Mutual impregnation process method of insulating paint and application thereof

Abstract

The invention relates to a mutual impregnation process method of insulating paint and application of the mutual impregnation process method. The mutual impregnation process method comprises the following steps of: respectively impregnating the stator of the traction motor with insulating paint 1 and insulating paint 2 to finish mutual impregnation of the insulating paint; the insulating paint 1 comprises any one of polybutadiene paint, organic silicon paint or epoxy anhydride paint; and the insulating paint 2 comprises epoxy modified polyesterimide paint. The mutual impregnation process method of the insulating paint provided by the invention is simple to operate, the electrical performance, the moisture-proof sealing performance and the damp-heat aging resistance of the traction motor can be obviously improved through secondary impregnation of the specific high-performance insulating paint, the environmental adaptability is good, and the comprehensive performance is excellent.

Description

Technical Field

[0001] This invention relates to the field of insulating varnish technology, and in particular to a method for mutual impregnation of insulating varnishes and its application. Background Technology

[0002] The development of railway transportation towards high speed and heavy load places higher demands on the performance of locomotives, which are the core power equipment. The traction motor is a core component of the locomotive, and its safety and reliability are paramount. The insulation performance of the motor windings is a key factor determining the overall performance and lifespan of the traction motor, and the insulating varnish, as the core material of the winding insulation system, directly affects the insulation level of the motor.

[0003] Under harsh conditions of high speed and heavy load, traction motor windings are subjected to higher voltage stress, current load, and temperature rise. This poses a severe challenge to the overall performance of insulating varnish, especially its electrical insulation, heat resistance, mechanical strength, and adaptability to extreme environments (particularly moisture resistance and resistance to environmental corrosion).

[0004] Insulating varnish plays multiple key roles in traction motors: (1) Electrical insulation barrier: It forms a reliable insulation layer between windings and between windings and iron core, withstands thousands of volts of working voltage, prevents current leakage, insulation breakdown and grounding short circuit, and ensures safe operation. (2) Moisture-proof sealing protection: It fills the micropores and gaps of windings and insulation materials to form a dense protective layer, effectively isolates the intrusion of environmental moisture, rainwater and other substances, and maintains stable insulation resistance. Moisture intrusion is one of the main causes of insulation deterioration, increased leakage current and even failure. (3) Auxiliary heat dissipation: It has good thermal conductivity and efficiently conducts the heat generated by the windings to the motor casing, which is then dissipated by the heat dissipation device, reducing the temperature rise of the windings and ensuring the performance and life of the motor (the thermal conductivity of high-performance insulating varnish is much higher than that of air). (4) Enhanced mechanical strength: After curing, it forms a strong varnish film on the surface of the windings, bonds the wires into a whole, resists mechanical stress such as electromagnetic force and vibration, reduces wire wear and insulation layer damage, and improves mechanical reliability. (5) Resisting chemical corrosion: forming a protective layer to resist the erosion of oil, acid and alkali and other chemical substances, protecting the integrity of the winding and extending its service life.

[0005] However, existing mainstream insulating varnishes exhibit poor environmental adaptability and insufficient moisture-proof sealing performance when dealing with complex and humid environments (such as rainy and snowy weather, and car washing operations). They cannot effectively prevent moisture from penetrating the windings, leading to frequent degradation of the insulation performance and fault alarms in the traction motor, which has become a critical problem that urgently needs to be solved. Therefore, it is of great significance to provide a mutual impregnation process for insulating varnishes that can achieve excellent moisture and water penetration resistance. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for mutual impregnation of insulating varnishes and its application. The mutual impregnation process is simple to operate and, through secondary impregnation with a specific high-performance insulating varnish, can significantly improve the insulation performance of the traction motor, thereby giving it excellent moisture-proof sealing properties, good environmental adaptability, and superior overall performance.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for mutual impregnation of insulating varnishes, the method comprising the following steps:

[0009] After impregnating the stator of the traction motor with insulating varnish 1 and insulating varnish 2 respectively, the mutual impregnation of the insulating varnishes is completed.

[0010] The insulating varnish 1 includes any one of polybutadiene varnish, silicone varnish, or epoxy anhydride varnish.

[0011] The insulating varnish 2 includes epoxy-modified polyesterimide varnish.

[0012] The insulating varnish 1 (polybutadiene varnish, silicone varnish, or epoxy anhydride varnish) and insulating varnish 2 (epoxy-modified polyesterimide varnish) provided by this invention have good leveling properties and strong adhesion, and the two have good compatibility. By impregnating insulating varnish 1 and insulating varnish 2 twice, a composite insulation system with an extremely dense film structure and strong interfacial bonding is formed, thereby significantly improving the electrical performance of the traction motor. This results in a traction motor with high insulation resistance and low dielectric loss, as well as excellent moisture-proof sealing performance and resistance to damp heat aging, and good environmental adaptability. It effectively solves the core problem of insufficient moisture-proof sealing performance of existing insulating varnishes in rainy, snowy, and humid environments and locomotive washing operations, leading to decreased insulation resistance and frequent fault alarms. At the same time, it comprehensively improves the insulation reliability, environmental durability, and structural protection of the traction motor, combining excellent processability and high cost-effectiveness, providing crucial protection for the safe operation of high-speed heavy-duty locomotives.

[0013] It should be noted that the stator in this invention contains windings.

[0014] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The purpose and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0015] As a preferred technical solution of the present invention, the order of impregnating the insulating varnish 1 and the insulating varnish 2 is not important, including impregnating the insulating varnish 1 first and then impregnating the insulating varnish 2, or impregnating the insulating varnish 2 first and then impregnating the insulating varnish 1.

[0016] As a preferred embodiment of the present invention, the polybutadiene varnish in the insulating varnish 1 includes PB302.

[0017] As a preferred embodiment of the present invention, the silicone varnish in the insulating varnish 1 includes H62C.

[0018] As a preferred embodiment of the present invention, the epoxy anhydride varnish in the insulating varnish 1 includes JF9960.

[0019] As a preferred embodiment of the present invention, the epoxy-modified polyesterimide varnish in the insulating varnish 2 includes 116HU.

[0020] The 116HU in this invention has excellent film-forming density and interfacial bonding strength. When combined with insulating varnish 1, it can significantly improve the insulation performance and moisture-proof sealing performance of the traction motor.

[0021] Preferably, the impregnation method includes vacuum pressure impregnation.

[0022] As a preferred technical solution of the present invention, the vacuum degree of the vacuum pressure impregnation is ≤100 Pa, for example, it can be 10 Pa, 20 Pa, 30 Pa, 40 Pa, 50 Pa, 60 Pa, 70 Pa, 80 Pa, 90 Pa or 100 Pa, as well as specific point values ​​between the above point values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific point values ​​included in the range.

[0023] This invention optimizes the vacuum degree of vacuum pressure impregnation to better adapt it to the specific insulating varnishes (insulating varnish 1 and insulating varnish 2) in the mutual impregnation process of insulating varnish provided by this invention, thereby ensuring sufficient impregnation of the stator windings and improving the electrical performance, moisture-proof sealing, and resistance to damp heat aging of the traction motor. When the vacuum degree is low (greater than 100 Pa), the gaps inside the motor stator windings cannot be completely impregnated with insulating varnish, thus affecting the corresponding performance of the traction motor. In particular, when the vacuum degree of secondary vacuum pressure impregnation is too low, the insulation resistance will be significantly reduced, the dielectric loss will be aggravated, the insulation resistance after water immersion and the insulation resistance under damp heat conditions will be significantly reduced, and the leakage phenomenon will be serious.

[0024] Preferably, the vacuum pressure impregnation time is ≥1 h, for example, it can be 1 h, 1.2 h, 1.5 h, 1.8 h, 2 h, 2.2 h, 2.5 h, 2.8 h, 3 h, 3.5 h or 4 h, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range, but it is further preferred to be 1-3 h.

[0025] Preferably, both the impregnation of insulating varnish 1 and insulating varnish 2 include a drying step.

[0026] Preferably, the drying temperature is 170-180℃, for example, it can be 170℃, 171℃, 172℃, 173℃, 174℃, 175℃, 176℃, 177℃, 178℃, 179℃ or 180℃, as well as specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0027] Preferably, the drying time is 10-12 h, for example, it can be 10 h, 10.2 h, 10.5 h, 10.8 h, 11 h, 11.2 h, 11.5 h, 11.8 h or 12 h, as well as specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0028] Preferably, the drying method includes oven drying.

[0029] Preferably, the mutual impregnation process of the insulating varnish includes the following steps:

[0030] After the stator of the traction motor is impregnated with insulating varnish 1 under vacuum pressure for the first time, it is dried at 170-180℃ for 10-12 hours. Then, it is impregnated with insulating varnish 2 under vacuum pressure for the second time and dried at 170-180℃ for 10-12 hours to complete the mutual impregnation of insulating varnish. The vacuum degree of both the first and second vacuum pressure impregnation is ≤100 Pa and the time is ≥1 hour.

[0031] Alternatively, the stator of the traction motor is first impregnated with insulating varnish 2 under vacuum pressure, then dried at 170-180℃ for 10-12 h, and then impregnated with insulating varnish 1 under vacuum pressure a second time, and dried at 170-180℃ for 10-12 h to complete the mutual impregnation of insulating varnish. The vacuum degree of both the first and second vacuum pressure impregnation is ≤100 Pa and the time is ≥1 h.

[0032] The insulating varnish 1 includes any one of polybutadiene varnish, silicone varnish, or epoxy anhydride varnish.

[0033] The insulating varnish 2 includes epoxy-modified polyesterimide varnish.

[0034] Secondly, the present invention provides an insulating varnish composite layer, which is prepared by the inter-impregnation process of insulating varnish as described in the first aspect.

[0035] Preferably, the insulating varnish composite layer includes an impregnated insulating layer 1 and an impregnated insulating layer 1.

[0036] Preferably, the impregnated insulating layer 1 comprises an insulating varnish 1.

[0037] Preferably, the impregnated insulating layer 2 comprises an insulating varnish 2.

[0038] The insulating varnish 1 and insulating varnish 2 provided in this invention have good compatibility, which enables the impregnated insulating layer 1 and the impregnated insulating layer 2 to be well compatible, thereby ensuring the integrity of the resulting insulating varnish composite layer and avoiding the risk of interlayer peeling.

[0039] Thirdly, the present invention provides a method for suppressing faults in a locomotive traction motor in a humid environment, the method comprising processing with an inter-impregnation process of insulating varnish as described in the first aspect.

[0040] The mutual impregnation process of insulating varnish provided by this invention can significantly block the intrusion of moisture along capillary pores / gap, and is especially suitable for scenarios involving rain and snow penetration and high-pressure water vapor impact during car washing. It can be used as a method to suppress malfunctions of locomotive traction motors in humid environments.

[0041] Compared with the prior art, the present invention has at least the following beneficial effects:

[0042] (1) The mutual impregnation process of insulating varnish provided by the present invention can fundamentally solve the problem of insulation failure of traction motor in humid environment: epoxy modified polyesterimide varnish (116HU) has excellent film density and interface bonding, significantly improves moisture-proof sealing performance, effectively prevents rain, snow moisture and high-pressure water from car washing from entering, significantly reduces the risk of insulation resistance drop, and completely solves the problem of frequent alarms (insulation resistance too low, grounding fault) caused by this.

[0043] (2) The mutual impregnation process of insulating varnish provided by the present invention can comprehensively improve the reliability of the insulation system: after impregnation with specific insulating varnish twice, the insulation resistance is significantly improved, the dielectric loss is effectively reduced, and the overall insulation performance is enhanced; the excellent resistance to damp heat aging and resistance to cold and heat shock ensure long-term performance stability in complex environments, extend the motor life and maintenance cycle, and have good environmental adaptability; the resulting insulating varnish composite layer is a high-strength and tough varnish film, which can effectively resist electromagnetic force and vibration impact, improve structural reliability, and strengthen mechanical protection.

[0044] (3) The mutual impregnation process of insulating varnish provided by the present invention has excellent process compatibility: the insulating varnish 1 and insulating varnish 2 provided by the present invention have excellent compatibility with other materials of motor, the process is smooth, and production efficiency and quality stability are guaranteed.

[0045] (4) The mutual impregnation process of insulating varnish provided by the present invention can achieve the goal of balancing high performance and economic benefits: The use of the mutual impregnation process of the present invention enables the traction motor to overcome the moisture-proof bottleneck while maintaining excellent electrical insulation, high heat resistance, high mechanical strength and flame retardancy. Detailed Implementation

[0046] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0047] Unless otherwise specified, all raw materials and reagents used in the following examples and comparative examples are commercially available products. Some raw material information is as follows:

[0048] Silicone varnish: H62C, purchased from Wacker Chemie, Germany;

[0049] Epoxy modified polyesterimide paint: 116HU, purchased from Guangzhou Better;

[0050] Polybutadiene paint: PB302, purchased from Allentas;

[0051] Epoxy anhydride paint: JF9960, purchased from Suzhou Jufeng.

[0052] Example 1

[0053] This embodiment provides a method for mutual impregnation of insulating varnishes, the method comprising the following steps:

[0054] The stator of the traction motor is first impregnated with insulating varnish H62C under vacuum pressure, and then dried in an oven at 175°C for 11 hours. It is then impregnated with insulating varnish 116HU under vacuum pressure for 11 hours under vacuum pressure, and then dried in an oven at 175°C for 11 hours. This process of mutual impregnation of the insulating varnishes completes the process, resulting in a stator with an insulating composite layer. The vacuum degree of both the first and second vacuum pressure impregnation is 10 Pa, and the time is 1 hour for each.

[0055] Example 2

[0056] This embodiment provides a method for mutual impregnation of insulating varnishes, the method comprising the following steps:

[0057] The stator of the traction motor is first vacuum pressure impregnated with insulating varnish JF9960, then dried in an oven at 170℃ for 12 hours. After a second vacuum pressure impregnation with insulating varnish 116HU, it is dried in an oven at 180℃ for 10 hours, completing the mutual impregnation of insulating varnishes and obtaining a stator with an insulating composite layer. The vacuum degree of the first vacuum pressure impregnation is 50 Pa and the time is 2 hours, while the vacuum degree of the second vacuum pressure impregnation is 100 Pa and the time is 3 hours.

[0058] Example 3

[0059] This embodiment provides a method for mutual impregnation of insulating varnishes, the method comprising the following steps:

[0060] The stator of the traction motor is first vacuum pressure impregnated with insulating varnish H62C, then dried in an oven at 180℃ for 10 h. After a second vacuum pressure impregnation with insulating varnish 116HU, it is dried in an oven at 170℃ for 12 h, completing the mutual impregnation of insulating varnishes and obtaining a stator with an insulating composite layer. The vacuum degree of the first vacuum pressure impregnation is 100 Pa and the time is 3 h, while the vacuum degree of the second vacuum pressure impregnation is 50 Pa and the time is 2 h.

[0061] Example 4

[0062] This embodiment provides a method for mutual impregnation of insulating varnishes, the method comprising the following steps:

[0063] The stator of the traction motor is first impregnated with insulating varnish 116HU under vacuum pressure, and then dried in an oven at 175°C for 11 hours. It is then impregnated with insulating varnish H62C under vacuum pressure for 11 hours under 175°C for 11 hours. This process of mutual impregnation of insulating varnishes completes the process, resulting in a stator with an insulating composite layer. The vacuum degree of both the first and second vacuum pressure impregnation is 10 Pa, and the time is 1 hour for each.

[0064] Example 5

[0065] This embodiment provides a method for mutual impregnation of insulating varnishes. The only difference between this embodiment and Embodiment 1 is that insulating varnish H62C is replaced with insulating varnish PB302. All other raw materials and mutual impregnation methods are the same as in Embodiment 1.

[0066] Example 6

[0067] This embodiment provides a method for mutual impregnation of insulating varnish. The only difference between this embodiment and Embodiment 1 is that the vacuum degree of the first vacuum pressure impregnation is adjusted from 10 Pa to 100 Pa. All other raw materials and mutual impregnation methods are the same as in Embodiment 1.

[0068] Example 7

[0069] This embodiment provides a method for mutual impregnation of insulating varnish. The only difference between this embodiment and Embodiment 1 is that the vacuum degree of the first vacuum pressure impregnation is adjusted from 10 Pa to 110 Pa. All other raw materials and mutual impregnation methods are the same as in Embodiment 1.

[0070] Example 8

[0071] This embodiment provides a method for mutual impregnation of insulating varnish. The only difference between this embodiment and Embodiment 1 is that the vacuum degree of the secondary vacuum pressure impregnation is adjusted from 10 Pa to 50 Pa. All other raw materials and mutual impregnation methods are the same as in Embodiment 1.

[0072] Example 9

[0073] This embodiment provides a method for mutual impregnation of insulating varnish. The only difference between this embodiment and Embodiment 1 is that the vacuum degree of the secondary vacuum pressure impregnation is adjusted from 10 Pa to 100 Pa. All other raw materials and mutual impregnation methods are the same as in Embodiment 1.

[0074] Example 10

[0075] This embodiment provides a method for mutual impregnation of insulating varnish. The only difference between this embodiment and Embodiment 1 is that the vacuum degree of the secondary vacuum pressure impregnation is adjusted from 10 Pa to 110 Pa. All other raw materials and mutual impregnation methods are the same as in Embodiment 1.

[0076] Comparative Example 1

[0077] This comparative example provides a method for mutual impregnation of insulating varnishes. The only difference between this example and Example 5 is that insulating varnish 116HU is replaced with insulating varnish JF9960. All other raw materials and mutual impregnation methods are the same as in Example 5.

[0078] Comparative Example 2

[0079] This comparative example provides a method for mutual impregnation of insulating varnishes, the method comprising the following steps:

[0080] The stator of the traction motor is first vacuum pressure impregnated with insulating varnish PB302, and then dried in an oven at 175℃ for 11 hours. After a second vacuum pressure impregnation with insulating varnish PB302, it is dried in an oven at 175℃ for 11 hours to complete the mutual impregnation of insulating varnishes, resulting in a stator with an insulating composite layer. The vacuum degree of the first vacuum pressure impregnation is 10 Pa, the vacuum degree of the second vacuum pressure impregnation is 110 Pa, and the time for both vacuum pressure impregnations is 1 hour.

[0081] The stators with insulating composite layers in Examples 1-10 and Comparative Examples 1-2 were subjected to performance tests, and the test methods / standards are as follows:

[0082] (1) Insulation resistance, dielectric loss and temperature rise test: all tests were conducted in accordance with the relevant requirements of TB / T3315 "3315-2013 AC drive locomotive asynchronous traction motor" and GB / T25123-2018 "Rotating motor for electric traction rail locomotives and road vehicles";

[0083] (2) Damp heat performance test: The periodic damp heat test was carried out in accordance with GB / T 2423.4-2008 "Environmental testing of electrical and electronic products - Part 2: Test methods - Test Db - Alternating damp heat (12h+12h cycle)" to measure the insulation resistance and leakage current under damp heat conditions.

[0084] The test results are shown in Table 1.

[0085] Table 1

[0086]

[0087] The test results show that:

[0088] (1) As can be seen from Examples 1 to 10, the present invention can significantly improve the electrical performance, moisture-proof sealing performance and resistance to damp heat aging of the traction motor by impregnating two specially selected insulating varnishes twice. The measured insulation resistance is 18.6-45.5 GΩ, the dielectric loss is 0.5-1.21%, the temperature rise is 60.1-64.4K, the insulation resistance after immersion in water is 3.3-25.0 GΩ, the insulation resistance under damp heat conditions is 0.36-1.1 GΩ, and the leakage current is 0.7-55 mA.

[0089] (2) By comparing Example 1 with Examples 6-10, it can be seen that by optimizing the vacuum degree of vacuum pressure impregnation in the mutual impregnation process (especially the vacuum degree of secondary vacuum pressure impregnation), the present invention can further improve the electrical performance, moisture-proof sealing performance and resistance to damp heat aging of the traction motor, thereby increasing the insulation resistance to 30.8-45.5 GΩ, reducing the dielectric loss to 0.5-0.92%, increasing the insulation resistance after water immersion to 9.3-25.0 GΩ, increasing the insulation resistance under damp heat conditions to 0.61-1.1 GΩ, and reducing the leakage current value to 0.7-2.8 mA.

[0090] (3) By comparing Examples 1-10 with Comparative Example 1, it can be seen that Comparative Example 1 uses two different insulating varnishes 1 but does not use insulating varnish 2. Its measured insulation resistance is only 9.8 GΩ, the dielectric loss is reduced to 2.55%, the insulation resistance after immersion in water is only 1.0 GΩ, the insulation resistance under humid heat conditions is only 0.31 GΩ, and the leakage current value is as high as 79.0 mA. This shows that the present invention can significantly improve the electrical performance, moisture-proof sealing performance and humid heat aging resistance of the traction motor by using a specific combination of insulating varnish 1 and insulating varnish 2 in the mutual immersion process.

[0091] (4) By comparing Examples 1-10 with Comparative Example 2, it can be seen that Comparative Example 2 uses a process of mutually impregnating insulating varnish 1 in two stages. The measured insulation resistance is 10.8 GΩ, the insulation resistance after water impregnation is 2.5 GΩ, the insulation resistance under humid heat conditions is only 0.19 GΩ, and the leakage current value is as high as 89.0 mA. That is, the insulation performance, moisture-proof sealing performance and resistance to humid heat aging are significantly worse. This shows that the present invention can significantly improve the electrical performance, moisture-proof sealing performance and resistance to humid heat aging of the traction motor by mutually impregnating specific insulating varnish 1 and insulating varnish 2 in the mutual impregnation process.

[0092] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for mutual impregnation of insulating varnish, characterized in that, The mutual immersion process includes the following steps: After impregnating the stator of the traction motor with insulating varnish 1 and insulating varnish 2 respectively, the mutual impregnation of the insulating varnishes is completed. The insulating varnish 1 includes any one of polybutadiene varnish, silicone varnish, or epoxy anhydride varnish. The insulating varnish 2 includes epoxy-modified polyesterimide varnish.

2. The mutual immersion process method according to claim 1, characterized in that, The order in which the insulating varnish 1 and the insulating varnish 2 are impregnated is not important; it may include impregnating the insulating varnish 1 first and then the insulating varnish 2, or impregnating the insulating varnish 2 first and then the insulating varnish 1.

3. The mutual immersion process method according to claim 1 or 2, characterized in that, The polybutadiene varnish in the insulating varnish 1 includes PB302; Preferably, the silicone varnish in the insulating varnish 1 includes H62C; Preferably, the epoxy anhydride varnish in the insulating varnish 1 includes JF9960.

4. The mutual immersion process method according to any one of claims 1-3, characterized in that, The epoxy-modified polyesterimide varnish in the insulating varnish 2 includes 116HU.

5. The mutual immersion process according to any one of claims 1-4, characterized in that, The impregnation method includes vacuum pressure impregnation; Preferably, the vacuum degree of the vacuum pressure impregnation is ≤100 Pa; Preferably, the vacuum pressure impregnation time is ≥1 h.

6. The mutual immersion process according to any one of claims 1-5, characterized in that, Both the impregnation of insulating varnish 1 and insulating varnish 2 include a drying step; Preferably, the drying temperature is 170-180℃; Preferably, the drying time is 10-12 hours; Preferably, the drying method includes oven drying.

7. The mutual immersion process according to any one of claims 1-6, characterized in that, The mutual immersion process includes the following steps: After the stator of the traction motor is impregnated with insulating varnish 1 under vacuum pressure for the first time, it is dried at 170-180℃ for 10-12 h. Then, it is impregnated with insulating varnish 2 under vacuum pressure for the second time and dried at 170-180℃ for 10-12 h to complete the mutual impregnation of insulating varnish. The vacuum degree of both the first and second vacuum pressure impregnation is ≤100 Pa and the time is ≥1 h. Alternatively, the stator of the traction motor is first impregnated with insulating varnish 2 under vacuum pressure, then dried at 170-180℃ for 10-12 hours, and then impregnated with insulating varnish 1 under vacuum pressure a second time, and dried at 170-180℃ for 10-12 hours to complete the mutual impregnation of insulating varnish. The vacuum degree of both the first and second vacuum pressure impregnation is ≤100 Pa, and the time is ≥1 hour. The insulating varnish 1 includes any one of polybutadiene varnish, silicone varnish, or epoxy anhydride varnish. The insulating varnish 2 includes epoxy-modified polyesterimide varnish.

8. An insulating varnish composite layer, characterized in that, The insulating varnish composite layer is prepared using the inter-impregnation process of the insulating varnish as described in any one of claims 1-7.

9. The insulating varnish composite layer according to claim 8, characterized in that, The insulating varnish composite layer includes an impregnated insulating layer 1 and a stained insulating layer 1; Preferably, the impregnated insulating layer 1 comprises an insulating varnish 1; Preferably, the impregnated insulating layer 2 comprises an insulating varnish 2.

10. A method for suppressing faults in a locomotive traction motor in a humid environment, characterized in that, The suppression method includes processing using the inter-impregnation process of insulating varnish as described in any one of claims 1-7.

Images