ASTM_D_4882_-_05_2012.pdf

Designation:D488205(Reapproved 2012)Standard Test Method forBond Strength of Electrical Insulating Varnishes by theTwisted-Coil Test1This standard is issued under the fixed designation D4882;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 the bondstrength of an electrical insulating varnish when applied to atwisted coil of film-insulated magnet wire.The use of aparticular type of film-insulated wire will show the values forthat combination of film coating and varnish.1.2 The values stated in inch-pound units are the standard.The values given in parentheses are for information only.NOTE1Although this standard and Method C of IEC 61033 differ inapproach or detail,data obtained using either are technically equivalent.1.3 This standard does not purport to address all,if any,ofthe safety 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 7.2.Referenced Documents2.1 ASTM Standards:2D115 Test Methods for Testing Solvent Containing Var-nishes Used for Electrical InsulationD1711 Terminology Relating to Electrical InsulationD2519 Test Method for Bond Strength of Electrical Insulat-ing Varnishes by the Helical Coil TestD6054 Practice for Conditioning Electrical Insulating Mate-rials for Testing(Withdrawn 2012)32.2IEC Standard:IEC 61033 Test Methods for the Determination of BondStrength of Impregnating Agents to an Enamelled WireSubstrate43.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 bond strength,na measure of the force required toseparate surfaces which have been bonded together.3.2 Refer to Terminology D1711 for definitions of otherterms.4.Summary of Test Method4.1 Flexural strength tests are made on twisted coils todetermine the force required to break the coils under specificconditions.5.Significance and Use5.1 Values obtained by flexural test can provide informationwith regard to the bond strength of the particular varnish incombination with a particular type of magnet wire,whenmeasured under conditions described in this test method.6.Apparatus6.1 Coil winder as shown in Fig.1 and Fig.2.6.2 Coil Twister as shown in Fig.3.6.3 Test apparatus as described in Test Method D2519.7.Safety Precautions7.1 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.8.Test Specimen Preparation8.1 The test specimen is a wound coil made from film-insulated magnet wire,28 AWG(0.320 mm).The coil shall be1This 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 D4882 05.DOI:10.1520/D4882-05R12.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from American National Standards Institute,25 W.43rd St.,4thFloor,New York,NY 10036.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 made by means of suitable winding equipment as shown in Fig.1.To prevent opening of the coil after removal from thewinding equipment,each end of the magnet wire,or shortpieces of film-insulated wire,may be wrapped around the coiltwo or three times.For this purpose the winding equipment isprovided with appropriate notches as shown in Fig.2.Forwinding the coil the following dimensions apply:Winding diameter2.25 0.05 in.(57 1 mm)Width of slot.25 0.05 in.(6 1 mm)Number of turns100(See Note 2)Nominal wire diameter28 AWG(0.320 mm)NOTE2Instead of 100 turns of a single wire,50 turns of two parallelwires may be used to provide a bifilar winding.8.1.1 After the coil has been wound,remove it from thewinding equipment and stretch into an oval shape as shown inFig.4.Twist the coil two full turns around its longitudinal axisby means of a twisting device as shown in Fig.3.The twistedcoil formed is about 0.28 in.(7 mm)in diameter and 3.25 to 3.5in.(85 to 90 mm)in length and serves as a substrate for thevarnish.8.2 The type of magnet wire and test conditions shall