Transformer Core and Transformer

Abstract

To provide a transformer core having an improved stiffness, and a transformer comprising such a transformer core.SOLUTION: A transformer core comprises a first yoke, a second yoke, a column (6) having a column main axis (8) and extending between the first yoke and the second yoke, and an elongate clamping structure (10) comprising an elongate rigid member (12) having a rigid member main axis (14). The column (6) includes an elongate opening (16) having an opening main axis (18) which is oriented transversely to the column main axis (8). The rigid member (12) is positioned within the elongate opening (16) such that the rigid member main axis (14) is oriented parallel to the opening main axis (18).SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a transformer core, and more particularly to a transformer core with improved rigidity. Further, the present disclosure relates to a transformer including such a transformer core.

Background Art

[0002] Conventional transformers generally include windings attached to a core made of a ferromagnetic material. These cores have their lower ends connected to a bottom yoke and their upper ends connected to an upper yoke. These yokes and columns are generally assembled as a laminate of magnetic sheets, such as oriented or non-oriented magnetic sheets. Further, it is known to use a frame for clamping and compressing the bottom yoke and the upper yoke.

[0003] However, in certain cases of dynamic loads, such as vibration loads caused by seismic activity, the structure of the transformer assembly, i.e., the "transformer frame structure", may be displaced such that high stress levels act on the important components of the assembly. This can lead to fatigue and crack propagation mechanisms as well as failure of the transformer. For example, when transformers are used in the fields of the nuclear industry, wind power industry, marine industry and other industries, corresponding loads may occur.

Summary of the Invention

Means for Solving the Problems

[0004] There is a need to improve the technology for reducing the risk of transformer failure. In particular, there is a need for a technology to mitigate the risk of crack formation in the transformer frame structure. These objectives are achieved by the independent claims. The dependent claims refer to preferred embodiments.

[0005] According to the present disclosure, there is provided a transformer core including a first yoke, a second yoke, a column having a column spindle and extending between the first yoke and the second yoke, and an elongated clamping structure including an elongated rigid member having a rigid member spindle. The column includes an elongated opening having an opening spindle oriented transverse to the column spindle. The rigid member is positioned within the elongated opening such that the rigid member spindle is oriented parallel to the opening spindle.

[0006] The elongated clamping structure enables the realization of controllable rigidity of the column. In this way, the mechanical properties of the column and the entire transformer core can be controlled or influenced. The rigidity of the column has a great influence on the dynamic response of the transformer core and the dynamic response of the transformer to external loads such as vibratory loads or impact loads. Furthermore, it affects the quality of the noise generated by the transformer core in response to such loads. More specifically, the elongated clamping structure enables the realization of an increase in the rigidity of the transformer core, and as a result, improves the response behavior of the transformer to external loads.

[0007] The rigidity of the transformer core plays a dominant role particularly in the dynamic response of the transformer to vibratory loads. The structural rigidity of the transformer core directly affects the mechanical resonance behavior of the transformer core and the corresponding associated mode shapes. Generally, when the overall mechanical resonance frequency is low, the displacement of the structure during vibration increases, resulting in high stress levels in important parts of the transformer frame structure. The rigidity and compactness of the core columns are the main factors regarding the minimization and dominance of the mechanical resonance of the core. This is due to the fact that the ratio of the rigidity to the mass of the column is not favorable in that regard. As schematically depicted in FIGS. 2a and 2b showing a side view of the transformer, the most critical vibration mode involves the bending of the column. The elongated clamping structure enables the realization of an increase in the bending rigidity of the column, and thus enables the realization of an increase in the mechanical resonance frequency of the transformer core, and as a result, the stress level decreases. Therefore, it is possible to realize a reduction in the risk of failure of the transformer.

[0008] Various embodiments may preferably achieve the following features. Preferably, the column comprises a laminate of sheets, such as a directional or non-directional sheet. The elongate clamping structure is particularly suitable in such cases as it enables reducing the movement of the sheets relative to each other.

[0009] Preferably, the elongate clamping structure comprises a first end portion and an opposite second end portion, and the first and second end portions are configured to compress a part of the column surrounding the elongate clamping structure. This enables realizing a force to compress or clamp the column. In this way, the rigidity of the column can be further improved.

[0010] Preferably, the first end portion and / or the second end portion of the elongate clamping structure comprises a fixing member having a conical head portion. The conical head portion helps to generate a particularly effective compressive force.

[0011] Preferably, the fixing member comprises, or is formed by, for example, a socket head bolt.

[0012] Preferably, the elongate opening comprises at least one conical end portion shaped corresponding to the conical head portion of the fixing member, and the transformer core is preferably designed such that the conical head portion of the fixing member is completely positioned within the elongate opening. Thus, the adverse effect of the fixing member on the winding of the coil of the transformer wound around the column can be eliminated or at least mitigated.

[0013] Preferably, the column comprises at least one leg plate extending parallel to the column spindle, and the at least one conical end portion of the elongate opening is formed in the at least one leg plate.

[0014] Preferably, the fixing member includes a screw that is screw-connectable to the rigid member. This makes it possible to realize a controllable compressive force acting on the column in a particularly suitable and easy-to-handle manner. Further, this facilitates the assembly of the transformer core.

[0015] Preferably, the transformer core further includes at least one washer positioned around the conical head portion of the fixing member.

[0016] Preferably, the washer is made of an insulating material. This makes it possible to reduce the risk of damaging the components of the transformer core during assembly.

[0017] Preferably, the elongate clamping structure includes an insulating tube positioned between the rigid member and the inner surface of the elongate opening and configured to achieve isolation between the rigid member and the column. The insulating tube may be a flexible insulating tube.

[0018] Preferably, the washer is formed as part of the insulating tube. In other words, the insulating tube preferably extends to the outer end of the conical head portion of the fixing member. Preferably, the insulating tube is designed to end in the same plane as the circumferential outer surface section of the column directly adjacent to the conical end portion of the elongate opening. Alternatively the washer is preferably positioned between the conical head portion of the fixing member and the insulating tube. Preferably, in either case, the insulating tube and the washer are formed so as not to protrude above the circumferential outer surface section of the column.

[0019] Preferably, the transformer core includes at least one additional elongate clamping structure constructed in the same manner as the aforementioned elongate clamping structure. Preferably, the elongate rigid member of the at least one additional elongate clamping structure is oriented parallel to the elongate rigid member of the aforementioned elongate clamping structure. The at least one additional elongate clamping structure enables further improvement in the rigidity and compactness of the column.

[0020] For example, preferably, at least three elongate clamping structures are provided such that a row of elongate clamping structures along the column is formed. The at least three elongate clamping structures include a first elongate clamping structure, a second elongate clamping structure, and a third elongate clamping structure in that order. A first distance between the first elongate clamping structure and the second elongate clamping structure is different from a second distance between the second elongate clamping structure and the third elongate clamping structure. This enables achieving a particular level of rigidity and compactness of the column with a particularly small number of elongate clamping structures.

[0021] Preferably, the row of elongate clamping structures is formed such that the distance between the elongate clamping structures increases as it moves away from the first yoke. Preferably, the first yoke is a bottom yoke and the second yoke is an upper yoke.

[0022] Preferably, the transformer core further includes at least one additional column. The main axis of the at least one additional column and the main axis of the aforementioned column are positioned in a common plane. The opening main axis of the elongate opening is further oriented perpendicular to the plane.

[0023] Preferably, at least one of the at least one additional column is constructed in the same manner as the aforementioned column. Preferably, the at least one additional column includes a corresponding elongated opening, and the rigid member of the corresponding additional elongated clamping structure is similarly positioned within the elongated opening.

[0024] In accordance with a further aspect of the present disclosure, a transformer is provided that includes a transformer core according to the present disclosure and a winding wound around the column.

[0025] The subject matter of the present disclosure will be described in more detail with reference to the preferred exemplary embodiments shown in the accompanying drawings.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2a

Figure 2b

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0027] Exemplary embodiments of the present disclosure will be described with reference to the drawings. In the figures, the same or similar reference numerals indicate the same or similar elements. The features of the embodiments may be combined with each other unless otherwise specified.

[0028] FIG. 1 is a schematic front view of a transformer core according to the present disclosure. The transformer including the transformer core may be, for example, a distribution transformer. The transformer core includes a first yoke 2, a second yoke 4, and a column 6. The first yoke 2 is a lower or bottom yoke, and the second yoke 4 is an upper yoke. The column 6 extends between the first yoke 2 and the second yoke 4. The column 6 preferably has a column main axis 8 that is at least essentially vertically oriented. The cross-section of the column 6 perpendicular to the column main axis 8 is preferably circular at least in a first approximation.

[0029] The transformer core further includes at least one additional column 6′, 6″, for example, two additional columns 6′, 6″, and the main axes 8′, 8″ of the at least one additional column 6′, 6″ and the main axis 8 of the aforementioned column 6 are positioned in a common plane, for example, a vertical plane. The at least one additional column 6′, 6″ is preferably constructed in the same manner as the aforementioned column 6. The transformer includes the transformer core according to the present disclosure and windings wound around each of the columns 6, 6, 6″.

[0030] The transformer core further includes an elongate clamping structure 10. FIG. 3 is a schematic cross-sectional view of the elongate clamping structure 10 and the peripheral portion of the column 6. Note that FIG. 3 shows an enlarged distance between corresponding components merely for improved recognition. The cross-sectional view of FIG. 3 is taken in a plane perpendicular to the common plane in which the main axes 8, 8′, 8″ of the columns 6, 6′, 6″ are positioned, that is, a plane perpendicular to the drawing plane of FIG. 1.

[0031] The elongate clamping structure 10 includes an elongate rigid member 12 having a rigid member main axis 14. The rigid member 12 is preferably made of a material including metal, particularly steel. The rigid member 12 preferably has a tubular shape, for example, the shape of a hollow core bolt. For example, the rigid member 12 is a steel pipe having the shape of a hollow core bolt.

[0032] Column 6 includes an elongated opening 16 having an opening spindle 18 oriented, for example, perpendicular to column spindle 8 so as to cross the column spindle 8. Preferably, the opening spindle 18 is oriented horizontally. The rigid member 12 is positioned within the elongated opening 16 such that the rigid member spindle 14 is oriented parallel to the opening spindle 18.

[0033] Figures 2a and 2b are schematically shown side views of a prior art transformer core generally showing the effect of a load acting on the transformer core. The transformer core includes a bottom yoke 200, a column 600, and an upper yoke 400. Figure 2a shows the state of the transformer core with no load acting on the transformer core, and Figure 2b shows the state with a load acting on the transformer core as indicated by the arrow. The load causes deformation of the transformer core as shown in Figure 2b, which, as described above, is generally undesirable as it is accompanied by an increased risk of a cracking mechanism and, in some cases, causes failure of the transformer. According to the present disclosure, the rigidity of the column and the transformer core can be suitably increased under the use of an elongated clamping structure so as to prevent the corresponding undesirable deformation of the transformer core.

[0034] Preferably, the elongated rigid member 12 is designed to extend over at least 80%, more preferably at least 90%, of the length of the elongated opening 16. Preferably, both ends of the elongated rigid member 12 do not project beyond the outer surface of the column 6.

[0035] The elongated clamping structure 10 includes a first end portion 20 and an opposite second end portion 22 and are provided with. The first and second end portions 20, 22 are configured to compress a part of the column 6 surrounding the long clamping structure 10. For this purpose, the first end portion 20 and / or the second end portion 22 of the long clamping structure 10 are provided with fixing members 24, 24' having conical head portions 26, 26'. Preferably, the fixing members 24, 24' are socket head bolts. Preferably, the fixing members 24, 24' are provided with or formed by screws screwed into the rigid member 12, for example screws having a shape of a hollow core bolt, which are screw-connectable to the rigid member 12. Thereby, the long clamping structure 10 can be easily connected to the column 6 during the assembly of the transformer core.

[0036] The long opening 16 is provided with at least one conical end portion 30, 30' shaped corresponding to the conical head portions 26, 26' of the fixing members 24, 24'. This enables easy fine adjustment of the compression force acting on the column 6 generated by the fixing member 24 in combination with the long rigid member 12.

[0037] The column 6 preferably includes at least one leg plate 66 extending parallel to the column spindle 8, and at least one conical end portion 30, 30' is formed on the at least one leg plate 66. For example, the leg plate 66 forms the outer surface of the column 6. In particular, the column 6 includes a laminate of sheets, and the inner surface of at least one leg plate 66 abuts against the laminate of sheets. For example, as shown in FIG. 3, the column 6 includes two leg plates 66 arranged on both sides of the column 6 with respect to the column spindle 8.

[0038] The transformer core is preferably designed such that the conical head portions 26, 26' of the fixing members 24, 24' are completely positioned within the long opening 16. Therefore, interference between the winding of the coil wound around the column 6 and the long clamping structure 10 can be eliminated or at least alleviated.

[0039] The long-strip clamping structure 10 preferably further includes an insulating tube 32 positioned between the rigid member 12 and the inner surface of the long-strip opening 16 and configured to achieve isolation between the rigid member 12 and the column 6. For example, the insulating tube 32 is made of a material containing polytetrafluoroethylene (PTFE). Preferably, the insulating tube 32 is a PTFE tube.

[0040] The transformer core may further include at least one washer positioned around the conical head portions 26, 26' of the fixing members 24, 24'. Preferably, the at least one washer is disposed between the head portions 26, 26' of the fixing members 26, 26' and the conical end portions 30, 30' of the long-strip opening 16.

[0041] The at least one washer may be associated with the insulating tube 32 or formed as part of the insulating tube 32. Alternatively, as shown in the cross-sectional view of FIG. 4, the at least one washer, herein indicated by reference numeral 34, may be an insulating washer disposed between the head portions 26, 26' and the surfaces of the conical end portions 30, 30' of the long-strip opening 16. This reduces the risk of damaging the insulating tube 32 during assembly, for example, while tightening the fixing members 26, 26'.

[0042] As exemplarily shown in FIG. 1, the transformer core preferably further includes at least one additional long-strip clamping structure 10', 10", 10'" constructed in the same manner as the aforementioned long-strip clamping structure 10. The long-strip rigid members of the at least one additional long-strip clamping structure 10', 10", 10'" are preferably oriented parallel to the long-strip rigid member 12 of the aforementioned long-strip clamping structure 10.

[0043] For example, the transformer core includes at least three elongated clamping structures 10, 10', 10'', 10''' such that a row of elongated clamping structures is formed along the column 6. The at least three elongated clamping structures 10, 10', 10'', 10''' include a first elongated clamping structure 10, a second elongated clamping structure 10', and a third elongated clamping structure 10'' in that order. A first distance d1 between the first elongated clamping structure 10 and the second elongated clamping structure 10' is different from a second distance d2 between the second elongated clamping structure 10' and the third elongated clamping structure 10''. According to the illustrated embodiment, the row of elongated clamping structures 10, 10', 10'', 10''' is formed such that the distances d1, d2, d3 between the elongated clamping structures 10, 10', 10'', 10''' increase as they are farther from the first yoke 2. For example, the distance d i is, d i+1 =d i x i (i = 1, 2, 3,... 1.05 ≤ x i ≤ 1.5 and x i+1 > x i ) may be selected.

[0044] Although the present invention has been described in detail in the drawings and the above description, such description should be considered to be not restrictive but illustrative or exemplary. Changes to the disclosed embodiments can be understood and implemented by those skilled in the art of implementing the invention according to the claims by considering the drawings, the present disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. The mere fact that specific elements or steps are recited in each claim does not indicate that combinations of these elements or steps cannot be used advantageously. Specifically, in addition to the actual claim dependencies, any further meaningful combinations of claims are considered to be disclosed.

Claims

1. A transformer core, comprising: a first yoke (2); a second yoke (4); a column spindle (8), and a column (6) extending between the first yoke (2) and the second yoke (4); a long clamping structure (10) comprising a long rigid member (12) having a rigid member spindle (14); the column (6) includes a long opening (16) having an opening spindle (18) oriented to be transverse to the column spindle (8); the rigid member (12) is positioned within the long opening (16) such that the rigid member spindle (14) is oriented parallel to the opening spindle (18); the long clamping structure (10) includes a first end portion (20) and an opposite second end portion (22), and the first and second end portions (20, 22) are configured to compress a portion of the column (6) surrounding the clamping structure (10); the first end portion (20) and / or the second end portion (22) of the long clamping structure (10) includes a fixing member (24, 24') having a conical head portion (26, 26'); the long opening (16) includes at least one conical end portion (30, 30') shaped to correspond to the conical head portion (26, 26') of the fixing member (24, 24'); the transformer core further includes at least one washer (34) positioned around the conical head portion (26, 26') of the fixing member (24, 24') and disposed between the conical head portion (26, 26') and the at least one conical end portion (30, 30') of the long opening (16).

2. The transformer core according to claim 1, wherein the transformer core is designed such that the conical head portion (26, 26') of the fixing member (24, 24') is completely positioned within the long opening (16).

3. The transformer core according to claim 1 or 2, wherein the fixing member (24, 24') includes a screw threadedly connectable to the rigid member (12).

4. The transformer core according to any one of claims 1 to 3, wherein the at least one washer is made of an electrically insulating material. **Claim 5**: The long clamping structure (10) further includes an insulating tube (32) positioned between the rigid member (12) and the inner surface of the long opening (16) and configured to achieve isolation between the rigid member (12) and the column (6). The transformer core according to any one of claims 1 to 4. **Claim 6**: The washer is formed as part of the insulating tube (32). The transformer core according to claim 5. **Claim 7**: The washer is positioned between the conical head portions (26, 26') of the fixing members (24, 24') and the insulating tube (32). The transformer core according to claim 5. **Claim 8**: The transformer core further includes at least one additional long clamping structure (10', 10'', 10''') constructed in the same manner as the aforementioned long clamping structure (10). Preferably, the long rigid member of the at least one additional long clamping structure (10', 10'', 10''') is oriented parallel to the long rigid member (12) of the aforementioned long clamping structure (10). The transformer core according to any one of claims 1 to 7. **Claim 9**: The transformer core includes at least three long clamping structures (10, 10', 10'', 10''') such that a row of long clamping structures is formed along the column (6). The at least three long clamping structures (10, 10', 10'', 10''') include a first long clamping structure (10), a second long clamping structure (10'), and a third long clamping structure (10'') in that order. A first distance (d1) between the first long clamping structure (10) and the second long clamping structure (10') is different from a second distance (d2) between the second long clamping structure (10') and the third long clamping structure (10''). The transformer core according to claim 8. **Claim 10**: The row of long clamping structures (10, 10', 10'', 10''') is formed such that the distances (d1, d2, d3) between the long clamping structures (10, 10', 10'', 10''') increase as they are farther from the first yoke (2). Preferably, the first yoke (2) is a bottom yoke and the second yoke (4) is an upper yoke. The transformer core according to claim 9. **Claim 11**: Further comprising at least one additional column (6'), the main axis (8') of the at least one additional column (6') and the main axis (8) of the aforementioned column (6) are positioned in a common plane, and the opening main axis (18) of the elongated opening (16) is further directed perpendicular to the plane, the transformer core according to any one of claims 1 to 10.

12. The transformer core according to claim 11, wherein the at least one additional column (6') is constructed in the same manner as the aforementioned column (6).

13. A transformer comprising the transformer core according to any one of claims 1 to 12 and a winding wound around the column (6).

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