Electrostatic ring structure for high-voltage and high-frequency transformer and preparation method of electrostatic ring structure

Abstract

The invention relates to an electrostatic ring structure for a high-voltage and high-frequency transformer and a preparation method of the electrostatic ring structure, and the electrostatic ring structure comprises a first insulating layer, a metal conductor belt, a semi-conductive layer and a second insulating layer which are sequentially arranged from inside to outside, and the metal conductor belt is attached to the outer surface of the first insulating layer in an incompletely closed structure; the semi-conductive layer is attached to the surface of the first insulating layer adhered with the metal conductor belt, the second insulating layer is attached outside the semi-conductive layer, and the electric potential of the metal conductor belt is connected with a potential outgoing line. According to the electrostatic ring structure for the high-voltage and high-frequency transformer, the high-frequency eddy current loss is effectively restrained while the good voltage-sharing shielding effect is guaranteed, the problems of insulation damage and local overheating of the high-voltage winding are solved, the shielding effect and the low-loss requirement are both considered, and the cost is reduced. And reliable introduction of the electrostatic ring structural potential is realized on the basis of not damaging insulation of the high-voltage wire, and the electrostatic ring is simple in structure, mature in process and high in reliability, and has remarkable technical advancement and engineering application value.

Description

Technical Field

[0001] This invention relates to the field of transformer manufacturing technology, and in particular to an electrostatic ring structure for high-voltage high-frequency transformers and its preparation method. Background Technology

[0002] With the rapid development of modern high-end equipment technology, high-voltage high-frequency transformers, as key components for voltage transformation and electrical isolation, are increasingly widely used in fields such as medical imaging equipment, industrial electrostatic dust removal systems, and special high-voltage power supplies. These applications place extremely high demands on the size, efficiency, reliability, and insulation performance of transformers, especially under conditions of large turns ratios and high frequencies. Therefore, their design and manufacturing technologies have become an important direction for current research and application in power electronics and high-voltage technology.

[0003] High-voltage, high-frequency transformers typically operate in frequency ranges of tens of kilohertz or even higher, requiring extremely high voltage turns ratios. Under these high turns ratios, a significant voltage difference exists between the high-voltage and low-voltage windings. Achieving reliable insulation is crucial not only for the equipment's performance indicators but also for the long-term stable operation of the system. Therefore, the insulation design of the high-voltage winding becomes one of the core technical issues affecting the overall equipment performance. To improve the overall power density and reduce high-frequency eddy current losses, the high-voltage winding is usually wound with a thinner Litz wire structure. However, the excessively small wire diameter also leads to problems such as extremely small end geometric curvature radii and localized field strength concentration, making the high-voltage winding ends highly susceptible to electric field distortion and partial discharge under high-frequency, high-voltage conditions. This accelerates the aging of the insulation material and can even cause breakdown accidents, seriously threatening the long-term reliable operation of the entire insulation system.

[0004] To alleviate the problem of electric field concentration at the ends of high-voltage windings, existing technologies typically draw on the experience of power transformers by adding electrostatic ring structures at the ends. The basic function of the electrostatic ring is to improve the electric field distribution at the ends. By establishing an artificial potential distribution match, it extends the electric field at the winding ends, thereby distributing the potential gradient as evenly as possible, reducing the peak value of local electric field intensity, minimizing the risk of partial discharge, and improving the insulation withstand voltage level. Although electrostatic ring structures are relatively mature in traditional low-frequency or power-frequency high-voltage equipment, the technology is still imperfect in terms of specific engineering structures, manufacturing processes, and potential connection methods for electrostatic rings applicable to high-frequency, high-ratio conditions. Existing research and applications mainly focus on the geometric parameter design of electrostatic rings, such as the simulation optimization of parameters like the ring's radius of curvature, insulation layer thickness, and installation distance, attempting to obtain the optimal parameter combination to improve the electric field distribution through finite element models or empirical rules. However, these works mainly remain at the level of parameter simulation and theoretical optimization, lacking in-depth revelation and systematic engineering implementation of the actual structural design, manufacturing process, and potential connection scheme of electrostatic rings for high-frequency, high-voltage operating conditions.

[0005] Specifically, existing technologies suffer from the following drawbacks: First, there is a contradiction between losses and shielding effectiveness. Traditional metal electrostatic rings experience severe high-frequency eddy current losses under high-frequency magnetic fields, leading to significant heating and even ablation of the insulation layer. Meanwhile, materials with excessively low conductivity cannot meet the voltage equalization and shielding requirements of the high-voltage side, making it difficult to achieve a balance between the two. Second, there is the challenge of reliable potential connection. Due to the thin wire diameter and high insulation requirements of high-voltage windings, traditional de-insulation connection methods easily create localized hot spots at the connection points, threatening the reliability of the insulation system.

[0006] In summary, for electrostatic ring structures operating under high-voltage, high-frequency transformer conditions with large turns ratios, there is still a lack of an engineering solution that can simultaneously achieve low loss, high electric field shielding effect, and high-reliability connection. Therefore, there is an urgent need to develop an electrostatic ring structure and its fabrication method suitable for high-voltage, high-frequency transformers with large turns ratios to address key issues in existing technologies, such as the contradiction between loss and shielding effect, and insufficient reliability of potential connections, thereby improving the overall performance and long-term operational reliability of high-voltage, high-frequency transformers. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide an electrostatic ring structure for high-voltage high-frequency transformers and its preparation method, which achieves both shielding effect and low loss requirements, and reliably introduces the electrostatic ring structure potential without damaging the insulation of the high-voltage conductor.

[0008] This invention is achieved through the following technical solution: An electrostatic ring structure for a high-voltage high-frequency transformer includes a first insulating layer, a metal conductor strip, a semi-conductive layer, and a second insulating layer arranged sequentially from the inside to the outside. The metal conductor strip is attached to the outer surface of the first insulating layer in a partially closed structure, and the metal conductor strip is potential-connected to a potential lead.

[0009] According to the above technical solution, preferably, the opening distance of the metal conductor strip is 20-100mm.

[0010] According to the above technical solution, preferably, the material of the metal conductor strip is copper foil or aluminum foil.

[0011] According to the above technical solution, preferably, the first insulating layer is a solid or hollow structure, and is cast from insulating material.

[0012] According to the above technical solution, preferably, the potential lead is made of high-strength enameled wire, which is welded to the metal conductor strip and electrically connected to the high-voltage winding output terminal closest to the equalizing ring.

[0013] According to the above technical solution, preferably, the semi-conductive layer is a semi-conductive tape, and semi-conductive crepe paper is selected, stretched and partially wrapped around the surface of the first insulating layer with the metal conductor tape attached.

[0014] According to the above technical solution, preferably, the second insulating layer is an insulating tape, such as Nomex paper or mica tape, which is stretched and partially wrapped around the surface of the semiconductive layer.

[0015] This application also discloses a method for preparing an electrostatic ring structure for a high-voltage high-frequency transformer, which includes the following steps: S1. Set the transformer insulation design voltage requirement V iso Determine the allowable field strength design limit E of the insulating material of the first insulating layer. limit ; S2. Determine the structural parameters of the first insulation layer based on the dimensions of the transformer high-voltage winding, including the width w of the first insulation layer and the side fillet curvatures r1 and r2; S3. Based on the structural parameters of the first insulating layer, draw a cross-section of the first insulating layer perpendicular to the current direction. Apply a voltage excitation to the outer contour of the first insulating layer and calculate the peak electric field E inside and around the first insulating layer under each set of structural parameters. max And determine the preferred values ​​of the structural parameters of the first insulating layer; S4. Determine the material parameters of the semiconductive layer, including resistivity ρ. c Relative permittivity ε c Thickness T c ; S5. Based on the preferred values ​​of the structural parameters of the first insulating layer and the material parameters of the semiconductive layer, draw the cross-section of the electrostatic ring structure perpendicular to the current direction, apply voltage excitation on the metal conductor strip, calculate the potential distribution along the outer contour of the semiconductive layer under the material parameters of each group of semiconductive layers, and determine the preferred values ​​of the material parameters of the semiconductive layer. S6. Based on the preferred values ​​of the structural parameters of the first insulating layer and the preferred values ​​of the material parameters of the semiconductive layer, draw the cross-section of the electrostatic ring structure parallel to the current direction, calculate the potential distribution of the semiconductive layer on the cross-section parallel to the current direction under the opening distance of each metal conductor strip, and determine the preferred value of the opening distance of the metal conductor strip.

[0016] The beneficial effects of this invention are: Firstly, this invention, by sequentially setting a metal conductor strip, a semi-conductive layer, and a second insulating layer outside the first insulating layer, creates a layered structure system of "inner insulation—conductivity—slow release—outer insulation" for the entire electrostatic ring. Each functional layer works in synergy with the others, with clearly defined functions, resulting in a compact and well-defined structure. This streamlined and compact structure greatly improves production efficiency and assembly convenience, significantly reducing manufacturing costs. It is particularly suitable for the small-batch, multi-specification engineering applications of high-voltage, high-frequency transformers.

[0017] Secondly, this invention introduces a composite structure combining a metal conductor strip and a semiconductive layer. Utilizing the low impedance characteristics of the metal conductor strip, combined with the resistivity of the optimized semiconductive material, effectively facilitates the establishment of an equipotential body. To further avoid excessive eddy current losses in the metal shielding strip itself at high frequencies, this invention employs a non-closed metal strip design and, through optimized opening distance, physically blocks the eddy current path of the metal strip. This design not only leverages the advantages of both the metal strip and the semiconductive layer to achieve reliable equipotential shielding but also eliminates high-frequency eddy current losses at their source.

[0018] Furthermore, this invention employs an independent potential lead wire welded to a metal conductor strip, directly connecting this potential lead wire to the high-voltage winding terminal closest to the electrostatic ring. During the establishment of the electrostatic ring potential, there is no need to remove the insulation from the high-voltage Litz wire winding body, thus fully preserving the external insulation and inter-strand insulation structure of the Litz wire. This effectively avoids the risk of short circuits or the formation of circulating current loops at the connection points of multiple conductors. This design structurally eliminates the additional eddy current losses and localized overheating hazards caused by inter-strand short circuits in the Litz wire under high-frequency magnetic fields, significantly improving the safety and long-term operational reliability of the high-voltage high-frequency transformer insulation system.

[0019] Meanwhile, from the perspective of overall engineering adaptability and reliability, this invention, through its multi-layered encapsulation structure of a first insulating layer, a semi-conductive layer, and a second insulating layer, effectively ensures the electrostatic ring's mechanical strength, electrical insulation performance, and environmental adaptability. Each layer can be made from mature and reliable electrical insulation materials and tapes, with stable processes and good consistency. This allows it to withstand the multiple effects of electrical stress, thermal stress, and mechanical vibration experienced by high-voltage, high-frequency transformers during long-term operation, significantly improving the durability and safety margin of the entire system. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the application scenario of the electrostatic ring structure provided by the present invention.

[0021] Figure 2 This is a schematic diagram of the cross-sectional structure of the electrostatic ring structure provided by the present invention.

[0022] Figure 3 This is a three-dimensional structural diagram of the electrostatic ring structure provided by the present invention.

[0023] Figure 4 This is a flowchart of the preparation method provided by the present invention.

[0024] Figure 5 This is a schematic diagram of the potential distribution along the outer contour of the semiconducting layer under the parameters of each group of semiconducting layers when a voltage excitation is applied to the metal conductor strip in Embodiment 3 of the present invention.

[0025] Figure 6 This is a schematic diagram of the maximum potential drop ΔV2 of the semiconducting layer on the cross section parallel to the current direction under the opening distance of each metal conductor strip in Embodiment 3 of the present invention. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0027] Example 1: As shown in the figure, the present invention includes a first insulating layer, a metal conductor strip, a semiconductive layer and a second insulating layer arranged sequentially from the inside to the outside. The metal conductor strip is attached to the outer surface of the first insulating layer in a partially closed structure. The metal conductor strip is potential-connected to a potential lead. The semiconductive layer is attached to the surface of the first insulating layer to which the metal conductor strip is attached. The second insulating layer is attached to the outside of the semiconductive layer.

[0028] The metal conductor strip is made of copper or aluminum foil, with an opening distance of 20-100mm. By designing the metal conductor strip as a partially closed structure, eddy currents cannot form complete closed loops, thus reducing eddy current losses. The first insulation layer is a solid or hollow structure, cast from an insulating material selected from epoxy resin and insulating silicone. High-strength enameled wire is used as the potential lead, welded to the metal conductor strip, and electrically connected to the high-voltage winding terminal closest to the equalizing ring. The semi-conductive layer is a semi-conductive tape, made from semi-conductive crepe paper, stretched and partially wrapped around the surface of the first insulation layer with the metal conductor strip attached. The second insulation layer is an insulating tape, made from Nomex paper or mica tape, stretched and partially wrapped around the surface of the semi-conductive layer.

[0029] Example 2: This application also discloses a method for preparing an electrostatic ring structure for a high-voltage high-frequency transformer, which includes the following steps: S1. Determine the required insulation design voltage V of the transformer according to standard GB 1094.11 "Power Transformers Part 11: Dry-type Transformers".iso Determine the allowable field strength design limit E of the insulating material of the first insulating layer. limit ; S2. Determine the structural parameters of the first insulation layer based on the dimensions of the transformer high-voltage winding, including the width w of the first insulation layer and the side fillet curvatures r1 and r2; S3. Based on the structural parameters of the first insulating layer, draw a cross-section of the first insulating layer perpendicular to the current direction, and apply a voltage excitation to the outer contour of the first insulating layer. The effective value of the voltage excitation is V. iso Calculate the peak electric field E inside the first insulating layer and in the space surrounding it for each set of structural parameters. max In conjunction with the design limits of each insulating material and the high power density design requirements, the preferred values ​​of the structural parameters of the first insulating layer are determined. S4. Determine the material parameters of the semiconductive layer, including resistivity ρ. c Relative permittivity ε c Thickness T c ; S5. Based on the preferred structural parameters of the first insulating layer and the material parameters of the semiconductive layer, draw the cross-section of the electrostatic ring structure perpendicular to the current direction, and apply a voltage excitation to the metal conductor strip. The effective value of the voltage excitation is V. iso Calculate the potential distribution along the outer contour of the semiconducting layer under the material parameters of each group of semiconducting layers, and obtain the maximum potential drop ΔV1 along the outer contour of the semiconducting layer to determine the preferred material parameters of the semiconducting layer. S6. Based on the preferred values ​​of the structural parameters of the first insulating layer and the preferred values ​​of the material parameters of the semiconductive layer, draw the cross-section of the electrostatic ring structure parallel to the current direction, calculate the potential distribution of the semiconductive layer on the cross-section parallel to the current direction under the opening distance of each metal conductor strip, and obtain the maximum potential drop value ΔV2 along the semiconductive layer, and determine the preferred value of the opening distance of the metal conductor strip.

[0030] Example 3: Based on Example 2 above, this example preferably discloses, but is not limited to, a method for preparing an electrostatic ring structure. The transformer in which this electrostatic ring is applied operates at a frequency of 20kHz, has a rated voltage of 10kV on the high-voltage side, a high-voltage winding width of 9mm, and uses epoxy resin casting as the main insulating material. Specifically, the method includes the following steps: (1) Based on the national standard GB 1094.11 "Power Transformers Part 11: Dry-type Transformers", set the insulation design voltage requirement V for this transformer. iso =35kV; Simultaneously, based on the characteristics of the insulating material, the allowable field strength design limit E of epoxy resin under long-term operation is determined. limit It is 8kV / mm; (2) Based on the actual physical dimensions of the transformer high-voltage winding, the width w of the first insulation layer is set to a value range of 4-6mm, and the curvatures r1 and r2 of the side fillets of the first insulation layer are set to a value range of 1-3mm; (3) Establish a two-dimensional finite element simulation model perpendicular to the current direction, apply voltage excitation to the outer contour of the first insulating layer, the effective value of the voltage excitation is 35kV, and calculate the peak field strength E inside the first insulating layer and the space around it under each set of structural parameters. max ; (4) Taking into account the allowable field strength design limit E of the insulation material limit Based on the design requirements of high power density, after optimization and screening, the final structural parameters of the first insulation layer are: w=5mm, r1=3mm, r2=1mm; (5) Determine the range of material parameters for the semiconductive layer and the semiconductive paper, including the resistivity ρ of the semiconductive paper. c 10 3 -10 8 Ω•m, relative permittivity ε c The value is 100, and the thickness T of the semi-conductive paper is... c The value is 0.5mm; (6) Draw the cross-section of the electrostatic ring structure perpendicular to the current direction. Apply a voltage excitation to the metal conductor strip. The effective value of the voltage excitation is 35kV. Calculate the potential distribution along the outer contour of the semiconducting layer under each set of semiconducting layer parameters, such as... Figure 5 As shown; (7) Based on the design requirement that the potential drop ΔV1 of the semiconducting layer under 35kV excitation is less than 0.5kV, the material parameters of the semiconducting paper are optimized, namely the resistivity ρ of the semiconducting paper. c 10 5 Ω•m; It should be noted here that a lower resistivity can result in a smaller potential drop, but it will also introduce more eddy current losses. (8) Draw the cross-section of the electrostatic ring structure parallel to the current direction and calculate the distance d between the openings of the metal conductor. c The maximum potential drop ΔV2 of the semiconducting layer on a cross section parallel to the current direction within the range of 20-100 mm is given by, for example... Figure 6 As shown; (9) Based on the design requirement that the potential drop ΔV2 of the semiconducting layer under 35kV excitation is less than 0.5kV, the opening distance of the metal conductor strip is preferably 60mm, and the design is completed.

[0031] In summary, the electrostatic ring structure for high-voltage high-frequency transformers proposed in this invention effectively suppresses high-frequency eddy current losses while ensuring good voltage equalization and shielding effects, avoiding high-voltage winding insulation damage and local overheating problems. It has a simple structure, mature technology, and high reliability, and has significant technological advancement and engineering application value.

[0032] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An electrostatic ring structure for a high-voltage high-frequency transformer, characterized in that, It includes, from the inside out, a first insulating layer, a metal conductor strip, a semiconducting layer, and a second insulating layer. The metal conductor strip is attached to the outer surface of the first insulating layer in a partially closed structure, and the metal conductor strip is electrically connected to a potential lead.

2. The electrostatic ring structure for a high-voltage high-frequency transformer according to claim 1, characterized in that, The opening distance of the metal conductor strip is 20-100mm.

3. The electrostatic ring structure for a high-voltage high-frequency transformer according to claim 1 or 2, characterized in that, The material of the metal conductor strip is copper foil or aluminum foil.

4. The electrostatic ring structure for a high-voltage high-frequency transformer according to claim 1, characterized in that, The first insulating layer is a solid or hollow structure, formed by casting insulating material.

5. The electrostatic ring structure for a high-voltage high-frequency transformer according to claim 4, characterized in that, The potential lead is made of high-strength enameled wire, which is welded to the metal conductor strip and electrically connected to the high-voltage winding output terminal closest to the equalizing ring.

6. The electrostatic ring structure for a high-voltage high-frequency transformer according to any one of claims 1, 2, 4, and 5, characterized in that, The semiconductive layer is a semiconductive tape, made of semiconductive crepe paper, stretched and partially wrapped around the surface of the first insulating layer to which the metal conductor tape is attached.

7. The electrostatic ring structure for a high-voltage high-frequency transformer according to claim 6, characterized in that, The second insulating layer is an insulating tape, made of Nomex paper or mica tape, stretched and partially wrapped around the surface of the semiconductive layer.

8. A method for preparing an electrostatic ring structure for a high-voltage high-frequency transformer, used to prepare the electrostatic ring structure for a high-voltage high-frequency transformer as described in claim 1, characterized in that, Includes the following steps: S1. Set the transformer insulation design voltage requirement V iso Determine the allowable field strength design limit E of the insulating material of the first insulating layer. limit ; S2. Determine the structural parameters of the first insulation layer based on the dimensions of the transformer high-voltage winding, including the width w of the first insulation layer and the side fillet curvatures r1 and r2; S3. Based on the structural parameters of the first insulating layer, draw a cross-section of the first insulating layer perpendicular to the current direction. Apply a voltage excitation to the outer contour of the first insulating layer and calculate the peak electric field E inside and around the first insulating layer under each set of structural parameters. max And determine the preferred values ​​of the structural parameters of the first insulating layer; S4. Determine the material parameters of the semiconductive layer, including resistivity ρ. c Relative permittivity ε c Thickness T c ; S5. Based on the preferred values ​​of the structural parameters of the first insulating layer and the material parameters of the semiconductive layer, draw the cross-section of the electrostatic ring structure perpendicular to the current direction, apply voltage excitation on the metal conductor strip, calculate the potential distribution along the outer contour of the semiconductive layer under the material parameters of each group of semiconductive layers, and determine the preferred values ​​of the material parameters of the semiconductive layer. S6. Based on the preferred values ​​of the structural parameters of the first insulating layer and the preferred values ​​of the material parameters of the semiconductive layer, draw the cross-section of the electrostatic ring structure parallel to the current direction, calculate the potential distribution of the semiconductive layer on the cross-section parallel to the current direction under the opening distance of each metal conductor strip, and determine the preferred value of the opening distance of the metal conductor strip.

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