Method for manufacturing an extraction positioning device and a low voltage coil

Abstract

This invention discloses a lead-out positioning device and a method for manufacturing a low-voltage coil. Applying the technical solution of this invention, a positioning method combining a detachable positioning pin and an end cap groove replaces the traditional integrated baffle structure. During the winding stage, the positioning pin and the groove work together to precisely restrict the axial, circumferential, and radial degrees of freedom of the lead-out, ensuring the stability of the winding process. After casting, because the positioning pin is a detachable component, it can be easily removed from the base, leaving only a smooth pin hole on the casting body, rather than a destructive groove. Simultaneously, the outer mold adopts a non-closed cylindrical structure, allowing for demolding clearance through the connecting lugs. This solution fundamentally eliminates the mechanical interlock between the traditional mold baffle and the casting body, achieving non-destructive, straight demolding after casting and curing, significantly reducing the risk of coil cracking and mold damage, and greatly improving product yield and reliability.

Description

Technical Field

[0001] This invention relates to the field of dry-type transformer manufacturing technology, specifically to a lead-out positioning device and a method for manufacturing a low-voltage coil. Background Technology

[0002] Dry-type transformers are widely used in modern power distribution systems due to their fire resistance, environmental friendliness, and excellent insulation performance. Especially in extremely harsh environments such as offshore wind turbine nacelles and offshore drilling platforms, where they face continuous vibration, high salt spray corrosion, and frequent thermal cycling, higher demands are placed on the mechanical stability and moisture and corrosion resistance of the transformers. To address these challenges, the industry commonly employs a process of aluminum foil winding combined with epoxy resin vacuum casting to manufacture low-voltage coils. This process combines aluminum foil conductors with epoxy resin, forming a dense and robust integral encapsulation through vacuum casting, thereby providing good electrical performance while ensuring the physical structural stability of the coil under extreme environments.

[0003] In the winding production of low-voltage coils, the precise positioning and fixing of the lead-out bars are crucial steps to ensure product quality. Existing traditional fixing methods largely borrow from the foil-wound, heat-pressed non-cast coil process, primarily relying on raised baffles on the mold surface to limit the position of the lead-out bars. This method is common in the production of non-cast coils, using the mechanical support of the baffles to achieve initial fixing of the lead-out bars, which can meet basic winding requirements, such as... Figure 9 and Figure 10 As shown.

[0004] However, traditional mold baffle fixing methods present significant structural contradictions and technical defects when applied to foil-wound vacuum casting processes. The core requirement of vacuum casting is that the mold cavity must remain highly smooth and intact to ensure smooth flow of liquid resin, filling the cavity and achieving non-destructive, straight demolding after curing. Existing mold baffles, acting as fixing protrusions on the mold surface, leave corresponding grooves on the cured epoxy resin casting, resulting in a strong mechanical interlocking effect between the coil and the mold. Since epoxy resin is a brittle composite material after curing and has a certain adhesive force to the mold side, this interlocking structure necessitates forced deformation of the casting to detach from the baffle during the demolding process. This process inevitably leads to cracking of the resin layer, damage to the internal insulation structure, and in severe cases, even mold damage or scrapping of the entire coil product. This physical structural interlocking conflict makes traditional fixing methods unable to meet the production requirements of vacuum casting processes, becoming a technical bottleneck restricting the quality improvement of high-performance dry-type transformers. Summary of the Invention

[0005] The purpose of this invention is to provide a solution to the technical problems of difficult demolding and easy damage to the coil structure in the existing method of fixing the lead-out bars of foil-wound low-voltage coils used in dry-type transformers.

[0006] To address the aforementioned problems, a first aspect of the present invention provides a lead-out positioning device for positioning the lead-outs of a low-voltage coil during the fabrication of a foil-wound low-voltage coil in a dry-type transformer. The positioning device includes a base, an end cap, an inner mold, and an outer mold. The outer mold is fitted over the inner mold. The base and end cap are connected to both ends of the outer mold, forming a casting cavity between the base, end cap, inner mold, and outer mold. The base is provided with a detachable positioning pin extending into the casting cavity. The positioning pin engages with a pin groove at the tail of the lead-out to constrain its tail. The end cap has a retaining groove on its circumference for fixing the head of the lead-out. The end cap also has a pouring port leading to the casting cavity.

[0007] Furthermore, the axial mid-surface of the positioning pin coincides with the axial mid-surface of the slot.

[0008] Furthermore, the radial cross-section of the outer mold is a non-closed cylindrical shape with a notch, and the notch is provided with an outwardly extending connecting lug.

[0009] Furthermore, a spacer strip is provided between the two connecting ears.

[0010] Furthermore, the free end of the positioning pin is provided with a demolding slope.

[0011] Furthermore, a support foot is provided at the end of the base away from the inner mold.

[0012] Furthermore, the end cap is provided with several connecting blocks.

[0013] Furthermore, the inner mold is provided with reinforcing ribs.

[0014] Furthermore, the slot 22 and the head of the lead-out row 6 are in clearance fit, with the clearance selected between 1 and 5 millimeters.

[0015] According to another aspect of the present invention, a method for manufacturing a low-voltage coil is provided, wherein the low-voltage coil is manufactured using the lead-out positioning device described in any one of the above embodiments; the method includes the following steps: Step 1: Connect one end of the inner mold to the base, and at the same time connect the positioning pin to the base; Step 2: Abut the lead-out strip against the outer surface of the inner mold, and simultaneously insert the pin slot and positioning pin on the lead-out strip into alignment; Step 3: Connect the end cap to the other end of the inner mold, and at the same time, make the head of the outlet insert into the slot and extend it axially for a certain length. Step 4: Wind the coil on the inner mold and cover the lead-out pin; Step 5: Place the outer mold onto the inner mold. One end of the outer mold is connected to the base, and the other end extends a certain length toward the end cap. Step 6: Pour the casting into the cavity formed by the base, end cap, inner mold, and outer mold; Step 7: After the casting is completed and cured, remove the outer mold and base, pull out the positioning pin, remove the end cap and inner mold to obtain the low-voltage coil.

[0016] The above-described technical solution of the present invention has the following beneficial technical effects: This invention provides a lead-out positioning device and a method for manufacturing a low-voltage coil. The lead-out positioning device is used to position the lead-out of the low-voltage coil in the fabrication of a dry-type transformer foil-wound low-voltage coil. The positioning device includes a base, an end cover, an inner mold, and an outer mold. The outer mold is fitted over the inner mold. The base and the end cover are respectively connected to both ends of the outer mold, forming a casting cavity between the base, end cover, inner mold, and outer mold. The base is provided with a detachable positioning pin extending into the casting cavity. The positioning pin is used to cooperate with the pin groove at the tail of the lead-out to constrain the tail of the lead-out. The end cover is provided with a slot on its circumference for fixing the head of the lead-out. The end cover is provided with a pouring port leading to the casting cavity. By using a positioning method combining a detachable positioning pin and an end cover slot, the traditional integrated retaining strip structure is replaced. During the winding stage, the locating pins and slots work together to precisely restrict the axial, circumferential, and radial degrees of freedom of the lead-out coil, ensuring the stability of the winding process. After casting, because the locating pins are detachable components, they can be easily removed from the base, leaving only smooth pin holes on the cast body, rather than destructive grooves. Simultaneously, the outer mold adopts a non-closed cylindrical structure, allowing for demolding clearance through the connecting ears. This solution fundamentally eliminates the mechanical interlock between the traditional mold baffles and the cast body, achieving non-destructive, straight demolding after casting and curing. This significantly reduces the risk of coil cracking and mold damage, greatly improving product yield and reliability. Attached Figure Description

[0017] Figure 1 This is an exploded structural diagram of the first direction of the outlet positioning device in this invention; Figure 2 This is an exploded structural diagram of the second orientation of the outlet positioning device in this invention; Figure 3 This is a schematic diagram of the structure of the lead-out positioning device in the first direction of the present invention; Figure 4 This is a schematic diagram of the second orientation of the outlet positioning device in this invention; Figure 5This is a schematic diagram of the third direction of the outlet positioning device in this invention (the outer mold is hidden). Figure 6 This is a schematic diagram of the planar structure of the outlet positioning device in one direction of the present invention; Figure 7 This is a cross-sectional view of the outlet positioning device in this invention from one direction. Figure 8 yes Figure 7 A magnified structural diagram of point A in the middle; Figure 9 This is a schematic diagram of one orientation of a mold in the prior art; Figure 10 This is a schematic diagram of another orientation of the mold in the existing technology.

[0018] Labels in the attached diagram: 1. Base; 11. Supporting foot; 2. End cap; 21. Pouring port; 22. Slot; 23. Connecting block; 3. Inner mold; 31. Reinforcing rib; 4. Outer mold; 41. Connecting ear; 42. Spacer strip; 5. Positioning pin; 51. Demolding slope; 52. Pull-out hole; 6. Lead-out outlet; 61. Pin slot. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0020] See Figures 1 to 8 The first aspect of the present invention provides a lead-out positioning device for positioning the lead-out 6 of a low-voltage coil in the fabrication of a foil-wound low-voltage coil for a dry-type transformer. The positioning device includes a base 1, an end cap 2, an inner mold 3, and an outer mold 4. The outer mold 4 is fitted over the inner mold 3. The base 1 and the end cap 2 are respectively connected to both ends of the outer mold 4, so that the base 1, the end cap 2, the inner mold 3, and the outer mold 4 form a casting cavity. The base 1 is provided with a positioning pin 5 that can be detachably extended into the casting cavity. The positioning pin 5 is used to cooperate with the pin groove 61 at the tail of the lead-out 6 to constrain the tail of the lead-out 6. The end cap 2 is provided with a slot 22 on its circumference for fixing the head of the lead-out 6. The end cap 2 is provided with a pouring port 21 leading to the casting cavity. This device is mainly used in the production process of dry-type transformers, especially for foil-wound cast low-voltage coils used in harsh environments such as offshore wind power or offshore drilling platforms, to achieve stable and detachable positioning of their lead-out row 6.

[0021] Specifically, the shape of the pin groove 61 is adapted to the cross-sectional profile of the positioning pin 5, generally adopting a rectangular groove and rectangular pin fit, to ensure that the lead-out pin 6 can be accurately fitted onto the positioning pin 5 through the pin groove 61, achieving preliminary circumferential and radial positioning. At the same time, the depth and width of the pin groove 61 must ensure a tight fit between the lead-out pin 6 and the positioning pin 5 to prevent loosening or displacement during subsequent coil winding or casting, while also allowing for a certain assembly gap to facilitate the quick installation and disassembly of the lead-out pin 6. In other words, the positioning pin 5 and the pin groove 61 are in clearance fit; the slot 22 and the head of the lead-out pin 6 are in clearance fit, and the size of the gap needs to be precisely designed according to the actual size of the head of the lead-out pin 6, usually controlled within the range of 1-5 mm. This gap setting effectively guides and limits the head of the lead-out strip 6, preventing lateral swaying during axial extension. It also reduces the risk of deformation of the lead-out strip 6 head or damage to the slot 22 due to improper fitting, ensuring that the lead-out strip 6 remains in the predetermined position after being inserted into the slot 22. This provides a reliable structural foundation for subsequent coil winding and casting processes. Furthermore, the inner wall of the slot 22 and the locating pin 5 undergo fine grinding to improve surface smoothness, reducing frictional resistance when the lead-out strip 6 head is inserted, enhancing assembly smoothness, and facilitating subsequent demolding.

[0022] The base 1 serves as the fundamental support platform for the entire casting mold, and its structural strength must be able to support the weight of the internal components and the dynamic tension during the winding process. A locating pin 5 mounting hole is provided on the support plane of the base 1. One end of the locating pin 5 is connected to the base 1, and the mounting hole is a through-hole in the base. During installation, the locating pin is inserted from the outside of the base 1 into the casting cavity and fixed to the base 1, while the other end extends into the casting cavity. The locating pin 5 provides radial constraint to one end of the lead-out strip 6. The end cap 2 has a groove 22, which provides radial constraint to the other end of the lead-out strip 6, thereby physically limiting the displacement of the lead-out strip 6. The groove 22 and the other end of the lead-out strip 6 are in clearance fit, which prevents large displacement of the lead-out strip 6 and also prevents forced positioning of the lead-out strip 6, which would generate stress inside it after casting and curing.

[0023] End cap 2 forms the upper boundary of the casting cavity. A groove 22 is specifically provided at the edge of end cap 2. The shape of the groove 22 matches the head contour of the lead-out pin 6 and is specifically used to constrain the head position of the lead-out pin 6. The groove 22 and the lead-out pin 6 are in clearance fit, with the clearance selected between 1 and 5 mm. If the clearance is too small, there is still a possibility of forcing the lead-out pin out, which could lead to stress inside the subsequent low-voltage coil. If the clearance is too large, there is a probability that the head of the lead-out pin will deviate from the predetermined position. For example, the width of the groove 22 is set to 182 mm and the depth to 25 mm. The width of the lead-out pin 6 can be a standard width of 180 mm and a thickness of 16 mm. A 1 mm clearance is reserved on one side in the width direction, for a total assembly tolerance compensation margin of 2 mm. The two-millimeter allowance absorbs machining errors in actual assembly scenarios. Even if there is a slight misalignment of the positioning pin 5 on the base 1 during installation, the head of the lead-out strip 6 can still slide smoothly into the slot 22, avoiding forced compressive stress caused by excessive tightness. If this stress is not eliminated during the subsequent resin curing process, it will often turn into internal structural defects in the product. In addition, the depth of the slot 22 is set at 25 mm, which is significantly greater than the 16 mm thickness of the lead-out strip 6. This ensures that the lead-out strip 6 is completely enclosed inside the slot 22 after mold closing, establishing its three-dimensional spatial coordinates within the casting cavity and preventing positional shifting during vacuum evacuation or high-speed resin flow.

[0024] The locating pin 5 is composed of an installation section and a positioning section connected together. The installation section achieves cantilever support by being vertically inserted into the mounting hole of the locating pin 5 in the mold base 1, and the tight fit between its outer periphery and the mounting hole of the locating pin 5 ensures the overall verticality of the locating pin 5. At the exposed end of the installation section, a pull-out hole 52 is provided. The purpose of the pull-out hole 52 is to provide a mechanical connection point through which a hook or bolt or other traction tool can be inserted during the demolding stage after the resin has cured, so that the operator can pull the locating pin 5 out of the hardened resin block by applying axial pulling force.

[0025] The positioning section extends upwards from the installation section and, in the assembled state, inserts into the pre-fabricated pin groove 61 at the tail of the lead-out strip 6 to position the tail of the lead-out strip 6. To address the strong adhesion of the cured epoxy resin to the metal surface and the mechanical interlocking issue, the surface of the positioning section is machined with a 4.9° draft angle. This specific angle is outside the self-locking angle range of the resin-steel friction pair, ensuring that the contact surface can quickly generate a small radial separation under axial tension, thereby significantly reducing demolding resistance. Simultaneously, considering that the edges of the pin groove 61 are usually chamfered during the processing of the lead-out strip 6, the root position where the positioning section contacts the lead-out strip 6 is designed with a rounded transition structure. The geometric curvature of this rounded transition structure matches the chamfered contour of the pin groove 61 at the tail of the lead-out strip 6, enabling the lead-out strip 6 to achieve surface contact rather than point contact under force, improving the rigidity and reliability of positioning and preventing localized plastic deformation of the lead-out strip 6 on the pin due to winding tension.

[0026] Preferably, the axial mid-surface of the positioning pin 5 coincides with the axial mid-surface of the slot 22. This design ensures that the lead-out 6 is positioned at the predetermined position on the outer mold 4.

[0027] Preferably, the radial cross-section of the outer mold 4 is a non-closed cylindrical shape with a notch, and the notch has an outwardly extending connecting lug 41. The connecting lug 41 has a through hole for inserting a fastening bolt. When the outer mold 4 is fitted onto the outside of the inner mold 3, the width of the notch can be gradually reduced by screwing the bolt into the through hole of the connecting lug 41 and gradually tightening it until the inner diameter of the outer mold 4 shrinks to a predetermined size. This non-closed cylindrical structure, combined with the design of the connecting lug 41, not only facilitates the quick assembly and disassembly of the outer mold 4, avoiding the squeezing damage to the coil that may be caused by traditional integral molds during demolding, but also allows for precise control of the inner diameter of the outer mold 4 by adjusting the tightness of the bolts, so as to adapt to the molding requirements of coils with different wire diameters and number of turns, and ensure that the winding maintains a stable external dimension and a tight arrangement structure during the casting and curing process.

[0028] Preferably, a spacer strip 42 is provided between the two connecting ears 41. The spacer strip 42 is made of a material with a certain degree of elasticity, and its thickness can be selected according to actual needs. When the connecting ears 41 are tightened by bolts, the spacer strip 42 can fill the gap between the two connecting ears 41 caused by the reduction of the notch, avoiding deformation or damage caused by direct rigid contact between the connecting ears 41. At the same time, the elasticity of the spacer strip 42 can also provide a certain buffer under the action of bolt tightening force, making the shrinkage adjustment of the inner diameter of the outer mold 4 more stable, and preventing impact on the outer mold 4 or the internal coil due to excessive instantaneous tightening force. In addition, the spacer strip 42 can also effectively isolate the two connecting ears 41, avoid gaps that may exist between the notches, prevent glue leakage when casting the coil, and seal the notch, further improving the overall service life and safety of the mold, and ensuring stable fastening effect and insulation performance during long-term use.

[0029] Preferably, the free end of the positioning pin 5 is provided with a demolding slope 51; the demolding slope 51 gradually slopes towards the center of the pin body along the insertion direction of the positioning pin 5, forming a smooth guide structure. When the mold needs to be demolded, as the outer mold 4 separates, the demolding slope 51 can form a wedge-shaped contact with the coil or the inner mold 3, decomposing the frictional force originally perpendicular to the demolding direction into a component force along the slope direction, thereby significantly reducing the demolding resistance. This design is particularly suitable for situations where the coil is tightly fitted to the inner wall of the outer mold 4 or there is slight adhesion, effectively avoiding the demolding jamming phenomenon caused by the flat end face of the traditional positioning pin 5, and preventing scratching, squeezing, or other damage to the end or surface of the coil during demolding. At the same time, the setting of the demolding slope 51 can also guide the positioning pin 5 to accurately insert into the corresponding pin slot 61 when the mold is closed, improving the mold closing efficiency and positioning accuracy, and ensuring that all parts of the mold maintain a good fit during use.

[0030] Preferably, a support foot 11 is provided at the end of the base 1 away from the inner mold 3. When the entire mold is adjusted to a vertical position, the support foot 11 can provide stable support for the entire mold, effectively dispersing the pressure generated by the mold during operation, preventing the base 1 from directly contacting the ground, and preventing deformation or tilting due to uneven force. The height of the support foot 11 can be finely adjusted according to actual installation requirements. By cooperating with the adjusting screw hole and adjusting bolt at the bottom of the support foot 11, the levelness of the mold can be precisely adjusted to ensure that the mold is in the optimal level state when the coil is poured, preventing uneven distribution of the pouring material due to mold tilt, which would affect the molding quality of the coil.

[0031] Preferably, the end cap 2 is provided with a plurality of connecting blocks 23; the connecting blocks 23 are used to lock the end cap 2 and the inner mold 3 together; the connecting blocks 23 are provided with through stepped screw holes, the axis of which is perpendicular to the end face of the inner mold 3. When the end cap 2 and the inner mold 3 are locked together by high-strength bolts passing through the screw holes, the tension of the bolts can be evenly distributed along the axial direction, so as to avoid the end cap 2 from warping due to excessive local stress.

[0032] Preferably, the inner mold 3 is provided with reinforcing ribs 31. It is understood that the device used to manufacture the low-voltage coil of the dry-type transformer is very large in volume and is mostly made of metal, which increases the weight. In order to reduce the weight of the device as much as possible without affecting the performance of the device, the thickness of the inner mold 3 can be as thin as possible. However, in order to prevent the inner mold 3 from deforming during use, several reinforcing ribs 31 are set at predetermined intervals inside the inner mold 3. These reinforcing ribs 31 are welded and formed using the same metal material as the inner mold 3. This not only significantly improves the overall structural strength and rigidity of the inner mold 3, but also effectively resists the radial pressure generated by the material on the inner wall during the coil casting process and the external force impact that may be received during mold handling and installation. This avoids deformation problems such as dents, bulges or bends in the inner mold 3, and ensures the dimensional accuracy and shape regularity of the inner surface of the coil. Meanwhile, the reinforcement ribs 31 can further optimize the stress performance of the inner mold 3 without increasing the overall thickness of the inner mold 3. This can be achieved through reasonable distribution design (e.g., equidistant along the axial direction of the inner mold 3 or non-equidistant according to the stress conditions, with the ribs extending radially to a certain height on the inner wall of the inner mold 3). This ensures that the inner mold 3 remains structurally stable during long-term use and extends its service life.

[0033] According to another aspect of the present invention, a method for manufacturing a low-voltage coil is provided, wherein the low-voltage coil is manufactured using the lead-out positioning device described in any one of the above embodiments; the method includes the following steps: Step 1: Connect one end of the inner mold 3 to the base 1 coaxially with bolts, and insert the positioning pin 5 from the back of the base 1 and fix it with bolts so that it protrudes into the casting cavity; and apply release agent to the positioning pin 5. Step 2: Place the lead-out strip 6 against the outer surface of the inner mold 3, adjust its position so that the pin groove 61 at the tail of the lead-out strip 6 is aligned with the positioning pin 5 and fully inserted to achieve preliminary radial and axial positioning. Step 3: Install the end cap 2 onto the other end of the inner mold 3. During the installation process, ensure that the head of the lead-out strip 6 is accurately embedded into the slot 22 of the end cap 2, and that the head of the lead-out strip 6 extends axially out of the end cap 2 for a certain length to facilitate subsequent connection with the external copper busbar. Thus, the position of the lead-out strip 6 is limited to a certain range. Step 4: Start the foil winding machine and wind the foil conductor of the low-voltage coil on the outer surface of the inner mold 3, and tightly wrap the tail of the lead-out row 6 inside the coil. Step 5: Place the outer mold 4 onto the inner mold 3 from above, and connect and fix the lower end of the outer mold 4 to the base 1. At this time, the upper end of the outer mold 4 extends towards the end cover 2, but it is usually not directly and rigidly connected to the end cover 2, leaving a certain fitting gap or achieving sealing through a sealing ring; Step 6: Preheat and vacuum the entire mold, then inject the preheated epoxy resin into the casting cavity through the pouring port 21 on the end cap 2 until it is completely filled. Step 7: After the epoxy resin has fully cured, first loosen the bolts on the connecting lug 41 of the outer mold 4, remove the pad 42, and allow the outer mold 4 to expand under its own tension for easy removal; then remove the base 1; next, use a tool to clamp the tail of the positioning pin 5 and use its demolding ramp 51 to easily pull it out of the coil; finally, remove the end cap 2 and the inner mold 3. Since the positioning pin 5 leaves only a smooth small hole after being pulled out, and the outer mold 4 is a non-interlocking structure, the entire demolding process will not cause any tensile or shear stress to the epoxy resin body of the coil, thus obtaining a complete and undamaged low-voltage coil product.

[0034] Specifically, the base 1 is placed horizontally in the work area, the inner mold 3 is fitted onto the base 1 using lifting equipment, and the inner mold 3 is locked and fixed to the base 1 using fasteners.

[0035] Place the end cap 2 on top of the inner mold 3, adjust the position of the specially designed fixing slot 22 on the end cap 2 so that it is opposite to the pin, and then use the connecting block 23 to lock the end cap 2 and the inner mold 3 into one piece.

[0036] Using lifting equipment, the assembled mold is slowly laid down and moved horizontally so that the square hole in the center of the mold fits into the square shaft of the foil winding machine. After the mold is fully in place, special mold fasteners are installed and tightened at both ends to prevent axial displacement of the mold during subsequent winding.

[0037] Apply release agent to the positioning pin 5, wrap it with polyester film, and then insert the positioning pin 5 with the release angle facing outwards vertically into the preset positioning pin 5 mounting hole on the mold base 1.

[0038] The welded coil lead is placed in the special fixing slot 22 of the upper support plate; at this point, the head of the lead is constrained by the end cover 2 slot 22 and the tail is positioned by the positioning pin 5, thus restricting the lead 6 within a certain range.

[0039] After the coil winding is completed and the resin has undergone vacuum casting and curing, proceed in the following order: First, disassemble the mold (i.e., outer mold 4) that wraps the coil.

[0040] Loosen the fasteners and separate the inner mold 3 from the base 1.

[0041] Use lifting equipment to lift the inner mold 3 assembly; at this time, part of the positioning pin 5 has been cured and encapsulated inside the resin; since the tail end of the positioning pin 5 (i.e. the end inserted into the base 1) is provided with a pull-out hole 52, and its surface is coated with a release agent and designed with a release slope, after the base 1 is separated, a traction tool can be inserted into the pull-out hole 52 and a small axial pulling force can be applied to easily pull out the positioning pin 5, thereby first releasing all constraints on the tail of the lead busbar.

[0042] Place the coil horizontally on the demolding platform, remove the upper cover 2, and release the constraint on the lead head.

[0043] Finally, the inner mold 3 is disassembled. Since the contact surface between the inner mold 3 and the coil is smooth and flat, without any protrusions or interlocking structures, the coil can smoothly and completely detach from the inner mold 3 along the axial direction, completing the final demolding.

[0044] In summary, by using a separable, independent locating pin 5 instead of a fixed stop bar integrated with the mold, this invention completely eliminates the "mechanical interlocking" effect present in traditional methods from a structural principle perspective. The locating pin 5 can be pulled out first during the demolding process, allowing complete separation between the casting body (coil) and the mold at the key fixing point, thereby achieving smooth and complete demolding of the coil.

[0045] This solution provides a more reliable and precise fixing effect. Through the coordinated use of "end cap 2 special slot 22 constraining the head" and "positioning pin 5 positioning the tail", it achieves rigid and stable constraint on the three-dimensional space of the outlet 6.

[0046] With its simple structure, good economy, and convenient operation, the entire fixing system mainly consists of an improved base 1, an end cap 2, and a positioning pin 5. The structure is simple and the manufacturing cost is low. The operation process is clear and standardized. The pull-out design of the positioning pin 5 (demolding slope, pull-out hole 52) makes demolding operation labor-saving and safe, reducing reliance on operator experience and helping to ensure product quality stability and production safety.

[0047] Ultimately, this ensures the reliability of the coil products. The culmination of all the aforementioned effects lies in guaranteeing the long-term operational reliability of dry-type transformers used in extreme environments (such as offshore wind power and offshore platform nacelles). This solution avoids internal stress or potential cracks that may be caused by fixing points, making the cast coil a defect-free and robust whole. This ensures high insulation reliability, long lifespan, and maintenance-free characteristics of the transformer under harsh conditions such as continuous vibration and salt spray corrosion, and has significant engineering application value.

[0048] Finally, it should be noted that due to the positioning pin 5, there is also a corresponding groove at the bottom of the formed low-voltage coil. This groove will not affect the overall performance of the low-voltage coil.

[0049] The reason is: 1. The groove is located in a non-critical stress and insulation area. The groove is located on the bottom end face of the coil, rather than the main insulation structure of the coil, such as the inter-turn insulation. During the operation of the nacelle transformer, the bottom end face mainly bears the mechanical support function and is not a critical part of electrical stress. Therefore, this local small hole will not cause electric field distortion or partial discharge risk.

[0050] 2. The integral casting process ensures the integrity of the overall structure. The low-voltage coil adopts the epoxy resin vacuum casting process. After the resin is cured, it forms a dense, continuous solid insulator without internal defects. The positioning pin 5 is pre-inserted before casting and pulled out after casting. The resulting groove is only a local geometric feature of the resin surface and does not damage the molecular structure inside the resin or introduce any microcracks. The mechanical strength and insulation performance of the overall casting body remain intact.

[0051] 3. The size of the groove is extremely small relative to the overall size of the coil, and the positioning pin 5 is extremely small compared to the overall size of the coil. From a mechanical point of view, the reduction of the pressure-bearing cross section of the coil by this small hole is negligible. From an electrical point of view, its depth is much smaller than the insulation thickness of the coil and will not reduce the insulation withstand voltage level.

[0052] 4. Simple glue filling measures can be taken (not necessary). If higher requirements are required for appearance, a small amount of the same type of epoxy resin can be filled into the groove after demolding. After curing, the surface will be restored to flatness. This operation is simple, low cost and does not affect the performance of the coil. However, in the actual production of the engine room, the groove is located on the bottom mounting surface and is usually covered by structural components. The appearance is not affected. Therefore, even if it is not treated, it will not affect the use of the product at all.

[0053] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. An extraction row positioning device, characterized by: The lead-out positioning device is used to position the lead-out (6) of the low-voltage coil in the production of foil-wound cast low-voltage coil of dry-type transformer. The positioning device includes a base (1), an end cover (2), an inner mold (3) and an outer mold (4). The outer mold (4) is fitted outside the inner mold (3). The base (1) and the end cover (2) are respectively connected to the two ends of the outer mold (4), so that the base (1), the end cover (2), the inner mold (3) and the outer mold (4) form a casting cavity. The base (1) is provided with a positioning pin (5) that can be detached and extended into the casting cavity. The positioning pin (5) is used to cooperate with the pin groove (61) at the tail of the lead-out (6) to constrain the tail of the lead-out (6). The end cover (2) is provided with a slot (22) on its circumference. The slot (22) is used to fix the head of the lead-out (6). The end cover (2) is provided with a pouring port (21) leading to the casting cavity.

2. The lead-out row positioning apparatus according to claim 1, characterized by: The axial mid-surface of the positioning pin (5) coincides with the axial mid-surface of the slot (22).

3. The outlet positioning device according to claim 1 or 2, characterized in that: The radial section of the outer mold (4) is a non-closed cylindrical shape with a notch, and the notch is provided with an outwardly extending connecting lug (41).

4. The outlet positioning device according to claim 3, characterized in that: A spacer (42) is provided between the two connecting ears (41).

5. The outlet positioning device according to claim 1 or 2, characterized in that: The free end of the positioning pin (5) is provided with a demolding slope (51).

6. The outlet positioning device according to claim 1 or 2, characterized in that: The base (1) is provided with a support foot (11) at one end away from the inner mold (3).

7. The outlet positioning device according to claim 1 or 2, characterized in that: The end cap (2) is provided with several connecting blocks (23).

8. The outlet positioning device according to claim 1 or 2, characterized in that: The inner mold (3) is provided with reinforcing ribs (31).

9. The outlet positioning device according to claim 1 or 2, characterized in that: The slot (22) and the head of the lead-out bar (6) are in clearance fit, with the clearance selected between 1 and 5 mm.

10. A method for manufacturing a low-voltage coil, characterized in that: A low-voltage coil is manufactured using the lead-out positioning device according to any one of claims 1 to 9; the method includes the following steps: Step 1: Connect one end of the inner mold (3) to the base (1), and at the same time connect the positioning pin (5) to the base (1); Step 2: Abut the lead-out strip (6) against the outer surface of the inner mold (3), and insert the pin groove (61) and the positioning pin (5) on the lead-out strip (6) into each other; Step 3: Connect the end cap (2) to the other end of the inner mold (3), and at the same time, make the head of the outlet (6) embed into the slot (22) and extend it along the axial direction for a certain length; Step 4: Wind the coil on the inner mold (3) and cover the lead-out bar (6); Step 5: Place the outer mold (4) onto the inner mold (3). One end of the outer mold (4) is connected to the base (1), and the other end extends a certain length toward the end cap (2). Step 6: Cast the casting cavity formed between the base (1), end cap (2), inner mold (3), and outer mold (4); Step 7: After the casting is completed and cured, remove the outer mold (4) and base (1), pull out the positioning pin (5), remove the end cover (2) and inner mold (3) to obtain the low voltage coil.

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