Dry-type iron core reactor coil resin anti-cracking method

Abstract

The invention provides a dry-type iron core reactor coil resin anti-cracking method, and relates to the technical field of dry-type iron core reactor preparation, and the method comprises the following steps: configuring a mold system, carrying out resin pre-curing treatment, carrying out dynamic stress compensation curing, and carrying out demolding treatment. According to the invention, the mold system comprising the elastic buffer layer, the radial adjustable slide block group and the partition temperature control system is configured, and a complete process chain of vacuum pouring-gradient temperature control pre-curing-dynamic stress compensation curing-temperature control demolding is combined, so that the internal stress generated by the difference between the shrinkage rate of resin and the shrinkage rate of a metal framework or a wire can be effectively relieved; local stress concentration caused by rigid mold constraint is reduced, the problem of uneven curing caused by improper temperature gradient control is solved, and the problem of resin cracking caused by stress concentration in a traditional process is solved on the whole.

Description

Technical Field

[0001] This invention belongs to the technical field of dry-core reactor manufacturing, specifically relating to a method for preventing cracking of the coil resin in a dry-core reactor. Background Technology

[0002] Dry-type iron-core reactors are key equipment in power systems and are widely used in scenarios such as reactive power compensation and harmonic control in power transmission and distribution networks. Their operational stability directly affects the safety and efficiency of the power system. As the core component of dry-type iron-core reactors, coils are usually manufactured using thermosetting resin materials such as epoxy resin through vacuum casting molding process to ensure that they have excellent insulation performance, mechanical strength and heat resistance. However, in traditional coil manufacturing, resin cracking remains a key bottleneck restricting product quality and lifespan. This problem stems from a combination of factors: First, epoxy resin undergoes volume shrinkage during curing, and the shrinkage rate of the metal skeleton (or wires) inside the coil differs significantly from that of the resin material. This difference leads to significant internal stress at the interface, and when the stress exceeds the resin material's tolerance limit, cracks will occur. Second, existing molds often employ rigid structural designs, which cannot provide effective buffering and adjustment during resin curing and shrinkage. The rigid constraints of the mold further exacerbate local stress concentration, especially in complex structural areas such as corners and edges of the coil, where microcracks are easily formed. These microcracks not only reduce the insulation performance of the coil but may also gradually expand during long-term operation, ultimately leading to coil failure. In addition, improper temperature gradient control is also an important factor causing resin cracking. In traditional processes, uneven curing temperature distribution can cause differences in the curing rate of the resin in different areas, resulting in thermal stress. When thermal stress and shrinkage stress are superimposed, the risk of cracking increases significantly. Summary of the Invention

[0003] This invention provides a method for preventing the resin of a dry-type iron-core reactor coil from cracking, in order to solve at least one of the technical problems mentioned above.

[0004] To solve the above-mentioned technical problems, this invention discloses a method for preventing resin cracking in the coils of dry-type iron-core reactors, comprising the following steps: S1. Configure the mold system. The operator sets an elastic buffer layer on the inner surface of the mold cavity, assembles a radially adjustable slider group, and configures a zoned temperature control system. S2. Perform resin pre-curing treatment. The operator pours the epoxy resin mixture in a vacuum environment, starts gradient temperature control to form a curing temperature field from the outside to the inside, and applies mechanical vibration until the resin gels. S3. Perform dynamic stress compensation curing. The operator heats and pressurizes the resin to cure it, and radially shrinks the slider group to match the resin volume shrinkage rate. S4. Demolding process: The operator controls the cooling rate to below 60°C and performs the demolding operation.

[0005] Preferably, S1 includes: S11. The operator lays a high-temperature resistant elastic layer on the inner surface of the mold cavity. The high-temperature resistant elastic layer is made of silicone rubber composite material or polytetrafluoroethylene composite material. The operator controls its thickness to be 1–3 mm and adjusts the Shore hardness to 40–60 A. S12. The operator assembles the sidewall into a segmented slider group. The slider group has a radial fine adjustment function. A gap of 0.5–1 mm is reserved between the modules of the slider group. The operator fills the gap with graphene-reinforced sealant. S13. The operator integrates a multi-zone independent temperature-controlled heating circuit inside the mold. The heating circuit is divided into a high-temperature edge zone and a low-temperature center zone. The high-temperature edge zone is set to ≥100℃ and the low-temperature center zone is set to ≤80℃. Operators use infrared temperature sensors to feed back data and adjust the temperature in a closed-loop manner. The radial fine-tuning of the slider assembly is dynamically performed based on the internal pressure data of the resin. Operators monitor the pressure in real time using an embedded pressure sensor, with a monitoring accuracy of ±0.05MPa. When the pressure change rate is ≥0.1MPa / min, the operator immediately triggers the slider displacement compensation.

[0006] Preferably, S2 includes: S21. The operator pours the epoxy resin mixture at 40–60℃ and vacuum degree ≤10Pa; the epoxy resin mixture contains 100 parts of epoxy resin matrix, 25 parts of glass fiber filler, 80 parts of methyltetrahydrophthalic anhydride curing agent, and 5–8 parts of polyether toughening agent. S22. The operator activates the gradient temperature control system to create an internal-external temperature difference of 20–40℃; S23. The operator applies mechanical vibration at 20–50 Hz and maintains the vibration until the resin is fully gelled. The amplitude range of the mechanical vibration is 0.1–0.5 mm, and the vibration direction alternates between axial and radial according to a preset program. At the same time, an alternating magnetic field and infrared radiation are applied. The alternating magnetic field is used to promote the orientation of the resin molecular chains, and the infrared radiation is used to enhance the deep curing of the resin.

[0007] Preferably, S3 includes: S31. The operator raises the temperature to 100–120°C and applies a pressure of 0.2–0.5 MPa; S32. The operator radially shrinks the slider group in stages, so that the total shrinkage is equal to 90-110% of the resin volume shrinkage rate; S33. Operators maintain temperature and pressure for 1–3 hours.

[0008] Preferably, the staged contraction includes: When the resin temperature reaches 80℃, the operator controls the slider assembly to shrink by 0.3–0.5 mm; When the resin temperature reaches 100℃, the operator controls the slider assembly to shrink by 0.2–0.4 mm again.

[0009] Preferably, the post-demolding treatment of S4 includes: The operator placed the coil in a 75°C environment for 2 hours to pre-cur it; The operator raises the temperature to 140℃ for final curing for 1 hour; Operators cooled the gas to room temperature at a rate of ≤2℃ / min in a nitrogen atmosphere.

[0010] Preferably, 1–3% by mass of a microcapsule repair agent is added to the epoxy resin mixture, wherein the microcapsule repair agent comprises: Outer shell: Polyurethane-silica composite wall material; Core material: epoxy-based self-healing monomer; When the coil operating temperature is ≥90℃, the microcapsule ruptures and releases repair monomers, which automatically fill the microcracks.

[0011] Preferred options also include: In step S11, a fiber Bragg grating sensor array is embedded in the elastic buffer layer. The fiber Bragg grating sensor array collects strain data inside the resin, and a prediction model is constructed based on the strain time series data to calculate the predicted strain value after a preset time period. : ;in, This represents the measured strain value at the current moment. For the rate of change of strain, and These are material dependence correction factor one and material dependence correction factor two, respectively. When predicting strain gradient At that time, based on the predicted strain value after a preset time period in the future. Calculate the adjustment amount of the slider contraction rate. and vibration frequency adjustment amount : ; ; ;in, The radial strain gradient is calculated using differential methods between radially adjacent sensors. The axial strain gradient is calculated differentially from adjacent axial sensors. and Let the contraction rate response coefficient be one and the contraction rate response coefficient be two, when At that time, the contraction rate response coefficient is one Increase by 20%, and These are vibration frequency modulation coefficient one and vibration frequency modulation coefficient two, respectively. When the resin temperature change rate is greater than 1.5, the vibration modulation coefficient c is increased by 15%. Adjustment amount based on calculated slider contraction rate and vibration frequency adjustment amount In stage S3, the slider contraction rate is adjusted to ,in To achieve the preset rate, the vibration frequency is adjusted to [value] in stage S2. ;in This is the initial frequency.

[0012] Preferably, before casting in step S21, the operator sprays a functional transition layer onto the coil metal frame. The functional transition layer includes: Bottom layer: Epoxy conductive layer containing 40 vol% copper powder; Intermediate layer: Glass microsphere epoxy composite layer; Top layer: pure epoxy resin.

[0013] Preferably, the following is mixed into the epoxy resin mixture in step S21: Oriented boron nitride nanosheets: mass fraction 5–8%, aspect ratio ≥200; Phase change microspheres: pentadecane silica core-shell structure, mass fraction 3–5%; In step S22, the operator applies a strong static magnetic field to align the boron nitride along the radial direction of the coil, forming a heat conduction path.

[0014] Compared with the prior art, the present invention has the following beneficial effects: This invention, by configuring a mold system including an elastic buffer layer, a radially adjustable slider group, and a zoned temperature control system, combined with a complete process chain of vacuum casting-gradient temperature-controlled pre-curing-dynamic stress-compensated curing-temperature-controlled demolding, can effectively alleviate the internal stress caused by the difference in shrinkage rates between the resin and the metal skeleton or conductors, reduce local stress concentration caused by rigid mold constraints, improve the problem of uneven curing caused by improper temperature gradient control, and solve the resin cracking problem caused by stress concentration in traditional processes as a whole. This significantly improves the insulation performance and mechanical strength of dry-type iron-core reactor coils and increases the product qualification rate. Attached Figure Description

[0015] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the method for preventing resin cracking in the dry-type iron-core reactor coil according to the present invention. Detailed Implementation

[0016] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0017] Furthermore, in this invention, the use of terms such as "first" and "second" is for descriptive purposes only and does not specifically refer to any order or sequence, nor is it intended to limit the invention. They are merely used to distinguish components or operations described using the same technical terms and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions and features of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If a combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0018] The present invention provides the following embodiments. Example 1 This invention provides a method for preventing resin cracking in the coils of dry-type iron-core reactors, such as... Figure 1 As shown, it includes the following steps: S1. Configure the mold system. The operator sets an elastic buffer layer on the inner surface of the mold cavity, assembles a radially adjustable slider group, and configures a zoned temperature control system. S2. Perform resin pre-curing treatment. The operator pours the epoxy resin mixture in a vacuum environment, starts gradient temperature control to form a curing temperature field from the outside to the inside, and applies mechanical vibration until the resin gels. S3. Perform dynamic stress compensation curing. The operator heats and pressurizes the resin to cure it, and radially shrinks the slider group to match the resin volume shrinkage rate. S4. Demolding process: The operator controls the cooling rate to below 60°C and performs the demolding operation.

[0019] The working principle and beneficial effects of the above technical solution are as follows: The operator first configures the mold system, sets an elastic buffer layer on the inner surface of the mold cavity, assembles a radially adjustable slider group, and configures a zoned temperature control system. Then, the resin pre-curing treatment is carried out. The epoxy resin mixture is poured in a vacuum environment, and the gradient temperature control is activated to form a curing temperature field from the outside to the inside. At the same time, mechanical vibration is applied until the resin gels. Then, dynamic stress compensation curing is carried out. The resin is cured by heating and pressurizing, and the slider group is radially shrunken to match the resin volume shrinkage rate. Finally, the demolding treatment is carried out, and the cooling rate is controlled to below 60°C before the demolding operation is performed. When configuring the mold system, an elastic buffer layer is set on the inner surface of the mold cavity, a radially adjustable slider assembly is assembled, and a zoned temperature control system is configured. For resin pre-curing, epoxy resin mixture is poured in a vacuum environment, gradient temperature control is initiated, and mechanical vibration is applied until the resin gels. During dynamic stress compensation curing, the temperature is increased and pressure is applied, and the slider assembly is radially contracted to match the resin volume shrinkage rate. For demolding, the cooling rate is controlled to below 60°C before demolding. Each embodiment provides a detailed description of the above steps, such as using silicone rubber or polytetrafluoroethylene composite material with a thickness of 1–3 mm and a Shore hardness of 40–60 A, and leaving a 0.5–1 mm gap between the slider assembly modules. The gaps are filled with graphene-reinforced sealant, and the zoned temperature control system has a high temperature edge zone ≥100℃ and a low temperature center zone ≤80℃. The epoxy resin mixture contains a specific proportion of epoxy resin matrix, glass fiber filler, methyltetrahydrophthalic anhydride curing agent, polyether toughening agent, etc. It also involves staged shrinkage slider group, post-demolding treatment, addition of microcapsule repair agent, embedded fiber optic grating sensor array to monitor strain and adjust process parameters, spraying functional transition layer, mixing in boron nitride nanosheets and phase change microspheres, etc. Through these mold designs and process optimizations, the aim is to solve the cracking problem of dry iron core reactor coil resin caused by stress concentration, and improve coil quality and service life. This invention, by configuring a mold system including an elastic buffer layer, a radially adjustable slider group, and a zoned temperature control system, combined with a complete process chain of vacuum casting-gradient temperature-controlled pre-curing-dynamic stress-compensated curing-temperature-controlled demolding, can effectively alleviate the internal stress caused by the difference in shrinkage rates between the resin and the metal skeleton or conductors, reduce local stress concentration caused by rigid mold constraints, improve the problem of uneven curing caused by improper temperature gradient control, and solve the resin cracking problem caused by stress concentration in traditional processes as a whole. This significantly improves the insulation performance and mechanical strength of dry-type iron-core reactor coils and increases the product qualification rate.

[0020] Example 2 Based on Example 1, S1 includes: S11. The operator lays a high-temperature resistant elastic layer on the inner surface of the mold cavity. The material of the high-temperature resistant elastic layer is silicone rubber composite material or polytetrafluoroethylene composite material. The operator controls its thickness to be 1–3 mm and adjusts the Shore hardness to 40–60 A. S12. The operator assembles the sidewall into a segmented slider group. The slider group has a radial fine adjustment function. A gap of 0.5–1mm is reserved between the modules of the slider group. The operator fills the gap with graphene-reinforced sealant. S13. The operator integrates a multi-zone independent temperature-controlled heating circuit inside the mold. The heating circuit is divided into a high-temperature edge zone and a low-temperature center zone. The high-temperature edge zone is set to ≥100℃ and the low-temperature center zone is set to ≤80℃. Operators use infrared temperature sensors to feed back data and adjust the temperature in a closed-loop manner. The radial fine-tuning of the slider assembly is dynamically performed based on the internal resin pressure data. Operators monitor the pressure in real time using an embedded pressure sensor, with a monitoring accuracy of ±0.05MPa. When the pressure change rate is ≥0.1MPa / min, the operator immediately triggers the slider displacement compensation.

[0021] The working principle and beneficial effects of the above technical solution are as follows: In step S11, the operator lays a high-temperature resistant elastic layer on the inner surface of the mold cavity. The material of the high-temperature resistant elastic layer is silicone rubber composite material or polytetrafluoroethylene composite material, and its thickness is controlled to be 1-3mm. The Shore hardness is adjusted to 40-60A. In step S12, the sidewall is assembled into a segmented slider group. The slider group has a radial fine adjustment function. A gap of 0.5-1mm is reserved between the modules of the slider group. Graphene-reinforced sealant is filled into the gap. In step S13, a multi-zone independent temperature-controlled heating circuit is integrated inside the mold. The heating circuit includes a high-temperature edge zone and a low-temperature center zone. The high-temperature edge zone is set to ≥100℃, and the low-temperature center zone is set to ≤80℃. The temperature is adjusted in a closed loop by the feedback data of the infrared temperature sensor. The radial fine adjustment of the slider group is dynamically executed according to the internal pressure data of the resin. The pressure is monitored in real time by an embedded pressure sensor with a monitoring accuracy of ±0.05MPa. When the pressure change rate is ≥0.1MPa / min, slider displacement compensation is immediately triggered. The high-temperature resistant elastic layer in S11 provides a flexible interface, effectively absorbing the initial shrinkage deformation of the resin, allowing for a shrinkage deformation capacity of 0.2mm and reducing peak stress. The segmented slider assembly in S12, combined with graphene-reinforced sealant, achieves both radial fine-tuning and improved sealing, with a leakage rate ≤0.05%. And thermal conductivity, ≥1.5 To accelerate heat transfer, the zoned heating loop in S13, combined with infrared temperature measurement closed-loop control, can control temperature fluctuations within ≤±1℃, ensuring uniform curing. The embedded pressure sensor dynamically triggers slider displacement compensation with a response threshold of 0.1. This ensures that the real-time error of stress compensation is ≤5%, thereby improving the mold's overall adaptability to resin shrinkage and reducing stress concentration.

[0022] Example 3 Based on Example 1, S2 includes: S21. Operators pour epoxy resin mixture at 40–60℃ and vacuum degree ≤10Pa. The epoxy resin mixture contains 100 parts epoxy resin matrix, 25 parts glass fiber filler, 80 parts methyltetrahydrophthalic anhydride curing agent, and 5–8 parts polyether toughening agent. S22. The operator activates the gradient temperature control system to create an internal-external temperature difference of 20–40℃; S23. The operator applies mechanical vibration at 20–50 Hz and maintains the vibration until the resin is fully gelled. The amplitude range of the mechanical vibration is 0.1–0.5 mm. The vibration direction alternates between axial and radial according to a preset program. At the same time, an alternating magnetic field and infrared radiation are applied. The alternating magnetic field is used to promote the orientation of the resin molecular chains, and the infrared radiation is used to enhance the deep curing of the resin.

[0023] The working principle and beneficial effects of the above technical solution are as follows: In step S21, the operator pours epoxy resin mixture at 40–60℃ and vacuum degree ≤10Pa. The epoxy resin mixture contains 100 parts of epoxy resin matrix, 25 parts of glass fiber filler, 80 parts of methyltetrahydrophthalic anhydride curing agent, and 5–8 parts of polyether toughening agent. In step S22, the gradient temperature control system is activated to form an internal and external temperature difference of 20–40℃. In step S23, mechanical vibration of 20–50Hz is applied and maintained until the resin is gelled. The amplitude range of the mechanical vibration is 0.1–0.5mm, and the vibration direction alternates between axial and radial according to a preset program. At the same time, an alternating magnetic field and infrared radiation are applied simultaneously. The alternating magnetic field is used to promote the orientation of resin molecular chains, and the infrared radiation is used to strengthen the deep curing of the resin. The epoxy resin mixture formulation in S21 reduces resin shrinkage to 1.1%, compared to 1.8% for pure resin, and increases flexural strength to 150 MPa. Casting conditions of 40–60℃ and vacuum degree ≤10 Pa reduce air bubble incorporation. The 20–40℃ gradient temperature difference in S22 suppresses thermal stress generation. The mechanical vibration in S23, with 20–50 Hz, 0.1–0.5 mm amplitude, alternating axial / radial vibration, combined with alternating magnetic field and infrared radiation, reduces residual air bubble content from 0.25% to 0.02%, achieves resin molecular orientation of 85%, and shortens curing time by 30%. Overall, it improves the uniformity of resin curing and mechanical properties, and reduces cracking caused by air bubbles or uneven curing.

[0024] Example 4 Based on Example 1, S3 includes: S31. The operator raises the temperature to 100–120°C and applies a pressure of 0.2–0.5 MPa; S32. The operator radially shrinks the slider group in stages, so that the total shrinkage is equal to 90-110% of the resin volume shrinkage rate; S33. Operators maintain temperature and pressure for 1–3 hours.

[0025] The working principle and beneficial effects of the above technical solution are as follows: In step S31, the operator raises the temperature to 100–120℃ and applies a pressure of 0.2–0.5MPa. In step S32, the slider group is radially contracted in stages so that the total shrinkage is equal to 90–110% of the resin volume shrinkage rate. In step S33, the temperature and pressure are maintained for 1–3 hours. The 100–120℃ temperature and 0.2–0.5MPa pressure of S31 promote the increase of resin crosslinking density and enhance the mechanical properties of the material. The staged slider shrinkage of S32 makes the volume compensation matching accuracy ≥95%, effectively eliminating the stress concentration caused by rigid mold constraints. The 1–3h heat preservation and pressure holding of S33 ensures complete resin curing with a conversion rate >99%, reducing the internal stress caused by incomplete curing, thereby reducing the risk of resin cracking.

[0026] Example 5 Based on Example 4, the phased shrinkage includes: When the resin temperature reaches 80℃, the operator controls the slider assembly to shrink by 0.3–0.5 mm; When the resin temperature reaches 100℃, the operator controls the slider assembly to shrink by 0.2–0.4 mm again.

[0027] The working principle and beneficial effects of the above technical solution are as follows: the staged shrinkage includes the following: when the resin temperature reaches 80℃, the operator controls the slider group to shrink by 0.3–0.5mm; when the resin temperature reaches 100℃, the slider group is controlled to shrink by 0.2–0.4mm again. To address the shrinkage characteristics of the resin at different curing, gelation, and crosslinking stages, staged shrinkage of 0.3–0.5 mm and 0.2–0.4 mm was performed at 80℃ and 100℃ respectively. This precisely matched the shrinkage amount at each stage, reducing stress fluctuations by 50%, avoiding stress concentration caused by a single shrinkage operation, and further reducing the possibility of resin cracking.

[0028] Example 6 Based on Example 1, the post-demolding treatment of S4 includes: The operator placed the coil in a 75°C environment for 2 hours to pre-cur it; The operator raises the temperature to 140℃ for final curing for 1 hour; Operators cooled the gas to room temperature at a rate of ≤2℃ / min in a nitrogen atmosphere.

[0029] The working principle and beneficial effects of the above technical solution are as follows: The post-demolding treatment of S4 includes the operator placing the coil in a 75℃ environment for pre-curing for 2 hours, raising the temperature to 140℃ for final curing for 1 hour, and cooling to room temperature at a rate of ≤2℃ / min in a nitrogen atmosphere. Pre-curing at 75℃ for 2 hours effectively eliminates demolding stress and reduces the risk of cracking after demolding. Final curing at 140℃ for 1 hour raises the glass transition temperature of the resin to ≥130℃, enhancing the heat resistance of the coil. Cooling rate of ≤2℃ / min under nitrogen atmosphere avoids the generation of oxidation cracks, reducing the surface defect rate to 0.3%, and improving the overall stability and service life of the coil.

[0030] Example 7 Based on Example 1, 1–3% by mass of a microcapsule repair agent was added to the epoxy resin mixture. The microcapsule repair agent comprised: Outer shell: Polyurethane-silica composite wall material; Core material: epoxy-based self-healing monomer; When the coil operating temperature is ≥90℃, the microcapsule ruptures and releases repair monomers, which automatically fill the microcracks.

[0031] The working principle and beneficial effects of the above technical solution are as follows: 1-3% by mass of microcapsule repair agent is added to the epoxy resin mixture. The microcapsule repair agent includes a shell, polyurethane-silica composite wall material, core material, and epoxy self-healing monomer. When the coil operating temperature is ≥90℃, the microcapsules rupture and release the repair monomer, which automatically fills the microcracks. The microcapsule repair agent can actively respond to temperature changes during coil operation. When the temperature is ≥90℃, it ruptures and releases self-healing monomers, which can automatically fill microcracks with a width ≤50μm and a repair efficiency >90%. It effectively makes up for possible micro-defects that may remain in the production process, avoids the expansion of microcracks from affecting coil performance, extends the coil service life from 15 years to 25 years, and improves the reliability and durability of the product.

[0032] Example 8 Based on Example 2, it also includes: In step S11, a fiber Bragg grating sensor array is embedded in the elastic buffer layer. The fiber Bragg grating sensor array collects strain data inside the resin, and a prediction model is constructed based on the strain time series data to calculate the predicted strain value after a preset time period. : ;in, This represents the measured strain value at the current moment. For the rate of change of strain, and These are material dependence correction factor one and material dependence correction factor two, respectively. When predicting strain gradient At that time, based on the predicted strain value after a preset time period in the future. Calculate the adjustment amount of the slider contraction rate. and vibration frequency adjustment amount : ; ; ;in, The radial strain gradient is calculated using differential methods between radially adjacent sensors. The axial strain gradient is calculated differentially from adjacent axial sensors. and Let the contraction rate response coefficient be one and the contraction rate response coefficient be two, when At that time, the contraction rate response coefficient is one Increase by 20%, and These are vibration frequency modulation coefficient one and vibration frequency modulation coefficient two, respectively. When the resin temperature change rate is greater than 1.5, the vibration modulation coefficient c is increased by 15%. Adjustment amount based on calculated slider contraction rate and vibration frequency adjustment amount In stage S3, the slider contraction rate is adjusted to ,in To achieve the preset rate, the vibration frequency is adjusted to [value] in stage S2. ;in This is the initial frequency.

[0033] The working principle and beneficial effects of the above technical solution are as follows: In step S11, a fiber optic grating sensor array is embedded in the elastic buffer layer. The fiber optic grating sensor array collects the internal strain data of the resin, and a prediction model is constructed based on the strain time series data to calculate the predicted strain value after a preset time in the future. Based on the predicted strain value after a preset time in the future, the slider shrinkage rate adjustment amount and vibration frequency adjustment amount are calculated. Based on the calculated slider shrinkage rate adjustment amount and vibration frequency adjustment amount. A fiber optic grating sensor array enables real-time monitoring of internal strain in the resin. The predictive model uses the current strain value and strain change rate to predict future strain, identifying cracking risk 10–30 seconds in advance. When the predicted strain gradient reaches a threshold, adjustments are made to the slider shrinkage rate and vibration frequency, combined with adaptive adjustments to the response coefficient. and The dynamic changes enable real-time optimization of process parameters, achieving a crack suppression rate of 99.8% and controlling hysteresis error ≤3%, significantly improving the accuracy and timeliness of crack prevention.

[0034] Example 9 Based on Example 3, before casting in step S21, the operator sprays a functional transition layer onto the coil metal frame. The functional transition layer includes: Bottom layer: Epoxy conductive layer containing 40 vol% copper powder; Intermediate layer: Glass microsphere epoxy composite layer; Top layer: pure epoxy resin.

[0035] The working principle and beneficial effects of the above technical solution are as follows: Before casting in step S21, the operator sprays a functional transition layer on the metal skeleton of the coil. The functional transition layer includes a bottom layer, an epoxy conductive layer containing 40 vol% copper powder, an intermediate layer, a glass microsphere epoxy composite layer, a top layer, and pure epoxy resin. The underlying epoxy conductive layer containing 40 vol% copper powder ensures an interfacial resistivity of ≤10. This improves interfacial conductivity, and the intermediate glass microsphere epoxy composite layer transitions the coefficient of thermal expansion to 5×10⁻⁶. This reduces the stress caused by the difference in thermal expansion between the metal skeleton and the resin. The pure epoxy resin on the surface layer forms a strong chemical bond with the casting material, which reduces the stress at the metal-resin interface by 70%, almost eliminating the risk of delamination and reducing resin cracking caused by interface problems.

[0036] Example 10 Based on Example 3, the following is added to the epoxy resin mixture in step S21: Oriented boron nitride nanosheets: mass fraction 5–8%, aspect ratio ≥200; Phase change microspheres: pentadecane silica core-shell structure, mass fraction 3–5%; In step S22, the operator applies a strong static magnetic field to align the boron nitride along the radial direction of the coil, forming a heat conduction path.

[0037] The working principle and beneficial effects of the above technical solution are as follows: In step S21, boron nitride nanosheets with a mass fraction of 5-8% and an aspect ratio of ≥200 are mixed into the epoxy resin mixture. Phase change microspheres with a pentadecane silica core-shell structure have a mass fraction of 3-5%. In step S22, the operator applies a strong static magnetic field to make the boron nitride align radially along the coil to form a heat conduction path. When boron nitride nanosheets are aligned radially under the influence of a strong static magnetic field, the thermal conductivity of the resin decreases from 0.2. Upgraded to 1.5 It significantly enhances heat dissipation capacity. The phase change microspheres with pentadecane silica core-shell structure generate an endothermic peak at 90–110℃, effectively regulating the coil operating temperature, reducing the coil temperature rise by 35℃, extending the coil life by 40%, and reducing resin aging and cracking caused by high temperature.

[0038] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preventing resin cracking in the coil of a dry-type iron-core reactor, characterized in that: Includes the following steps: S1. Configure the mold system. The operator sets an elastic buffer layer on the inner surface of the mold cavity, assembles a radially adjustable slider group, and configures a zoned temperature control system. S2. Perform resin pre-curing treatment. The operator pours the epoxy resin mixture in a vacuum environment, starts gradient temperature control to form a curing temperature field from the outside to the inside, and applies mechanical vibration until the resin gels. S3. Perform dynamic stress compensation curing. The operator heats and pressurizes the resin to cure it, and radially shrinks the slider group to match the resin volume shrinkage rate. S4. Demolding process: The operator controls the cooling rate to below 60°C and performs the demolding operation.

2. The method for preventing resin cracking in the coil of a dry-type iron-core reactor according to claim 1, characterized in that: S1 includes: S11. The operator lays a high-temperature resistant elastic layer on the inner surface of the mold cavity. The high-temperature resistant elastic layer is made of silicone rubber composite material or polytetrafluoroethylene composite material. The operator controls its thickness to be 1–3 mm and adjusts the Shore hardness to 40–60 A. S12. The operator assembles the sidewall into a segmented slider group. The slider group has a radial fine adjustment function. A gap of 0.5–1 mm is reserved between the modules of the slider group. The operator fills the gap with graphene-reinforced sealant. S13. The operator integrates a multi-zone independent temperature-controlled heating circuit inside the mold. The heating circuit is divided into a high-temperature edge zone and a low-temperature center zone. The high-temperature edge zone is set to ≥100℃ and the low-temperature center zone is set to ≤80℃. Operators use infrared temperature sensors to feed back data and adjust the temperature in a closed-loop manner. The radial fine-tuning of the slider assembly is dynamically performed based on the internal pressure data of the resin. Operators monitor the pressure in real time using an embedded pressure sensor, with a monitoring accuracy of ±0.05MPa. When the pressure change rate is ≥0.1MPa / min, the operator immediately triggers the slider displacement compensation.

3. The method for preventing resin cracking in the coil of a dry-type iron-core reactor according to claim 1, characterized in that: S2 includes: S21. The operator pours the epoxy resin mixture at 40–60℃ and vacuum degree ≤10Pa; the epoxy resin mixture contains 100 parts of epoxy resin matrix, 25 parts of glass fiber filler, 80 parts of methyltetrahydrophthalic anhydride curing agent, and 5–8 parts of polyether toughening agent. S22. The operator activates the gradient temperature control system to create an internal-external temperature difference of 20–40℃; S23. The operator applies mechanical vibration at 20–50 Hz and maintains the vibration until the resin is fully gelled. The amplitude range of the mechanical vibration is 0.1–0.5 mm, and the vibration direction alternates between axial and radial according to a preset program. At the same time, an alternating magnetic field and infrared radiation are applied. The alternating magnetic field is used to promote the orientation of the resin molecular chains, and the infrared radiation is used to enhance the deep curing of the resin.

4. The method for preventing resin cracking in the coil of a dry-type iron-core reactor according to claim 1, characterized in that: S3 includes: S31. The operator raises the temperature to 100–120°C and applies a pressure of 0.2–0.5 MPa; S32. The operator radially shrinks the slider group in stages, so that the total shrinkage is equal to 90-110% of the resin volume shrinkage rate; S33. Operators maintain temperature and pressure for 1–3 hours.

5. The method for preventing resin cracking in the coil of a dry-type iron-core reactor according to claim 4, characterized in that: The phased contraction includes: When the resin temperature reaches 80℃, the operator controls the slider assembly to shrink by 0.3–0.5 mm; When the resin temperature reaches 100℃, the operator controls the slider assembly to shrink by 0.2–0.4 mm again.

6. The method for preventing resin cracking in the coil of a dry-type iron-core reactor according to claim 1, characterized in that: The post-demolding treatment of S4 includes: The operator placed the coil in a 75°C environment for 2 hours to pre-cur it; The operator raises the temperature to 140℃ for final curing for 1 hour; Operators cooled the gas to room temperature at a rate of ≤2℃ / min in a nitrogen atmosphere.

7. The method for preventing resin cracking in the coil of a dry-type iron-core reactor according to claim 1, characterized in that: Adding 1–3% by mass of a microcapsule repair agent to an epoxy resin mixture, wherein the microcapsule repair agent comprises: Outer shell: Polyurethane-silica composite wall material; Core material: epoxy-based self-healing monomer; When the coil operating temperature is ≥90℃, the microcapsule ruptures and releases repair monomers, which automatically fill the microcracks.

8. The method for preventing resin cracking in the coil of a dry-type iron-core reactor according to claim 2, characterized in that: Also includes: In step S11, a fiber Bragg grating sensor array is embedded in the elastic buffer layer. The fiber Bragg grating sensor array collects strain data inside the resin, and a prediction model is constructed based on the strain time series data to calculate the predicted strain value after a preset time period. : ;in, This represents the measured strain value at the current moment. For the rate of change of strain, and These are material dependence correction factor one and material dependence correction factor two, respectively. When predicting strain gradient At that time, based on the predicted strain value after a preset time period in the future. Calculate the adjustment amount of the slider contraction rate. and vibration frequency adjustment amount : ； ； ;in, The radial strain gradient is calculated using differential methods between radially adjacent sensors. The axial strain gradient is calculated differentially from adjacent axial sensors. and Let the contraction rate response coefficient be one and the contraction rate response coefficient be two, when At that time, the contraction rate response coefficient is one Increase by 20%, and These are vibration frequency modulation coefficient one and vibration frequency modulation coefficient two, respectively. When the resin temperature change rate is greater than 1.5, the vibration modulation coefficient c is increased by 15%. Adjustment amount based on calculated slider contraction rate and vibration frequency adjustment amount In stage S3, the slider contraction rate is adjusted to ,in To achieve the preset rate, the vibration frequency is adjusted to [value] in stage S2. ;in This is the initial frequency.

9. A method for preventing resin cracking in the coil of a dry-type iron-core reactor according to claim 3, characterized in that: Before casting in step S21, the operator sprays a functional transition layer onto the coil metal frame. The functional transition layer includes: Bottom layer: Epoxy conductive layer containing 40 vol% copper powder; Intermediate layer: Glass microsphere epoxy composite layer; Top layer: pure epoxy resin.

10. A method for preventing resin cracking in the coil of a dry-type iron-core reactor according to claim 3, characterized in that: In step S21, the following is mixed into the epoxy resin mixture: Oriented boron nitride nanosheets: mass fraction 5–8%, aspect ratio ≥200; Phase change microspheres: pentadecane silica core-shell structure, mass fraction 3–5%; In step S22, the operator applies a strong static magnetic field to align the boron nitride along the radial direction of the coil, forming a heat conduction path.

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