Iron core structure for oil-immersed transformer and oil-immersed transformer

Abstract

The utility model relates to the technical field of transformers, in particular to an iron core structure for an oil-immersed transformer and the oil-immersed transformer, the iron core structure comprises silicon steel sheets, the silicon steel sheets are horizontally overlapped to form an iron core, the cross section of the iron core comprises a first arc line, a second arc line, a third arc line and a fourth arc line, the first arc line, the second arc line, the third arc line and the fourth arc line are closed to form a ring, the first arc line and the third arc line are of a symmetrical structure, the second arc line and the fourth arc line are of a symmetrical structure, the radius ratio of the first arc line to the second arc line is 0.236-0.275, and the arc length ratio of the first arc line to the second arc line is 1.621-1.679. By controlling the ratio of the long axis to the short axis and using the seven-stage multi-stage inclined lap joints, the loss of the transformer is superior to that of a common structure by more than 2%, the noise is reduced by more than 3dB, and the no-load current is reduced by more than 5%. During assembly, the whole iron core is pressed by uniform pressure, and the transformer iron core cannot be loosened due to vibration of transportation and operation.

Description

Technical Field

[0001] The utility model relates to the technical field of transformers, in particular to an iron core structure for an oil-immersed transformer and the oil-immersed transformer. Background Art

[0002] Distribution transformers are one of the important equipment in the power supply and distribution systems of industrial and mining enterprises and civil buildings. At the end of the 19th century, transformers began to use transformer oil as an insulating and cooling medium, and oil-immersed transformers appeared. Transformers can be divided into iron core transformers and iron shell transformers according to the different winding methods of the winding group. If the winding is wrapped around the iron core, it is an iron core transformer; if the iron core is wrapped around the winding, it is an iron shell transformer. The two are slightly different in structure, but there is no essential difference in principle. Power transformers are all iron core type. The transformer is mainly composed of an iron core, a winding, an oil tank, an oil pillow, an insulating bushing, a tap changer and a gas relay.

[0003] The iron core is the magnetic circuit part of the transformer. During operation, hysteresis loss and eddy current loss will generate heat. In order to reduce heat loss and reduce volume and weight, the iron core is made of cold-rolled grain-oriented silicon steel sheets with a high magnetic permeability of less than 0.35mm. According to the arrangement of the winding in the iron core, there are iron core type and iron shell type.

[0004] In large-capacity transformers, cooling oil channels are often provided in the core to ensure that the heat generated by core loss can be fully carried away by the insulating oil during circulation to achieve a good cooling effect.

[0005] Under the guidance of the "30·60 dual carbon target", solar energy and wind energy, as a sustainable and renewable clean energy, will enter a new stage of accelerated quality development in the new energy industry. The industry has accelerated the investment in the research and development of new energy transformers. The traditional transformer cores are round or runway round. The round core has strong resistance to sudden short circuits, high processing and manufacturing efficiency, safe and reliable operation, but high cost and weak market competitiveness; the runway round core has low cost and strong market competitiveness, but poor resistance to sudden short circuits, low processing and manufacturing efficiency, and poor safety and reliability in operation.

[0006] Therefore, the problems of poor short-circuit resistance and low processing efficiency of the racetrack round core in the prior art and the high cost and poor market competitiveness of the round core are urgently needed to be solved by those skilled in the art. Summary of the invention

[0007] In view of the problems existing in the prior art, the purpose of the utility model is to provide a method that can solve the problems of poor short-circuit resistance and low processing efficiency of the runway round iron core, while also solving the problems of high cost and poor market competitiveness of the round iron core.

[0008] To achieve the above-mentioned purpose, the technical solution adopted by the utility model is: a core structure for an oil-immersed transformer, including silicon steel sheets, which are horizontally stacked to form an iron core, and the cross-section of the iron core includes a first arc, a second arc, a third arc, and a fourth arc. The first arc, the second arc, the third arc, and the fourth arc are closed to form a ring. The first arc and the third arc are symmetrical structures, and the second arc and the fourth arc are symmetrical structures. The radius ratio of the first arc to the second arc is 0.236-0.275, and the arc length ratio of the first arc to the second arc is 1.621-1.679.

[0009] In the above-mentioned core structure for oil-immersed transformer, the long axis is between the first arc and the third arc, the short axis is between the second arc and the fourth arc, and the ratio between the long axis and the short axis ranges from 1.42 to 1.55.

[0010] The iron core structure for the oil-immersed transformer adopts a three-phase three-column structure, and multi-step oblique lap joints are adopted on the core column and the iron yoke of the iron core structure.

[0011] An oil-immersed transformer comprises a winding circuit structure, a lead connection structure, a bushing external control structure, and an oil tank heat dissipation structure. The winding circuit structure comprises any one of the above-mentioned core structures for the oil-immersed transformer.

[0012] The above-mentioned oil-immersed transformer has a winding circuit structure including a high-voltage winding and a low-voltage winding.

[0013] In the above-mentioned oil-immersed transformer, the oil tank heat dissipation structure includes an oil tank and a tank cover. The oil tank includes a tank wall and a tank edge. The tank cover and the tank edge are provided with rounded corners. The tank wall is bent to form the oil tank, and the seams of the tank wall are welded.

[0014] In the above-mentioned oil-immersed transformer, the outer surface of the box wall is provided with an uneven polished surface, and the outer side of the polished surface is coated with paint.

[0015] In the above-mentioned oil-immersed transformer, the bushing external control structure includes a low partial discharge resin dry bushing and a low partial discharge porcelain bushing. The low partial discharge resin dry bushing is used to connect to high voltage, and the low partial discharge porcelain bushing is used to connect to low voltage.

[0016] The utility model discloses an iron core structure for an oil-immersed transformer and the beneficial effects of the oil-immersed transformer are as follows: compared with the traditional transformer iron core which adopts a round or runway round shape, it has a strong ability to resist sudden short circuits and the transformer operation is safer and more reliable; the four-section arc-shaped iron core structure has a low cost and strong market competitiveness; the processing and manufacturing efficiency is high and the process assurance is good, which effectively solves the industry problem of the contradiction between safe operation and equipment cost during the rapid expansion of new energy.

[0017] By controlling the ratio of the long and short axes and using seven-level multi-step oblique lap joints, the transformer loss is 2% better than that of ordinary structures, the noise is reduced by more than 3dB, and the no-load current is reduced by more than 5%. During assembly, the entire core is pressed with uniform pressure, and the transformer core should not loosen due to vibration during transportation and operation.

[0018] By bending the tank wall and welding the oil tank with a single weld, the number of welds is reduced, the mechanical strength is increased, the heat dissipation surface of the body is expanded, and the heat dissipation effect is improved. At the same time, the bent tank wall has a divergent effect, thereby reducing noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the iron core structure of the utility model;

[0020] Figure 2 This is a cross-sectional view of the iron core of the utility model;

[0021] Figure 3 This is a schematic diagram of the transformer structure of the utility model.

[0022] Explanation of the accompanying drawings: core structure 10, including silicon steel sheets 11, core 20, first arc 21, second arc 22, third arc 23, fourth arc 24, winding circuit structure 30, lead connection structure 40, bushing external control structure 50, mailbox heat dissipation structure 60. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is described below in conjunction with specific implementation methods and drawings.

[0024] Example 1

[0025] like Figure 1-2 As shown, a core structure 10 for an oil-immersed transformer includes silicon steel sheets 11, which are horizontally stacked to form a core 20. The cross-section of the core includes a first arc 21, a second arc 22, a third arc 23, and a fourth arc 24. The first arc, the second arc, the third arc, and the fourth arc are closed to form a ring. The first arc and the third arc are symmetrical structures, and the second arc and the fourth arc are symmetrical structures. The radius ratio of the first arc to the second arc is 0.236-0.275, and the arc length ratio of the first arc to the second arc is 1.621-1.679.

[0026] The long axis is between the first arc and the third arc, the short axis is between the second arc and the fourth arc, and the ratio between the long axis and the short axis ranges from 1.42 to 1.55.

[0027] The core structure adopts a three-phase three-column structure, including three sets of iron cores arranged side by side, the bottom of the iron cores are connected, and multi-step oblique lap joints are adopted on the core column and the iron yoke of the core structure.

[0028] The core magnetic circuit system uses high-quality low-loss, grain-oriented cold-rolled silicon steel sheets from Wuhan Iron and Steel Corporation, and uses seven-level multi-step inclined lap joints on the core column and iron yoke. The loss is more than 2% better than that of ordinary structures, the noise is reduced by more than 3dB, and the no-load current is reduced by more than 5%. During assembly, the entire core is pressed with uniform pressure, and the transformer core should not loosen due to vibration during transportation and operation.

[0029] Example 2

[0030] The similarities between this embodiment and embodiment 1 are not described in detail, and the difference between them is that:

[0031] like Figure 3 As shown, an oil-immersed transformer includes a winding circuit structure 30, a lead connection structure 40, a bushing external control structure 50, and an oil tank heat dissipation structure 60. The iron core structure of the winding circuit structure uses the iron core structure recorded in Example 1 to form an iron core magnetic circuit system.

[0032] The core section of the core magnetic circuit system is formed by closing four arcs: the first arc, the second arc, the third arc, and the fourth arc. The first arc and the third arc are symmetrical structures, and the distance between them is the long axis; the second arc and the fourth arc are symmetrical structures, and the distance between them is the short axis. The ratio of the long axis to the short axis is controlled between 1.42-1.55. The core adopts a three-phase three-column structure, using Wuhan Iron and Steel's high-quality low-loss, grain-oriented cold-rolled silicon steel sheets, and uses seven-level multi-stage oblique lap joints on the core column and the iron yoke. The loss is more than 2% better than the ordinary structure, the noise is reduced by more than 3dB, and the no-load current is reduced by more than 5%. During assembly, the entire core is pressed with uniform pressure, and the transformer core should not loosen due to vibration during transportation and operation.

[0033] The winding circuit structure includes high-voltage winding and low-voltage winding, which are high voltage (35-38.5kV) and low voltage (0.69~1.14kV). All windings adopt a four-section arc structure, which has stronger short-circuit resistance than the runway circular structure; the low-voltage winding is wound with high-quality and high-ductility copper foil, lined with a high-strength internal support cardboard structure. After the winding is completed, the winding end is brushed with transformer-specific high-strength curing paint to enhance the short-circuit resistance; the winding has a good impulse voltage wave distribution, and the transformer does not use non-linear resistors to limit overvoltage; the allowable field strength should be strictly controlled, and heat-resistant, high-density, low-ash insulating paper should be used as turn-to-turn insulation to ensure that no local discharge and insulation breakdown occur in the winding.

[0034] The lead wire connection structure adopts the overall set when the winding is set, and the set is carried out in a hot state to ensure that the set gap is small. After the lead wire is assembled, it is dried several times in the imported fully automatic kerosene vapor phase drying equipment to ensure that the insulation parts are fully contracted and the short circuit resistance is improved.

[0035] The heat dissipation structure of the oil tank includes the oil tank and the tank cover. The transformer body is placed in the oil tank. The body can be lifted out for maintenance by opening the tank cover. The oil tank includes the tank wall and the tank edge. The tank cover and the tank edge are all chamfered. When the oil tank is welded, the welding quality is poor, there are defects such as cold welding, desoldering, pinholes and sand holes in the weld. The oil-immersed transformer is covered with flux and paint when it leaves the factory, and the hidden dangers are exposed after operation. In addition, electromagnetic vibration will cause welding vibration and cracking, causing leakage. The tank wall adopts a bending type, and the seams of the tank wall are welded, which reduces the welds, increases the mechanical strength, expands the heat dissipation surface of the body, and improves the heat dissipation effect. At the same time, the bending tank wall has a divergent effect, which plays a role in reducing noise. Advanced surface treatment technology is adopted: advanced shot peening equipment is used to grind the oil tank to obtain a polished surface, so that the oil tank has a uniform uneven surface, which increases the adhesion of the paint. At the same time, high-quality paint is used for special treatment to ensure the beauty and long-term durability of the product.

[0036] The bushing is externally connected to the control system. The high voltage adopts 40.5kV low partial discharge resin dry bushing, and the low voltage adopts 5kV low partial discharge porcelain bushing. It is the connection control port between the power supply system and the transformer, and is a key component for connecting the transformer to external lines.

[0037] The above embodiments are only for illustrating the structural concept and features of the utility model, and their purpose is to enable ordinary technicians in the field to understand the content of the utility model and implement it accordingly, and they cannot be used to limit the protection scope of the utility model. Any equivalent changes or modifications made according to the essence of the content of the utility model should be included in the protection scope of the utility model.

Claims

1. A core structure for an oil-immersed transformer, comprising silicon steel sheets, characterized in that: The silicon steel sheets are horizontally stacked to form an iron core, and the cross-section of the iron core includes a first arc, a second arc, a third arc, and a fourth arc. The first arc, the second arc, the third arc, and the fourth arc are closed to form a ring. The first arc and the third arc are symmetrical structures, and the second arc and the fourth arc are symmetrical structures. The radius ratio of the first arc to the second arc is 0.236-0.275, and the arc length ratio of the first arc to the second arc is 1.621-1.

679.

2. The core structure for an oil-immersed transformer according to claim 1, characterized in that: The long axis is between the first arc and the third arc, the short axis is between the second arc and the fourth arc, and the ratio between the long axis and the short axis ranges from 1.42 to 1.

55.

3. The core structure for an oil-immersed transformer according to claim 2, characterized in that: The iron core structure adopts a three-phase three-column structure, and multi-step oblique lap joints are adopted on the core column and the iron yoke of the iron core structure.

4. An oil-immersed transformer, comprising a winding circuit structure, a lead connection structure, a bushing external control structure, and an oil tank heat dissipation structure, characterized in that: The winding circuit structure comprises an iron core structure for an oil-immersed transformer as described in any one of claims 1-3.

5. The oil-immersed transformer according to claim 4, characterized in that: The winding circuit structure includes a high-voltage winding and a low-voltage winding.

6. The oil-immersed transformer according to claim 4, characterized in that: The oil tank heat dissipation structure comprises an oil tank and a tank cover. The oil tank comprises a tank wall and a tank edge. The tank cover and the tank edge are provided with rounded corners. The tank wall is bent to form the oil tank. The seams of the tank wall are welded.

7. The oil-immersed transformer according to claim 6, characterized in that: The outer surface of the box wall is provided with an uneven polished surface, and the outer side of the polished surface is coated with paint.

8. The oil-immersed transformer according to claim 4, characterized in that: The bushing external control structure includes a low partial discharge resin dry bushing and a low partial discharge porcelain bushing. The low partial discharge resin dry bushing is used to connect to high voltage, and the low partial discharge porcelain bushing is used to connect to low voltage.

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