ASTM D1932-2018 Standard Test Method for Thermal Endurance of Flexible Electrical Insulating Varnishes.pdf

1、Designation: D1932 13D1932 18Standard Test Method forThermal Endurance of Flexible Electrical InsulatingVarnishes1This standard is issued under the fixed designation D1932; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o

2、f last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope*1.1 This test method covers the d

3、etermination of the relative thermal endurance of flexible electrical insulating varnishes bydetermining the time necessary at elevated temperatures to decrease the dielectric breakdown of the varnish to an arbitrarilyselected value when applied to a standard glass fiber fabric.1.2 This test method

4、does not apply to varnishes that lose a high percentage of their dielectric breakdown voltage when flexedbefore elevated temperature exposure as prescribed in the screening test (Section 9). Examples of such varnishes are those usedfor high speed armatures and laminated structures. Also, this test m

5、ethod is not applicable to varnishes which distort sufficientlyduring thermal elevated temperature exposure so that they cannot be tested using the curved electrode assembly.1.3 Thermal endurance is expressed in terms of a temperature index.1.4 The values stated in SI units are to be regarded as sta

6、ndard. No other units of measurement are included in this standard.NOTE 1There is no equivalent IEC or ISO standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate

7、 safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use. For specific hazard statements, see Section 7.1.6 This international standard was developed in accordance with internationally recognized principles on standardizationesta

8、blished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D149 Test Method for Dielectric Breakdown Voltage and Dielectr

9、ic Strength of Solid Electrical Insulating Materials atCommercial Power FrequenciesD374D374/D374M Test Methods for Thickness of Solid Electrical Insulation (Metric) D0374_D0374MD580D580/D580M Specification for Greige Woven Glass Tapes and WebbingsD618 Practice for Conditioning Plastics for TestingD1

10、346 Test Method for Testing Electrical Insulating Varnishes for 180 C and Above (Withdrawn 1986)3D1711 Terminology Relating to Electrical InsulationD2307 Test Method for Thermal Endurance of Film-Insulated Round Magnet WireD2518 Specification for Woven Glass Fabrics for Electrical Insulation (Withdr

11、awn 2013)3D5423 Specification for Forced-Convection Laboratory Ovens for Evaluation of Electrical InsulationD6054 Practice for Conditioning Electrical Insulating Materials for Testing (Withdrawn 2012)32.2 IEEE Publications:4IEEE No. 101A Guide for the Statistical Analysis of Thermal Life Test Data (

12、including Appendix A)1 This test method is under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and is the direct responsibility of SubcommitteeD09.01 on Electrical Insulating Varnishes, Powders and Encapsulating CompoundsProducts.Current edition approved Ap

13、ril 1, 2013Nov. 1, 2018. Published April 2013November 2018. Originally approved in 1967. Last previous edition approved in 20092013 asD1932 04 (2009).D1932 13. DOI: 10.1520/D1932-13.10.1520/D1932-18.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service

14、at serviceastm.org. ForAnnual Book ofASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 The last approved version of this historical standard is referenced on www.astm.org.This document is not an ASTM standard and is intended only to provide the user

15、 of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as

16、published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12.2 IEC Publications:IEC 60216 Guide for the Determination of

17、 Thermal Endurance Properties of Electrical Insulating Materials (Part 1)43. Terminology3.1 Definitions:3.1.1 temperature index (TI), na number which permits comparison of the temperature/time characteristics of an electricalinsulating material, or a simple combination of materials, based on the tem

18、perature in degrees Celsius which is obtained byextrapolating the Arrhenius plot of endpoint time versus temperature to a specified time, usually 20 000 h.3.1.2 thermal endurance graph, nan Arrhenius plot.3.1.3 thermal endpoint time, nthe time necessary for a specific property of a material, or a si

19、mple combination of materials,to degrade to a defined end point when aged at a specified temperature.3.1.4 thermal life endpoint time, na graphical representation of thermal endpoint time at a specified exposure temperature inwhich the value of a property of a material, or a simple combination of ma

20、terials, is measured at room temperature and the valuesplotted as a function of time.3.1.5 Refer to Terminology D1711 for definitions of other terms.4. Summary of Test Method4.1 Specimens are prepared using glass cloth coated with the selected varnish to a specified build.4.2 Specimens are exposed i

21、n air at a minimum of three temperatures above the expected use temperature of the material.Dielectric breakdown voltage tests in air at room temperature are periodically made to determine the exposure time at each testtemperature required to reduce the breakdown voltage to a value of 12 kV/mm (300

22、V/mil) of original thickness. These values areused to construct a thermal endurance graph for use to estimate temperature indices.4.3 This test method is not applicable to materials having an initial dielectric breakdown voltage of less than 12 kV/mm (300V/mil) of original thickness unless lower end

23、point values are agreed upon or indicated in the applicable material specifications.5. Significance and Use5.1 Amajor factor affecting the long term performance of insulating materials is thermal degradation. It is possible that factors,such as moisture and vibration, will cause failures after the m

24、aterial has been weakened by thermal degradation.5.2 An electrical insulating varnish is effective in protecting electrical equipment only as long as it retains its physical andelectrical integrity.5.3 The thermal degradation of the varnish results in weight loss, porosity, crazing, and generally a

25、reduction in flexibility.Degradation of the varnish can be detected by a decrease in dielectric strength, which is therefore used as the failure criterion forthis test method.5.4 Electrical insulating varnishes undergo flexing in service due to vibration and thermal expansion. For this reason, thisf

26、unctional test includes flexing and elongation of the insulation. The electrodes used in this test method are designed to elongatethe outer surface of the specimen 2 % with respect to the neutral axis of the base fiber while being tested for dielectric breakdown.6. Apparatus6.1 Electrode Test Fixtur

27、eThe fixture shall be in accordance with the dimensions shown in Fig. 1 and Fig. 2. Electrodes shallbe of polished brass, with the upper electrode having a mass of 1.8 6 0.05 kg (4.0 6 0.1 lb).6.2 Dielectric Breakdown Test SetThe set shall meet the requirements of Test Method D149.6.3 OvensA forced

28、draft constant-temperature oven conforming to Specification D5423, Type II.6.4 MicrometerDead-weight type specified in Test Methods D374D374/D374M, having a presser foot 6.35 6 0.03 mm (0.256 0.001 in.) in diameter and an anvil of at least 50 mm (2 in.) diameter and shall exert a pressure of 0.17 6

29、0.01 MPa (25 6 2psi) on the pressure foot.6.5 Test Specimen FrameA frame for each test specimen made from a straight length (approximately 1 m (39 in.) of roundheat resistant wire such as Nichrome AWG No. 14 wire. Bend the wire to form a rectangle having inside dimensions of 150 by300 mm (6 by 12 in

30、.). Overlap the ends of the wire approximately 50 mm (2 in.) at one corner. Attach the specimen to the frame.6.6 Test Fixture for Exposing Specimen to Elevated TemperatureA suitable fixture for mounting the specimen frames aminimum of 25 mm (1 in.) apart so that they are secured at top and bottom.4

31、Available from the Institute of Electrical and Electronics Engineers, 1828 L St., NW, Suite 1202, Washington, DC 200365104.4 Available from American National Standards Institute, 25 West 43rd St., 4th Floor, New York, NY 10036.D1932 1826.7 Dipping ApparatusAn apparatus capable of removing the specim

32、en from the varnish at the rate of 90110 mm (3.54.3in.)/min.7. Safety Precautions7.1 It is unsafe to use varnish at temperatures above the flash point without adequate ventilation, especially if the possibilityexists that flames or sparks are present. Store varnish in sealed containers.Insulation Th

33、ickness Dimension R Dimension H Dimension Dcm in. cm in. cm in. cm in.0.018 0.007 0.455 0.179 0.815 0.321 0.871 0.344Tolerance for R and D = 0.003 cm (0.001 in.)Tolerance for H = 0.005 cm (0.002 in.)FIG. 1 Single-Shot Curved Electrode DetailsFIG. 2 Curved Electrode and HolderD1932 1838. Test Specime

34、ns8.1 Prepare glass cloth panels 150 by 300 mm (6 by 12 in.) with the 300 mm (12 in.) dimension parallel to the warp threads.Use fabric style No. 116 in accordance with Specification D2518. Heat clean the specimens as specified in Methods D1346 toarrive at a volatile content not to exceed 0.1 % in a

35、ccordance with Specification D580D580/D580M.8.2 Prepare the test specimen by dipping a glass cloth panel described in 8.1 in the varnish at the standard laboratory atmospheredescribed in Practice D6054D618. Prior to dipping panels, adjust the viscosity of the varnish to be tested by trial so that tw

36、o coatswill give an over-all thickness of 0.178 6 0.0127 mm (0.007 6 0.0005 in.).8.3 Immerse the panel in the varnish in the direction of the 300 mm (12 in.) length until bubbling stops, mechanically withdrawat the rate of 90110 mm (3.54.3 in.)/min, and then allow to drain for 12 h at the standard l

37、aboratory atmosphere.8.4 Bake the specimen in the same vertical position as dipped. Reverse the specimen, dip a second time, and drain as above.Bake the specimen at such a temperature and for such a time as specified by the varnish manufacturer.8.5 Prepare a set of twelve or more specimens for each

38、exposure temperature.9. Screening Test9.1 Prepare one test specimen. Condition the specimen 48 h in the standard laboratory atmosphere. Cut five 25 by 300 mm (1by 12 in.) test strips from the center of the specimen, discarding the 12.5 by 300 mm (12 by 12 in.) portion from each side. Bendeach of the

39、 five test strips once, 115 mm (412 in.) from one end, 180 around a mandrel 3.175 mm (0.125 in.) in diameter.9.2 Measure the dielectric breakdown voltage on the bent area of each five test strips. In like manner, make five breakdown testson the unbent area at a distance of 75 mm (3 in.) (3 in.) from

40、 the bend. Use the apparatus described in 6.2 in accordance with theprocedure described in 11.2, except use 6.4 mm (14 in.) diameter electrodes as specified in Test Method D149.9.3 Average the dielectric breakdown voltage for the five bent and unbent areas respectively. The ratio of average breakdow

41、nvoltage of the bent area to the unbent area shall be greater than 0.5, if this method is to be considered applicable.10. Selection of Test Temperatures10.1 Expose the material to at least three temperatures. Choose the lowest temperature such that it is not more than 25C higherthan the estimated te

42、mperature index. Exposure temperatures shall differ by at least 10C and preferably 20C.10.2 Select exposure temperatures in accordance with those shown in Table 1 as indicated by the anticipated temperature indexof the material under test. It is recommended that exploratory tests be first made at th

43、e highest temperature to obtain dataestablishing the validity of the 100 h minimum endpoint time requirement and that this be used as a guide for the selection of thelower test temperatures.11. Procedure11.1 Thickness MeasurementMeasure the average thickness of one representative specimen from each

44、set at five points alongits center before heat exposure. Determine the thickness along the center of the specimen parallel to its 300 mm (12 in.) lengthusing the apparatus described in 6.4 and Test Methods D374D374/D374M. Allow the presser foot to remain on the test specimenfor 2 s before taking a r

45、eading.11.2 Dielectric Breakdown Voltage (Initial)Condition one specimen from each set of specimens for at least 48 h in thestandard laboratory atmosphere for dielectric breakdown voltage by the short-time method, using a rate of rise of 500 V/s. MakeTABLE 1 Suggested Exposure Temperatures and Cycle

46、 DurationsATemperatures Corresponding to the Estimated Temperature Index Range, C,B,CCycleDuration,daysClass 105 Class 130 Class 155 Class 180 Class 200 Class220100to109110to119120to129130to139140to149150to159160to169170to179180to189190to199200to209210to219220to229230to2391 170 180 190 200 210 220 2

47、30 240 250 260 270 280 290 3002 160 170 180 190 200 210 220 230 240 250 260 270 280 2904 150 160 170 180 190 200 210 220 230 240 250 260 270 2807 140 150 160 170 180 190 200 210 220 230 240 250 260 27014 130 140 150 160 170 180 190 200 210 220 230 240 250 26028 120 130 140 150 160 170 180 190 200 21

48、0 220 230 240 25049 110 120 130 140 150 160 170 180 190 200 210 220 230 240A Taken from IEC Publication 60216-1.B Exposure temperatures above and below those given are to be selected by experimentation.C Range to which the temperature is assumed to correspond to an extrapolated 20 000 h time to fail

49、ure.D1932 184six dielectric breakdown measurements, 45 mm (134 in.) apart and starting 40 mm (112 in.) from one end of the specimen. Insertthe specimen in the curved electrode fixture (Fig. 2) so that the warp threads are bent. Lower the electrode slowly on the specimen.11.3 Exposure and Testing of the SpecimensTag five specimens with aluminum foil or otherwise permanently identify them,and place in the test fixture described in 6.5. Place the fixture containing the specimens in the oven which has previously beenbrought up to the highest selec