ASTM_A_772_-_A_772M_-_00_2016.pdf

Designation:A772/A772M00(Reapproved 2016)Standard Test Method forAC Magnetic Permeability of Materials Using SinusoidalCurrent1This standard is issued under the fixed designation A772/A772M;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 provides a means for determination ofthe impedance permeability(z)of ferromagnetic materialsunder the condition of sinusoidal current(sinusoidal H)exci-tation.Test specimens in the form of laminated toroidal cores,tape-wound toroidal cores,and link-type laminated coreshaving uniform cross sections and closed flux paths(no airgaps)are used.The method is intended as a means fordetermining the magnetic performance of ferromagnetic striphaving a thickness less than or equal to 0.025 in.0.635 mm.1.2 This test method shall be used in conjunction with thoseapplicable paragraphs in Practice A34/A34M.1.3 The values and equations stated in customary(cgs-emuand inch-pound)or SI units are to be regarded separately asstandard.Within this standard,SI units are shown in bracketsexcept for the sections concerning calculations where there areseparate sections for the respective unit systems.The valuesstated in each system may not be exact equivalents;therefore,each system shall be used independently of the other.Combin-ing values from the two systems may result in nonconformancewith this standard.1.4 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 Testing3.Terminology3.1 DefinitionsThe terms and symbols used in this testmethod are defined in Terminology A340.4.Significance and Use4.1 The permeability determined by this method is theimpedance permeability.Impedance permeability is the ratio ofthe peak value of flux density(Bmax)to the assumed peakmagnetic field strength(Hz)without regard to phase.Ascompared to testing under sinusoidal flux(sinusoidal B)conditions,the permeabilities determined by this method arenumerically lower since,for a given test signal frequency,therate of flux change(dB/dt)is higher.4.2 This test method is suitable for impedance permeabilitymeasurements at very low magnetic inductions at powerfrequencies(50 to 60 Hz)to moderate inductions below thepoint of maximum permeability of the material(the knee of themagnetization curve)or until there is visible distortion of thecurrent waveform.The lower limit is a function of sample area,secondary turns,and the sensitivity of the flux-reading voltme-ter used.At higher inductions,measurements of flux-generatedvoltages that are appreciably distorted mean that the flux hasappreciable harmonic frequency components.The upper limitis given by the availability of pure sinusoidal current,which isa function of the power source.In addition,a large ratio(10)of the total series resistance of the primary circuit to theprimary coil impedance is required.With proper test apparatus,this test method is suitable for use at frequencies up to 1 MHz.4.3 This test method is suitable for design,specificationacceptance,service evaluation,quality control,and researchuse.5.Apparatus5.1 The test circuit,which is schematically illustrated in Fig.1,shall consist of the following components.5.2 Power SupplyFor power frequency(50-or 60-Hz)testing,a suitable power supply consists of two or three seriesconnected autotransformers of sufficient power rating.This1This 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 April 1,2016.Published April 2016.Originallyapproved in 1980.Last previous edition approved in 2011 as A772/A772M 00(2011)1.DOI:10.1520/A0772_A0772M-00R16.2For 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 will provide a continuously variable current source to excitethe test specimen.For testing at other than power frequency,anac power source consisting of a low distortion sinusoidal signalgenerator and linear amplifier are required.The use of feedbackcontrol of the power amplifier is permitted.5.3 Isolation/Stepdown TransformerThe use of a lowdistortion isolation/