Method for determining softening breakdown test temperature of 200-grade directly-welded enameled winding wire

Abstract

The invention relates to the technical field of manufacturing of electrical insulating materials, and discloses a method for determining a softening breakdown test temperature of a 200-level direct-welding enameled winding wire, which comprises the following steps of: a) performing a softening breakdown test of preset temperature steps on an enameled wire sample, keeping the temperature of each step for a constant time, and recording the breakdown condition of the sample; b) counting the breakdown ratio at different temperatures, and determining a main breakdown temperature interval with the breakdown rate greater than or equal to 80%; c) adding a safety margin temperature to the lower limit temperature value of the main breakdown interval to obtain a softening breakdown test temperature; d) verifying by thermogravimetric analysis that the temperature of the cut-through test is at least 20 DEG C lower than the starting temperature of thermal decomposition of the material; 5 DEG C is used as a stepping step of the temperature step. Through stepped temperature rise, statistical analysis and thermal decomposition temperature verification, the softening breakdown test temperature of the enameled winding wire is accurately determined, and the accuracy and reliability of a test result are ensured.

Description

Technical Field

[0001] The invention relates to the technical field of electrical insulation material manufacturing, in particular to a method for determining a softening breakdown test temperature of a 200-level direct-weldability enameled winding wire. Background Art

[0002] As electrical equipment places increasing demands on the performance of enameled wire, its high-temperature resistance has become a crucial indicator for evaluating its quality and reliability. Especially in high-temperature operating environments, the insulation performance of enameled wire is crucial for ensuring long-term stable operation. However, existing softening breakdown test methods have several limitations and require urgent improvement.

[0003] Currently, traditional methods for softening breakdown testing of enameled wire typically rely on empirically set fixed test temperatures. This approach fails to account for the material's actual thermal properties and the dynamic changes in the test environment, often resulting in significant deviations. Specifically, existing methods lack scientific and systematic approach to test temperature selection, potentially leading to temperature settings that are too high or too low, affecting the accuracy and reliability of test results. Fixed set temperatures fail to reflect the differences between materials and the insulation properties of enameled wire in different temperature ranges.

[0004] Furthermore, existing technologies generally fail to consider the impact of temperature on the thermal stability of enameled wire materials. At high temperatures, the thermal decomposition and softening of materials directly affect their breakdown characteristics. However, traditional testing methods fail to verify key parameters such as the thermal decomposition onset temperature. This can result in some test temperatures exceeding the material's thermal decomposition temperature range, distorting test results and failing to accurately reflect the material's performance in actual operating environments. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention provides a method for determining the softening breakdown test temperature of 200-level direct-weldable enameled winding wire, which solves the problems of inaccurate test temperature setting and lack of thermal stability verification in the existing technology.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: A method for determining the softening breakdown test temperature of a 200-level direct-weldable enameled winding wire comprises the following steps: a) Perform softening breakdown test on enameled wire samples at preset temperature steps, keep each step temperature constant for a certain period of time, and record the breakdown of the samples; b) Count the breakdown ratios at different temperatures and determine the main breakdown temperature range where the breakdown rate is greater than or equal to 80%; c) adding a safety margin temperature to the lower limit temperature value of the main breakdown interval to obtain a softening breakdown test temperature; d) verifying by thermogravimetric analysis that the softening breakdown test temperature is at least 20° C. lower than the thermal decomposition starting temperature of the material.

[0007] Preferably, the temperature steps are in 5° C. steps, starting from 85% of the theoretical temperature of the 200th thermal stage, and each step is maintained for 180±10 seconds.

[0008] Preferably, the number of test samples at each temperature step of the temperature step is not less than 10, and a breakdown test is performed using a DC voltage with a voltage of 100±10V.

[0009] Preferably, the main breakdown region is an interval in which the cumulative proportion of breakdown samples in two or more consecutive temperature steps is greater than or equal to 80%, and the statistical confidence level is not less than 95%.

[0010] Preferably, the safety margin temperature is 3°C-10°C.

[0011] Preferably, the TGA thermal decomposition starting temperature refers to the inflection point temperature at which the thermal weight loss rate of the sample first significantly increases, and the temperature difference between the thermal decomposition starting temperature and the test temperature is not less than 20°C.

[0012] Preferably, the enameled winding wire is polyurethane, and TDI and HDI are used as a compound curing agent in a mass ratio of 3:1. The coating speed is 12±0.5 m / s, and the three-stage curing temperatures are 280°C, 320°C and 300°C respectively.

[0013] Preferably, the enameled winding wire is polyesterimide, contains 25wt% of nano-SiO2 additive, has a particle size of 50100nm, and adopts a double-layer coating process with coating speeds of 8m / s and 10m / s respectively.

[0014] Preferably, the softening breakdown test uses testing equipment that complies with the IEC60851 standard.

[0015] Preferably, the test method is applicable to enameled winding wires within the range of DV=20, where D is the wire diameter and V is the production speed.

[0016] The present invention provides a method for determining the softening breakdown test temperature of a 200-level direct-weldable enameled winding wire. The method has the following beneficial effects: 1. This invention uses a stepped temperature rise test method, combined with breakdown statistical analysis, to determine the primary breakdown interval and establish a safety margin based on this interval. This effectively avoids the biased determination that can result from traditional methods that rely on empirically set fixed temperatures. This method improves the objectivity and consistency of test temperature selection for enameled winding wire and is particularly suitable for applications where the thermal softening threshold is sensitive in directly solderable structures.

[0017] 2. This invention tests temperature zones by setting a certain number of samples. During the test, the main breakdown zone is determined by a breakdown ratio of 80% or greater, eliminating interference from localized abnormal samples. This statistical principle enhances the adaptability of the test temperature to actual quality control and accurately reflects the insulation softening properties of 200-grade direct-solderable enameled winding wire in different temperature zones.

[0018] 3. After the test temperature is set, the present invention further verifies the thermal decomposition starting point of the material through thermogravimetric analysis, ensuring that the test temperature is at least 20°C below this starting point, thereby avoiding the influence of thermal decomposition during the test. This step not only improves the technical integrity of the test method, but also strengthens the systematic guarantee of the high-temperature performance evaluation process.

[0019] 4. The method developed in this invention is applicable to a variety of Class 200 direct-solderable enameled winding wires, including polyurethane and polyesterimide types. Regardless of differences in nano-additives, compounded curing agents, and other factors, a unified procedure for temperature setting and verification can be used. This eliminates the issue of inconsistent evaluation standards due to material differences across different enameled wires, supporting consistent quality management across the industry chain. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A diagram showing the steps of the method of the present invention. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the present specification. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0022] Please see the attached Figure 1 The embodiment of the present invention provides a method for determining the softening breakdown test temperature of a 200-level direct-weldable enameled winding wire, comprising the following steps: a) Perform softening breakdown test on enameled wire samples at preset temperature steps, keep each step temperature constant for a certain period of time, and record the breakdown of the samples; In this step, a softening breakdown test is performed on the enameled winding wire to be tested in a step temperature rise manner to obtain breakdown data at different temperature points.

[0023] Temperature rise setting: The starting temperature is 85% of the theoretical temperature of the corresponding 200-level thermal stage, that is, starting from 230°C; Temperature rise step: Each step temperature rises by 5°C, and each step is maintained for 180±10 seconds; Sample setup: 10 independent samples were tested at each temperature point; Test equipment: Use softening breakdown test equipment that complies with IEC60851 standard, such as XHTC500; Voltage setting: Apply 100±10V DC voltage according to GB / T4074 standard to monitor the insulation breakdown status of the enamel layer.

[0024] Polyurethane and polyesterimide enameled wires should be tested separately. Each sample should be continuously pressurized under specified temperature conditions to observe whether insulation breakdown occurs and record the test results.

[0025] b) Count the breakdown ratios at different temperatures and determine the main breakdown temperature range where the breakdown rate is greater than or equal to 80%; In this step, the breakdown data of all temperature steps in step S1 are collected and the number of breakdown samples is counted.

[0026] Count the breakdown ratio of each step; The main breakdown interval is determined to be the temperature section where the cumulative breakdown rate among the continuous temperature points reaches or exceeds 80%; The main breakdown region is required to have a clear boundary, that is, most samples below the temperature range do not break down, and most samples above the temperature range break down; The data credibility must reach a confidence interval of more than 95% to ensure that the results are stable and reliable.

[0027] This step ensures that the test temperature is set based on objective evidence rather than empirical judgment.

[0028] c) adding a safety margin temperature to the lower limit temperature value of the main breakdown interval to obtain a softening breakdown test temperature; After confirming the main breakdown interval, determine the test temperature according to the set rules.

[0029] Test temperature = lower limit temperature of main breakdown range + safety margin; The safety margin is 5°C; The obtained temperature is the softening breakdown test temperature of this type of 200 grade direct solderable enameled wire; This temperature is used as the indicator temperature for production quality control. Any temperature that breaks through is judged as unqualified, and any temperature that does not break through is qualified.

[0030] In this way, a robust method for evaluating the breakdown temperature that is applicable to different material systems (polyurethane or polyesterimide) can be established.

[0031] d) verifying by thermogravimetric analysis that the softening breakdown test temperature is at least 20° C. lower than the thermal decomposition starting temperature of the material; To ensure that the determined softening breakdown test temperature is within the thermally stable working range of the material, the thermal decomposition behavior of the enameled wire material is verified by thermogravimetric analysis (TGA).

[0032] The test was carried out using a thermogravimetric analyzer under nitrogen or air atmosphere; Obtain the thermal gravimetric curve of the material; Determine the starting temperature of thermal decomposition of the material; The verification rule is: the softening breakdown test temperature should be at least 20°C lower than the thermal decomposition starting temperature.

[0033] This verification ensures that the insulation performance of the material will not be affected by thermal decomposition at the set test temperature, and provides a matching relationship between the safety margin and the reasonable use range of the material.

[0034] Example 1: Polyurethane Class 200 Enameled Winding Wire Curing agent combination: TDI and HDI are compounded in a mass ratio of 3:1; Coating line speed: 12m / s; Curing temperature: three sections of the furnace are 280℃, 320℃, and 300℃ respectively; Test results: The main breakdown range is 255℃~260℃; Calibration test temperature: 260℃; The thermal decomposition starting temperature verified by TGA was 282°C.

[0035] Example 2: Polyesterimide Class 200 Enameled Winding Wire Material additives: Add 3wt% nano-SiO2, particle size 80nm; Coating method: double-layer coating, first layer speed 8m / s, second layer speed 10m / s; Curing temperature: 300℃, 340℃, 320℃; Test results: The main breakdown range is 280℃~285℃; Calibration test temperature: 285℃; The thermal decomposition starting temperature verified by TGA was 308°C.

[0036] Comparative Example Implementation Method The comparative example adopts the conventional empirical temperature setting method to conduct softening breakdown temperature test: Directly set the target test temperature (e.g. 250°C for polyurethane and 275°C for polyesterimide); The step temperature rise process is not set; At each temperature, 10 samples are tested for breakdown as the basis for evaluation; No statistical analysis of the main breakdown region is performed, and no safety margin temperature is set; TGA thermal decomposition temperature verification was not performed.

[0037] Comparison condition settings:

[0038] Comparison Results Overview Polyesterimide 200 grade enameled wire:

[0039] In the comparative example, the test temperature does not cover the main breakdown area, so the results may be biased; The lack of use of the concept of "main breakdown zone" results in unrepresentative test temperature determinations; There is no safety margin setting, and the test temperature may be too low or too high; The comparative example did not use TGA analysis, so it is impossible to confirm whether the test temperature is within the thermally stable working range. While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for determining the softening breakdown test temperature of a 200-level direct-weldable enameled winding wire, characterized in that: The steps include: a) Perform softening breakdown test on enameled wire samples at preset temperature steps, keep each step temperature constant for a certain period of time, and record the breakdown of the samples; b) Count the breakdown ratios at different temperatures and determine the main breakdown temperature range where the breakdown rate is greater than or equal to 80%; c) adding a safety margin temperature to the lower limit temperature value of the main breakdown interval to obtain a softening breakdown test temperature; d) verifying by thermogravimetric analysis that the softening breakdown test temperature is at least 20° C. lower than the thermal decomposition starting temperature of the material.

2. The method for determining the softening breakdown test temperature of a 200-level direct-weldable enameled winding wire according to claim 1, characterized in that: The temperature step is 5° C., starting from 85% of the theoretical temperature of the 200th thermal stage, and each step is maintained for 180±10 seconds.

3. The method for determining the softening breakdown test temperature of a 200-level direct-weldable enameled winding wire according to claim 1, characterized in that: The number of test samples at each temperature step of the temperature step is no less than 10, and a breakdown test is applied using a DC voltage with a voltage of 100±10V.

4. The method for determining the softening breakdown test temperature of a 200-level direct-weldable enameled winding wire according to claim 1, characterized in that: The main breakdown zone is an interval in which the cumulative proportion of breakdown samples in two or more consecutive temperature steps is greater than or equal to 80%, and the statistical confidence level is not less than 95%.

5. The method for determining the softening breakdown test temperature of a 200-level direct-weldable enameled winding wire according to claim 1, characterized in that: The safety margin temperature is 3°C-10°C.

6. The method for determining the softening breakdown test temperature of a 200-level direct-weldable enameled winding wire according to claim 1, characterized in that: The TGA thermal decomposition starting temperature refers to the inflection point temperature at which the thermal weight loss rate of the sample first significantly increases. The temperature difference between the thermal decomposition starting temperature and the test temperature is not less than 20°C.

7. The method for determining the softening breakdown test temperature of a 200-level direct-weldable enameled winding wire according to claim 1, characterized in that: The enameled winding wire is polyurethane, and TDI and HDI are used as a compound curing agent in a mass ratio of 3:

1. The coating speed is 12±0.5m / s, and the three-stage curing temperatures are 280°C, 320°C and 300°C respectively.

8. The method for determining the softening breakdown test temperature of a 200-level direct-weldable enameled winding wire according to claim 1, characterized in that: The enameled winding wire is polyesterimide, contains 25wt% of nano-SiO2 additive, has a particle size of 50100nm, and adopts a double-layer coating process with coating speeds of 8m / s and 10m / s respectively.

9. The method for determining the softening breakdown test temperature of a 200-level direct-weldable enameled winding wire according to claim 1, characterized in that: The softening breakdown test uses a test device that complies with the IEC60851 standard.

10. The method for determining the softening breakdown test temperature of a 200-level direct-weldable enameled winding wire according to claim 1, characterized in that: The test method is applicable to enameled winding wires within the range of DV=20, where D is the wire diameter and V is the production speed.

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