A core clamp structure for an ultra-high capacity transformer and a manufacturing method thereof

Abstract

The application discloses a core clamp structure for a super large capacity transformer and a manufacturing method thereof, which comprises a main column pull plate, a core binding belt and a core, the main column pull plate is integrated with the core binding belt and the core by binding, the main column pull plate is a plane plate with a symmetrical structure, the front surface and the back surface of the main column pull plate are two parallel planes, the front surface of the main column pull plate is in contact with the core through an insulating paper plate, the back surface of the main column pull plate is provided with the core binding belt, the area of the front surface of the main column pull plate is larger than that of the back surface, and the thickness of the two sides of the main column pull plate gradually decreases along the direction of the two side edges to form an inclined side edge or a circular arc side edge structure; the core clamp structure is improved, the conformal design of the pull plate structure can reduce the size of the insulating structure while ensuring the strength of the main column pull plate structure, effectively improves the core space ratio, ensures that the parameters of the transformer meet the design requirements, and realizes the cost reduction and benefit increase of the super large capacity transformer.

Description

Technical Field

[0001] This invention relates to the field of transformer technology, and specifically to a core clamping structure and manufacturing method for ultra-large capacity transformers. Background Technology

[0002] The transformer core is the magnetic circuit part of the transformer, serving to conduct magnetism. The core is clamped by structural components such as clamps, tie plates, and support beams. These structural components are interconnected to form the frame of the transformer body. Coils are wound on the main column of the core. The tie plates and clamps are connected by a pin hole structure. Holes are opened on the tie plates, and pins are installed on the clamps.

[0003] Transformer losses are mainly divided into no-load losses and load losses. No-load losses occur in the core and are caused by hysteresis and eddy current effects, and are related to changes in magnetic flux. Reducing the thickness of the silicon steel sheets and using silicon steel sheets with low unit loss density can significantly reduce core losses. Load losses originate from heat loss due to winding current passing through resistance and stray losses in metal structural components caused by coil leakage flux. Load losses increase with increasing load current. Optimizing these losses is crucial for improving the overall efficiency of the transformer. Adopting loss reduction measures can effectively reduce energy consumption and operating costs.

[0004] Core fill factor refers to the ratio of the effective cross-sectional area of ​​the core to its geometric cross-sectional area. A higher fill factor means that the silicon steel sheets are stacked more tightly, reducing air gaps and magnetic resistance in the magnetic circuit. This directly reduces the hysteresis component in no-load losses and improves flux transmission efficiency. At the same time, a higher fill factor can effectively reduce iron losses. For the same core cross-sectional area, the core diameter can be reduced, and consequently, the coil diameter can also be reduced, thus reducing the amount of copper used and achieving cost reduction. This lays the foundation for high-efficiency and energy-saving transformers.

[0005] The tie plate is a structural component connecting the upper and lower clamps of the core. It bears significant tensile loads during transformer lifting, coil clamping, and coil short-circuiting. Existing tie plates connect to the clamps via a pin hole structure. To ensure the connection strength between the tie plate and the clamps, the pin end extends beyond the tie plate to ensure the pin is installed along the entire length of the pin hole. To avoid interference between the pin and the core, an insulating plug is required to control the distance between the tie plate and the core, ensuring proper pin installation. However, the insulating plug occupies space in the core, reducing the core's floor area ratio. To maintain a reasonable core floor area ratio, the tie plate thickness must be reduced to correspondingly increase the floor area ratio, which can affect the tie plate's strength. Especially for ultra-large capacity transformers, due to the large dimensions of the core and coils, existing core clamping structures cannot guarantee both structural strength and a good core floor area ratio.

[0006] In view of the above-mentioned defects, the inventors of this invention have finally obtained this invention after a long period of research and practice. Summary of the Invention

[0007] To address the aforementioned technical deficiencies, the present invention provides a core clamping structure for ultra-large capacity transformers, comprising a main column pull plate, a core binding strap, an upper clamp, a lower clamp, and a core. The main column pull plate is configured corresponding to the main column of the core, and a coil is sleeved on the outside of the main column. Two main column pull plates are symmetrically arranged on both sides of the core, and the main column pull plates are bound together with the core by the core binding strap. The upper and lower ends of the main column pull plate are respectively connected to the upper clamp and the lower clamp via pins. The main column tie plate is a symmetrical planar plate with two parallel planes on its front and back sides. The front side of the main column tie plate is in contact with the iron core through insulating paperboard, and the back side of the main column tie plate is corresponding to the iron core binding strap. The area of ​​the front side of the main column tie plate is larger than the area of ​​the back side. The thickness of the two sides of the main column tie plate gradually decreases towards the two side edges to form an inclined side or arc side structure.

[0008] Preferably, a stop is provided between the main column tie plate and the core binding strap. The stop is correspondingly provided on the back of the main column tie plate. The stop has a first contact surface and a second contact surface. The first contact surface is a plane. The stop is attached to the back of the main column tie plate through the first contact surface. The second contact surface is an arc surface. The center of the second cross-section is located on the axis of the main column. The core binding strap is tied to the second contact surface.

[0009] Preferably, the main column tie plate is made of high-strength non-magnetic steel with a tensile strength of 1000MPa and a relative permeability of 1; the core is made of 0.2mm ultra-thin high-permeability silicon steel sheet.

[0010] Preferably, the upper clamp is provided with an upper clamp main support plate and an upper clamp secondary support plate, the upper clamp main support plate being positioned directly above the coil, and the upper clamp secondary support plate being positioned corresponding to the outer edge of the coil; the lower clamp is provided with a lower clamp main support plate and a lower clamp secondary support plate, the lower clamp main support plate being positioned directly below the coil, and the lower clamp secondary support plate being positioned corresponding to the outer edge of the coil; the clamp magnetic shield is disposed in the mounting grooves on the upper clamp main support plate, the upper clamp secondary support plate, the lower clamp main support plate, and the lower clamp secondary support plate; one end of the clamp magnetic shield is close to the iron core, used to guide the coil leakage magnetic flux into the iron core.

[0011] Preferably, a method for manufacturing the core clamp structure for an ultra-large capacity transformer includes the following steps: S1, the shearing and stacking of the iron core; S2, the assembly of the iron core, the main column tie plate, and the side column tie plate; S3, assemble the iron core, the upper clamp, and the lower clamp on the platform.

[0012] Preferably, in step S1, the ultra-thin high-permeability silicon steel sheet is sheared to form a sheet, and the sheet is stacked to obtain the core; during the shearing process, the dimensional error of the sheet is controlled within 0 to -0.2 mm during longitudinal shearing, and the dimensional error of the sheet is controlled within 0 to -0.15 mm during transverse shearing. The shearing speed of the sheet corresponding to the core column is controlled at 13 sheets / min, and the shearing speed of the sheet corresponding to the yoke is controlled at 22 sheets / min.

[0013] Preferably, in step S1, when stacking the material sheets of the core column, the deviation of the column core position is controlled at ≤1mm per 1000mm stacking height, based on the stacking height.

[0014] Preferably, in step S2, the main column tie plate and the core are bound together by the core binding strap, which is made of PET material. The core column is provided with a centralized binding area and a regular binding area. The centralized binding area corresponds to the upper and lower parts of the core column, and the regular binding area is equidistant from the two centralized binding areas. Both the centralized binding area and the regular binding area are formed by binding the main column tie plate and the core with the core binding strap, and the number of core binding straps in the centralized binding area is greater than the number of core binding straps in the regular binding area.

[0015] Preferably, in step S3, the upper clamp and the lower clamp on one side of the core are set on the same horizontal plane via a clamping platform. The upper clamp and the lower clamp on the same horizontal plane are symmetrically arranged. Each upper clamp and the lower clamp is provided with a central positioning hole and two side positioning holes symmetrically arranged around the central positioning hole. The central positioning hole of the upper clamp and the two side positioning holes of the lower clamp are connected to form a first diagonal. The central positioning hole of the lower clamp and the two side positioning holes of the upper clamp are connected to form a second diagonal. The error between the first diagonal and the second diagonal on the same side of the upper clamp and the lower clamp is within ±1mm. The error between the distance between the upper clamp and the lower clamp and the value specified in the drawing is within ±1mm. The difference in plane height between the upper clamp and the lower clamp on the same horizontal plane is within 0~0.5mm.

[0016] Preferably, in step S3, when the core column is installed, the verticality is controlled within ±1mm; the error of the two diagonals of each core window of the core is within ±3mm; and the error of the width dimension of the core window corresponding to both ends of the core column is within ±1mm.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention improves the core clamping structure. Through the conformal design of the tie plate structure, the insulation structure size can be reduced while ensuring the strength of the main column tie plate structure, effectively improving the core area ratio, ensuring that the transformer parameters meet the design requirements, and realizing cost reduction and efficiency improvement of ultra-large capacity transformers. Attached Figure Description

[0018] Figure 1 This is a front view of the core clamping structure for the ultra-large capacity transformer. Figure 2 This is a top view of the core clamping structure for the ultra-large capacity transformer. Figure 3 This is a structural side view of the core clamping structure for the ultra-large capacity transformer. Figure 4 for Figure 1 Schematic diagram of the structure of AA; Figure 5 for Figure 4 Enlarged view of the local structure at point B; Figure 6 This is a front view of the structure of the main column tie plate and the iron core; Figure 7 This is a schematic diagram of the deviation of the column center position in step S1; Figure 8 This is a schematic diagram of the binding process in step S2. Figure 9 This is a schematic diagram of the clamping platform size control in step S3; Figure 10 This is a schematic diagram of core verticality control in step S3. Figure 11 This is a schematic diagram of the core window size control in step S3; Figure 12 This is a schematic diagram of the core platform structure in step S3. The numbers in the image represent: 1-Core; 2-Upper clamp; 3-Lower clamp; 4-Main column tie plate; 5-Side column tie plate; 6-Coil; 7-Oil guide pipe; 8-Clamp magnetic shield; 9-Lifting tool; 11-Core binding strap; 12-Centralized binding area; 13-Regular binding area; 14-Plumb line; 15-Support fixture; 21-Upper clamp main support plate; 22-Upper clamp auxiliary support plate; 23-Upper support beam; 24-Upper side beam; 25-Upper pressure block; 31-Lower clamp main support plate; 32-Lower clamp auxiliary support plate; 33-Lower support beam; 34-Lower side beam; 35-Lower pressure block; 41-Insulating cardboard; 42-Stop. Detailed Implementation

[0019] The above-mentioned and other technical features and advantages of the present invention will be described in more detail below with reference to the accompanying drawings. Example 1

[0020] like Figure 1 , Figure 2 and Figure 3 As shown, Figure 1 This is a front view of the core clamping structure for the ultra-large capacity transformer. Figure 2 This is a top view of the core clamping structure for the ultra-large capacity transformer. Figure 3 This is a structural side view of the core clamping structure for the ultra-large capacity transformer.

[0021] The core clamping structure for ultra-large capacity transformers of the present invention includes a main column pull plate 4, a core binding strap 11, an upper clamp 2, a lower clamp 3, and a core 1. The main column pull plate 4 is set corresponding to the main column of the core 1, and a coil 6 is sleeved on the outside of the main column. The two main column pull plates 4 are symmetrically arranged on both sides of the core 1, and the main column pull plates 4 are bound together with the core 1 by the core binding strap 11. The upper and lower ends of the main column pull plate 4 are respectively connected to the upper clamp 2 and the lower clamp 3 by pins.

[0022] To increase the floor area ratio of the core 1, the main column tie plate 4 adopts a conformal design, which is as close as possible to the outer circle of the core 1 to increase the effective contact area between the main column tie plate 4 and the core 1, and to ensure the mechanical strength of the main column tie plate 4 under conditions such as coil fastening, body lifting, and coil short circuit.

[0023] like Figure 4 , Figure 5 and Figure 6 As shown, Figure 4 for Figure 1 Schematic diagram of the structure of AA; Figure 5 for Figure 4 Enlarged view of the local structure at point B; Figure 6 This is a front view of the structure of the main column tie plate and the iron core.

[0024] Since the core 1 is formed by stacking multiple layers of silicon steel sheets, the cross-section of the main column is approximately circular. The two sides of the main column corresponding to the main column pull plate 4 are complete planes of silicon steel sheets. Therefore, the conformal design of the main column pull plate 4 is as follows: the main column pull plate 4 is a symmetrical planar plate, and the front and back sides of the main column pull plate 4 are two parallel planes. The front side of the main column pull plate 4 is in contact with the core 1 through the insulating cardboard 41. The back side of the main column pull plate 4 is set corresponding to the core binding strap 11, and the front area of ​​the main column pull plate 4 is larger than the back area of ​​the main column pull plate 4. The thickness of the two sides of the main column pull plate 4 gradually decreases along the direction of the two side edges to form an inclined side or arc side structure, thereby realizing the conformal design, ensuring the roundness of the core binding strap 11 after binding, and making it easier to fit and support the inner wall of the coil 6.

[0025] This structural design allows the main column pull plate 4 to be in close contact with the outer circle of the iron core 1, while also increasing the contact range between the main column pull plate 4 and the inner wall of the coil 6. This results in the coil 6 having better short-circuit resistance when subjected to an inward radial short-circuit force under short-circuit conditions.

[0026] By ensuring the thickness of the plate, i.e. the depth of the pin hole, through the conformal design of the main column pull plate 4, or by improving the material, the pin of the pull plate is set in the connecting pin hole. Under the premise that the pull plate and the clamping connection structure are well matched, this structure saves the space occupied by the insulating plug by 5mm compared with the existing structure. The insulating paperboard 41 with only 2mm is set between the iron core 1 and the main column pull plate 4 to ensure the insulation between the main column pull plate 4 and the iron core 1, which greatly reduces the space occupied by the insulation structure in the iron core 1.

[0027] The conformal design ensures the intermediate thickness of the core tie plate. Compared with the existing method of increasing the core volume by simply thinning the core tie plate, it improves the bending resistance of the core tie plate. When inserting the upper yoke laminations, the tie plate is not easy to bend, and the overall rigidity of the core 1 is improved, avoiding the problem of the core 1 tilting.

[0028] Preferably, a stop 42 is provided between the main column tie plate 4 and the core binding strap 11. The stop 42 is correspondingly provided on the back of the main column tie plate 4. The stop 42 is provided with a first contact surface and a second contact surface. The first contact surface is a plane. The stop 42 is attached to the back of the main column tie plate 4 through the first contact surface. The second contact surface is an arc surface. The center of the second cross-section is located on the axis of the main column. The core binding strap 11 is tied to the second contact surface, thereby further improving the roundness of the core binding strap 11 and ensuring that the core 1 and the main column tie plate 4 are tightly bound.

[0029] Preferably, the main column pull plate 4 is provided with a magnetic shielding groove to separate the leakage magnetic path and reduce the loss caused by leakage magnetic field and the temperature rise caused by the loss.

[0030] It is worth noting that the main column tie plate 4 can be made of high-strength non-magnetic steel with a tensile strength of 1000MPa and a relative permeability of 1. The high-strength non-magnetic steel utilizes key technologies such as steel nano-precipitation alloy design, the development of enhanced heat treatment technology, and optimization of manufacturing processes. The resulting high-strength non-magnetic steel achieves a tensile strength of 1000MPa and a relative permeability of 1, significantly improving strength and reducing permeability compared to the original Q690C. Due to the extremely low permeability, there is no need to design magnetically shielding grooves to limit eddy currents on the main column tie plate 4, allowing for an increase in the effective cross-sectional area of ​​the tie plate within the same length and width dimensions, thus improving its strength. The increased material strength of the main column tie plate 4 allows for a reduction in its cross-sectional dimensions, thereby increasing the core footprint. High-strength non-magnetic steel can also be used to manufacture core clamping components. While improving the strength of the clamping components, its non-magnetic properties reduce eddy current losses caused by coil leakage magnetic flux incident on the clamping components.

[0031] The core 1 is made of 0.2mm ultra-thin high-permeability silicon steel sheet, which is grade B20R065. From the physical parameters, the unit iron loss is ≤0.65W / kg (1.7T / 50Hz). By comparing the energy efficiency with traditional silicon steel sheets, it can be seen that its unit iron loss is reduced by about 15% compared with traditional products. This characteristic can effectively reduce the no-load loss of the transformer.

[0032] This invention improves the core clamping structure. Through the conformal design of the tie plate structure, the insulation structure size can be reduced while ensuring the structural strength of the main column tie plate 4, effectively increasing the core area and ensuring that the transformer parameters meet the design requirements, thus achieving cost reduction and efficiency improvement for ultra-large capacity transformers. Example 2

[0033] The upper clamp 2 is provided with two pieces. The two upper clamps 2 are connected by an upper support beam 23 and an upper side beam 24 and are set on the upper part of the core 1. The upper support beam 23 bears the mechanical load under working conditions such as coil fastening, body lifting, and coil short circuit. The upper side beam 24 is used to bear the impact load of the core 1 when the transformer is transported.

[0034] The lower clamp 3 is provided with two pieces. The two lower clamps 3 are connected by a lower support beam 33 and a lower side beam 34 and are set at the lower part of the core 1. The lower support beam 33 bears the mechanical load under working conditions such as lifting of the transformer body, and the lower side beam 34 is used to bear the impact load of the core 1 when the transformer is transported.

[0035] The core 1 also includes a side column. The main column tie plate 4 is provided corresponding to the main column, and the side column is provided with a side column tie plate 5. The upper clamp 2 and the lower clamp 3 are connected by the main column tie plate 4 and the side column tie plate 5 to form a frame. The main column tie plate 4 and the side column tie plate 5 bear the mechanical loads under working conditions such as coil fastening, core lifting, and coil short circuit.

[0036] The upper clamp 2 is provided with an upper clamp main support plate 21 and an upper clamp secondary support plate 22. The upper clamp main support plate 21 is positioned directly above the coil 6, and the upper clamp secondary support plate 22 is positioned at the outer edge of the coil 6. The clamp magnetic shield 8 is disposed in the mounting grooves on the upper clamp main support plate 21 and the upper clamp secondary support plate 22. One end of the clamp magnetic shield 8 is close to the iron core 1 and is used to guide the leakage magnetic flux of the coil into the iron core 1. By increasing the width of the upper clamp main support plate 21 and adding the upper clamp secondary support plate 22, the arrangement range of the clamp magnetic shield 8 is increased, thereby improving the leakage magnetic flux shielding effect. An upper pressure block 25 is installed at the lower part of the clamp magnetic shield 8 to press the coil 6.

[0037] The lower clamp 3 is provided with a main clamp support plate 31 and a secondary clamp support plate 32. The main clamp support plate 31 is positioned directly below the coil 6, and the secondary clamp support plate 32 is positioned at the outer edge of the coil 6. The clamp magnetic shield 8 is disposed in the mounting grooves on the main clamp support plate 31 and the secondary clamp support plate 32. One end of the clamp magnetic shield 8 is close to the iron core 1 and is used to guide the leakage magnetic flux of the coil into the iron core 1. By increasing the width of the main clamp support plate 31 and adding the secondary clamp support plate 32, the arrangement range of the clamp magnetic shield 8 is increased, thereby improving the leakage magnetic flux shielding effect. A lower pressure block 35 is installed on the upper part of the clamp magnetic shield 8 to support the coil 6.

[0038] In addition to the main support plate, an auxiliary support plate is added, thereby increasing the arrangement range of the magnetic shield. The proportion of the magnetic shield covering the coil 6 is increased from 30% to 50%, reducing the number of coil leakage magnetic incident clamps and reducing the stray loss of the transformer. Compared with the method of using a lung-shaped magnetic shield to reduce losses, it has the advantages of simple structure, convenient installation and low cost.

[0039] The upper clamp 2 is equipped with a lifting device 9 for lifting the transformer body as a whole.

[0040] An oil guide pipe 7 is provided next to the lower clamp 3 to guide external cooling oil flow into the coil 6 to cool the transformer. Example 3

[0041] As this is the first time that ultra-thin, high-permeability silicon steel sheets have been used, the fabrication of core 1 faces dual challenges in design and process. To ensure that the final core 1 meets the standards in terms of electromagnetic performance and structural stability, process optimization and control need to be carried out from multiple dimensions.

[0042] Therefore, the manufacturing method of the core clamping structure for ultra-large capacity transformers described in this invention includes the following steps: S1, the shearing and stacking of the iron core 1; S2, the assembly of the iron core 1, the main column tie plate 4, and the side column tie plate 5; S3, assemble the iron core 1, the upper clamp 2, and the lower clamp 3 on the platform.

[0043] Preferably, in step S1, the ultra-thin high-permeability silicon steel sheet is sheared to form a sheet, and the sheet is stacked to obtain the core 1; during the shearing process, the dimensional error of the sheet is controlled within 0 to -0.2 mm during longitudinal shearing, and the dimensional error of the sheet is controlled within 0 to -0.15 mm during transverse shearing. The shearing speed of the sheet corresponding to the core column is controlled at 13 sheets / min, and the shearing speed of the sheet corresponding to the yoke is controlled at 22 sheets / min.

[0044] Preferably, in step S1, when stacking the material sheets of the core column, the deviation of the column core position is controlled at ≤1mm per 1000mm stacking height, based on the stacking height.

[0045] Specifically, in step S2, the main column tie plate 4 and the iron core 1 are bound together by the iron core binding strap 11. The iron core binding strap 11 is made of PET material, which has high strength and low relaxation mechanical properties. Under the thermo-mechanical coupling environment of the iron core 1 during long-term operation, it can effectively maintain the binding pre-tightening force.

[0046] In step S2, the core column is provided with a centralized binding area 12 and a regular binding area 13. The centralized binding area 12 corresponds to the upper and lower parts of the core column, and the regular binding area 13 is equidistant from the two centralized binding areas 12. Both the centralized binding area 12 and the regular binding area 13 are formed by binding the main column tie plate 4 and the iron core 1 with iron core binding straps 11. The number of iron core binding straps 11 in the centralized binding area 12 is greater than the number of iron core binding straps 11 in the regular binding area 13. This is to prevent the core column from becoming unstable or twisted due to insufficient rigidity of the silicon steel sheet caused by the thinning of the silicon steel sheet. The core column is reinforced by binding at the parts of the core column that are prone to instability and twisting (the upper and lower parts of the iron window of the core column).

[0047] In step S3, the upper clamp 2 and the lower clamp 3 on one side of the core 1 are set on the same horizontal plane by a clamping platform. The upper clamp 2 and the lower clamp 3 on the same horizontal plane are symmetrically arranged. The upper clamp 2 and the lower clamp 3 are each provided with a central positioning hole and two side positioning holes symmetrically arranged with the central positioning hole as the center. The central positioning hole of the upper clamp 2 and the two side positioning holes of the lower clamp 3 are connected to form a first diagonal. The central positioning hole of the lower clamp 3 and the two side positioning holes of the upper clamp 2 are connected to form a second diagonal. The error between the first diagonal and the second diagonal on the same side of the upper clamp 2 and the lower clamp 3 is within ±1mm. The error between the distance between the upper clamp 2 and the lower clamp 3 and the value specified in the drawing is within ±1mm. The plane height difference between the upper clamp 2 and the lower clamp 3 on the same horizontal plane is within 0~0.5mm.

[0048] In step S3, the iron core 1 is set on the stacking platform of the iron core 1 by the support fixture 15. The support fixtures 15 are symmetrically arranged in pairs to effectively support the iron core 1, effectively disperse the stress on the iron core 1 when it is lying horizontally, and avoid deformation, warping and other adverse phenomena of the lower iron core 1 due to gravity and other factors during the stacking process.

[0049] When the core column is installed, the verticality must be controlled within ±1mm, that is, the symmetrical size difference of the core column symmetrical structure is guaranteed to be within ±1mm.

[0050] The error between the two diagonals of each core 1 window is within ±3mm, and the error in the width of the core 1 window corresponding to both ends of the core column is within ±1mm. Example 4

[0051] In a specific transformer embodiment with a five-column core 1 structure, core 1 shearing is a fundamental step in core 1 fabrication, and its precision directly affects subsequent stacking and overall performance. Considering the characteristics of ultra-thin, high-permeability silicon steel sheets, a full-process equipment overhaul was first conducted, calibrating and inspecting the mechanical transmission and tool precision of the shearing machine. Simultaneously, to prevent problems during the shearing process and to verify the feasibility of the finished product, trial shearing and debugging of the silicon steel sheet were performed. An optical measuring platform was introduced to construct a high-precision detection system, based on which the shearing dimensions were dynamically monitored.

[0052] The parameters for a standard large silicon steel sheet cross-cutting line are as follows (maximum sheet width: 1250mm): Strip width: 120–1250mm Film length: 800–6000mm Speed: 200–240 m / min Accuracy: Length ±0.15mm, Angle ±0.01° Burrs: ≤0.02mm Hole punch: up to 6, hole diameter 8–40mm. V-punch: 2 CNC transverse strokes.

[0053] Unwinding: 4–6 heads, roll weight ≤ 3000 kg This invention employs a conventional large-scale silicon steel sheet cross-cutting line. However, in terms of dimensional control, by optimizing the cutting program and mechanical limits, the longitudinal cutting dimensional error is ensured to be controlled within 0 to -0.2 mm, and the transverse cutting dimensional error within 0 to -0.15 mm. This precision range effectively avoids the problem of uneven stacking gaps in the core 1 caused by silicon steel sheet dimensional deviations. To address the issue of shearing burrs and prevent increased local eddy current losses that could affect insulation performance, a separate trial shearing scheme was developed based on the characteristics of ultra-thin high-permeability silicon steel sheets. Through repeated trials, the optimal shearing speed was selected, as shown in Table 1. Table 1 compares the shearing speeds of the core column and yoke described in this invention with those in conventional production.

[0054] During the trial shearing process, the shearing speed and tool gap were controlled by variables and repeatedly adjusted to select the optimal parameter combination, ensuring that all shearing burrs were strictly controlled below 0.015mm, laying the foundation for high-quality stacking and low-loss operation of core 1.

[0055] like Figure 7 As shown, Figure 7 This is a schematic diagram of the column center position deviation in step S1. When the column centers are stacked, the stacking height is used as a reference, and the column center position deviation is controlled with an accuracy of 1 / 1000 (i.e., for every 1000mm stacking height, the column center offset is ≤1mm). The column center position deviation is measured using a plumb line.

[0056] In the research and development and manufacturing of ultra-large capacity power plant transformers, core assembly is the core link that determines the performance and reliability of the equipment. This project adopts a three-phase, five-column, six-lapped core, whose structural parameters are characterized by being ultra-thin, ultra-large, and ultra-heavy. Taking the core parameters of a 1170MVA / 500kV transformer as an example: the main column diameter reaches 1522mm, with a single column weighing approximately 46t, and the side column weighing approximately 23t. This is the first time that this type of silicon steel sheet has been used in ultra-large capacity power plant transformers. Due to the huge amount of silicon steel sheet used, in order to ensure that the final core performance meets the standards, the quality is stable and reliable, and to prevent deformation during the core erection process, the traditional PG tape is abandoned and PET tape is used instead. PET material has high strength and low relaxation mechanical properties, which can effectively maintain the binding preload under the thermo-mechanical coupling environment of long-term core operation.

[0057] like Figure 8 As shown, Figure 8This is a schematic diagram of the binding process in step S2. To further improve the structural stability of core 1 and prevent insufficient stiffness of the silicon steel sheets due to thinning, which could lead to instability and torsion of the core column, an innovative high-density binding strategy with unequal spacing is implemented. Binding is reinforced at locations prone to instability and torsion (the upper and lower parts of the core column's iron window) to ensure that core 1 does not experience instability or torsion after being erected. Simultaneously, the surface pressure of the core 1 binding is optimized: through relevant calculations, this project uses 66 turns of PET tape with a surface pressure of 0.25 MPa, while conventional projects use PG tape (surface pressure of 0.2 MPa). Compared to the surface pressure standard of conventional projects, the higher surface pressure in this project enhances the fit between the core 1 sheets, suppresses inter-sheet vibration during operation, and reduces losses. Furthermore, to ensure the assembly accuracy of core 1, a full-process quality control system is constructed, strictly controlling each assembly procedure to ensure that the performance and structural stability of core 1 meet the standards.

[0058] like Figure 9 As shown, Figure 9 This is a schematic diagram illustrating the control of the clamping platform dimensions in step S3. Strict control is maintained over the clamping platform dimensions, particularly in the horizontal direction, ensuring that the diagonal differences a-a' and b-b' are within ±1mm, and that the dimension d between the upper and lower clamps is within ±1mm of the value specified on the drawing. For the height direction, the clamping platform dimensions are controlled by measuring and adjusting the height difference between the clamping planes using an optical theodolite and a ruler to within 0~0.5mm.

[0059] like Figure 10 As shown, Figure 10 This is a schematic diagram of core verticality control in step S3; when the core column is installed, the verticality must be controlled within ±1mm (XY). Figure 5 (XY=±1mm), the perpendicularity is measured using a plumb line 1414.

[0060] like Figure 11 As shown, Figure 11 This is a schematic diagram of the core window size control in step S3; the diagonal differences C-C' and D-D' between the core columns are controlled within ±3mm, and the spacings A, A', B, and B' between the core columns are controlled within ±1mm.

[0061] like Figure 12 As shown, Figure 12This is a schematic diagram of the core platform in step S3. During the core platform construction, to prevent the core 1 sheet from bending under gravity, a support fixture 15 is specifically designed based on the structural characteristics and process requirements of the core 1. Multiple support fixtures 15 provide reliable support for the core 1. The support fixture 15 is a screw structure, and its height can be adjusted according to the height of the core 1 to effectively support the core 1, effectively dispersing the stress on the core 1 when it lies horizontally, and preventing deformation, warping, or other adverse phenomena of the lower core 1 due to gravity and other factors during the core platform construction process.

[0062] The above description is merely a preferred embodiment of the present invention and is illustrative rather than restrictive. Those skilled in the art will understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, all of which will fall within the protection scope of the present invention.

Claims

1. A core clamping structure for ultra-large capacity transformers, characterized in that, The device includes a main column tie plate, a core binding strap, an upper clamp, a lower clamp, and a core. The main column tie plate is set corresponding to the main column of the core, and a coil is sleeved on the outside of the main column. The two main column tie plates are symmetrically arranged on both sides of the core, and the main column tie plates are bound to the core together by the core binding strap. The upper and lower ends of the main column tie plate are connected to the upper clamp and the lower clamp respectively by pins. The main column tie plate is a symmetrical planar plate with two parallel planes on its front and back sides. The front side of the main column tie plate is in contact with the iron core through insulating paperboard, and the back side of the main column tie plate is corresponding to the iron core binding strap. The area of ​​the front side of the main column tie plate is larger than the area of ​​the back side. The thickness of the two sides of the main column tie plate gradually decreases towards the two side edges to form an inclined side or arc side structure.

2. The core clamping structure for ultra-large capacity transformers as described in claim 1, characterized in that, A stop is provided between the main column tie plate and the core binding strap. The stop is correspondingly provided on the back of the main column tie plate. The stop has a first contact surface and a second contact surface. The first contact surface is a plane. The stop is attached to the back of the main column tie plate through the first contact surface. The second contact surface is an arc surface. The center of the second cross-section is located on the axis of the main column. The core binding strap is tied to the second contact surface.

3. The core clamping structure for ultra-large capacity transformers as described in claim 2, characterized in that, The main column tie plate is made of high-strength non-magnetic steel with a tensile strength of 1000MPa and a relative magnetic permeability of 1, and the core is made of 0.2mm ultra-thin high-permeability silicon steel sheet.

4. The core clamping structure for ultra-large capacity transformers as described in claim 3, characterized in that, The upper clamp is provided with an upper clamp main support plate and an upper clamp secondary support plate. The upper clamp main support plate is positioned directly above the coil, and the upper clamp secondary support plate is positioned corresponding to the outer edge of the coil. The lower clamp is provided with a lower clamp main support plate and a lower clamp secondary support plate. The lower clamp main support plate is positioned directly below the coil, and the lower clamp secondary support plate is positioned corresponding to the outer edge of the coil. The clamp magnetic shield is disposed in the mounting grooves on the upper clamp main support plate, the upper clamp secondary support plate, the lower clamp main support plate, and the lower clamp secondary support plate. One end of the clamp magnetic shield is close to the iron core and is used to guide the leakage magnetic flux of the coil into the iron core.

5. A method for manufacturing a core clamping structure for an ultra-large capacity transformer as described in claim 4, characterized in that, Including the following steps: S1, the shearing and stacking of the iron core; S2, the assembly of the iron core, the main column tie plate, and the side column tie plate; S3, assemble the iron core, the upper clamp, and the lower clamp on the platform.

6. The manufacturing method as described in claim 5, characterized in that, In step S1, ultra-thin high-permeability silicon steel sheets are sheared to form sheets, and the sheets are stacked to obtain an iron core. During the shearing process, the dimensional error of the sheets is controlled within 0 to -0.2 mm during longitudinal shearing and within 0 to -0.15 mm during transverse shearing. The shearing speed of the sheets corresponding to the core column is controlled at 13 sheets / min, and the shearing speed of the sheets corresponding to the yoke is controlled at 22 sheets / min.

7. The manufacturing method as described in claim 5, characterized in that, In step S1, when stacking the material sheets of the core column, the core position deviation is controlled to be ≤1mm for every 1000mm of stacking height, based on the stacking height.

8. The manufacturing method as described in claim 5, characterized in that, In step S2, the main column tie plate and the core are bound together by the core binding strap, which is made of PET material. The core column is provided with a centralized binding area and a regular binding area. The centralized binding area corresponds to the upper and lower parts of the core column, and the regular binding area is equidistant from the two centralized binding areas. Both the centralized binding area and the regular binding area are formed by binding the main column tie plate and the core with the core binding strap, and the number of core binding straps in the centralized binding area is greater than the number of core binding straps in the regular binding area.

9. The manufacturing method as described in claim 5, characterized in that, In step S3, the upper clamp and the lower clamp on one side of the core are set on the same horizontal plane by a clamping platform. The upper clamp and the lower clamp on the same horizontal plane are symmetrically arranged. Each upper clamp and the lower clamp is provided with a central positioning hole and two side positioning holes symmetrically arranged with the central positioning hole as the center. The central positioning hole of the upper clamp and the two side positioning holes of the lower clamp are connected to form a first diagonal. The central positioning hole of the lower clamp and the two side positioning holes of the upper clamp are connected to form a second diagonal. The error between the first diagonal and the second diagonal on the same side of the upper clamp and the lower clamp is within ±1mm. The error between the distance between the upper clamp and the lower clamp and the value specified in the drawing is within ±1mm. The difference in plane height between the upper clamp and the lower clamp on the same horizontal plane is within 0~0.5mm.

10. The manufacturing method as described in claim 5, characterized in that, In step S3, when the core column is installed, the verticality is controlled within ±1mm; the error of the two diagonals of each core window of the core is within ±3mm; and the width dimension error of the core window corresponding to both ends of the core column is within ±1mm.

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