheet is a transformer core having a thickness of 0.05 to 5.0 mm in the first direction.

9. A processing step for forming a stepped portion or an inlet groove shape on the end of the cut electrical steel sheet; A lamination step of laminating the above electrical steel sheets in a step-lap manner; and A method for manufacturing a transformer core comprising: a fixing step of fixing a first laminate and a second laminate, which are a plurality of laminated electrical steel sheets, by combining their shapes.

10. In Paragraph 9, A method for manufacturing a transformer core, comprising the step of forming an inclined surface by obliquely cutting or slicing the end of the electrical steel sheet in the above processing step.

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