A method for preparing a high-breakdown-voltage enameled wire

Abstract

This invention relates to the field of enameled wire manufacturing technology, and in particular to a method for preparing high breakdown voltage enameled wire. Isophorone diisocyanate trimer and 1,1,2,2-tetrahydroperfluoro-1-decyl alcohol are added to a reaction vessel in an equimolar ratio. Xylene is used as a solvent, and a catalyst is added to obtain a monoisocyanate-terminated isocyanate trimer solution. Isophorone diisocyanate is added to the isocyanate trimer solution, and perfluoropolyether diol is added dropwise to obtain a branched fluorinated polyurethane resin solution. The branched fluorinated polyurethane resin solution is mixed with a xylene-cresol mixed solvent to prepare an enameled wire topcoat. A coating and curing process is used to obtain the finished product. By utilizing precisely controlled end-capping reactions, it is beneficial to reduce group defects during the reaction process, thereby synthesizing a branched fluorinated polyurethane resin with a regular molecular structure and uniformly grafted fluorinated side chains. Furthermore, the synergistically optimized coating and curing processes help improve the breakdown voltage performance of the coating film.

Description

Technical Field

[0001] This invention relates to the field of enameled wire manufacturing technology, and in particular to a method for preparing high breakdown voltage enameled wire. Background Technology

[0002] As the core insulating conductor of electrical equipment such as motors and transformers, the insulation performance of enameled wire directly determines the operational stability and service life of electrical equipment. Among them, breakdown voltage is the core indicator for measuring the insulation performance of enameled wire.

[0003] With the rapid development of new energy vehicles, high-voltage electrical equipment and other fields towards high power and high voltage, higher requirements have been placed on the breakdown voltage of enameled wires. In particular, under 800V high-voltage platforms and high-frequency pulse conditions, conventional enameled wires can no longer meet the usage requirements.

[0004] Currently, the core technological bottleneck of conventional polyurethane enameled wires on the market is insufficient breakdown voltage, mainly due to deficiencies in their manufacturing process: the insulating varnish film uses ordinary polyurethane resin as the main film-forming material, and the resin molecular structure lacks functional groups that can significantly improve insulation performance. Furthermore, unreacted monomers and small molecule impurities are easily left behind during the resin polymerization process, resulting in insufficient film density and the presence of minor internal defects. In addition, the uneven dispersion of resin and unreasonable curing process during conventional topcoat application further exacerbate the problem of weak film insulation, ultimately leading to a generally low breakdown field strength in conventional enameled wires, making them unsuitable for high-voltage operating conditions.

[0005] Therefore, it is urgent for technical personnel to solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing high breakdown voltage enameled wire, which aims to solve the problems of insufficient breakdown voltage, poor enamel film density, easy insulation defects, and inability to adapt to high voltage conditions in existing designs.

[0007] This invention relates to a method for preparing high breakdown voltage enameled wire, comprising the following steps: S1. Isophorone diisocyanate trimer and 1,1,2,2-tetrahydroperfluorodecyl alcohol are added to a reaction vessel in an equimolar ratio. Xylene is used as a solvent, and 0.1% to 0.3% of dibutyltin dilaurate catalyst is added. The reaction is carried out under nitrogen protection and constant temperature of 70℃ to 90℃ for 2 to 4 hours to obtain a monoisocyanate-terminated isocyanate trimer solution. S2. Add isophorone diisocyanate to the isocyanate trimer solution, stir evenly, and then add perfluoropolyether diol dropwise. Continue the reaction at 70℃~90℃. Use di-n-butylamine titration to monitor the isocyanate group content in the system until the isocyanate groups are completely consumed and the theoretical reaction endpoint is reached to obtain a branched fluorinated polyurethane resin liquid. S3. Mix the branched fluorinated polyurethane resin liquid with xylene-cresol mixed solvent, and ultrasonically disperse for 20 min to 40 min to prepare the enameled wire topcoat liquid. S4. Using copper wire as a conductor, perform wire laying and annealing processes in sequence; S5. The annealed conductor is cured by a two-coating process of primer and topcoat. The primer is an industrial-grade polyurethane primer, and the topcoat is the enameled wire topcoat liquid prepared in step S3. The conductor is cured by high-temperature baking in an oven, and the total thickness of the coating film is controlled to be 0.025mm to 0.035mm. The high breakdown voltage enameled wire is obtained by winding the wire.

[0008] As a further improvement to the technical solution disclosed in this invention, after the end-capping reaction in S1 is completed, the reaction system is purified by vacuum distillation. The distillation temperature is controlled at 80℃~90℃, the vacuum degree is not greater than 0.08MPa, and the distillation time is 1h~2h. The content of free isocyanate monomer in the purified monoisocyanate-terminated product is not higher than 0.5wt%, and the monoisocyanate-termination rate is not lower than 98%.

[0009] As a further improvement to the technical solution disclosed in this invention, the number average molecular weight of the perfluoropolyether diol in S2 is 800-1000, and the terminal hydroxyl functionality is not less than 98%. It adopts a two-stage dropping rate control, with a rapid initial dropping rate of 1.0 mL / min to 1.5 mL / min and a slow dropping rate of 0.3 mL / min to 0.8 mL / min in the initial stage and a slow dropping rate in the later stage. The total dropping time is controlled to be 1.5 h to 2.5 h, and the stirring rate of the system is maintained at 300 r / min to 500 r / min during the dropping process.

[0010] As a further improvement to the technical solution disclosed in this invention, 0.05% to 0.2% of a hindered phenolic heat stabilizer is added in S2 while the perfluoropolyether diol is added dropwise; the hindered phenolic heat stabilizer is 2,6-di-tert-butyl-p-cresol.

[0011] As a further improvement to the technical solution disclosed in this invention, the mass ratio of xylene-cresol mixed solvent in S3 is 1:1 to 1:2, the ultrasonic dispersion power is 200W to 400W, and the ultrasonic dispersion temperature is controlled at 25℃ to 35℃; the solid content of the enameled wire surface coating is controlled at 14% to 16%, and the viscosity is 20s to 30s.

[0012] As a further improvement to the technical solution disclosed in this invention, the curing oven in S5 adopts a three-stage stepped heating method: the first stage temperature is 80℃~120℃, and the holding time is 5min~8min; the second stage temperature is 180℃~220℃, and the holding time is 4min~6min; the third stage temperature is 280℃~320℃, and the holding time is 3min~5min.

[0013] As a further improvement to the technical solution disclosed in this invention, after the primer coating is completed and the surface is dry, the conductor surface is subjected to corona activation treatment. The corona treatment intensity is controlled at 10 N·min to 30 N·min, the treatment time is 10 s to 20 s, and the wetting angle of the conductor surface after treatment is not greater than 30°. Then, the topcoat is applied, and the topcoat thickness is 0.015 mm to 0.025 mm.

[0014] As a further improvement to the technical solution disclosed in this invention, the finished enameled wire is equipped with an online laser thickness measurement and high-frequency breakdown continuous detection device. The laser thickness measurement accuracy is ±0.001mm, and the coating thickness deviation is controlled within ±3%. The high-frequency breakdown detection voltage is 20kV~30kV, the detection frequency is 50Hz~60Hz, and the breakdown field strength is not less than 18kV / mm.

[0015] In practical applications, the high breakdown voltage enameled wire preparation method disclosed in this invention can achieve at least the following beneficial technical effects, specifically: Each step works in a synergistic manner. In step S1, through the equimolar ratio of isophorone diisocyanate trimer and 1,1,2,2-tetrahydroperfluoro-1-decyl alcohol, under the catalysis of dibutyltin dilaurate and nitrogen protection, the isocyanate groups are efficiently capped, forming a structurally regular monoisocyanate-capped product, reducing group defects from the source and providing stable active sites for subsequent resin branch growth; in step S2, through the controllable dropping rate of the perfluoropolyether diol and the di-n-butylamine titration... The endpoint monitoring of the process ensures complete reaction of the isocyanate groups, promoting the uniform grafting of fluorinated side chains onto the polyurethane backbone to construct a branched molecular structure. The low dielectric properties of fluorine enhance the resin's insulating properties. S3 to S5 work in tandem. The ultrasonic dispersion in S3 ensures that the branched fluorinated polyurethane resin is uniformly dispersed in the mixed solvent, avoiding film defects caused by resin agglomeration. The conductor annealing treatment in S4 enhances surface activity. The primer-topcoat double-layer coating and high-temperature curing in S5 form a dense cross-linked insulating film. The hydrophobic properties of fluorine and the dense film structure work together to block charge migration, achieving high breakdown characteristics for the product. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is an infrared (IR) spectrum analysis diagram of the branched fluorinated polyurethane resin disclosed in this invention. Detailed Implementation

[0018] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. By synthesizing branched fluorinated polyurethane resin, applying a double-layer primer and topcoat, and implementing a three-stage stepped curing process, the enameled wire achieves a denser coating, a breakdown field strength ≥18kV / mm, and adaptability to high-voltage operating conditions. Specific embodiments are as follows: The enameled wire coating liquid used in this invention uses branched fluorinated polyurethane resin as the main film-forming substance. The branched fluorinated polyurethane resin is prepared by isophorone diisocyanate trimer, 1,1,2,2 tetrahydroperfluorodecyl alcohol, isophorone diisocyanate and perfluoropolyether diol through end-capping reaction and chain extension branching reaction.

[0019] The perfluoropolyether diol has a number-average molecular weight of 800-1000 and a terminal hydroxyl functionality of not less than 98%; the reaction catalyst is dibutyltin dilaurate, and the amount added is 0.1%-0.3% of the total mass of the reaction system; the reaction heat stabilizer is 2,6-di-tert-butyl-p-cresol, and the amount added is 0.05%-0.2% of the total mass of the reaction system.

[0020] Detailed preparation steps for the synthesis of branched fluorinated polyurethane resins: 1) Weigh isophorone diisocyanate trimer and 1,1,2,2 tetrahydroperfluorodecyl alcohol in equimolar ratio and add them together to a reaction vessel. Use xylene as the reaction solvent and add 0.1% to 0.3% of dibutyltin dilaurate catalyst according to the total mass of the reaction system. Stir the reaction under nitrogen protection and constant temperature of 70℃ to 90℃ for 2h to 4h to obtain a monoisocyanate-terminated isocyanate trimer solution. 2) The isocyanate trimer solution with monoisocyanate groups capped was purified by vacuum distillation. The distillation temperature was controlled at 80℃~90℃, the vacuum degree was not greater than 0.08MPa, and the distillation time was 1h~2h. The content of free isocyanate monomer in the purified product was not higher than 0.5wt%, and the monoisocyanate group capping rate was not less than 98%. 3) Add isophorone diisocyanate to the purified monoisocyanate-terminated product solution, stir evenly, and then add perfluoropolyether diol dropwise in a two-stage manner. The initial drop rate is 1.0 mL / min to 1.5 mL / min, and the subsequent drop rate is 0.3 mL / min to 0.8 mL / min. The total drop time is controlled to be 1.5 h to 2.5 h. During the drop process, the system stirring speed is maintained at 300 r / min to 500 r / min. At the same time, add 0.05% to 0.2% of 2,6-di-tert-butyl-p-cresol heat stabilizer. 4) The system is kept at 70℃~90℃ for further reaction. The content of isocyanate groups in the system is monitored by di-n-butylamine titration until the isocyanate groups are completely consumed and the theoretical reaction endpoint is reached, thus obtaining a branched fluorinated polyurethane resin liquid.

[0021] Preparation method of enameled wire topcoat: A branched fluorinated polyurethane resin liquid was mixed with xylene-cresol mixed solvent in a mass ratio of 1:1 to 1:2 and ultrasonically dispersed for 20 to 40 minutes under ultrasonic dispersion power of 200W to 400W and dispersion temperature of 25℃ to 35℃ to prepare a topcoat liquid for enameled wire with a solid content of 14% to 16% and a viscosity of 20s to 30s.

[0022] High breakdown voltage enameled wire manufacturing process Example 1 S1. Isophorone diisocyanate trimer and 1,1,2,2 tetrahydroperfluorodecyl alcohol were added to a reaction vessel in an equimolar ratio. Xylene was used as a solvent, and 0.2% of dibutyltin dilaurate catalyst was added. The reaction was carried out under nitrogen protection and constant temperature of 80°C for 3 hours to obtain a monoisocyanate-terminated isocyanate trimer solution. S2. The isocyanate trimer solution with monoisocyanate groups was distilled under reduced pressure at 85°C and 0.07 MPa for 1.5 h. After purification, the free isocyanate monomer content was 0.4 wt% and the monoisocyanate group end-capping rate was 98.5%. Isophorone diisocyanate was added to the purified solution, and perfluoropolyether diol was added dropwise in two stages for a total dropwise time of 2 h. The system was stirred at 400 r / min and kept at 80°C until the isocyanate groups were completely consumed to obtain a branched fluorinated polyurethane resin liquid. S3. Mix the branched fluorinated polyurethane resin liquid with xylene-cresol mixed solvent at a mass ratio of 1:1.5, and ultrasonically disperse it for 30 minutes at 300W and 30℃ to prepare the enameled wire topcoat liquid. S4. Using pure copper wire as the conductor, perform wire laying and annealing processes in sequence; S5. Coat the annealed copper wire conductor with industrial-grade polyurethane primer. After the primer is surface dry, perform corona activation treatment with a corona treatment intensity of 15 N·min and a treatment time of 15 s, resulting in a conductor surface wetting angle of 26°. Then, apply the above-mentioned enameled wire topcoat and cure it using a three-stage stepped temperature increase: the first stage temperature is 100℃ and the holding time is 6 min; the second stage temperature is 200℃ and the holding time is 5 min; and the third stage temperature is 300℃ and the holding time is 4 min. Control the total coating thickness to be 0.030 mm and the topcoat coating thickness to be 0.020 mm. S6. After passing the online laser thickness gauge test and the 25kV, 50Hz high-frequency breakdown continuous test, the high breakdown voltage enameled wire is obtained by winding.

[0023] Example 2 S1. Isophorone diisocyanate trimer and 1,1,2,2 tetrahydroperfluorodecyl alcohol were added to a reaction vessel in an equimolar ratio. Xylene was used as a solvent, and 0.15% of dibutyltin dilaurate catalyst was added. The reaction was carried out under nitrogen protection and constant temperature of 75°C for 3.5 h to obtain a monoisocyanate-terminated isocyanate trimer solution. S2. The isocyanate trimer solution with monoisocyanate groups was distilled under reduced pressure at 82℃ and 0.075MPa for 1.8h, and the monoisocyanate group end-capping rate was 98.2% after purification. Isophorone diisocyanate and 0.1% of 2,6-di-tert-butyl-p-cresol heat stabilizer were added to the purified solution. The perfluoropolyether diol was added dropwise in two stages for a total dropwise time of 2.2h. The system was stirred at 350r / min and kept at 75℃ until the isocyanate groups were completely consumed to obtain a branched fluorinated polyurethane resin liquid. S3. Mix the branched fluorinated polyurethane resin liquid with xylene-cresol mixed solvent in a mass ratio of 1:1, and ultrasonically disperse it for 35 minutes at 250W and 28℃ to prepare the enameled wire topcoat liquid. S4. Using pure copper wire as the conductor, perform wire laying and annealing processes in sequence; S5. Coat the annealed copper wire conductor with industrial-grade polyurethane primer. After the primer is surface dry, perform corona activation treatment with a corona treatment intensity of 20 N·min and a treatment time of 12 s, resulting in a conductor surface wetting angle of 24°. Then, apply the above-mentioned enameled wire topcoat and cure it using a three-stage stepped temperature increase: the first stage temperature is 90℃ and the holding time is 7 min; the second stage temperature is 190℃ and the holding time is 5.5 min; and the third stage temperature is 290℃ and the holding time is 4.5 min. Control the total coating thickness to 0.032 mm and the topcoat coating thickness to 0.022 mm. S6. After passing the online laser thickness gauge test and the 28kV, 50Hz high-frequency breakdown continuous test, the high breakdown voltage enameled wire is obtained by winding.

[0024] Example 3 S1. Isophorone diisocyanate trimer and 1,1,2,2 tetrahydroperfluorodecyl alcohol were added to a reaction vessel in an equimolar ratio. Xylene was used as a solvent, and 0.25% of dibutyltin dilaurate catalyst was added. The reaction was carried out under nitrogen protection and constant temperature of 85°C for 2.5 h to obtain a monoisocyanate-terminated isocyanate trimer solution. S2. The isocyanate trimer solution with monoisocyanate groups capped was distilled under reduced pressure at 88℃ and 0.065MPa for 1.2h, and the monoisocyanate group capping rate was 98.8% after purification. Isophorone diisocyanate was added to the purified solution, and perfluoropolyether diol was added dropwise in two stages for a total dropwise time of 1.8h. The system was stirred at 450r / min and kept at 85℃ until the isocyanate groups were completely consumed to obtain a branched fluorinated polyurethane resin liquid. S3. Mix the branched fluorinated polyurethane resin liquid with xylene-cresol mixed solvent at a mass ratio of 1:2, and ultrasonically disperse it for 25 minutes at 350W and 32℃ to prepare the enameled wire topcoat liquid. S4. Using pure copper wire as the conductor, perform wire laying and annealing processes in sequence; S5. Coat the annealed copper wire conductor with industrial-grade polyurethane primer. After the primer is surface dry, perform corona activation treatment with a corona treatment intensity of 25 N·min and a treatment time of 18 s, resulting in a conductor surface wetting angle of 22°. Then, apply the above-mentioned enameled wire topcoat and cure it using a three-stage stepped temperature increase: the first stage temperature is 110℃ and the holding time is 5.5 min; the second stage temperature is 210℃ and the holding time is 4.5 min; and the third stage temperature is 310℃ and the holding time is 3.5 min. Control the total coating thickness to 0.028 mm and the topcoat coating thickness to 0.018 mm. S6. After passing the online laser thickness gauge test and the 23kV, 60Hz high-frequency breakdown continuous test, the high breakdown voltage enameled wire is obtained by winding.

[0025] Comparative Example S1. Conventional industrial-grade polyurethane resin is used, and conventional enameled wire topcoat liquid is prepared by stirring and dissolving it with conventional mixed solvents. S2. Using pure copper wire as the conductor, the wire laying and annealing processes are carried out in sequence. S3. Apply a conventional one-time coating process of primer and topcoat to the annealed copper wire conductor. S4. Curing is carried out using constant temperature baking; S5, retract the line.

[0026] Figure 1 The infrared spectrum (IR) analysis of the branched fluorinated polyurethane resin disclosed in this invention is shown. It can be seen that the pure polyurethane resin (curve a) has an infrared spectrum (IR) of 3325 cm⁻¹. -1 There is a distinct absorption peak of amino stretching vibration at 1703 cm⁻¹. -1 There is an absorption peak for carbonyl stretching vibration at 1538 cm⁻¹. -1 1462cm -1 There are absorption peaks for amino bending and carbon-nitrogen stretching vibrations at 1108 cm⁻¹. -1An absorption peak for ether bond stretching vibration is present at the location, and the above absorption peaks are typical characteristic absorption peaks of polyurethane resins. The branched fluorinated polyurethane resins prepared in Examples 1, 2, and 3 of this invention (curves b, c, and d) completely retain the characteristic absorption peaks of the polyurethane main chain, indicating that the modification process did not damage the polyurethane resin matrix structure; and the branched fluorinated polyurethane resin at 1205 cm⁻¹ exhibits an absorption peak for ether bond stretching vibration. -1 A distinct carbon-fluorine bond stretching vibration characteristic absorption peak appears at 3325 cm⁻¹, and the intensity of the absorption peak gradually increases with the increase of the amount of fluorine-containing component grafted, reaching 3325 cm⁻¹. -1 The significantly weakened intensity of the amino absorption peak indicates that the isocyanate group reaction was complete, the fluorinated group was successfully grafted onto the polyurethane molecular chain, and the synthesis of branched fluorinated polyurethane resin was effective.

[0027] Furthermore, the insulation performance of the enameled wires obtained in Examples 1-3 and the comparative example was tested, and the test results are shown in the table below: Test results show that the high breakdown voltage enameled wire preparation method adopted in Examples 1-3 of this invention, through the synergistic effect of branched fluorinated polyurethane resin synthesis, corona activation interface treatment, and three-stage stepped temperature curing, achieves a breakdown field strength significantly higher than that of conventional enameled wire preparation processes, stably reaching over 18kV / mm. The enameled wire exhibits good uniformity, small thickness deviation, strong interfacial adhesion, and excellent film density, meeting the requirements for use under 800V high-voltage platforms and high-frequency pulse conditions, with a 100% high-frequency breakdown pass rate. Among these, Example 2 demonstrates the best overall performance in terms of breakdown field strength, enameled wire uniformity, conductor surface wetting effect, and enameled wire density.

[0028] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing high breakdown voltage enameled wire, characterized in that, Includes the following steps: S1. Isophorone diisocyanate trimer and 1,1,2,2-tetrahydroperfluorodecyl alcohol are added to a reaction vessel in an equimolar ratio. Xylene is used as a solvent, and 0.1% to 0.3% of dibutyltin dilaurate catalyst is added. The reaction is carried out under nitrogen protection and constant temperature of 70℃ to 90℃ for 2 to 4 hours to obtain a monoisocyanate-terminated isocyanate trimer solution. S2. Add isophorone diisocyanate to the isocyanate trimer solution, stir evenly, then add perfluoropolyether diol dropwise, and continue the reaction at 70℃~90℃. Monitor the isocyanate group content in the system by di-n-butylamine titration until the isocyanate groups are completely consumed and the theoretical reaction endpoint is reached to obtain a branched fluorinated polyurethane resin liquid. S3. Stir and mix the branched fluorinated polyurethane resin liquid with xylene-cresol mixed solvent, and ultrasonically disperse for 20 min to 40 min to prepare enameled wire topcoat liquid; S4. Using copper wire as a conductor, perform wire laying and annealing processes in sequence; S5. The annealed conductor is cured by a two-coating process of primer and topcoat. The primer is an industrial-grade polyurethane primer, and the topcoat is the enameled wire topcoat liquid prepared in step S3. The conductor is cured by high-temperature baking in an oven, and the total thickness of the coating film is controlled to be 0.025mm to 0.035mm. The high breakdown voltage enameled wire is obtained by winding the wire.

2. The method for preparing high breakdown voltage enameled wire according to claim 1, characterized in that, After the end-capping reaction in S1 is completed, the reaction system is purified by vacuum distillation. The distillation temperature is controlled at 80℃~90℃, the vacuum degree is not greater than 0.08MPa, and the distillation time is 1h~2h. The content of free isocyanate monomer in the purified monoisocyanate-capped product is not higher than 0.5wt%, and the monoisocyanate-capping rate is not less than 98%.

3. The method for preparing high breakdown voltage enameled wire according to claim 1, characterized in that, The perfluoropolyether diol described in S2 has a number average molecular weight of 800-1000 and a terminal hydroxyl functionality of not less than 98%. It adopts a two-stage dropping rate control, with a rapid initial dropping rate of 1.0 mL / min to 1.5 mL / min and a slow dropping rate of 0.3 mL / min to 0.8 mL / min in the later stage. The total dropping time is controlled to be 1.5 h to 2.5 h, and the stirring rate of the system is maintained at 300 r / min to 500 r / min during the dropping process.

4. The method for preparing high breakdown voltage enameled wire according to claim 3, characterized in that, In S2, 0.05% to 0.2% of a hindered phenolic heat stabilizer is added simultaneously with the addition of the perfluoropolyether diol; the hindered phenolic heat stabilizer is 2,6-di-tert-butyl-p-cresol.

5. The method for preparing high breakdown voltage enameled wire according to claim 1, characterized in that, The mass ratio of the xylene-cresol mixed solvent in S3 is 1:1 to 1:2, the ultrasonic dispersion power is 200W to 400W, and the ultrasonic dispersion temperature is controlled at 25℃ to 35℃; the solid content of the enameled wire surface coating is controlled at 14% to 16%, and the viscosity is 20s to 30s.

6. The method for preparing high breakdown voltage enameled wire according to claim 1, characterized in that, The S5 oven curing process uses a three-stage stepped heating method: the first stage temperature is 80℃~120℃, and the holding time is 5min~8min; the second stage temperature is 180℃~220℃, and the holding time is 4min~6min; the third stage temperature is 280℃~320℃, and the holding time is 3min~5min.

7. The method for preparing high breakdown voltage enameled wire according to claim 6, characterized in that, After the primer is applied and the surface is dry, the conductor surface is subjected to corona activation treatment. The corona treatment intensity is controlled at 10 N·min to 30 N·min, and the treatment time is 10 s to 20 s. After treatment, the wetting angle of the conductor surface is not greater than 30°. Then, the topcoat is applied with a thickness of 0.015 mm to 0.025 mm.

8. The method for preparing high breakdown voltage enameled wire according to claim 1, characterized in that, The finished enameled wire is equipped with an online laser thickness measurement and high-frequency breakdown continuous detection device. The laser thickness measurement accuracy is ±0.001mm, and the coating thickness deviation is controlled within ±3%. The high-frequency breakdown detection voltage is 20kV~30kV, the detection frequency is 50Hz~60Hz, and the breakdown field strength is not less than 18kV / mm.

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