1、Designation: D1932 04 (Reapproved 2009)D1932 13 An American National StandardStandard 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
2、adoption or, in the case of revision, the year of 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 Department of Defense
3、.1. Scope Scope*1.1 This test method covers the determination 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
4、standard glass fiber fabric.1.2 This test method 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 arma
5、tures and laminated structures. Also, this test method 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 va
6、lues stated in SI units are to be regarded as standard. 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 t
7、he user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use. For specific hazard statements, see Section 7.2. Referenced Documents2.1 ASTM Standards:2D149 Test Method for Dielectric Breakdown Voltage and Dielectr
8、ic Strength of Solid Electrical Insulating Materials atCommercial Power FrequenciesD374 Test Methods for Thickness of Solid Electrical Insulation (Withdrawn 2013)3D580 Specification for Greige Woven Glass Tapes and WebbingsD1346 Test Method for Testing Electrical Insulating Varnishes for 180 C and A
9、bove (Withdrawn 1986)3D1711 Terminology Relating to Electrical InsulationD2518 Specification for Woven Glass Fabrics for Electrical Insulation (Withdrawn 2013)3D5423 Specification for Forced-Convection Laboratory Ovens for Evaluation of Electrical InsulationD6054 Practice for Conditioning Electrical
10、 Insulating Materials for Testing (Withdrawn 2012)32.2 IEEE Publications:4IEEE No. 101A Guide for the Statistical Analysis of Thermal Life Test Data (including Appendix A)2.3 IEC Publications:IEC 60216 Guide for the Determination of Thermal Endurance Properties of Electrical Insulating Materials (Pa
11、rt 1)51 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 Compounds.Current edition approved Oct. 1, 2009April 1, 2013
12、. Published February 2010April 2013. Originally approved in 1967. Last previous edition approved in 20042009 asD1932 04.D1932 04 (2009). DOI: 10.1520/D1932-04R09.10.1520/D1932-13.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org.
13、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.4 Available from the Institute of Electrical and Electronics Engineers, 1828 L St., NW, Suite 1202
14、, Washington, DC 200365104.5 Available from American National Standards Institute, 25 West 43rd St., 4th Floor, New York, NY 10036.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version.
15、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 published by ASTM is to be considered the official document.*A Summary of Changes section a
16、ppears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13. Terminology3.1 Definitions:3.1.1 temperature index (TI), na number which permits comparison of the temperature/time characteristics of an electricali
17、nsulating material, or a simple combination of materials, based on the temperature 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 endpoin
18、t time, nthe time necessary for a specific property of a material, or a simple 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 in
19、which the value of a property of a material, or a simple combination of materials, 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
20、with the selected varnish to a specified build.4.2 Specimens are exposed in 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 testtempera
21、ture required to reduce the breakdown voltage to a value of 12 kV/mm (300 V/mil) of original thickness. These values areused to construct a thermal endurance graph by which temperature indices may be estimated. for use to estimate temperatureindices.4.3 This test method is not applicable to material
22、s having an initial dielectric breakdown voltage of less than 12 kV/mm (300V/mil) of original thickness unless lower endpoint values are agreed upon or indicated in the applicable material specifications.5. Significance and Use5.1 A major factor affecting the long term performance of insulating mate
23、rials is thermal degradation. Other It is possible thatfactors, such as moisture and vibration, maywill cause failures after the material 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 physi
24、cal andelectrical integrity.5.3 The thermal degradation of the varnish results in weight loss, porosity, crazing, and generally a 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 me
25、thod.5.4 Electrical insulating varnishes undergo flexing in service due to vibration and thermal expansion. For this reason, thisfunctional 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 % wi
26、th respect to the neutral axis of the base fiber while being tested for dielectric breakdown.6. Apparatus6.1 Electrode Test FixtureThe 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
27、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 draft constant-temperature oven conforming to Specification D5423, Type II.6.4 MicrometerDead-weight type specified in Test Methods D374, having a presser foot 6.35 6 0.0
28、3 mm (0.25 6 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 0.01 MPa (25 6 2 psi) on thepressure foot.6.5 Test Specimen FrameA frame for each test specimen made from a straight length (approximately 1 m (39 in.) of roundNichromeAWG No. 14 w
29、ire. Bend the wire to form a rectangle having inside dimensions of 150 by 300 mm (6 by 12 in.). Overlapthe 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 sp
30、ecimen frames aminimum of 25 mm (1 in.) apart so that they are secured at top and bottom.6.7 Dipping ApparatusAn apparatus capable of removing the specimen 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 po
31、int without adequate ventilation, especially if the possibilityexists that flames or sparks are present. Store varnish in sealed containers.D1932 1328. Test Specimens8.1 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
32、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 accordance with Specification D580.Insulation Thickness Dimension R Dimension H Dimension Dcm in. cm in. cm in. cm in.0.018 0.007 0.455 0
33、.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 1338.2 Prepare the test specimen by dipping a glass cloth panel described in 8.1 in the varnish at the stan
34、dard laboratory atmospheredescribed in Practice D6054. Prior to dipping panels, adjust the viscosity of the varnish to be tested by trial so that two coats willgive 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
35、 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 laboratory 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
36、 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 exposure temperature.9. Screening Test9.1 Prepare one test specimen. Condition the specimen 48 h in the standard laboratory atmosphere. Cut five 25 by 3
37、00 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 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 voltag
38、e 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.) from 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
39、Test Method D149.9.3 Average the dielectric breakdown voltage for the five bent and unbent areas respectively. The ratio of average breakdownvoltage 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 Exp
40、ose the material to at least three temperatures. Choose the lowest temperature such that it is not more than 25C higherthan the estimated temperature index. Exposure temperatures shouldshall differ by at least 10C and preferably 20C.10.2 Select exposure temperatures in accordance with those shown in
41、 Table 1 as indicated by the anticipated temperature indexof the material under test. It is recommended that exploratory tests be first made at the 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 sele
42、ction of thelower test temperatures.11. Procedure11.1 Thickness MeasurementMeasure the average thickness of one representative specimen from each 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.) lengthus
43、ing the apparatus described in 6.4 and Test Methods D374. Allow the presser foot to remain on the test specimen for 2 s beforetaking a reading.11.2 Dielectric Breakdown Voltage (Initial)Condition one specimen from each set of specimens for at least 48 h in thestandard laboratory atmosphere for diele
44、ctric breakdown voltage by the short-time method, using a rate of rise of 500 V/s. Makesix 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
45、. 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
46、up to the highest selected temperature and positioned so that it is at least 100 mm (4 in.) from the walls at any point.TABLE 1 Suggested Exposure Temperatures and Cycle DurationsATemperatures Corresponding to the Estimated Temperature Index Range, C,B,CCycleDuration,daysClass 105 Class 130 Class 15
47、5 Class 180 Class 200 Class220100to109110to119120to129130to139140to149150to159160to169170to179180to189190to199200to209210to219220to229230to2391 170 180 190 200 210 220 230 240 250 260 270 280 290 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 25
48、0 260 270 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 120 130 140 150 160 170 180 190 200 210 220 230 240 25049 110 120 130 140 150 160 170 180 190 200 210 220 230 240A Taken from IEC Publication 60216-1.B Exposure temperat
49、ures 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 failure.D1932 134Remove one specimen at each of three time intervals equivalent approximately to 25, 50, and 100 % of the estimated insulationendpoint time at the selected temperature. Immediately after removal, condition the specimen for 4 h in the standard laboratoryatmosphere and test for dielectric breakdown voltage in the standard laboratory atmosphere as specified in 11.2.11.
