Edge expanding and pouring device for insulation narrow-band high-voltage test of variable frequency motor

Abstract

An edge expanding and pouring device for a variable frequency motor insulation narrow-band high-voltage test comprises an upper plate, a lower plate and an insulation narrow-band sample located between the upper plate and the lower plate, wherein the upper plate above the insulated narrow-band sample is provided with an upper cavity positive pressure air curtain seepage prevention assembly, and the lower plate below the insulated narrow-band sample is provided with a lower cavity vacuum adsorption and anti-blocking maintenance assembly and a temperature control curing assembly; the pouring exhaust defoaming assembly, the lower cavity vacuum adsorption and anti-blocking maintenance assembly and the temperature control curing assembly are connected with the control module, and the upper plate is connected with a pouring source through an epoxy injection port and connected with the pouring exhaust defoaming assembly through an exhaust port. Epoxy resin edge expanding treatment is carried out on the narrow-width insulating strip to increase the creepage distance, a pollution-free voltage-withstanding test is carried out in an air medium, insulating edge expanding on the two sides of the sample is achieved, and the high-field-intensity test requirement is met on the premise that it is guaranteed that the sample body is not polluted.

Description

Technical Field

[0001] This invention relates to a technology in the field of electrical insulation testing and experimentation, specifically an expansion casting device for narrow-band high-voltage insulation testing of variable frequency motors. Background Technology

[0002] In high-voltage (especially high-frequency high-voltage) insulation performance testing, insufficient creepage distance between the electrode edge and the sample edge can easily lead to air ionization and surface discharge, causing surface flashover before bulk breakdown, thus affecting the effective measurement of the material's bulk breakdown voltage / electrical strength. To suppress surface flashover, existing technologies typically immerse the electrode system and sample in insulating oil (such as transformer oil or silicone oil) for withstand voltage or breakdown tests. However, for narrow-strip insulation materials of variable frequency motors with porous or laminated structures, such as low-resin-powder mica tape, polyimide film reinforcing tape, and anti-corona tape, the oil medium may penetrate into the material or fill micropores after impregnation, thereby changing the material's original dielectric constant and dielectric loss factor. This makes it difficult for the test results to reflect the insulation performance of the material under typical operating conditions such as "dry" or "after resin impregnation and curing." In addition, sample cleaning after oil bath testing is difficult, easily causing environmental pollution and potentially affecting subsequent physicochemical property analysis and life assessment. Summary of the Invention

[0003] This invention addresses the problems of insufficient creepage distance leading to surface flashover in high-voltage testing of narrow-band insulation materials for variable frequency motors, and the distortion of dielectric properties caused by oil contamination introduced during oil bath testing. It proposes an edge-expanding casting device for high-voltage testing of narrow-band insulation materials for variable frequency motors. This device significantly increases the creepage distance by applying epoxy resin to both sides of the narrow-band sample and includes a contamination-free testing chamber within the device, ensuring the central area of ​​the sample remains clean and dry during the edge-expanding casting process. Simultaneously, it employs a differential pressure bonding active air seal with a combination of upper chamber micro-positive pressure and lower chamber negative pressure, along with casting degassing and temperature-controlled curing, resulting in fewer defects and higher consistency in curing quality during the edge-expanding sample preparation process. This enables oil-free and contamination-free high-field-strength withstand voltage / breakdown testing in air, ensuring that high-field-strength testing requirements are met without contaminating the sample body and improving the reliability and repeatability of test results.

[0004] This invention is achieved through the following technical solution:

[0005] This invention relates to an expansion casting device for high-voltage testing of narrow-band insulation in variable frequency motors, comprising an upper plate, a lower plate, and an insulation narrow-band sample located between them. The upper plate has an upper cavity positive pressure air curtain barrier component, and the lower plate has a lower cavity vacuum adsorption and anti-clogging maintenance component and a temperature-controlled curing component. A casting groove for epoxy resin expansion casting is formed between the upper and lower plates, and includes an epoxy injection port and an exhaust port connected to the casting groove. The exhaust port is connected to a casting exhaust degassing component. The casting exhaust degassing component, the lower cavity vacuum adsorption and anti-clogging maintenance component, and the temperature-controlled curing component are each connected to a control module to achieve inter-condition control.

[0006] A high-temperature resistant outer sealing silicone rubber strip, a high-temperature resistant inner primary sealing silicone rubber strip, and a high-temperature resistant inner secondary sealing silicone rubber strip are respectively provided between the upper plate and the lower plate, between the upper plate and the insulating narrow strip sample, and between the lower plate and the insulating narrow strip sample. The cavity formed between the upper and lower plates and the high-temperature resistant outer sealing silicone rubber strip constitutes a casting groove, which is used to perform epoxy resin edge expansion molding on both sides of the narrow strip sample.

[0007] The inner cavity area defined by the high-temperature resistant primary sealing silicone rubber strip and the high-temperature resistant secondary sealing silicone rubber strip is preferably used as the inner cavity of the non-contamination test area to retain the central area of ​​the sample that is not contaminated by resin for subsequent high-pressure testing.

[0008] To prevent the positive pressure gas in the upper cavity from leaking into the casting tank and introducing air gap / bubble defects under sealed micro-leakage conditions, a pressure relief valve is installed between the high-temperature resistant inner primary sealing silicone rubber strip and the high-temperature resistant inner secondary sealing silicone rubber strip. This valve is used to release the leaking positive pressure gas that may occur in the upper cavity in a controlled manner, so that the leaking gas is preferentially discharged through the relief passage rather than entering the casting tank, thereby reducing the risk of air gaps and partial discharge defects forming at the casting interface.

[0009] The aforementioned upper cavity positive pressure air curtain barrier assembly includes: an upper plate positive pressure vent array disposed in the upper plate and an upper cavity positive pressure gas source connected thereto. Under the control of the control module, the upper cavity positive pressure gas source continuously supplies gas to the upper cavity to maintain a slight positive pressure, forming a uniformly distributed positive pressure air curtain / air seal barrier facing the upper surface of the sample through the upper plate positive pressure vent array. On one hand, the slight positive pressure in the upper cavity and the negative pressure in the lower cavity work together to form a differential pressure bonding state of "upper pressure and lower suction," enhancing the bonding stability of the sample and suppressing wrinkles. On the other hand, the positive pressure in the upper cavity forms a pressure barrier during the casting process, inhibiting epoxy resin from seeping from the outside inwards towards the uncontaminated test area.

[0010] The lower chamber vacuum adsorption and anti-clogging maintenance component includes: a microporous fluoropolymer liquid-repellent and breathable membrane, a replaceable porous vacuum adsorption panel, and a resin collection chamber located sequentially below the insulating narrow strip sample, and connected to the lower chamber adsorption vacuum pump and the lower chamber backflushing gas source, respectively. Under the control of the control module, the lower chamber adsorption vacuum pump establishes a negative pressure adsorption force, so that the sample is tightly attached to the lower adsorption panel and fits with the sealing interface, thereby (i) significantly reducing the micro-seam leakage channel between the sample and the platform, and inhibiting the resin from creeping along the seam into the non-contamination test area; (ii) forcibly flattening the flexible narrow strip, eliminating physical wrinkles and improving the geometric flatness of the expanded edge casting.

[0011] The microporous fluoropolymer liquid-repellent and breathable membrane is used to isolate resin infiltration and allow gas extraction channels to exist, thereby preventing accidentally infiltrated epoxy resin from being drawn into the porous structure and causing blockage.

[0012] The resin collection chamber is used to settle and collect a very small amount of resin that has seeped in, thus providing secondary protection for the lower chamber air passage.

[0013] The lower chamber backflushing gas source is used to assist in demolding after curing and to perform short-term backflushing cleaning and maintenance on the porous adsorption panel.

[0014] The aforementioned casting venting and degassing assembly includes: an overflow trapping buffer tank connected to the vent, and a casting degassing vacuum pump connected to the overflow trapping buffer tank. During the casting process, the casting degassing vacuum pump performs vacuum-assisted venting of the casting tank / mold cavity to expel air from the mold cavity and helps remove micro-bubbles from the resin system, improving resin wetting and molding density. The overflow trapping buffer tank is connected in series in the venting passage to capture overflowing resin or droplets, preventing backflow into the vacuum pump and causing pump contamination or damage, thereby improving the long-term reliability and safety of the system.

[0015] The temperature-controlled curing component includes a heating resistance element and a temperature sensor disposed in the lower plate. The control module implements closed-loop regulation (preferably PID control) on the heating resistance element based on the real-time temperature feedback information collected by the temperature sensor and the preset curing process temperature curve information. This ensures that the curing process after edge expansion casting strictly follows the preset temperature curve, thereby improving the consistency of the curing quality of the edge expansion insulation layer and reducing the risk of internal stress, warping, or interface defects caused by temperature fluctuations.

[0016] The control module is connected to the upper chamber positive pressure gas source, the lower chamber adsorption vacuum pump, the casting degassing vacuum pump, the lower chamber backflush gas source, the heating resistance sheet, and the temperature sensor. It is used to uniformly schedule and switch the working conditions such as bonding, casting, degassing, curing, demolding, and cleaning and maintenance, and to monitor and adjust key parameters such as chamber pressure, gas flow rate, and temperature, so as to realize the automation and repeatability of the edge expansion sample preparation process.

[0017] Technical effect

[0018] This invention increases creepage distance and reduces the risk of surface flashover by expanding the edge of epoxy resin molding; the inner chamber serves as a pollution-free testing area, and the lower chamber negative pressure adsorption ensures that the sample is tightly attached to the replaceable porous adsorption panel, which, together with the liquid-repellent and breathable membrane, achieves seepage barrier isolation and smoothing and wrinkle removal, reducing the risk of resin creepage and contamination along micro-seams; the upper chamber, through the positive pressure air curtain and the lower chamber negative pressure, forms a differential pressure bonding and active air seal of "upper pressure and lower suction", and the pressure relief valve is used to suppress positive pressure from entering the casting tank and introducing air gaps; during the casting stage, the degassing vacuum pump, together with the overflow trap buffer tank, completes the degassing and degassing of the mold cavity and prevents overflow backflow; during the curing stage, the temperature-controlled curing component cures in situ according to the preset curve under the closed-loop control of the control module, improving the consistency of curing quality and the reliability of sample preparation; after curing, pneumatic backflushing can be used to assist demolding and cleaning maintenance. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the present invention;

[0020] Figure 2 This is a side view of the present invention;

[0021] Figure 3 A simplified three-dimensional structural diagram of the insulation narrow strip edge expansion casting and clamping device;

[0022] In the diagram: 1. Epoxy injection port; 2. High-temperature resistant inner primary sealing silicone rubber strip; 3. High-temperature resistant inner secondary sealing silicone rubber strip; 4. Exhaust port; 5. Metal base; 6. High-temperature resistant outer sealing silicone rubber strip; 7. Casting tank; 8. Seepage trap; 9. Replaceable porous vacuum adsorption panel; 10. Microporous fluoropolymer liquid-repellent and breathable membrane; 11. Resin collection chamber; 12. Heating resistance element; 13. Temperature sensor; 14. Lower chamber backflush gas source; 15. Lower chamber adsorption vacuum pump; 16. Control module; 17. Upper plate positive pressure vent array; 18. Upper chamber positive pressure gas source; 19. Pressure relief valve; 20. Insulating narrow strip sample; 21. Casting degassing vacuum pump; 22. Overflow adhesive collection buffer tank; 23. Tensioning adjustment mechanism; 24. Upper plate; 25. Lower plate. Detailed Implementation

[0023] like Figure 1 As shown in this embodiment, an edge-expanding casting device for high-voltage testing of narrow-band insulation in variable frequency motors is used to expand the edge of an insulating narrow-band sample 20 with a width of 20-25 mm by epoxy resin casting and curing to form an insulating edge-expanding wing. This significantly increases the creepage distance in air, allowing the sample to be tested using standard electrodes for withstand voltage or breakdown. At the same time, through differential pressure bonding, anti-seepage sealing, degassing and de-bubbling, and temperature-controlled curing, the edge-expanding sample preparation process is ensured to be stable and controllable, and the effective test area of ​​the sample is not contaminated.

[0024] The aforementioned expansion casting device includes: upper and lower plates 24 and 25 arranged opposite to each other, and an insulating narrow strip sample 20 located therein. The upper plate 24 above the insulating narrow strip sample 20 is provided with an upper cavity positive pressure air curtain barrier component, and the lower plate 25 below the insulating narrow strip sample 20 is provided with a lower cavity vacuum adsorption and anti-blocking maintenance component and a temperature control curing component. The casting degassing and defoaming component, the lower cavity vacuum adsorption and anti-blocking maintenance component, and the temperature control curing component are respectively connected to the control module 16. The upper plate 24 is connected to the casting source through the epoxy injection port 1 and to the casting degassing and defoaming component through the exhaust port 4.

[0025] The upper and lower plates 24 and 25 are provided with tensioning and stretching adjustment mechanisms 23 at their ends, which are used to clamp the sample 20 to be widened and apply axial pretension so that the sample remains straight throughout the entire process of pouring, pumping and curing, avoiding sealing failure and contamination path formation caused by wrinkles, displacement or local warping, and improving the geometric consistency of the expansion wing.

[0026] The upper and lower plates 24 and 25, the upper plate 24 and the insulating narrow strip sample 20, and the lower plate 24 and the insulating narrow strip sample 20 are respectively provided with a high-temperature resistant outer sealing silicone rubber strip 6, a high-temperature resistant inner primary sealing silicone rubber strip 2, and a high-temperature resistant inner secondary sealing silicone rubber strip 3.

[0027] The cavity formed between the upper and lower plates 24 and 25, the high-temperature resistant outer sealing silicone rubber strip 6, and the high-temperature resistant inner primary sealing silicone rubber strip 2 is the casting groove 7.

[0028] The lower chamber vacuum adsorption and anti-clogging maintenance component includes: a microporous fluoropolymer liquid-repellent and breathable membrane 10 located sequentially below the insulating narrow strip sample 20, a replaceable porous vacuum adsorption panel 9, and a resin trapping chamber 11, as well as a lower chamber adsorption vacuum pump 15 and a lower chamber backflushing gas source 14 connected thereto. The lower chamber adsorption vacuum pump 15 and the lower chamber backflushing gas source 14, which are used for vacuum adsorption and bonding of the sample, are respectively connected to the temperature control curing component and the centralized control unit. The replaceable porous vacuum adsorption panel 9 and the resin trapping chamber 11 are fixedly installed by a metal base 5, which serves as a structural support and mounting base.

[0029] The replaceable porous vacuum adsorption panel 9 provides a uniform adsorption surface and establishes negative pressure adsorption force under the action of the lower chamber adsorption vacuum pump 15. When the sample 20 is not in close contact with the lower support / adsorption interface, micro-cracks are easily formed. During the casting stage, epoxy resin may capillarily seep along the micro-cracks and enter the inner cavity area, thus contaminating the uncontaminated test area. By establishing negative pressure adsorption in the lower chamber, the sample 20 can be pressed tightly against the replaceable porous vacuum adsorption panel 9 and its sealing interface, significantly reducing the micro-crack leakage path and improving the protection effect of the uncontaminated test area. The uniformly distributed vacuum negative pressure can produce a planar flattening effect on the flexible insulating narrow strip sample, suppressing wrinkling, warping, and local edge curling caused by the material flexibility during casting and curing. This allows the sample to maintain good geometric flatness and positioning stability throughout the edge expansion casting process, thereby improving the consistency of edge expansion molding and the repeatability of subsequent tests.

[0030] The microporous fluoropolymer liquid-repellent and breathable membrane 10 is used to filter out a small amount of epoxy resin that accidentally seeps into the porous structure and causes blockage during the casting process. It has the characteristics of being breathable but impermeable to liquid, allowing gas to pass through to maintain adsorption, while liquid resin is difficult to penetrate into the porous adsorption panel 9, thereby significantly reducing the risk of pore blockage. At the same time, the breathable membrane 10 can also play a supporting and isolating role, and together with negative pressure adsorption, it can reduce the tiny air gap between the sample and the adsorption panel, improve the consistency of adhesion, and enhance the anti-pollution capability of the pollution-free test area.

[0031] The area on the lower plate 25 between the high-temperature resistant inner primary sealing silicone rubber strip 2 and the high-temperature resistant inner secondary sealing silicone rubber strip 3 is further provided with a seepage trapping groove 8. The inner cavity area defined by the seepage trapping groove 8 and the high-temperature resistant inner primary sealing silicone rubber strip 2 and the high-temperature resistant inner secondary sealing silicone rubber strip 3 is preferably used as the inner cavity of the non-contamination test area to retain a section of material in the insulating narrow strip sample 20 that has not been contaminated by epoxy resin casting for subsequent high voltage withstand / breakdown tests.

[0032] When a very small amount of resin accidentally seeps into the lower area, it preferentially enters the seepage trap 8 and settles and collects at the resin collection chamber 11, thereby reducing the risk of resin entering the lower chamber backflush gas source 14 or the lower chamber adsorption vacuum pump 15, and achieving secondary protection of the lower chamber gas path.

[0033] The upper cavity positive pressure air curtain barrier assembly includes: an upper plate positive pressure vent array 17 disposed in an upper plate 24 located above the insulating narrow strip sample 20 and an upper cavity positive pressure gas source 18 connected thereto.

[0034] The casting degassing and degassing assembly includes an overflow trapping buffer tank 22 connected to the exhaust port 4 and a casting degassing vacuum pump 21, used to expel gas from the casting tank 7 and promote degassing during the casting process. The casting degassing vacuum pump 21 pumps out gas from the exhaust passage to reduce residual bubbles / air gaps in the resin; the overflow trapping buffer tank 22 is connected in series between the exhaust port 4 and the vacuum pump 21 to trap and buffer overflow or resin droplet carryover, preventing resin backflow into the vacuum pump and causing blockage or damage, thus improving the reliability of system operation.

[0035] The temperature-controlled curing assembly and centralized control unit include a heating resistor 12 and a temperature sensor 13 arranged sequentially in the lower plate 25 to provide heat for resin curing. The control module 16 is connected to the heating resistor 12 and the temperature sensor 13 respectively to output heating signals and collect temperature signals, thereby realizing closed-loop regulation of the heating resistor 12, ensuring that the curing temperature is stable within the set range, improving curing quality and reducing the risk of defects caused by temperature fluctuations.

[0036] The control module 16 is electrically / signally connected to the heating resistor 12, temperature sensor 13, upper chamber positive pressure gas source 18, lower chamber adsorption vacuum pump 15, lower chamber backflushing gas source 14, and casting degassing vacuum pump 21. It is used to uniformly control the temperature closed-loop regulation and the extraction / supply process of each gas path, and to control the start / stop, output intensity, gas flow rate / pumping speed, and switching of working modes (fitting / casting / degassing / curing / demolding / cleaning) of each gas source / vacuum pump. The control module 16 includes: a temperature closed-loop control unit, a pneumatic push-pull adsorption unit, a vacuum-assisted casting unit, and a pneumatic demolding and maintenance unit. The temperature closed-loop control unit performs PID closed-loop calculations and power adjustment processing based on real-time temperature feedback information collected by the temperature sensor 13 and preset curing process temperature curve information, and generates control commands which are then output to the heating resistor 12 for precise temperature control of in-situ curing heating power. The pneumatic push-pull adsorption unit... Based on the sample loading and bonding instruction information, the upper and lower chamber gas paths are coordinated and processed, and control instructions are generated and output to the lower chamber adsorption vacuum pump 15 to establish negative pressure. After generating control instructions, the instructions are output to the upper chamber positive pressure gas source 18 to establish a preset positive pressure (or adjustable positive pressure), thereby constructing a differential pressure bonding and active gas sealing state with upper pressure and lower suction. The vacuum-assisted casting unit performs negative pressure extraction logic processing based on the casting process start information, and generates control instructions and outputs them to the casting degassing vacuum pump 21 to adjust its pumping rate (or vacuum degree / pumping speed) to achieve mold cavity exhaust and bubble removal. The pneumatic demolding and maintenance unit performs gas path logic switching and reverse purging processing based on the curing completion signal or cleaning and maintenance instruction information, and generates control instructions and outputs them to the lower chamber adsorption vacuum pump 15 and / or the casting degassing vacuum pump 21. After generating control instructions, the instructions are output to the lower chamber backflushing gas source 14 and the upper chamber positive pressure gas source 18 to achieve pneumatic non-destructive demolding of the sample and / or purging, cleaning and maintenance of the replaceable porous vacuum adsorption panel 9.

[0037] Under the unified scheduling of the control module 16, the lower chamber adsorption vacuum pump 15 establishes negative pressure on the replaceable porous vacuum adsorption panel 9, so that the sample 20 is tightly attached and inhibits micro-crack seepage; the upper chamber positive pressure gas source 18 supplies gas to the upper chamber through the upper plate positive pressure vent array 17 to maintain positive pressure, forming a positive pressure air curtain to inhibit resin leakage from the outside to the inside and together with the lower chamber negative pressure to form a differential pressure bonding state; during the casting process, the exhaust port 4 is connected to the casting degassing vacuum pump 21 to realize exhaust and degassing, and the overflow glue collection buffer tank 22 is used to collect overflow glue / mist droplets to protect the vacuum pump; the curing stage is completed by the temperature control component under the closed-loop control of the control module 16; after curing, the control module 16 switches to the back-blowing / positive pressure assisted demolding and cleaning maintenance mode.

[0038] When the positive pressure gas source 18 in the upper cavity maintains the positive pressure in the upper cavity, if a micro-leakage occurs in the positive pressure gas at the sealing interface, in order to prevent it from entering the casting area and forming an air gap or inducing bubble defects, a pressure relief valve 19 is set between the inner primary sealing silicone rubber strip 2 and the inner secondary sealing silicone rubber strip 3, so that the leaked gas preferentially enters the relief passage and is released in a controlled manner, thereby reducing the probability of positive pressure gas entering the casting tank and improving the quality and consistency of edge expansion molding.

[0039] The upper plate positive pressure vent array 17 is connected to the upper cavity positive pressure gas source 18, continuously supplying gas to the upper cavity to maintain positive pressure during the casting stage. On the one hand, the positive pressure in the upper cavity and the negative pressure in the lower cavity work together to form differential pressure bonding, improving the bonding stability and flatness of the sample; on the other hand, the positive pressure in the upper cavity forms a pressure barrier during the casting and curing process, inhibiting epoxy resin from leaking from the outside to the inside into the inner cavity or the effective test area.

[0040] This embodiment relates to a method for expanding the edge of the above-mentioned device by casting, including:

[0041] S1. Sample laying and tensioning positioning: The sample 20 to be widened is laid flat on the microporous fluoropolymer liquid-repellent and breathable membrane 10, so that it is in corresponding contact with the replaceable porous vacuum adsorption panel 9; the axial pretension is applied to the sample through the tensioning adjustment mechanism 23 to make the sample flat and wrinkle-free.

[0042] S2. The differential pressure bonding and pollution-free test area protection are uniformly scheduled by the control module 16: The control module 16 controls the start of the lower chamber adsorption vacuum pump 15, so that the adsorption panel 9 establishes negative pressure adsorption and tightly attaches the sample 20 to the adsorption / sealing interface, reducing the risk of resin creeping into the pollution-free test area of ​​the inner chamber along the micro-slit; at the same time, the control module 16 controls the start of the upper chamber positive pressure gas source 18, which supplies gas to the upper chamber through the upper plate positive pressure vent array 17 and maintains positive pressure, forming a differential pressure bonding state with positive pressure on the upper side and negative pressure on the lower side; if necessary, the control module 16 adjusts the suction / gas supply intensity to stabilize the bonding state.

[0043] S3. Mold Closure and Sealing Compaction: Close the upper and lower molds to press and seal the sample and mold cavity with the high-temperature resistant inner primary sealing silicone rubber strip 2, the high-temperature resistant inner secondary sealing silicone rubber strip 3, and the high-temperature resistant outer sealing silicone rubber strip 6; the pressure relief valve 19 is in a release state to release the micro-leakage positive pressure gas that may occur in the upper cavity in a controlled manner.

[0044] S4. Casting and degassing are uniformly scheduled by the control module 16: The prepared epoxy resin is injected into the casting tank 7 through the epoxy injection port 1; during the casting process, the control module 16 controls the start of the casting degassing vacuum pump 21, so that the exhaust port 4 is pumped out through the overflow trap 22 to remove air from the casting tank and promote degassing, thereby reducing resin bubble / air gap defects; the overflow trap 22 is used to collect overflow and droplets to protect the vacuum pump 21, and the control module 16 can adjust the pumping intensity according to process requirements.

[0045] S5. Temperature-controlled curing closed-loop control: The control module 16 reads the feedback signal from the temperature sensor 13 and performs closed-loop adjustment on the heating resistor 12, and performs curing control according to the set temperature curve until the expansion resin is cured and formed.

[0046] S6. Pressure relief / backflushing demolding and cleaning maintenance are uniformly scheduled by the control module 16: After curing, the control module 16 controls the shutdown of the casting degassing vacuum pump 21 and the lower chamber adsorption vacuum pump 15, and controls the upper chamber positive pressure gas source 18 and the lower chamber backflushing gas source 14 to blow air to assist in demolding and sampling; at the same time, the control module 16 can control the lower chamber to perform short-term backflushing cleaning to remove dust or volatiles from the porous structure and improve the reliability of repeated use. If a small amount of resin accidentally seeps in, it will be collected and isolated by the seepage trap 8 and the resin collection chamber 11 to reduce the risk of damage to the gas source and vacuum pump.

[0047] The expanded edge sample obtained through the above steps forms cured epoxy insulating expanded edge wings on both sides, and the inner cavity retains an uncontaminated material segment as a pollution-free test area, which can be used with standard electrodes in air medium to carry out withstand voltage or breakdown tests, thereby avoiding the pollution effect of oil bath test on the dielectric properties of narrow band insulating material.

[0048] Through specific practical experiments, single-sided polyimide-reinforced mica tape with low adhesive powder, commonly used in variable frequency motor insulation systems, was selected as the narrow-strip insulation sample to be tested (model: DECJ1034, nominal thickness 0.14 mm, width 25 mm, insulation class H). The experimental equipment included the edge-expanding casting device described in this invention, a 50 kV power frequency high-voltage test transformer, a broadband dielectric spectrum analyzer, and a partial discharge detector. The experimental environment temperature was controlled at (23±2)℃, and the relative humidity at (50±5)%. In this embodiment, the start-up, shutdown, and output adjustment of each air pump / air source, as well as the temperature-controlled curing process, were all uniformly scheduled and controlled by the control module 16.

[0049] Four control groups were set up in the experiment: Control group A used the relevant electrode system of GB / T 1408.1, and selected Φ6 mm cylindrical electrodes to directly clamp the single-layer sample in air for withstand voltage test; Control group B immersed the single-layer sample in transformer oil for withstand voltage test; Control group C used a simple silicone frame mold to simulate manual atmospheric pressure expansion and casting sample preparation; The experimental group used the device of this invention for in-situ expansion and solidification sample preparation. The operating parameters were: opening the lower chamber adsorption vacuum (relative pressure about -80 kPa), opening the upper chamber positive pressure gas source to establish micro positive pressure (relative atmospheric pressure about +5 kPa, i.e. about 1.05 atm), and connecting the casting degassing vacuum pump through the exhaust port to implement the vacuum-assisted exhaust / degassing process.

[0050] In the power frequency withstand voltage and flashover characteristic tests (sample size N=10, voltage ramp rate 500 V / s), the performance of each group showed significant differences. Control group A, due to insufficient creepage distance (sample width 25 mm, creepage margin on both sides after clamping with Φ6 mm electrodes approximately (25-6) / 2=9.5 mm), experienced surface flashover when the voltage reached an average of 4.8 kV, failing to measure the material's true breakdown voltage and thus being deemed a test failure. Control group B effectively suppressed flashover in an oil bath environment, measuring an average breakdown voltage of 7.9 kV; however, the sample exhibited significant oil absorption and swelling after removal, and the interlayer bonding state deteriorated. In contrast, the experimental group using the device of this invention also successfully suppressed surface flashover, measuring an average breakdown voltage of 8.1 kV; simultaneously, its results showed lower dispersion, indicating that the device of this invention can achieve flashover prevention effects comparable to the oil bath method in air medium and stably obtain intrinsic breakdown performance data of the material.

[0051] In terms of anti-pollution performance verification, the change in dielectric loss factor tanδ (50Hz, 1 kV) in the central region of the sample before and after the withstand voltage test was measured, and the influence of different sample preparation / testing methods on the ability to maintain the uncontaminated test area was compared. In control group C, due to the lack of active adsorption and sealing mechanisms, the low-viscosity epoxy resin underwent significant interfacial leakage along the microscopic folds and gaps on the sample surface under gravity and capillary action. Experimental observation showed that resin creep traces appeared in the central test area of ​​approximately 40% of the samples, causing this area to no longer maintain a dry insulation state. This resulted in a significant increase in the dispersion of the tanδ data, with the tanδ of some contaminated samples deviating from the initial value by more than 50%, making it difficult to truly reflect the intrinsic properties of the material. Although control group B could suppress surface flashover, the tanδ in the central region of the sample increased from the initial 0.0065 to 0.0142 after oil immersion, a change rate as high as +118.5%, indicating that the insulating oil severely penetrated the microporous / interlayer structure of the low-resin mica tape and significantly altered its dielectric properties. In contrast, the experimental group (the present invention) benefited from the active gas-sealing barrier of the inner chamber and the blocking effect of negative pressure adsorption in the lower chamber on the micro-slit path. The central area of ​​all samples remained clean and dry with no visible leakage. The tanδ only increased slightly from the initial 0.0064 to 0.0065, and the rate of change was controlled at +1.6%. This verifies that the present invention can effectively maintain a pollution-free test area and maintain the intrinsic dielectric properties of the material in the dry state.

[0052] Regarding the verification of casting quality and partial discharge characteristics, the control group C sample exhibited micro-wrinkles at the edge region, and microscopic observation of the interface revealed bubble aggregation with a diameter of 0.1–0.3 mm. Its partial discharge initiation voltage (PDIV) was only 1.2 kV. The experimental group, benefiting from the vacuum-assisted degassing / debubbling and differential pressure bonding and flattening mechanism, had a smooth sample surface and dense interface, with no obvious bubble aggregation or interconnecting air gaps. Its PDIV increased to 2.8 kV, indicating that this invention can effectively reduce the interference of sample defects on subsequent high-frequency high-voltage / partial discharge tests, improving the reliability and repeatability of the test results.

[0053] Compared with existing technologies, the advantages of this invention in terms of differential pressure bonding active air sealing, liquid-repellent and breathable isolation, pressure limiting and venting, vacuum-assisted degassing, and closed-loop temperature control in the processes of bonding and sealing, casting and degassing, maintaining the pollution-free test area, and curing and molding include:

[0054] 1) Significantly improves the effectiveness of withstand voltage testing of narrow-band samples in air medium and suppresses test failures caused by surface flashover. Compared with the control group A, which experienced surface flashover at an average of 4.8 kV and could not obtain the true bulk breakdown voltage when directly clamped in air (creep margin of about 9.5 mm), this invention constructs a differential pressure bonding and active gas seal state with upper pressure and lower suction by adsorbing vacuum (-80 kPa) in the lower chamber and micro-positive pressure (about 1.05 atm) in the upper chamber. This allows the expanded sample to stably suppress flashover and obtain the true breakdown performance data of the material in air medium (average breakdown voltage of 8.1 kV in the experimental group).

[0055] 2) Achieving flashover prevention comparable to the oil bath method while maintaining performance measurability without introducing oil contamination. Control group B, using transformer oil bath, suppressed flashover and measured an average breakdown voltage of 7.9 kV, but experienced problems such as oil absorption swelling and interlayer bonding deterioration. The experimental group of this invention successfully suppressed flashover in air medium, achieving an average breakdown voltage of 8.1 kV, thus obtaining withstand voltage testing effectiveness comparable to or even better than the oil bath method while avoiding oil bath contamination.

[0056] 3) Significantly improves the ability to maintain the contamination-free test zone and preserves the intrinsic dielectric properties of the insulating tape in the dry state. This invention sets up a contamination-free test zone within the inner chamber and uses vacuum adsorption in the lower chamber to tightly adhere the sample to the porous adsorption panel, further isolated by a microporous fluoropolymer liquid-repellent and breathable membrane. This significantly weakens the resin seepage contamination path along the micro-slits. Simultaneously, the positive pressure in the upper chamber forms a pressure barrier to inhibit resin leakage from the outside inwards, and a pressure relief valve allows for controlled release of any potentially leaking positive pressure gas to prevent gas from entering the casting tank and forming an air gap. Compared to the control group B oil bath, which caused a significant drift in the tanδ (50 Hz, 1 kV) of the sample's central region from 0.0065 to 0.0142 (a change rate of +118.5%), the experimental group of this invention only slightly increased the tanδ from 0.0064 to 0.0065 (a change rate of +1.6%), demonstrating that this invention can effectively maintain the intrinsic dielectric properties of the material in the dry state and avoid test deviations caused by dielectric contamination.

[0057] 4) Improve casting quality and significantly enhance partial discharge performance, reducing the interference of sample preparation defects on high-frequency high-voltage testing. Compared to the control group C, which suffered from edge micro-wrinkles, 0.1–0.3 mm bubble aggregation at the interface, and a PDIV of only 1.2 kV due to manual atmospheric pressure edge expansion casting, this invention utilizes a vacuum-assisted degassing process connected to a casting degassing vacuum pump via an exhaust port, combined with a differential pressure bonding and flattening mechanism. This results in a smooth sample surface, dense interface, and significantly reduced defects, increasing the PDIV to 2.8 kV. Consequently, it improves sample quality consistency and the reliability of subsequent withstand voltage tests.

[0058] 5) Improve the controllability and repeatability of the process. This invention uses a temperature closed-loop control unit to perform PID adjustment on the heating resistance element based on temperature sensor feedback, achieving precise tracking of the curing temperature curve; at the same time, the control module uniformly schedules the upper chamber positive pressure gas source, the lower chamber adsorption vacuum pump, the lower chamber backflushing gas source, and the casting degassing vacuum pump, realizing the linkage switching of bonding / casting / degassing / curing / demolding / cleaning conditions, thereby reducing fluctuations caused by human operation and improving sample preparation repeatability.

[0059] 6) Improved system reliability and ease of maintenance. This invention incorporates an overflow adhesive trapping buffer between the exhaust port and the vacuum pump to prevent overflow adhesive / droplets from being drawn into the vacuum pump and causing damage. Backflushing in the lower chamber enables the cleaning and maintenance of the porous adsorption panel, improving the long-term stable operation and reusability of the device.

[0060] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. A widening casting device for narrow-band high-voltage insulation testing of variable frequency motors, characterized in that, include: The upper and lower plates are arranged opposite each other, and the insulating narrow strip sample is located in them. The upper plate above the insulating narrow strip sample is equipped with an upper cavity positive pressure air curtain barrier component, and the lower plate below the insulating narrow strip sample is equipped with a lower cavity vacuum adsorption and anti-clogging maintenance component and a temperature control curing component. The casting venting and degassing component, the lower cavity vacuum adsorption and anti-clogging maintenance component, and the temperature control curing component are respectively connected to the control module. The upper plate is connected to the casting source through the epoxy injection port and to the casting venting and degassing component through the vent.

2. The expansion casting device for narrow-band high-voltage insulation testing of variable frequency motors according to claim 1, characterized in that, The upper and lower plates are equipped with tensioning and stretching adjustment mechanisms at their ends, which are used to clamp the sample to be widened and apply axial pretension to keep the sample straight throughout the entire process of pouring, pumping, and curing, avoiding sealing failure and contamination path formation caused by wrinkles, offsets, or local warping, and improving the geometric consistency of the expansion wing.

3. The expansion casting device for narrow-band high-voltage insulation testing of variable frequency motors according to claim 1, characterized in that, A high-temperature resistant outer sealing silicone rubber strip, a high-temperature resistant inner primary sealing silicone rubber strip, and a high-temperature resistant inner secondary sealing silicone rubber strip are respectively provided between the upper and lower plates, between the upper plate and the insulating narrow strip sample, and between the lower plate and the insulating narrow strip sample. The cavity formed between the upper and lower plates, the high-temperature resistant outer sealing silicone rubber strip, and the high-temperature resistant inner primary sealing silicone rubber strip is the casting groove.

4. The expansion casting device for narrow-band high-voltage testing of insulation in variable frequency motors according to claim 1, characterized in that, The lower chamber vacuum adsorption and anti-clogging maintenance component includes: a microporous fluoropolymer liquid-repellent and breathable membrane located sequentially below the insulating narrow strip sample, a replaceable porous vacuum adsorption panel and a resin trapping chamber, and a lower chamber adsorption vacuum pump and a lower chamber backflushing gas source connected to them respectively. The lower chamber adsorption vacuum pump and the lower chamber backflushing gas source used for vacuum adsorption bonding of the sample are respectively connected to the temperature control curing component and the centralized control unit. The replaceable porous vacuum adsorption panel and the resin trapping chamber are fixedly installed by a metal base that serves as a structural support and mounting base. The replaceable porous vacuum adsorption panel provides a uniform adsorption surface and establishes negative pressure adsorption force under the action of the lower chamber adsorption vacuum pump; The microporous fluoropolymer liquid-repellent and breathable membrane is used to filter out a small amount of epoxy resin that accidentally seeps into the porous structure during the casting process and causes blockage.

5. The expansion casting device for narrow-band high-voltage insulation testing of variable frequency motors according to claim 1, characterized in that, The area between the high-temperature resistant primary sealing silicone rubber strip and the high-temperature resistant secondary sealing silicone rubber strip on the lower plate is further provided with a seepage trap. The inner cavity area defined by the seepage trap and the high-temperature resistant primary sealing silicone rubber strip and the high-temperature resistant secondary sealing silicone rubber strip is preferably used as the inner cavity of the pollution-free test area. When a very small amount of resin accidentally seeps into the lower area, it will preferentially enter the seepage trap and settle and collect at the resin collection cavity, thereby reducing the risk of resin entering the lower cavity backflushing gas source or the lower cavity adsorption vacuum pump, and realizing secondary protection of the lower cavity gas path.

6. The expansion casting device for narrow-band high-voltage testing of insulation in variable frequency motors according to claim 1, characterized in that, The upper cavity positive pressure air curtain barrier assembly includes: an upper plate positive pressure vent array disposed in an upper plate located above the insulating narrow strip sample and an upper cavity positive pressure gas source connected thereto.

7. The expansion casting device for narrow-band high-voltage insulation testing of variable frequency motors according to claim 1, characterized in that, The casting venting and degassing assembly includes: an overflow trap buffer tank connected to the vent and a casting degassing vacuum pump, used to discharge gas in the casting tank and promote degassing during the casting process.

8. The expansion casting device for narrow-band high-voltage insulation testing of variable frequency motors according to claim 1, characterized in that, The temperature-controlled curing component and centralized control unit include: a heating resistor and a temperature sensor arranged sequentially in the lower plate to provide heat for resin curing; wherein: the control module is connected to the heating resistor and the temperature sensor respectively to output heating signals and collect temperature signals, thereby realizing closed-loop regulation of the heating resistor, ensuring that the curing temperature is stable within the set range, improving curing quality and reducing the risk of defects caused by temperature fluctuations.

9. The expansion casting device for narrow-band high-voltage testing of insulation in variable frequency motors according to claim 1, characterized in that, The control module includes: a temperature closed-loop control unit, a pneumatic push-pull adsorption unit, a vacuum-assisted casting unit, and a pneumatic demolding and maintenance unit. Specifically: the temperature closed-loop control unit performs PID closed-loop calculations and power regulation based on real-time temperature feedback information collected by temperature sensors and preset curing process temperature curves, generating control commands which are then output to the heating resistance element for precise temperature control of in-situ curing. The pneumatic push-pull adsorption unit performs coordinated scheduling of the upper and lower chamber gas paths based on sample loading and bonding instructions, generating control commands which are then output to the lower chamber adsorption vacuum pump to establish negative pressure and to the upper chamber positive pressure gas source to establish a preset positive pressure or adjustable positive pressure. As a result, a differential pressure bonding and active air-sealing state with upper pressure and lower suction is constructed; the vacuum-assisted casting unit performs negative pressure extraction logic processing and generates control commands based on the casting process start information, and outputs them to the casting degassing vacuum pump to adjust its pumping rate or vacuum degree / pumping speed, so as to realize mold cavity degassing and bubble removal; the pneumatic demolding and maintenance unit performs gas path logic switching and reverse purging processing based on the curing completion signal or cleaning and maintenance command information, and generates control commands and outputs them to the lower chamber adsorption vacuum pump and / or casting degassing vacuum pump, generates control commands and outputs them to the lower chamber backflushing gas source, and adjusts the upper chamber positive pressure gas source to realize pneumatic non-destructive demolding of the sample and / or purging and cleaning maintenance of the replaceable porous vacuum adsorption panel.

10. A method for expanding the edge of a casting vessel based on the apparatus described in any one of claims 1-9, characterized in that, include: S1. Sample laying and tensioning positioning: Lay the sample to be widened flat on the microporous fluoropolymer liquid-repellent and breathable membrane, so that it corresponds to the replaceable porous vacuum adsorption panel; apply axial pretension to the sample through the tensioning and stretching adjustment mechanism to make the sample flat and wrinkle-free. S2. The differential pressure bonding and contamination-free test zone protection are uniformly scheduled by the control module: The control module controls the start of the lower chamber adsorption vacuum pump to establish negative pressure adsorption on the adsorption panel and tightly adhere the sample to the adsorption / sealing interface, reducing the risk of resin seeping into the contamination-free test zone of the inner chamber along the micro-slits; at the same time, the control module controls the start of the upper chamber positive pressure gas source, supplying gas to the upper chamber through the upper plate positive pressure vent array and maintaining positive pressure, forming a differential pressure bonding state with positive pressure on the upper side and negative pressure on the lower side; if necessary, the control module adjusts the suction / gas supply intensity to stabilize the bonding state. S3. Mold Closure and Sealing Compaction: Close the upper and lower molds to press and seal the sample and mold cavity with the high-temperature resistant inner primary sealing silicone rubber strip, the high-temperature resistant inner secondary sealing silicone rubber strip, and the high-temperature resistant outer sealing silicone rubber strip; the pressure relief valve is in a release state to controllably release any micro-leakage positive pressure gas that may occur in the upper cavity. S4. Casting and degassing are uniformly scheduled by the control module: The prepared epoxy resin is injected into the casting tank through the epoxy injection port; during the casting process, the control module controls the start of the casting degassing vacuum pump, so that the exhaust port is pumped out through the overflow trap buffer tank to remove air from the casting tank and promote degassing, reducing resin bubble / air gap defects; the overflow trap buffer tank is used to capture overflow and droplets to protect the vacuum pump, and the control module can adjust the pumping intensity according to process requirements. S5. Temperature-controlled curing closed-loop control: The control module reads the feedback signal from the temperature sensor and performs closed-loop adjustment of the heating resistor, and performs curing control according to the set temperature curve until the expanded resin is cured and formed. S6. Pressure relief / backflushing demolding and cleaning maintenance are uniformly scheduled by the control module: After curing, the control module controls the shutdown of the casting degassing vacuum pump and the lower chamber adsorption vacuum pump, and controls the upper chamber positive pressure gas source and the lower chamber backflushing gas source to blow air to assist in demolding and sampling; at the same time, the control module can control the lower chamber to perform short-term backflushing cleaning to remove dust or volatiles in the porous structure, improve the reliability of repeated use. If a small amount of resin accidentally seeps in, it will be collected and isolated by the seepage trap and resin collection chamber to reduce the risk of damage to the gas source and vacuum pump.

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