ASTM_A_927_-_A_927M_-_11.pdf

Designation:A927/A927M11Standard Test Method forAlternating-Current Magnetic Properties of Toroidal CoreSpecimens Using the Voltmeter-Ammeter-WattmeterMethod1This standard is issued under the fixed designation A927/A927M;the number immediately following the designation indicates the yearof original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon()indicates an editorial change since the last revision or reapproval.1.Scope1.1 This test method covers the determination of several acmagnetic properties of either laminated ring or toroidal tapewound cores made from flat rolled product.1.2 This test method covers test equipment and proceduresfor determination of specific core loss,specific exciting power,and peak permeability for power and audio frequencies(50 to20 000 Hz)under sinusoidal flux conditions.1.3 This test method,because of the use of a feedback-controlled power amplifier,is well suited for determination ofac magnetic properties at magnetic flux densities above theknee of the magnetization curve and is particularly useful fortesting of high-saturation iron-cobalt alloys(for example,alloys listed in Specification A801),although use of this testmethod is not restricted to a particular type of material.1.4 This test method shall be used in conjunction withPractice A34/A34M and Terminology A340.1.5 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard.The values stated ineach system may not be exact equivalents;therefore,eachsystem shall be used independently of the other.Combiningvalues from the two systems may result in non-conformancewith the standard.1.6 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.2.Referenced Documents2.1 ASTM Standards:2A34/A34M Practice for Sampling and Procurement Testingof Magnetic MaterialsA340 Terminology of Symbols and Definitions Relating toMagnetic TestingA697/A697M Test Method forAlternating Current MagneticProperties of Laminated Core Specimen Using Voltmeter-Ammeter-Wattmeter MethodsA801 Specification for Wrought Iron-Cobalt High MagneticSaturation Alloys(UNS R30005 and K92650)3.Significance and Use3.1 This test method is a derivative of Test Method A697/A697M specifically designed for testing of toroidal coreswhich are not covered in Test Method A697/A697M and fortesting at magnetic flux densities above the knee of themagnetization curve.3.2 Specimen size typically ranges from 1 to 1.25 in.25.4to 31.8 mm in inside diameter to 1.5 in.38.1 mm in outsidediameter with weights ranging from 30 to 60 g.Provided thetest equipment is suitably chosen,there is no obvious limit tothe overall size of core that can be tested.If basic materialproperties are desired,then the requirements of 5.1 must beobserved.3.3 The reproducibility and repeatability of this test methodare such that this test method is suitable for design,specifica-tion acceptance,service evaluation,and research and develop-ment.3.4 When testing under sinusoidal flux conditions at mag-netic flux densities approaching saturation,highly peakedmagnetizing waveforms will be present,and the test instru-ments used must have crest factor capabilities of at least 3;otherwise erroneous results will be obtained.1This test method is under the jurisdiction of ASTM Committee A06 and is thedirect responsibility of Subcommittee A06.01 on Test Methods.Current edition approved Aug.1,2011.Published August 2011.Originallyapproved in 1994.Last previous edition approved in 2004 as A927/A927M04.DOI:10.1520/A0927_A0927M-11.2For 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 4.Apparatus4.1 The apparatus for testing under this test method shallconsist of as many of the components,described below andschematically illustrated in Fig.1,as required to perform themeasurements.4.2 Signal GeneratorFor testing at other than line fre-quency(50 or 60 Hz),a low distortion sine wave signalgenerator is required.The frequency accuracy of the signalgenerator should be within 60.1%.To prevent dc biasing ofthe magnetizing current waveform,a blocking capacitor orisolation transformer should be installed between the signalgenerator and power amplifier.4.3 Power AmplifierA linear power amplifier should beused(see Note 1).The signal from the secondary winding ofthe test specimen is used for negative feedback control of themagnetizing waveform.Depending on the power amplifierused,it may be necessary to install