ASTM_A_912_-_A_912M_-_11.pdf

Designation:A912/A912M11Standard Test Method forAlternating-Current Magnetic Properties of AmorphousMaterials at Power Frequencies Using Wattmeter-Ammeter-Voltmeter Method with Toroidal Specimens1This standard is issued under the fixed designation A912/A912M;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 tests for various magneticproperties of amorphous materials at power frequencies 25 to400 Hz using a toroidal test transformer.The term“toroidaltest transformer”is used to describe the test device,reservingthe term“specimen”to refer to the material used in the test.The test specimen consists of toroidally wound flat strip.1.2 This test method covers the determination of core loss,exciting power,rms and peak exciting current,several types ofac permeability,and related properties under ac magnetizationat moderate and high inductions at power frequencies 25 to 70Hz.1.3 With proper instrumentation and specimen preparation,this test method is acceptable for measurements at frequenciesfrom 5 Hz to 100 kHz.Proper instrumentation implies that alltest instruments have the required frequency bandwidth.Alsosee Annex A2.1.4 This test method also provides procedures for calculat-ing impedance permeability from measured values of rmsexciting current and for calculating ac peak permeability frommeasured peak values of total exciting current at magnetic fieldstrengths up to about 10 Oe 796 A/m.1.5 Explanations of symbols and brief definitions appear inthe text of this test method.The official symbols and definitionsare listed in Terminology A340.1.6 This test method shall be used in conjunction withPractice A34/A34M.1.7 The values and equations stated in customary(cgs-emuand inch-pound)units or SI units are to be regarded separatelyas standard.Within this standard,SI units are shown inbrackets.The values stated in each system may not be exactequivalents;therefore,each system shall be used independentlyof the other.Combining values from the two systems mayresult in nonconformance with this standard.1.8 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 TestingA343/A343M Test Method for Alternating-Current Mag-netic Properties of Materials at Power Frequencies UsingWattmeter-Ammeter-Voltmeter Method and 25-cm Ep-stein Test FrameA901 Specification for Amorphous Magnetic Core Alloys,Semi-Processed TypesC693 Test Method for Density of Glass by Buoyancy3.Significance and Use3.1 This test method provides a satisfactory means ofdetermining various ac magnetic properties of amorphousmagnetic materials.3.2 The procedures described herein are suitable for use byproducers and users of magnetic materials for materials speci-fication acceptance and manufacturing control.3.3 The procedures described herein may be adapted for usewith specimens of other alloys and other toroidal forms.4.Interferences4.1 Test methods using toroidal test transformers are espe-cially useful for evaluating the magnetic properties of a1This test method is under the jurisdiction of ASTM Committee A06 onMagnetic Properties and is the direct responsibility of Subcommittee A06.01 on TestMethods.Current edition approved Oct.1,2011.Published November 2011.Originallyapproved in 1992.Last previous edition approved in 2004 as A912/A912M04.DOI:10.1520/A0912_A0912M-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 material.There are,however,several important requirementsto be met when determining the material characteristics.4.1.1 The ratio of inside to outside diameter must be 0.82 orgreater,or the magnetic field strength will be excessivelynonuniform throughout the test specimen and the measuredparameters will not represent the basic material properties.4.1.2 To best represent the average material properties,thecross-sectional area of the toroid should be uniform and thewinding should be designed to avoid nonuniform induction.4.1.3 Preparation of test specimens,especially of stresssensitive alloys,is critical.Stresses that are introduced into flatstrip material when it is wound into a toroid depend on