Transformer coil winding and dry-type transformer with same

Abstract

The transformer coil winding comprises an insulating resin barrel, a first coil winding, a second coil winding and a shielding element, and the invention further relates to a dry type transformer with the transformer coil winding. According to the dry-type transformer, the shielding element is arranged, so that when the first coil winding and the second coil winding are electrified, at least one part of displacement current in the insulating resin barrel is grounded through the grounding end of the shielding element, the safety distance of the dry-type transformer is reduced, and therefore the space occupied by the dry-type transformer in the using process is reduced; and therefore, the safety of the dry-type transformer in the use process is improved.

Description

Technical Field

[0001] The invention relates to the field of transformers, in particular to a transformer coil winding and a dry-type transformer having the transformer coil winding. Background Art

[0002] The transformer coil of a dry-type transformer is a whole made of epoxy resin and conductor cast. The existing dry-type transformer cools the transformer coil by driving air through a fan installed under or outside the transformer coil. The cooling medium is air, which is mainly guided through the air duct set between the high-voltage coil and the low-voltage coil, thereby taking away the heat generated by the coil.

[0003] When the coil is energized, a displacement current is inevitably generated in the epoxy resin material. The electric field generated by the displacement current will diffuse to the surrounding environment of the dry-type transformer. This requires a designed safety distance to be set around the dry-type transformer to ensure the safety of the dry-type transformer during use.

[0004] However, when the operating environment of the dry-type transformer changes, dust may be deposited on the outer surface of the insulating resin cylinder or the air humidity may increase, thereby reducing the surface resistance of the insulating resin cylinder, thereby generating dangerous leakage surface current, which requires the dry-type transformer to be set with a safety distance larger than the designed safety distance during use. Summary of the invention

[0005] The present invention provides a transformer coil winding and a dry-type transformer having the transformer coil winding, the main purpose of which is to overcome the defect that the dry-type transformer occupies a large amount of space due to an excessively large safety distance during use.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: In the first aspect, a transformer coil winding comprises an insulating resin cylinder, a first coil winding, a second coil winding and a shielding element, wherein a cavity extending vertically from top to bottom is arranged in the insulating resin cylinder, and the cavity is used to assemble an iron core column; at least a portion of the resin insulation layer of the insulating resin cylinder is wrapped on the outer surface of the first coil winding; at least a portion of the resin insulation layer of the insulating resin cylinder is wrapped on the outer surface of the second coil winding; a portion of the shielding element is arranged between the first coil winding and the second coil winding, and the shielding element is made of a conductive metal material; wherein the first coil winding, the shielding element and the second coil winding are coaxially arranged and integrally encapsulated in the insulating resin cylinder, and when the first coil winding and the second coil winding are energized, at least a portion of the displacement current in the insulating resin cylinder is grounded through the grounding end of the shielding element.

[0007] In a possible implementation, the insulating resin cylinder is formed by pouring epoxy resin.

[0008] In a possible implementation, the shielding element has a first fiberglass layer and a first electrically conductive metal mesh. A low-voltage coil is disposed within the first coil winding. The power connection end of the low-voltage coil extends upward and passes through the upper surface of the insulating resin cylinder. The outer surface of the low-voltage coil is wrapped with the resin insulation layer. The first metal mesh covers the outer side surface of the low-voltage coil. The inner side surface of the low-voltage coil is wrapped and disposed on one side of the first fiberglass layer. The other side of the first fiberglass layer is wrapped with the resin insulation layer. The first fiberglass layer is disposed in a direction away from the shielding element.

[0009] In a possible implementation, at least a portion of the first fiberglass layer is bent according to the bending direction of the low-voltage coil, such that the cross-section of the first fiberglass layer is C-shaped.

[0010] In a possible implementation, the shielding element has a second fiberglass layer and a second electrically conductive metal mesh. A plurality of meshed holes are arranged at intervals on the second metal mesh. A high-voltage coil is disposed within the second coil winding. The second metal mesh covers the outer side surface of the high-voltage coil. The inner side surface of the high-voltage coil is wrapped and disposed on one side of the second fiberglass layer. The outer surface of the high-voltage coil is wrapped with the resin insulation layer. The other side of the second fiberglass layer is wrapped with the resin insulation layer to form a high-voltage winding. When pouring the insulating resin cylinder, the resin pouring liquid flows into and fills the space between the high-voltage coil and the second metal mesh through the meshed holes, such that the high-voltage coil of the high-voltage winding is wrapped and disposed within the insulating resin cylinder.

[0011] In a possible implementation, a first solder joint is provided on the first metal mesh, and the first solder joint is electrically connected to a first grounding element to achieve grounding.

[0012] In a possible implementation, a second solder joint is provided on the second metal mesh, and the second solder joint is electrically connected to a second grounding element to achieve grounding.

[0013] In a possible implementation, at least a portion of the second fiberglass layer is bent according to the bending direction of the high-voltage coil, such that the cross-section of the second fiberglass layer is C-shaped.

[0014] In a possible implementation, a convex portion is provided on the front part of the insulating resin cylinder body. A first electrical connection terminal and a second electrical connection terminal are provided on the convex portion. A first opening is provided on the front part of the second glass fiber layer. A second opening is provided on the front part of the second metal mesh. A first electrical wire on the high-voltage coil is electrically connected to the first electrical connection terminal by passing through the first opening and the second opening respectively. A second electrical wire on the high-voltage coil is electrically connected to the second electrical connection terminal by passing through the first opening and the second opening respectively.

[0015] In a second aspect, a dry-type transformer includes an iron core and a transformer coil winding provided on the iron core, and the transformer coil winding is the above-mentioned transformer coil winding.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: The structure of the present invention is simple and practical. By providing a shielding element, when the first coil winding and the second coil winding are energized, at least a part of the displacement current in the insulating resin cylinder body is grounded through the grounding end of the shielding element, so as to reduce the safety distance of the dry-type transformer, thereby reducing the space occupied by the dry-type transformer during use, and further improving the safety during the use of the dry-type transformer. Description of the Drawings

[0017] Figure 1 It is a schematic structural diagram of the transformer coil winding Figure 2 It is an exploded view of the transformer coil winding.

[0018] Figure 3 It is an exploded view of the dry-type transformer.

[0019] Figure 4 It is a transmission electron microscope photo of the flame-retardant epoxy resin composition, where (a) is the magnification of 10k and (b) is the magnification of 100k.

[0020] Figure 5 It is a TGA overlay graph of the flame-retardant epoxy resin compositions with different composition ratios Figure 6 It is a stress-strain relationship curve graph.

[0021] Figure 7 It is the cross-path of air and water in the flame-retardant material.

[0022] Figure 8 It is a measurement graph of the water vapor passing amount and moisture absorption amount with different ratios in the flame-retardant epoxy resin composition.

[0023] Figure 9 It is a measurement graph of the gas permeation amount with different ratios in the flame-retardant epoxy resin composition.

[0024] Figure 10 It is the process flow chart of Embodiment 9. Detailed implementation manners

[0025] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Apparently, the described embodiments are some but not all of the embodiments of the present invention.

[0026] Unless otherwise defined, the technical terms or scientific terms used herein shall have the ordinary meanings as understood by those of ordinary skill in the art to which the present invention belongs. The "first", "second" and similar terms used in the specification and claims of this patent application for the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. The terms such as "comprising" or "having" mean that the elements or items appearing before this word cover the elements or items listed after this word and their equivalents, without excluding other elements or items. The terms such as "inside", "outside", "above", "below", etc. are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly. "Plural" means at least two.

[0027] Embodiment 1, referring to Figure 1 、 Figure 2 and Figure 3 , a transformer coil winding and a dry-type transformer having the transformer coil winding. The dry-type transformer includes an iron core 11 and a transformer coil winding 10 provided on the iron core 11. The iron core 11 is installed on a base 12, and a fan (not shown in the figure) is provided on the base 12. The fan is used to dissipate heat from the iron core 11 and the transformer coil winding 10 by air cooling.

[0028] Referring to Figure 1 、 Figure 2 and Figure 3 , the transformer coil winding 10 includes an insulating resin cylinder 21, a first coil winding 31, a second coil winding 30, and a shielding element 40.

[0029] Referring to Figure 1 、 Figure 2 and Figure 3 , a cavity 22 extending vertically from top to bottom is arranged inside the insulating resin cylinder 21, and the cavity 22 is used to assemble the iron core column 23.

[0030] Referring to Figure 1 、 Figure 2 and Figure 3, at least a part of the resin insulation layer 23 of the insulating resin cylinder 21 is wrapped on the outer surface of the first coil winding 31.

[0031] Referring to Figure 1 , Figure 2 and Figure 3 , at least a part of the resin insulation layer 23 of the insulating resin cylinder 21 is wrapped on the outer surface of the second coil winding 30. A part of the shielding element 40 is arranged between the first coil winding 31 and the second coil winding 30, at least a part of the shielding element 40 is arranged along the extending direction of the first coil winding 31, and the shielding element 40 is made of a conductive metal material.

[0032] Referring to Figure 1 , Figure 2 and Figure 3 , the first coil winding 31, the shielding element 40 and the second coil winding 30 are coaxially arranged and integrally encapsulated in the insulating resin cylinder 21. When the first coil winding 31 and the second coil winding 30 are energized, at least a part of the displacement current in the insulating resin cylinder 21 is grounded through the grounding end of the shielding element 40.

[0033] Referring to Figure 1 , Figure 2 and Figure 3 , by arranging the shielding element 40, when the first coil winding 31 and the second coil winding 30 are energized, at least a part of the displacement current in the insulating resin cylinder 21 is grounded through the grounding end of the shielding element 40, so as to reduce the safety distance of the dry-type transformer, thereby reducing the space occupied by the dry-type transformer during use, and further improving the safety during the use of the dry-type transformer.

[0034] Referring to Figure 1 , Figure 3 and Figure 3 , the insulating resin cylinder 21 is made of epoxy resin by casting.

[0035] Referring to Figure 1 , Figure 2 and Figure 3 , the shielding element 40 has a first fiberglass layer 28, a conductive first metal mesh 26, a second fiberglass layer 24 and a conductive second metal mesh 22.

[0036] Referring to Figure 1 , Figure 2 and Figure 3, a low-voltage coil 27 is provided inside the first coil winding 31. The power connection end of the low-voltage coil 27 extends upward and passes through the upper surface of the insulating resin cylinder 21. The outer surface of the low-voltage coil 27 is wrapped with a resin insulation layer 23. The first metal mesh 26 covers the outer side surface of the low-voltage coil 27. The inner side surface of the low-voltage coil 27 is wrapped and disposed on one side of the first fiberglass layer 28. The other side of the first fiberglass layer 28 is wrapped by the resin insulation layer 23. The first fiberglass layer 28 is disposed in a direction away from the shielding element 40. In this embodiment, specifically, the first metal mesh 26 is disposed between the low-voltage coil 27 and the second fiberglass layer 24. In another embodiment, a low-voltage copper bar is configured on the power connection end of the low-voltage coil 27 and the low-voltage copper bar extends upward and passes through the upper surface of the insulating resin cylinder 21.

[0037] Refer to Figure 1 , Figure 2 and Figure 3 , at least a part of the first fiberglass layer 28 is bent according to the bending direction of the low-voltage coil 27, so that the cross-section of the first fiberglass layer 28 is C-shaped.

[0038] Refer to Figure 1 , Figure 2 and Figure 3 , in another embodiment, the first coil winding 31 is placed in a mold. The first coil winding 31 is composed of two appropriately spaced low-voltage coils 27 and a first fiberglass layer 28.

[0039] Refer to Figure 1 , Figure 2 and Figure 3 , a first solder joint is provided on the first metal mesh 26, and the first solder joint is electrically connected to a first grounding element to achieve grounding.

[0040] Refer to Figure 1 , Figure 2 and Figure 3 , a folding portion is provided at the edge of the first metal mesh 26, and a layer of double-sided tape is inserted into the folding portion to maintain the stretched state of the shielding on the surface of the first coil winding 31 and prevent the formation of a closed circuit at the same time.

[0041] Refer to Figure 1 , Figure 2 and Figure 3 , by arranging the inner side surface of the low-voltage coil 27 to be wrapped and disposed on one side of the first fiberglass layer 28, the first coil winding 31 is made into a rigid whole, thereby playing an accurate positioning role for the first metal mesh 26.

[0042] Refer to Figure 1 , Figure 2 and Figure 3, the bottom and top of the first metal mesh 26 can be set to fold outwards, thus having a relatively large radius of curvature and extension.

[0043] Referring to Figure 1 , Figure 2 and Figure 3 , in another embodiment, a first welding point 41 is configured on the upper part of the first metal mesh 26 for connection to a grounding element (such as the magnetic core of a transformer or its mechanical support frame).

[0044] Referring to Figure 1 , Figure 2 and Figure 3 , a plurality of meshed holes arranged at intervals are provided on the second metal mesh 22, a high-voltage coil 29 is arranged inside the second coil winding 30, the second metal mesh 22 covers the outer side surface of the high-voltage coil 29, the inner side surface of the high-voltage coil 29 is wrapped on one side of the second fiberglass layer 24, the outer surface of the high-voltage coil 29 is wrapped with a resin insulation layer 23, and the other side of the second fiberglass layer 24 is wrapped by the resin insulation layer 23 to form a high-voltage winding. When the epoxy resin is poured into the insulating resin cylinder 21, the resin pouring liquid flows into and fills the space between the high-voltage coil 29 and the second metal mesh 22 through the meshed holes, so that the high-voltage coil 29 of the high-voltage winding is wrapped and arranged inside the insulating resin cylinder 21. A part of the second metal mesh 22 is wrapped with the resin insulation layer 23.

[0045] Referring to Figure 1 , Figure 2 and Figure 3 , a second welding point 25 is provided on the second metal mesh 22, and the second welding point 25 is electrically connected to a second grounding element to achieve grounding.

[0046] Referring to Figure 1 , Figure 2 and Figure 3 , at least a part of the second fiberglass layer 24 is bent according to the bending direction of the high-voltage coil 29, so that the cross-section of the second fiberglass layer 24 is C-shaped.

[0047] Referring to Figure 1 , Figure 2 and Figure 3, a convex portion 32 is provided on the front part of the insulating resin cylinder 21. The convex portion 32 is longitudinally extended from top to bottom on the front part of the insulating resin cylinder 21. A first electrical connection terminal 33 and a second electrical connection terminal 34 are provided on the convex portion 32. A first opening 35 is provided on the front part of the second fiberglass layer 24. A second opening 34 is provided on the front part of the second metal mesh 22. The first electrical wire on the high-voltage coil 29 is electrically connected to the first electrical connection terminal 33 by passing through the first opening 35 and the second opening 34 respectively. The second electrical wire on the high-voltage coil 29 is electrically connected to the second electrical connection terminal 34 by passing through the first opening 35 and the second opening 34 respectively.

[0048] Refer to Figure 1 , Figure 2 and Figure 3 , in this embodiment, specifically, the top edge and the bottom edge of the second metal mesh 22 are folded inwards, while the axial (vertical) edges do not overlap, but maintain a convenient gap for passing through two first electrical connection terminals and three or more second electrical connection terminals for adjusting the turn ratio.

[0049] Refer to Figure 1 , Figure 2 and Figure 3 , the second metal mesh 22 is also equipped with a second soldering point on its top edge for connection to a grounding element (such as the magnetic core of a transformer or its mechanical support frame).

[0050] Refer to Figure 1 , Figure 2 and Figure 3 , the second opening 34 of the second metal mesh 22 provides a passage for the terminals of the second coil winding 30, is conveniently folded outwards, and is received within the convex portion 32 of the insulating resin cylinder 21.

[0051] Refer to Figure 1 , Figure 2 and Figure 3 , by setting the top edge and the bottom edge of the second metal mesh 22 to be folded inwards, the folded edges prevent the local generation of a high voltage gradient and also serve as mechanical reinforcement elements.

[0052] Refer to Figure 1 , Figure 2 and Figure 3 , the proper mechanical adhesion between the shielding element 40 and the resin insulation layer 23 requires the shielding element 40 to have relatively high plasticity and elastic properties. This is achieved by using a mesh structure of braided metal wires with a diameter ranging from 0.1 to 0.5 millimeters.

[0053] Refer to Figure 1 , Figure 2 and Figure 3, in another embodiment, by setting the top and bottom edges of the first metal mesh 26 to fold inwards respectively, and the top and bottom edges of the second metal mesh 22 to fold inwards respectively, in most cases it allows the structure to be strong enough for subsequent processing and accurate positioning in the mold.

[0054] Referring to Figure 1 , Figure 2 and Figure 3 , assuming the thickness of the resin insulation layer 23 is about 10 mm, as required outside the second coil winding 30 to ensure its dielectric insulation, any offset of the shielding element 40 relative to the surface of the resin insulation layer 23, even by a few millimeters, significantly reduces the safety distance of the insulation thus formed.

[0055] Referring to Figure 1 , Figure 2 and Figure 3 , in another embodiment, to further reinforce the shielding, especially if the metal mesh (the first metal mesh 23 or the second metal mesh 22) is formed of very thin wires (with a diameter of 0.1 - 0.2 mm), a cylindrical glass fiber second glass fiber layer 24 is conveniently provided, presented in the form of a split elastic band, whose diameter is equal to or slightly larger than the peripheral wall of the mold.

[0056] Referring to Figure 1 , Figure 2 and Figure 3 , the second glass fiber layer 24 is reinforced by epoxy resin spraying without reducing the porosity, thus facilitating the support of the second metal mesh 22.

[0057] Referring to Figure 1 , Figure 2 and Figure 3 , the assembly of the low - voltage coil 27, the first glass fiber layer 28, the first metal mesh 26, the second glass fiber layer 24, the high - voltage coil 29 and the second metal mesh 22 is introduced into the casting mold such that the second metal mesh 22 fits perfectly against the peripheral wall of the mold.

[0058] Referring to Figure 1 , Figure 2 and Figure 3 , the first electrical connection terminal 33 and the second electrical connection terminal 34 of the high - voltage coil 29 are connected through their respective connectors to the terminal block at the protrusion 32 arranged on the mold wall.

[0059] Referring to Figure 1 , Figure 2 and Figure 3 , in another embodiment, by setting the diameter of the upper folding edges of the first metal mesh 26 and the second metal mesh 22 to be less than the diameter of the second glass fiber layer 24 and greater than the outer diameter of the cavity 22. Thus, it is convenient to insert the second coil winding 30 into the mold for pouring.

[0060] Referring to Figure 1 、 Figure 2 and Figure 3 , the casting mold can be filled with flowing epoxy resin, which penetrates all the free cavities in the mold, impregnates the various forms or cores of reinforcing glass fibers therein, and after curing, firmly combines the coil winding and the shielding element 40 arranged therein in one casting step.

[0061] Referring to Figure 1 、 Figure 2 and Figure 3 , in another embodiment, a long strip is pre-inserted into the mold so that the long strip forms an air duct 29 after demolding. Since the low-voltage first coil winding 31 is formed by two spaced and concentric low-voltage coils 27, the shown air duct 29 can be inserted between the two low-voltage coils 27, thereby ensuring effective heat dissipation of the first coil winding 31, wherein due to the high current involved, the resistance loss usually requires a higher heat dissipation amount than the second coil winding 30.

[0062] Referring to Figure 1 、 Figure 2 and Figure 3 , in a dry-type transformer, the iron core 11 is usually sequentially provided with three spaced iron core columns 23. An upper yoke iron is provided on the top of the iron core column 23, and a lower yoke iron is provided on the bottom of the iron core column 23. The iron core column 23, the upper yoke iron and the lower yoke iron are all composed of a plurality of silicon steel sheets laminated together.

[0063] Referring to Figure 1 、 Figure 2 and Figure 3 , the insulating resin cylinder 21 is coaxially arranged with each iron core column 23 and encapsulates the second coil winding 30 and the first coil winding 31. The first coil winding 31 is coaxially arranged inside the second coil winding 30.

[0064] Referring to Figure 1 、 Figure 2 and Figure 3, the insulating resin cylinder 21, the first coil winding 31 and the second coil winding 30 inside it are obtained through a simple manufacturing process. This process includes arranging the first coil winding 31, the second coil winding 30 and the shielding element 40 to be encapsulated with resin in a casting mold, and then filling the mold with flowing epoxy resin. After the epoxy resin and the curing agent are cured, the insulating resin cylinder 21 is formed. A cylindrical core is placed in the center of the casting mold. The mold is known to consist of a cylindrical container (preferably composed of multiple separable parts for easier demolding), having a side groove or compartment corresponding to the raised portion 32 of the insulating resin cylinder 21 for forming a central axial channel to pass through the iron core column 23. A non-stick glue is applied to the inner wall of the mold and the central core to facilitate demolding. The resin casting machine disclosed in the Chinese Utility Model Patent (Application No.: 202020970090.8, Publication No.: CN212750618U) can be referred to for pouring.

[0065] Embodiment 2, referring to Figure 1 , the difference between this Embodiment 2 and Embodiment 1 is that only epoxy resin is used for pouring in the dry-type transformer, and the finally cast insulating resin cylinder 21 has poor flame retardancy and is difficult to slow down its burning speed when burning. In this embodiment, the insulating resin cylinder 21 is formed by pouring and curing a flame-retardant epoxy resin composition.

[0066] Referring to Figure 4 , the flame-retardant epoxy resin composition consists of a resin component and modified clay. The cured resin component forms a resin insulation layer 23, and the modified clay forms a flame-retardant layer. Among them, the resin component is composed of the following components in parts by mass: Epoxy resin: 50 - 62 parts; N,N-dimethylacetamide: 10 - 21 parts; 1.3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane: 3 - 9 parts; The modified clay is composed of the following components in parts by mass: Inorganic layered clay: 50 - 60 parts; Tetradecyltrimethylammonium chloride: 25 - 30 parts.

[0067] The structural formula of the inorganic layered clay is: Ca0.084Na0.143(Al1.69Mg0.31)Si4O10(OH)2×2H2O. The CEC value is 115 meq / 100g.

[0068] By adding modified clay to the resin component, the inorganic layered clay can cover the voids in the epoxy resin, thereby isolating oxygen and achieving a flame retardant effect. On the other hand, since the intrusion of oxygen is blocked, it can also slow down the oxidation rate of the copper wire in the dry-type transformer coil, improve the stability during use, and extend the service life.

[0069] Example 3. The difference between this Example 3 and Example 2 is that: the flame-retardant epoxy resin composition consists of a resin component and modified clay. After curing, the resin component forms a resin insulation layer 23, and the modified clay forms a flame-retardant layer. Among them, the resin component consists of the following components in parts by mass: Epoxy resin: 52 parts; N,N-dimethylacetamide: 10 parts; 1.3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane: 4 parts; The modified clay consists of the following components in parts by mass: Inorganic layered clay: 51 parts; Tetradecyltrimethylammonium chloride: 27 parts.

[0070] Other structures are similar to those in Example 2 and will not be elaborated here.

[0071] Example 4. The difference between this Example 4 and Example 2 is that: the mass of tetradecyltrimethylammonium chloride is X, where the value of X is based on the formula: inorganic layered clay CEC value (meq) / 100g * Clay grams * 1.5 = Z / molecular weight of tetradecyltrimethylammonium chloride * 1000.

[0072] Other structures are similar to those in Example 2 and will not be elaborated here.

[0073] Example 5. The difference between this Example 5 and Example 2 is that: the content of inorganic layered clay is Y, where the value range of Y is 1wt.% < Y < 7wt.%.

[0074] The following is the test part: Refer to Figure 5 , thermogravimetric analyzer (TGA): Through the TGA tests of flame-retardant epoxy resin compositions with various different percentages of inorganic layered clay content, the changes in the thermal cracking temperature (Td) and carbon residue content between the epoxy resin without clay and the flame-retardant epoxy resin compositions with different composition percentages of clay can be compared.

[0075] Among them, Td is the cracking temperature, which is defined as the temperature at which the epoxy resin has a thermal weight loss of 5 wt%. Since the initial thermal weight loss of about 5 wt% is due to the thermal weight loss of some small molecules or solvents such as water, rather than the weight loss of the epoxy resin itself caused by the cleavage of the polymer main chain due to heating, the temperature at which the epoxy resin has a thermal weight loss of 5 wt% is the thermal cracking temperature of the epoxy resin itself.

[0076] Refer to Figure 5 , when the weight loss of the flame-retardant epoxy resin composition is 5 wt%, the temperature of the epoxy resin is 304 °C, while the T5% of CLMA7 has been increased to 343 °C. When the amount of montmorillonite added is more, Td increases slightly. Coupled with the interaction between the clay platelets and the epoxy resin, the addition of layered clay increases the gas barrier property of the material, resulting in an increase in its pyrolysis temperature and further improving the thermal stability of the overall material. In addition, the carbon residue content (increases with the increase of the clay content, and this trend is predictable because clay is an inorganic substance (containing Al2O3, MgO, SiO2), and inorganic substances may not be completely burned out even at temperatures above 600 °C, but most organic substances have been burned out at this temperature. However, the carbon residue content of CLMA7 remains 20% by weight at 650 °C, mainly for two reasons: one is that inorganic substances have good flame retardancy, and the clay we added has a layered structure, and polymers interpenetrate among them, thus increasing its flame retardant effect. The other is that a layer of carbon residue is formed on the surface of the epoxy resin at high temperature, that is to say, the epoxy resin is wrapped in the carbon residue, and the carbon residue has a flame retardant effect, making the epoxy resin wrapped in the carbon residue not easily burned out at high temperature.

[0077] Thermomechanical analyzer (TMA): When no clay is added, the thermal expansion coefficients before and after Tg are 175 µm / m-°C and 291 µm / m-°C respectively. However, when the content of inorganic layered clay is added to 5 wt%, its thermal expansion coefficients are reduced to 126 µm / m-°C and 254 µm / m-°C respectively. It can be seen that when inorganic layered clay is in the epoxy resin, the thermal expansion coefficient of the material will decrease, and with the increase of the content of inorganic layered inorganic layered clay, the thermal expansion coefficient decreases more. This is because inorganic layered clay itself is a ceramic material with a very low thermal conductivity and thermal expansion coefficient. So when the surface of the material contains nano-scale inorganic layered clay, when the material is heated, the heat energy will not be transferred to the whole material in large quantities, enabling the polymer to obtain energy and causing twisting and rotation, resulting in material deformation. At the same time, it can provide a large surface area on the material surface to absorb a large amount of heat energy, and most of the energy is absorbed by the inorganic layered clay. Therefore, it has a great impact on reducing the thermal expansion coefficient of the whole material. And the reduction of the thermal expansion coefficient is very beneficial for the epoxy resin as a packaging material because it can reduce the occurrence of cracking.

[0078] Table 1, Thermal analyzer data.

[0079]

[0080] Refer to Figure 6 , when the addition amount of inorganic layered clay is below 5 wt%, the elongation at break increases with the increase of the content of inorganic layered clay, that is, the toughness is relatively improved. Because the size of toughness can be seen from the area under the stress-strain curve of the tensile test until the fracture point. Thus, it can be known that the toughness increases before the content of inorganic layered clay reaches 5 wt%. However, when the content of inorganic layered clay reaches 7 wt%, the elongation at break and toughness of the material both decrease significantly. This may be caused by two phenomena. First, phase separation occurs between the epoxy resin and the inorganic layered clay; second, the interaction force between the epoxy resin and the inorganic layered clay weakens. Because adding inorganic layered clay to the epoxy resin material is usually to reinforce the disadvantage of poor mechanical strength of the epoxy resin, but at this time, the material will become harder and more brittle due to the addition of inorganic layered clay, so the elongation at break of the material decreases. That is to say, this is related to the dispersion of clay in the epoxy resin. If the clay is well dispersed, the epoxy resin will have more opportunities to interact with the clay, so the toughness of the material will increase. And the increase in toughness can reduce the occurrence of cracking when the epoxy resin is used as a packaging material. Therefore, for the whole material, the total interaction force between the epoxy resin and the clay is proportional to the content of inorganic layered clay in the composite material.

[0081] Refer to Figure 7 , Figure 8 and Figure 9, Barrier property test: Since oxygen and water vapor in the air will corrode the metal surface, causing physical and chemical damage to the chip (temperature, humidity, stress, etc.), which in turn causes cracking or popcorning of the packaging material. Therefore, due to the properties of clay, for O2 and H2O to reach the metal surface for corrosion, they need to take a longer path and consume more time than before to reach the metal surface. This delays the time of metal rusting and thus has an anti-corrosion effect. Coupled with the protection of the oxide formed on the metal surface, it further increases the corrosion resistance of the material and enables it to effectively achieve the performance of packaging. As can be seen from the figure, after the intercalation structure is formed, since each silicate layer is still uniformly dispersed in the polymer substrate in a layered structure, when external gas molecules enter the polymer substrate and diffuse, the silicate will prevent the molecules from diffusing in a straight line, forcing the gas molecules to take a detour, increasing the diffusion path, so the gas barrier or water barrier property will be improved. In addition, epoxy resin has polar functional groups (-OH), so it is easy to absorb water vapor. The silicate layer of clay can avoid the contact opportunity between the polar group and water molecules, so the moisture absorption rate can be reduced. Through the measurement of gas permeability GPA and vapor permeability analysis VPA, both the water vapor passing amount and the hygroscopicity decrease with the increase of the content of inorganic layered clay. Taking the addition of 5% clay as an example, its water vapor passing amount and water absorption rate can be decreased by 61% and 53% respectively. It can be seen that dispersing the clay arranged in a layered structure in the epoxy resin substrate can make the path for water molecules to pass more tortuous and delay the penetration of water molecules. The same effect also applies to blocking gas penetration. Table 2 Water Vapor Passing Amount and Water Absorption Rate of Flame Retardant Epoxy Resin Composition

[0082] CLMA1 is the content of inorganic layered clay with a value of 1 wt.%, CLMA3 is the content of inorganic layered clay with a value of 3 wt.%, CLMA5 is the content of inorganic layered clay with a value of 5 wt.%, and CLMA7 is the content of inorganic layered clay with a value of 7 wt.%.

[0083] Other structures are similar to those in Example 2 and will not be elaborated here.

[0084] Example 6. The difference between this Example 6 and Example 2 is that: the flame retardant epoxy resin composition is composed of a resin component and modified clay. After curing, the resin component forms a resin insulation layer 23, and the modified clay forms a flame retardant layer. Among them, the resin component is composed of the following components in parts by mass: Epoxy resin: 50 parts; Dimethylacetamide: 10 parts; 1.3-Bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane: 3 parts; The modified clay is composed of the following components in parts by mass: Inorganic layered clay: 50 parts; Tetradecyltrimethylammonium chloride: 25 parts.

[0085] The other structures are similar to those in Example 2 and will not be elaborated here.

[0086] Example 7. The difference between this Example 7 and Example 2 lies in that: the flame-retardant epoxy resin composition is composed of a resin component and modified clay. After curing, the resin component forms a resin insulation layer 23, and the modified clay forms a flame-retardant layer. Among them, the resin component is composed of the following components in parts by mass: Epoxy resin: 62 parts; Dimethylacetamide: 21 parts; 1,3-Bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane: 9 parts; The modified clay is composed of the following components in parts by mass: Inorganic layered clay: 60 parts; Tetradecyltrimethylammonium chloride: 30 parts.

[0087] The other structures are similar to those in Example 2 and will not be elaborated here.

[0088] Example 8. The difference between this Example 8 and Example 2 lies in that: the flame-retardant material further contains a fiberglass grid and / or aramid fiber insulating paper. The fiberglass grid is covered with the flame-retardant epoxy resin composition, and the aramid fiber insulating paper is covered with the flame-retardant epoxy resin composition.

[0089] By providing the pre-impregnated aramid fiber insulating paper with the flame-retardant epoxy resin composition, since the modified clay isolates oxygen after covering the voids in the epoxy resin, it effectively protects the conductive copper wire wrapped in the pre-impregnated aramid fiber insulating paper and delays the oxidation rate of the conductive copper wire.

[0090] The production method of the dry-type transformer includes the following steps: Step 1, respectively weigh inorganic layered clay and tetradecyltrimethylammonium chloride. Stir and dissolve the inorganic layered clay in ionic water. Dissolve the tetradecyltrimethylammonium chloride in deionized water and adjust the pH value to 3-4 with 1 mol of HCl, then continuously drop it into the solution of the inorganic layered clay. After repeated stirring, centrifuge and filter, and dry to obtain the modified clay preparation; When stirring and dissolving the inorganic layered clay, it should be stirred for at least 8 h until the inorganic layered clay is completely dissolved.

[0091] Step 2, weigh epoxy resin, N,N-dimethylacetamide, and 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, add the modified clay preparation obtained in Step 1, and mix and stir for 48-56 hours to obtain the flame-retardant epoxy resin composition; By adding modified clay to the resin component, the inorganic layered clay can cover the voids in the epoxy resin, thereby isolating oxygen and achieving a flame retardant effect.

[0092] Step 3, production of the wire-wound coil green body: Wind the glass fiber grid, aramid fiber insulating paper, and copper electromagnetic wire on the inner casting mold according to a predetermined electromagnetic structure to make a wire-wound coil green body with a flame-retardant epoxy resin composition; Step 4, production of the foil coil green body: Wind the pre-impregnated aramid fiber insulating paper with a flame-retardant epoxy resin composition and the conductive copper wire on the mold according to a predetermined number of layers, and lead out the conductive copper wire with a conductive copper bar to make a foil coil green body with a flame-retardant epoxy resin composition; Step 5, pre-curing of the foil coil: Put the foil coil green body with a flame-retardant epoxy resin composition into a curing furnace for curing; Step 6, repeatedly stack the glass fiber grid and aramid paper in the casting mold according to a predetermined thickness to make an insulating spacer green body with a flame-retardant epoxy resin composition, a foil coil support plate green body with a flame-retardant epoxy resin composition, and a core insulating plate green body with a flame-retardant epoxy resin composition; Step 7, after the wire-wound coil green body with a flame-retardant epoxy resin composition, the foil coil green body with a flame-retardant epoxy resin composition, the insulating spacer green body with a flame-retardant epoxy resin composition, the foil coil support plate green body with a flame-retardant epoxy resin composition, and the core insulating plate green body with a flame-retardant epoxy resin composition are dried at normal pressure, put their casting molds into a vacuum pressure casting container, and use the flame-retardant epoxy resin composition for casting; Step 8, after casting is completed, put the casting mold into a curing furnace and cure it according to a predetermined curing temperature and curing time; Step 9, after the wire-wound coil with a flame-retardant epoxy resin composition, the foil coil with a flame-retardant epoxy resin composition, the insulating spacer with a flame-retardant epoxy resin composition, the foil coil support plate with a flame-retardant epoxy resin composition, and the core insulating plate with a flame-retardant epoxy resin composition are cured and formed, take them out of the curing furnace, remove the casting molds from the components, and polish the sharp edges of each component smooth to make a wire-wound coil with a flame-retardant epoxy resin composition, a foil coil with a flame-retardant epoxy resin composition, an insulating spacer with a flame-retardant epoxy resin composition, a foil coil support plate with a flame-retardant epoxy resin composition, and a core insulating plate with a flame-retardant epoxy resin composition.

[0093] By setting the insulating spacer green body to have a flame-retardant epoxy resin composition, the flame retardant performance of the insulating spacer after casting is improved, thereby delaying the burning speed of the insulating spacer.

[0094] By setting the blank of the foil coil support plate to have a flame-retardant epoxy resin composition, the flame-retardant performance of the foil coil support plate after pouring is improved, thereby delaying the burning speed of the foil coil support plate.

[0095] By setting the blank of the iron core insulating plate to have a flame-retardant epoxy resin composition, the flame-retardant performance of the iron core insulating plate after pouring is improved, thereby delaying the burning speed of the iron core insulating plate.

[0096] By setting the blank of the wire-wound coil with a flame-retardant epoxy resin composition and placing it in a pouring mold to be cast into an insulating resin cylinder 21. On the one hand, the modified clay can cover the voids in the epoxy resin, thus isolating oxygen and further achieving a flame-retardant effect, thereby improving the overall flame-retardant performance of the insulating resin cylinder 21. When the insulating resin cylinder 21 catches fire, the spread speed of the fire is delayed. On the other hand, due to the air isolation effect of the modified clay, the copper electromagnetic wire inside the insulating resin cylinder 21 is effectively protected, the oxidation speed of the copper electromagnetic wire is delayed, the stability during long-term use is improved, and thus the service life of the insulating resin cylinder 21 is effectively extended, achieving a two-in-one effect.

[0097] In this embodiment, the structural formula of the inorganic layered clay is: Ca0.084Na0.143(Al1.69Mg0.31)Si4O10(OH)2×2H2O. The CEC value is 115 meq / 100g.

[0098] By setting the blank of the wire-wound coil with a flame-retardant epoxy resin composition and placing it in a pouring mold to be cast into an insulating resin cylinder. On the one hand, the modified clay can cover the voids in the epoxy resin, thus isolating oxygen and further achieving a flame-retardant effect, thereby improving the overall flame-retardant performance of the insulating resin cylinder. When the insulating resin cylinder catches fire, the spread speed of the fire is delayed. On the other hand, due to the air isolation effect of the modified clay, the copper electromagnetic wire inside the insulating resin cylinder is effectively protected, the oxidation speed of the copper electromagnetic wire is delayed, the stability during long-term use is improved, and thus the service life of the insulating resin cylinder is effectively extended, achieving a two-in-one effect.

[0099] Other structures are similar to those in Embodiment 2 and will not be elaborated here.

[0100] Embodiment 9, referring to 3, the difference between this Embodiment 9 and Embodiment 2 is that: in Step 4, a conductive copper bar 15 is provided on the low-voltage side of the dry-type transformer. A part of the conductive copper bar 15 is covered by a flame-retardant epoxy resin composition, and the other part of the conductive copper bar 15 is exposed to the air. At least one layer of conductive antioxidant layer is electroplated on the exposed part of the conductive copper bar 15 in contact with the air, and the conductive antioxidant layer is a tin-cerium alloy.

[0101] Referring to 3, a conductive anti-oxidation layer is formed by plating a tin-cerium alloy on the conductive copper busbar 15, thereby protecting the portion of the conductive copper busbar 15 exposed to the air, slowing down its oxidation rate, extending the service life of the conductive copper busbar 15, and maintaining good conductive properties of the conductive copper busbar 15.

[0102] Reference Figure 10 The electroplating method comprises the following steps: step S100, pre-plating treatment; step S200, tin-cerium alloy plating; step S300, post-plating treatment.

[0103] Reference Figure 10 In step S100, step S101 is also included, spraying and washing: after the conductive copper busbar 15 is hung, the spraying and washing process is firstly performed, and the conductive copper busbar 15 is sprayed and washed with tap water to preliminarily remove stains and dust attached to the surface of the conductive copper busbar 15; Reference Figure 10 , Step S102, Ultrasonic degreasing: Ultrasonic degreasing places the conductive copper bus 15 in a degreasing liquid in an ultrasonic field of a certain frequency, and uses the shock wave generated by the ultrasonic wave to destroy the oil film and the strong stirring effect generated by the cavitation phenomenon to effectively remove the oil stains on the conductive copper bus 15. The chemical degreasing powder in the tank (the chemical degreasing powder is a white powdery solid. pH value: 11.5-14.0 (3% aqueous solution), the composition of the chemical degreasing powder is 30-40% sodium hydroxide, 30-40% sodium carbonate, and 2-5% surfactant)) has a concentration of about 40-50g / L, a temperature of about 60-70°C, and a processing time of 3min. In order to ensure the cleaning quality of the conductive copper bus 15, the required concentration of the degreasing liquid needs to be maintained. Regular analysis is performed, and the degreasing agent is added in time according to the analysis results or the cleaning quality of the conductive copper bus 15. When the degreasing effect of the cleaning liquid is significantly reduced, the new liquid needs to be replaced as a whole. In order to avoid the accumulation of oil and other impurities, the ultrasonic degreasing tank is designed with oil-water separation or filtration treatment. The tank liquid is extracted online and purified by the oil-water separator and filter before reuse. The degreasing tank liquid is replaced once every 6 months and the tank liquid is re-prepared. After ultrasonic degreasing treatment, the process enters the water washing and spray water washing process. The medium is preferably recycled water, and the insufficient part is supplemented with tap water; Reference Figure 10 Step S103, pickling and polishing: In order to improve the compactness of the surface coating of the conductive copper busbar 15, the pre-plating chemical polishing method is used to improve the surface finish of the conductive copper busbar 15. The tinned conductive copper busbar 15 is mostly a stamping part, and the surface roughness Ra is greater than 6.3μm, and the roughness is relatively large. The above problem can be solved by chemical polishing, and the surface roughness can reach Ra=1.6μm. The chemical polishing tank liquid is composed of: H2O2 (content 50%) 8~12%, sulfuric acid 0.5~1.0%, polishing additive 5~8%.

[0104] ReferenceFigure 10 The polishing additive consists of sulfuric acid, surfactant, H2O2 stabilizer (a compound of magnesium salt, aminoethanol phosphate, and picolinic acid), oxidizer, etc. The chemical polishing process generally can be divided into three stages: etching, brightening, and over-etching. In the etching stage of the polishing process, since the metal is in an activated state, the non-uniform dissolution of the metal surface occurs due to the differences in the electrochemical and physicochemical properties of different parts of the metal surface, thus generating a corroded surface. As the polishing process progresses, the metal surface gradually changes from the activated state to the passivated state, and at this time, the polishing process enters the brightening stage. Due to the different degrees of passivation of the convex and concave parts of the metal surface, the high activity of the convex parts relative to the concave parts and the high-speed diffusion of metal ions from the convex parts to the polishing solution, as well as the high-speed diffusion of the new polishing solution to the convex parts, lead to the preferential dissolution of the convex parts. In addition, the incomplete and porous nature of the passivation film formed on the convex parts of the metal surface also accelerates the dissolution of the convex parts. As a result, the corroded metal surface is replaced by a bright surface. As the polishing time prolongs, the passivated state of the metal surface is broken, and an over-etched metal surface is generated. By appropriately controlling the polishing reaction time, the adverse effects of over-etching can be reduced. In this embodiment, there is no nitric acid or nitrate, and no NOx is generated during the pickling process. The chemical polishing reaction temperature is at room temperature, and the time is 30 s.

[0105] Refer to Figure 10 The main reaction formulas involved in pickling and polishing are as follows: 2H2O2 → H+ + HO2-; Me + HO2- → MeO + OH- (Me is a metal element); H+ + OH- → H2O; MeO + H2SO4 → MeSO4 + H2O (Me is a metal element). Due to the improvement of the pickling solution formula and the requirements of the electroplating process of the conductive copper busbar 15, after pickling and polishing treatment, there is no nitric acid film removal process, and it directly enters the water washing and spray water washing processes. The medium is water, which can be tap water; Refer to Figure 10 Step S101, activation: 5% - 10% sulfuric acid solution is used for activation to remove the oxide scale and rust on the surface of the conductive copper busbar 15, clean the thin film such as metal surface oxides, and the activation treatment is 30 s.

[0106] Refer to Figure 10 The chemical reaction formulas involved in the activation process are as follows: MeO + H2SO4 → MeSO4 + H2O (Me is a metal element); Me + H2SO4 → MeSO4 + H2↑ (Me is a metal element). After the activation treatment, the process enters the water washing and spray water washing processes. The medium is water, which can be tap water; Refer to Figure 10, step S200 also includes step S201, tin-cerium alloy plating: the process parameters used are stannous sulfate: 30-40 g / L, cerium sulfate: 5-7 g / L, sulfuric acid: 140-160 g / L, brightener: 20-25 g / L, temperature: 10-30°C, current density: 1-4 A / dm2, cathode movement: 20-30 times / min, stroke: 10-15 cm; Stannous sulfate: provides Sn2+ required for cathode discharge. High content allows high cathode current density and fast plating speed. When the content is too high, the cathode polarization is poor, the dispersibility of the plating solution decreases, the coating crystal is coarse, the color is dark, and even burrs are generated, resulting in large carry-out losses and high costs. When the content is too low, the plating speed is slow and the coating is easy to burn, but the deep plating ability is good.

[0107] Cerium sulfate: Cerium sulfate in the electroplating of tin-cerium alloy can make the coating bright, enhance the conductivity and purification of the plating solution, improve the high temperature resistance and oxidation resistance of the coating, and eliminate the drawbacks of "tin dripping" and "tin disease".

[0108] Sulfuric acid: Adding sufficient sulfuric acid can firstly inhibit the hydrolysis of Sn2+ or Sn4+ to prevent the plating solution from becoming turbid. Second, it can increase the conductivity of the plating solution, thereby reducing the tank voltage and improving the dispersion ability of the plating solution. Third, it can promote the dissolution of the anode. If the sulfuric acid content is too high, the color of the coating will gradually change from bright silver-white to gray to dark gray. The reason is that the anode dissolution is accelerated and the tin content in the plating solution increases; if the sulfuric acid concentration is too low, the tin salt will hydrolyze, the plating solution will become turbid, and precipitation will occur.

[0109] Hydrolysis of Sn2+: SnSO4+2H2O→Sn(OH)2↓+H2SO4↓ Hydrolysis of Sn4+: Sn(SO4)2+4H2O→Sn(OH)4↓+2H2SO4 Brightener: A water solution mixed with various organic substances, the main components of which are OP emulsifier, benzyl acetone, water, etc. The functions of brightener include improving cathode polarization and making the coating uniform, delicate and bright.

[0110] Anode: Use high-purity tin (purity above 99.8%) and cover it with a pure polyester bag to prevent the anode mud from entering the plating solution in the form of fine powder.

[0111] After treatment, the plated parts enter the water washing and spray water washing process, and the medium is pure water.

[0112] Reference Figure 10 , step S202, neutralization: using 3%-5% sodium carbonate for neutralization, the processing time is 15-20s; The purpose of using sodium carbonate for rinsing and neutralization is to effectively prevent the residual acid that may be adsorbed or not rinsed clean from affecting the quality of the plated products.

[0113] After the tin-cerium alloy plating, the plated parts enter the water washing and spray water washing processes, and the medium is pure water.

[0114] Refer to Figure 10 , step S203, hot water washing: After the neutralization treatment, the plated parts enter the hot water washing process, the medium is pure water, the water washing temperature is between 40 - 60 °C, and the water washing time is about 10 - 20 s.

[0115] The purpose of hot water washing is to improve the hardness of the coating. Hot water washing can remove water stains and keep the appearance of the passivation film clear.

[0116] By setting a conductive oxide layer, on the one hand, it delays the oxidation rate of the exposed copper bar part, thereby extending the service life of the copper bar. On the other hand, it maintains the good electrical conductivity of the copper bar during long-term use, achieving a two-fold effect.

[0117] Cerium elements have a strong affinity for elements such as sulfur and oxygen, and have a strong desorption ability for oxygen, sulfur, and nitrogen, reducing the impurity content in the coating, enhancing the conductivity and purification effect of the plating solution, thereby improving the antioxidant ability of the tin-cerium alloy coating; the atomic radius of cerium metal is much larger than that of tin. When tin and cerium ions co-deposit on the cathode, cerium can fill the surface defects at the grain discontinuities of tin, preventing the grains from growing further, thereby refining the grains of tin, increasing the density of the tin coating, and further improving the corrosion resistance of the tin coating; due to the addition of cerium atoms, the crystal structure of tin is changed, improving the high-temperature resistance and antioxidant ability of the coating, and eliminating defects such as "tin dripping" and "tin pest".

[0118] The acidic bright electroplating tin-cerium alloy process has the advantages of good covering power and dispersion ability of the plating solution; excellent stability and easy maintenance; high current efficiency, fast deposition speed, low cost; and little environmental pollution. The obtained coating has fine crystals, is bright, and has excellent corrosion resistance and solderability. Among various tin alloy coatings, the tin-cerium alloy coating has the most excellent comprehensive performance. The addition of rare earth element cerium can make the coating crystals finer, the surface brighter and denser, improving the corrosion resistance and high-temperature resistance. Due to the reduction of the surface oxide layer thickness, the solderability is also very ideal.

[0119] Other structures are similar to those in the second embodiment and will not be elaborated here.

[0120] The above is only the specific implementation manner of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantive modification made to the present invention using this concept shall fall within the scope of infringement of the protection of the present invention.

Claims

1. Transformer coil winding, characterized in that: include An insulating resin cylinder, wherein a cavity extending vertically from top to bottom is arranged in the insulating resin cylinder, and the cavity is used for assembling the iron core column; a first coil winding, wherein the outer surface of the first coil winding is wrapped with at least a portion of the resin insulation layer of the insulating resin cylinder; a second coil winding, wherein the outer surface of the second coil winding is wrapped with at least a portion of the resin insulation layer of the insulating resin cylinder; as well as a shielding element, a portion of which is disposed between the first coil winding and the second coil winding, and the shielding element is made of a conductive metal material; Wherein, the first coil winding, the shielding element and the second coil winding are coaxially arranged and integrally encapsulated in the insulating resin cylinder. When the first coil winding and the second coil winding are energized, at least a portion of the displacement current in the insulating resin cylinder is grounded through the grounding end of the shielding element.

2. The transformer coil winding according to claim 1, characterized in that: The insulating resin cylinder is cast by epoxy resin.

3. The transformer coil winding according to claim 1, characterized in that: The shielding element comprises a first glass fiber layer and a first conductive metal mesh. A low-voltage coil is arranged in the first coil winding. The power connection end of the low-voltage coil extends upward and passes through the upper surface of the insulating resin cylinder. The outer surface of the low-voltage coil is wrapped with the resin insulation layer. The first metal mesh covers the outer surface of the low-voltage coil. The inner side surface of the low-voltage coil is wrapped on one side of the first glass fiber layer. The other side of the first glass fiber layer is wrapped by the resin insulation layer. The first glass fiber layer is arranged in a direction away from the shielding element.

4. The transformer coil winding according to claim 3, characterized in that: At least a portion of the first glass fiber layer is bent according to a bending direction of the low-voltage coil, so that a cross section of the first glass fiber layer is C-shaped.

5. The transformer coil winding according to claim 3, characterized in that: The shielding element has a second glass fiber layer and a second conductive metal mesh, the second metal mesh is provided with a plurality of mesh holes arranged at intervals, a high-voltage coil is arranged in the second coil winding, the second metal mesh covers the outer side of the high-voltage coil, the inner side of the high-voltage coil is wrapped on one side of the second glass fiber layer, the outer surface of the high-voltage coil is wrapped with the resin insulation layer, and the other side of the second glass fiber layer is wrapped by the resin insulation layer to form a high-voltage winding, when the insulating resin cylinder is cast, the resin casting liquid flows into the space between the high-voltage coil and the second metal mesh through the mesh holes, so that the high-voltage coil of the high-voltage winding is wrapped in the insulating resin cylinder.

6. The transformer coil winding according to claim 3, characterized in that: A first welding point is arranged on the first metal mesh, and the first welding point is electrically connected to a first grounding element to achieve grounding.

7. The transformer coil winding according to claim 5, characterized in that: A second welding point is arranged on the second metal mesh, and the second welding point is electrically connected to a second grounding element to achieve grounding.

8. The transformer coil winding according to claim 5, characterized in that: At least a portion of the second glass fiber layer is bent according to a bending direction of the high-voltage coil, so that a cross section of the second glass fiber layer is C-shaped.

9. The transformer coil winding according to claim 5, characterized in that: A protrusion is provided on the front part of the insulating resin cylinder, and a first power terminal and a second power terminal are provided on the protrusion. A first opening is provided on the front part of the second glass fiber layer, and a second opening is provided on the front part of the second metal mesh. The first electrical conductor on the high-voltage coil is electrically connected to the first power terminal by passing through the first opening and the second opening respectively, and the second electrical conductor on the high-voltage coil is electrically connected to the second power terminal by passing through the first opening and the second opening respectively.

10. Dry-type transformer, characterized in that: It comprises an iron core and a transformer coil winding arranged on the iron core, wherein the transformer coil winding is the transformer coil winding according to any one of claims 1 to 9.

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