1、Designation: D 3145 08An American National StandardStandard Test Method forThermal Endurance of Electrical Insulating Varnishes by theHelical Coil Method1This standard is issued under the fixed designation D 3145; the number immediately following the designation indicates the year oforiginal adoptio
2、n 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.1. Sco
3、pe*1.1 This test method covers the determination of the thermalendurance of electrical insulating varnishes alone or in com-binations with magnet wire insulation. Changes in the helicalcoil bond strength are used as the test criteria. The coils aremade from bare aluminum or copper wire, or from film
4、- orfiber-insulated magnet wire.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitati
5、ons prior to use. For a specificprecautionary statement, see Section 7.1.3 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.NOTE 1There is
6、 no similar or equivalent IEC standard.2. Referenced Documents2.1 ASTM Standards:2D 1711 Terminology Relating to Electrical InsulationD 1932 Test Method for Thermal Endurance of FlexibleElectrical Insulating VarnishesD 2307 Test Method for Thermal Endurance of Film-Insulated Round Magnet WireD 2519
7、Test Method for Bond Strength of Electrical Insu-lating Varnishes by the Helical Coil TestD 3251 Test Method for Thermal Endurance Characteristicsof Electrical Insulating Varnishes Applied Over Film-Insulated Magnet WireD 3850 Test Method for Rapid Thermal Degradation ofSolid Electrical Insulating M
8、aterials By Thermogravimet-ric Method (TGA)D 5423 Specification for Forced-Convection LaboratoryOvens for Evaluation of Electrical InsulationD 6054 Practice for Conditioning Electrical Insulating Ma-terials for Testing2.2 International Electrotechnical Commission Publica-tions:3IEC 60216-1 Guide for
9、 the Determination of Thermal En-durance Properties of Electrical Insulation Materials (Part1)3. Terminology3.1 Definitions3.1.1 For definitions of terms used in the test method, referto Terminology D 1711.3.2 Definitions of Terms Specific to This Standard:3.2.1 bond strength, na measure of the forc
10、e required toseparate surfaces which have been bonded together.3.2.2 magnet wire, na metal electrical conductor, coveredwith electrical insulation, for use in the assembly of electricalinductive apparatus such as coils for motors, transformers,generators, relays, magnets, etc.3.2.2.1 DiscussionThe e
11、lectrical insulation is usuallycomposed of a film covering formed from a magnet wireenamel applied over a bare conductor. In some specificapplications, fibrous coverings, either taped or linear filamentserved, are also used as electrical insulation.3.2.3 varnish, electrical insulating, n a liquid re
12、sin sys-tem that is applied to and cured on electrical componentsproviding electrical, mechanical and environmental protection.3.2.3.1 DiscussionThere are two types of electrical insu-lating varnishessolvent-containing and solventless. Solvent-containing types are solutions, dispersions or emulsions
13、 of apolymer or a mixture of polymers in a volatile, nonreactableliquid. Solventless types are liquid resin systems free ofvolatile, nonreactable solvents.1This test method is under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and is the direct responsibili
14、ty ofSubcommittee D09.01 on Electrical Insulating Varnishes, Powders and Encapsulat-ing Compounds.Current edition approved May 1, 2008. Published June 2008. Originallyapproved in 1973. Last previous edition approved in 2003 as D 3145 03.2For referenced ASTM standards, visit the ASTM website, www.ast
15、m.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.o
16、rg.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4. Summary of Test Method4.1 Flexural strength of the helical coils is measured peri-odically after exposure to seve
17、ral exposure temperatures. Thetime to reach an arbitrarily selected value of bond strength ateach exposure temperature is determined. The logarithms ofthese times in hours are plotted as a function of the reciprocaltemperature (1/K) to give an Arrhenius plot.5. Significance and Use5.1 This test meth
18、od is used to determine the effect ofexposure to elevated temperatures on the bond strength ofcombinations of magnet wire insulations and electrical insu-lating varnishes. The results are used as a guide for thecomparison and selection of varnishes and combinations ofvarnishes and magnet wire insula
19、tion for specific applications.Test Methods D 1932, D 3251, and D 3850 describe additionaltests for determining the thermal endurance of insulatingvarnishes. A comprehensive evaluation of thermal characteris-tics includes a comparison of the thermal endurance deter-mined in these different ways.5.2
20、This test method is useful for research and productqualifications purposes.6. Apparatus6.1 Testing Machine, see Test Method D 2519.6.2 Test Fixture, see Test Method D 2519.6.3 Ovens, see Specification D 5423, Type II.7. Hazards7.1 It is unsafe to use varnish at temperatures above flashpoint without
21、adequate ventilation, especially if the possibilityexists that flames or sparks are present. Store varnish in sealedcontainers.8. Test Specimen8.1 Prepare 60 or more specimens for each exposure tem-perature, following the procedure specified in Test MethodD 2519.9. Selection of Test Temperatures9.1
22、Expose the material to at least three temperatures.Choose the lowest temperature such that it is not more than 25C higher than the estimated temperature index. Separateexposure temperatures from each other by at least 10 C,preferably 20 C.9.2 Select exposure temperatures in accordance with thoseshow
23、n in Table 1 as indicated by the anticipated temperatureindex of the material under test. It is recommended thatexploratory tests be first made at the highest temperature toobtain data establishing the 100 h minimum endpoint timerequirement, and that this be used as a guide for the selectionof the l
24、ower test temperatures.9.3 Choose the exposure temperature so that any essentiallylinear portions of the Arrhenius plot (log of time to failureversus the reciprocal of the absolute temperature) is wellestablished; that is, confirm the suspicion of significant non-linearity by test at one or more add
25、itional temperatures.Generally the additional temperatures are lower than the onespreviously tested.10. Procedure10.1 Suspend at least 20 sets of coils containing at least 3coils in each set vertically in each oven.10.2 Periodically remove one set of coils and condition 2 hat standard laboratory con
26、ditions in accordance with PracticeD 6054. Measure flexural strength at room temperature inaccordance with Test Method D 2519.10.3 The length of the exposure period and the number ofcoils tested per cycle will depend on the deterioration rate ateach exposure temperature. The exposure period will be
27、longerat the start, shorter as the deterioration rate increases.10.4 Continue the test until the breaking strength reachesless than 22 N (5 lbf). The end point is that point where thecurve intersects the 22-N (5-lbf) line, or other specified value.11. Calculation11.1 Plot the breaking strength value
28、 after each exposureperiod versus time in hours on a three-decade semilog paperwith time as the ordinate.11.2 From the curve, pick the 22-N (5-lbf) point, or speci-fied value, and record the number of hours to reach this point.This is to be done for each temperature and will be known asthe end point
29、 at that temperature.11.3 In order to calculate the temperature index, data mustbe available from a minimum of three exposure temperatures.TABLE 1 Suggested Exposure Temperatures and Cycle DurationsACycleDuration,dayTemperatures Corresponding to the Estimated Temperature Index Range, CB,CClass 105 C
30、lass 130 Class 155 Class 180 Class 200 Class 220100 to109110 to119120 to129130 to139140 to149150 to159160 to169170 to179180 to189190 to199200 to209210 to219220 to229230 to2391 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 17
31、0 180 190 200 210 220 230 240 250 260 270 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 120 130 140 150 160 170 180 190 200 210 220 230 240 25049 110 120 130 140 150 160 170 180 190 200 210 220 230 240ATaken from IEC Publicat
32、ion 60216-1.BExposure temperatures above and below those given are to be selected by experimentation.CRange to which the temperature is assumed to correspond to an extrapolated 20 000 h time to failure.D3145082The highest exposure temperature must have a thermal end-point time of at least 100 h. The
33、 endpoint time at the lowestexposure temperature must have a thermal life of at least5000 h.11.4 Plot the end points at each temperature on graph paperhaving a logarithmic time scale as the ordinate and thereciprocal of the absolute temperature as the abscissa. Draw thebest fit straight line through
34、 all points. For definition of how todraw the best fit line, see the Annex of Test Method D 2307 forcalculation of the regression line.11.5 The temperature where the line crosses the specifiedhour line is the temperature index for the combination used forthe test. Unless otherwise specified, use an
35、hour line of 20 000h.12. Report12.1 Report the following information:12.1.1 Identification of the varnish,12.1.2 Identification of the magnet wire insulation,12.1.3 Cure schedule used,12.1.4 Exposure temperatures, and12.1.5 Temperature index.13. Precision and Bias13.1 PrecisionData from a between-la
36、boratory study4involving three laboratories testing a single unsaturated poly-ester resin yielded:Average temperature index 204Range of values 8Standard deviation 413.2 BiasThis test method has no bias because the valuefor the thermal endurance of insulating varnish using thehelical coil method is d
37、efined in terms of this test method.14. Keywords14.1 electrical insulating; helical coil; magnet wire; thermalendurance; varnishSUMMARY OF CHANGESCommittee D09 has identified the location of selected changes to this test method since the last issue,D 3145 03, that may impact the use of this test met
38、hod. (Approved May 1, 2008)(1) Revised the text throughout to remove nonmandatorylanguage.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination
39、of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn
40、. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your com
41、ments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or
42、 multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: D09-1033.D3145083
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