ASTM_D_4881_-_05_2012.pdf

Designation:D488105(Reapproved 2012)Standard Test Method forThermal Endurance of Varnished Fibrous-or Film-WrappedMagnet Wire1This standard is issued under the fixed designation D4881;the number immediately following the designation indicates the year oforiginal 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.1.Scope1.1 This test method covers the determination of thermalendurance of rectangular and square fibrous-or film-wrappedmagnet wire coated with an insulating varnish.1.2 The values given in SI units are the standard.The valuesgiven in parentheses are for information only.1.3 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 limitations prior to use.A specific precau-tionary statement is given in Section 5.NOTE1There is no similar or equivalent IEC Standard.2.Referenced Document2.1 ASTM Standards:2D1711 Terminology Relating to Electrical InsulationD2307 Test Method for Thermal Endurance of Film-Insulated Round Magnet WireD3353 Test Methods for Fibrous-Insulated Magnet Wire3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 varnish,electrical insulating,n a liquid resin systemthat is applied to and cured on electrical components providingelectrical,mechanical,and environmental protection.3.1.1.1 DiscussionThere are two types of electrical insu-lating varnishes:solvent-containing and solventless.Solvent-containing types are solutions,dispersions,or emulsions of apolymer or a mixture of polymers in a volatile,nonreactableliquid.Solventless types are liquid resin systems free ofvolatile,nonreactable solvents.3.1.2Refer to Terminology D1711 for definitions of otherterms.4.Significance and Use4.1 Individual varnishes behave differently when applied tothe same fibrous-or film-wrapped magnet wire when exposedto elevated temperatures.Likewise,a varnish does not alwaysbehave the same when applied to different types of fibrous orfilm-wrapped magnet wires and when exposed to elevatedtemperatures.5.Safety Precautions5.1 It is unsafe to use varnish at temperatures above theflash point without adequate ventilation,especially if thepossibility exists that flames or sparks are present.Storevarnish in sealed containers.6.Test Specimens6.1 Construction of Test Specimens:6.1.1 Cut two 250-mm(10-in.)lengths of wire for eachspecimen to be made.6.1.2 Determine the thickness dimensions per Test MethodD3353.6.1.3 Form each length in a fixture as shown in Fig.1.6.1.4 Prepare a test specimen by placing the two formedwires together back to back and wrap tightly with a minimumof 6 turns of glass yarn over the middle 6-in.(150-mm)section.The glass yarn shall have a gap between turns and there mustbe intimate contact of the two wires.6.1.5 Prepare ten specimens for each test temperature.6.2 Varnishing the Test Specimens:6.2.1 Adjust the consistency of a solvent-containing varnishto give a 0.025 6 0.005-mm(0.0010 6 0.0002-in.)cured filmon each side of a 0.13-mm(0.005-in.)copper strip withdrawnat a rate of 100 mm/min(4 in./min).Use solventless varnish asreceived.6.2.2 Submerge the test specimens vertically in the varnishto be tested.Withdraw them at a rate of 100 mm/min(4in./min).Drain the test specimens for 10 to 12 min.Cureaccording to the manufacturers recommendations.If a1This test method is under the jurisdiction of ASTM Committee D09 onElectrical and Electronic Insulating Materials and is the direct responsibility ofSubcommittee D09.01 on Electrical Insulating Varnishes,Powders and Encapsulat-ing Compounds.Current edition approved Jan.1,2012.Published January 2012.Originallyapproved in 1988.Last previous edition approved in 2005 as D4881 05.DOI:10.1520/D4881-05R12.2For referenced ASTM standards,visit the ASTM website,www.astm.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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 solvent-containing varnish is being tested,the test specimensshall be dipped in the reverse direction and cured as before.6.2.3 Expose12in.of bare conductor at one end of eachwire to facilitate electrical connections.7.Procedure7.1 After selecting the test voltage from Table 1,follow theprocedure in Test Method D2307 with the following excep-tions:7.1.1 The described specimen holder and electrical connec-tion device are not required.Instead,lay samples flat on avented tray during oven exposure.7.1.2 Test individual specimens by carefully attaching testleads to each specimen.8.Calculation8.1 After all specimens have failed,calculate the endpointtime at