Polyether-ether-ketone insulated power transformer iron core pulling plate structure

Abstract

The invention discloses a polyetheretherketone insulated power transformer iron core pulling plate structure. The problems of local heating and energy loss caused by eddy current accumulation in a metal steel iron core pulling plate structure are solved. The longitudinal long hole is formed in the center of the pulling plate, and the round blocking holes are formed in the four corners, so that an eddy current path is effectively cut off, the local current density is reduced, the heat productivity is reduced, and the overall insulation reliability and the operation efficiency of the transformer are improved. A long-strip-shaped hole with the width being 6 mm and the length being 1.5 m is formed in the middle of the pulling plate in the longitudinal direction, and meanwhile a round hole with the radius being 0.06 m is formed in the symmetrical positions of the four corners respectively. Based on PEEK insulation characteristics and electromagnetic simulation results, a'partition blocking 'slotting strategy is provided: four-corner round holes are formed in an eddy current concentrated edge region, and a corner current aggregation effect is dispersed to reduce local loss; a longitudinal long hole is formed in the center of the pulling plate, a low-eddy-current channel is formed in the main magnetic flux direction, and magnetic circuit integrity is prevented from being interfered.

Description

Technical Field

[0001] The invention relates to the technical field of transformer structural component design and insulation, and in particular to a polyetheretherketone (PEEK) power transformer iron core pull plate structure. Background Art

[0002] As a key equipment in the power system, the operating stability of the power transformer is closely related to the structural design of its internal components. As an important component that connects the upper and lower pressure plates of the core and maintains its mechanical strength and positioning accuracy, the transformer core pull plate is usually made of metal or high-strength composite materials. While meeting the mechanical support, it must also have good electrical insulation performance and electromagnetic compatibility characteristics. The design of the transformer core pull plate usually takes into account the overall structure and connection method of the transformer to ensure its accuracy and stability. In some designs, the pull plate may be composed of a U-shaped clamp and an iron core, and the U-shaped clamp is tightly connected to the iron core by a pull plate bolt. In power transformers, a core pull plate is required to fix the core. However, there is leakage magnetic flux between the core and the coil. When the leakage magnetic flux passes through the core pull plate, since the material of the core pull plate is a whole piece of steel plate, a large amount of eddy current loss will be generated, which will eventually lead to an increase in the temperature of the core pull plate, which will cause the nearby insulating oil to crack, thereby generating a large amount of harmful gases, which will seriously affect the safe operation of the transformer.

[0003] When operating at high frequencies or high currents, traditional metal pull plates are prone to forming eddy current loops in their bodies, which in turn leads to local heating, increased losses, and even insulation aging, which seriously affects the operating efficiency and life of the transformer. In order to reduce such losses, studies have attempted to optimize the design by replacing non-metallic materials, breaking currents, and grooving structures. Among them, structural improvements based on epoxy resins, fiber-reinforced composite materials, etc. have achieved certain results in terms of insulation performance, but there are still limitations in terms of structural strength, thermal stability, and processability.

[0004] In recent years, polyetheretherketone (PEEK) insulation has gradually become a potential application material in composite insulation structures due to its excellent electrical insulation performance, moderate mechanical strength and processing flexibility. On this basis, how to combine material properties and effectively suppress the closed-loop path of the induced current inside the pull plate through reasonable structural design and reduce the eddy current effect has become an important topic of research and engineering practice in this field.

[0005] However, there is still a lack of systematic hole-opening strategies for composite insulation materials such as PEEK in transformer core drawplates, and their comprehensive impact on electromagnetic field distribution, local eddy current suppression and mechanical structure stability still needs further exploration. Therefore, it is necessary to propose a PEEK insulation drawplate hole-opening structure design with reasonable structure, feasible processing, and consideration of insulation performance and mechanical strength to meet the actual needs of the new generation of high-efficiency, low-loss transformers. Summary of the invention

[0006] The object of the present invention is to provide an opening structure for the transformer core tie plate made of PEEK to improve the problems of local heating and energy loss caused by eddy current concentration in the traditional metal iron core tie plate structure, and to balance the structural strength and electromagnetic performance. The invention designs a new type of PEEK-insulated core tie plate structure. By opening a longitudinal long hole in the center of the tie plate and setting circular blocking holes at the four corners, the eddy current path is effectively cut off, the local current density is reduced, the heat generation is reduced, and the reliability of the overall insulation and the operation efficiency of the transformer are improved.

[0007] The present invention adopts the following technical solution: a power transformer core tie plate structure insulated with polyetheretherketone, a tie plate main body made of polyetheretherketone insulating material, a longitudinal long hole is opened at the position of the central axis along the length direction of the tie plate main body, and the extending direction of the longitudinal long hole is consistent with the length direction of the tie plate main body; four circular blocking holes are symmetrically distributed in the four corner areas of the tie plate main body, the circular blocking holes are respectively located on the upper and lower sides of the longitudinal long hole, and are symmetrically arranged along the width direction of the tie plate main body; the width of the longitudinal long hole is 6 mm, and the length is 75% - 90% of the length of the tie plate main body; the radius range of the circular blocking hole is 1.5 - 2.5 times the thickness of the tie plate main body, and the distance from the center of the circle to the edge of the tie plate main body is 1.2 - 1.8 times its radius.

[0008] Based on the insulation characteristics of PEEK and the electromagnetic simulation results, a "zone blocking" slotting strategy is proposed: circular holes are opened at the four corners in the edge area where eddy currents are concentrated to disperse the current concentration effect at the corners and reduce local losses; a longitudinal long hole is opened in the center of the tie plate to form a low-eddy current channel along the main magnetic flux direction to avoid interfering with the integrity of the magnetic circuit. The core idea of the design is to increase the impedance of the eddy current path through physical isolation while avoiding interfering with the main magnetic flux, so as to balance the magnetic performance and loss control. In addition, the slotting design also combines the lightweight requirement, reducing the material usage while ensuring the structural strength, and giving full play to the high insulation and mechanical strength of PEEK.

[0009] The PEEK-insulated tie plate structure proposed by the present invention is designed as follows: a long strip-shaped hole with a width of 6 mm and a length of 1.5 m is opened longitudinally in the middle of the tie plate, and a circular hole with a radius of 0.06 m is set at each of the four symmetric positions. The above structure is verified by finite element simulation analysis. Without significantly weakening the overall mechanical strength of the tie plate, it can effectively suppress the circulating current and eddy current loss in the local area of the iron core, thereby improving the electrical and thermal stability of the transformer under long-term operating conditions. Description of the Drawings

[0010] To more clearly illustrate the technical solutions in the embodiments of the present invention or in the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0011] Figure 1 is the geometric structure of the PEEK insulating pull plate for the transformer core; Figure 2 is the eddy current density of the unperforated PEEK insulating pull plate; Figure 3 is the eddy current density of the perforated PEEK insulating pull plate. Detailed implementation manners

[0012] To describe the present invention more specifically, the following will detail the technical solutions and their related principles of the present invention in combination with the drawings and specific implementation manners. A structure of a pull plate for a power transformer core insulated with polyetheretherketone (PEEK), and the typical characteristic parameters of the PEEK insulating material are shown in Table 1. It can be seen that PEEK insulation has good mechanical, heat-resistant and insulating characteristics.

[0013] The following will further describe the present invention in detail with reference to the drawings: The present invention provides a PEEK-insulated pull plate for a transformer core and its perforated structure design. In the design, the specific structure modeling and simulation calculation include the following steps: Step S101: Construct a geometric model of the PEEK insulating pull plate according to Table 1, as Figure 1 shown. And fix the PEEK insulating pull plate in the simulation model of the transformer.

[0014] Step S102: Model according to the existing data. Among them, the slot of the pull plate is in the center, and the four round holes are evenly distributed on the upper and lower sides of the slot. For the convenience of model convergence, after making two symmetries (xz axis and xy axis), delete the remaining 3 / 4 content to reduce the calculation amount.

[0015] Step S103: Model the core, pull plate and winding and set the parameters.

[0016] Step S104: Set the low-frequency electromagnetic field calculation parameters. The silicon steel sheet B-H magnetization curve is used for the core. The primary and secondary coils are set for the coil and the current direction is selected to generate a magnetic field. The core is grounded.

[0017] Step S105: configure the internal circuit of the winding coil, the primary coil and the secondary coil are set according to the transformer ratio, and the primary and secondary winding voltages are set. At this point, the voltage configuration of the coil is completed, and an alternating electric field can be generated to generate a magnetic field that enters the iron core magnetic circuit and generates leakage magnetic flux in the transformer structure.

[0018] Step S106: Set the grid solution domain, and use a grid of appropriate thickness to enhance convergence.

[0019] Step S107: The obtained eddy current density ( Figure 2 and Figure 3 ) results are compared with the eddy current density of the PEEK insulation plate without holes.

[0020] The comparison before and after slotting shows that the magnetic flux density distribution is not significantly affected, and the maximum magnetic flux density is always maintained at the level of 0.1T, which verifies the protective effect of the slot layout on the main magnetic circuit. The eddy current density distribution characteristics of the PEEK insulation pull plate after the hole is opened have changed significantly: before the hole is opened, the eddy current fluctuates periodically in the time dimension, and the spatial distribution shows a polarization characteristic of "high at the edge and low at the center". The eddy current density peak in the edge area is as high as 140~100A / m² (the maximum peak is located at the four corners), and the central area is significantly attenuated to 80~40A / m²; after slotting, the eddy current distribution tends to be spatially balanced as a whole, forming a symmetrical diffusion pattern along the axis, and the density difference between the edge and the center area is greatly reduced. The overall eddy current density is roughly 40~90A / m². This change shows that the slot design effectively breaks the concentration of the original eddy current loop and achieves global optimization of energy dissipation.

[0021] This solution transforms the edge eddy current "hot spots" of the traditional pull plate into a wide-area uniform distribution through precise slot layout, significantly reducing the risk of local overheating. The long hole in the center suppresses the convergence of longitudinal currents, and the round holes in the four corners relieve the electromagnetic stress at the corners. The synergistic effect of the two makes the eddy current density gradient flat. This distribution optimization not only reduces the overall loss, but also improves the thermal stability and long-term reliability of the pull plate. In addition, the slot design further reduces the weight of the structure, allowing the lightweight advantages of PEEK materials to be fully released, providing a new path for the compact design of transformers.

[0022] Table 1 PEEK insulation parameters and pull plate structure

Claims

1. A structure of a pull plate for the core of a power transformer insulated by polyetheretherketone, characterized in that it includes a pull plate main body made of polyetheretherketone insulating material. A longitudinal long hole is opened at the central axis position of the pull plate main body along its length direction, and the extending direction of the longitudinal long hole is consistent with the length direction of the pull plate main body; four circular blocking holes are symmetrically distributed in the four corner regions of the pull plate main body. The circular blocking holes are respectively located on the upper and lower sides of the longitudinal long hole and are symmetrically arranged along the width direction of the pull plate main body; the width of the longitudinal long hole is 6 mm, and the length is 75% - 90% of the length of the pull plate main body; the radius range of the circular blocking hole is 1.5 - 2.5 times the thickness of the pull plate main body, and the distance from the center of the circle to the edge of the pull plate main body is 1.2 - 1.8 times its radius.

2. The structure of the core pull plate of the power transformer insulated by polyether ether ketone according to claim 1, characterized in that, The length of the longitudinal long hole is 1.5 meters, the radius of the circular blocking hole is 0.06 meters, the central points of the four circular blocking holes are respectively located at the geometric symmetry positions of the four corners of the pull plate main body, and the distance from the center of each circular blocking hole to the edge of the longitudinal long hole is 0.12 - 0.18 meters.

3. The structure of the core pull plate of the power transformer insulated by polyetheretherketone according to claim 1, characterized in that, The total length of the pull plate main body is 0.40 meters, the thickness is 0.03 meters, and the height is 2.40 meters; the distance between the starting end of the longitudinal long hole and the end of the pull plate main body is 5% to 10% of its total length.

4. The structure of the pull plate of the iron core of the power transformer insulated with polyetheretherketone according to claim 1, characterized in that, Fixed grooves for connecting the upper and lower pressing plates of the core are symmetrically arranged on both sides of the longitudinal long hole of the pull plate main body. The depth of the fixed groove is 1 / 3 to 1 / 2 of the thickness of the pull plate main body; the four circular blocking holes are respectively located on the upper and lower sides of the fixed groove and are equidistantly distributed along the width direction of the pull plate main body.

5. The structure of the core tie plate of the power transformer insulated with polyetheretherketone according to claim 1, wherein, The pull plate main body is connected to the upper and lower pressing plates of the core through bolts. The installation positions of the bolts avoid the areas of the longitudinal long hole and the circular blocking hole and are located in the fixed grooves of the pull plate main body.

6. The structure of the core pull plate of the power transformer insulated by polyether ether ketone according to claim 1, characterized in that, Both ends of the longitudinal long hole are provided with a chamfered corner structure, and the radius of the chamfered corner is 1 / 2 - 2 / 3 of its width; the edge of the circular blocking hole is provided with an annular reinforcing rib, and the width of the annular reinforcing rib is 10% - 15% of its radius.

7. The structure of the core pull plate of the power transformer insulated with polyetheretherketone according to claim 1, wherein The inner wall of the longitudinal long hole of the pull plate main body is covered with a conductive shielding layer. The thickness of the conductive shielding layer is 0.1 - 0.3 mm, and it is adhesively fixed to the polyetheretherketone material through an insulating adhesive layer.

8. The structure of the core pull plate of the power transformer insulated with polyetheretherketone according to claim 1, characterized in that, Reinforcing ribs extending along the length direction are arranged on the upper and lower surfaces of the pull plate main body. The cross-section of the reinforcing rib is trapezoidal, and the height is 1 / 4 - 1 / 3 of the thickness of the pull plate main body, and they are parallelly distributed on both sides of the longitudinal long hole.

9. The structure of the core pull plate of the power transformer insulated with polyetheretherketone according to claim 1, characterized in that, An annular groove is provided at the edge of the circular blocking hole. The depth of the annular groove is 0.5 - 1 mm, the width is 8% to 12% of the radius of the corresponding circular blocking hole, and an insulating sealing adhesive layer is embedded in the annular groove.

Images