Designation: A1013 − 00 (Reapproved 2013)´1Standard Test Method forHigh-Frequency (10 kHz-1 MHz) Core Loss of Soft MagneticCore Components at Controlled Temperatures Using theVoltmeter-Ammeter-Wattmeter Method1This standard is issued under the fixed designation A1013; 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.ε1NOTE—Language in the units statement was editorially corrected in June 2013.1. Scope1.1 This test method covers the equipment, procedures, andmeasurement of core loss of either toroidal or mated softmagnetic core components, such as soft ferrite cores, ironpowder cores, and so forth, over ranges of controlled ambienttemperatures typically from −20 to +120°C, frequencies from10 kHz to 1 MHz, under sinusoidal flux conditions.1.2 The values and equations stated in customary (cgs-emuand inch-pound) or SI units are to be regarded separately asstandard. Within this test method, SI units are shown inbrackets except for the sections concerning calculations wherethere are separate sections for the respective unit systems. Thevalues stated in each system may not be exact equivalents;therefore, each system shall be used independently of the other.Combining values from the two systems may result in noncon-formance with this standard.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.2. Referenced Documents2.1 ASTM Standards:2A34/A34M Practice for Sampling and Procurement Testingof Magnetic MaterialsA340 Terminology of Symbols and Definitions Relating toMagnetic TestingE177 Practice for Use of the Terms Precision and Bias inASTM Test Methods3. Terminology3.1 The definitions of terms, symbols, and conversion fac-tors relating to magnetic testing, used in this test method, arefound in Terminology A340.3.2 Definitions of Terms Specific to This Standard:3.2.1 bifilar transformer—a transformer in which the turnsof the primary and secondary windings are wound together sideby side and in the same direction. This type of winding resultsin near unity coupling, so that there is a very efficient transferof energy from primary to secondary.3.2.2 core-loss density, Pcd—core loss per unit volume inmW/cm3[W⁄m3].3.2.3 effective permeability—the relative permeability of amagnetic circuit including the effect of air gaps in the magneticpath length.3.2.4 mated core set—two or more core segments assembledwith the magnetic flux path perpendicular to the matingsurface.4. Significance and Use4.1 This test method is designed for testing of either toroidalor mated soft magnetic core components over a range oftemperatures, frequencies, and flux densities.4.2 The reproducibility and repeatability of this test methodare such that it is suitable for design, specification acceptance,service evaluation, and research and development.5. Apparatus5.1 The apparatus shall consist of as many of the componentparts as shown in the block circuit diagrams (Figs. 1 and 2) anddescribed as follows and in the appendix, as required toperform the tests.5.2 Signal Generator—A low distortion sine wave signalgenerator is required. The frequency accuracy of the signalgenerator should be within 60.1 % with an output amplituderange from 1-mV to 10-V p-p.1This 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 May 1, 2013. Published June 2013. Originallyapproved in 2000. Last previous edition approved in 2005 as A1013 – 00 (2005).DOI:10.1520/A1013–00R13E01.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at

[email protected] For Annual Book of ASTMStandards volume information, refer to the standard’s Document Summary page onthe ASTM website.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States15.3 Broadband Power Amplifier, capable of amplifying theoutput of the signal source by 50 dB.5.4 Volt-Amp-Watt Meter with Current Transformer, ac-coupled, broadband, power factor independent, true RMSreading instrument. Voltage channel minimum input imped-ance 1 MΩ, voltage range from 2 to 100 V, current ranges from5 mA to 5A, power ranges from 100 mW to 500 W. Thefull-scale accuracy of the wattmeter shall not exceed 0.75 % ofthe product of the input voltage and current ranges.5.5 Flux Voltmeter—A full-wave true-averaging voltmeterwith scale reading in average volts times 1.111 so that itsindications will be identical with those of a true rms voltmeteron a pure sinusoidal voltage. Input impedance of at least 2 MΩ.To produce the estimated precision of test under this testmethod, the full-scale meter errors shall not exceed 0.25 %.5.6 Temperature Chamber, heated with electric elements,cooled by injecting liquid CO2or liquid nitrogen into the airstream through an expansion nozzle or equivalent methods.5.7 Temperature with Platinum RTD or Type T Thermo-couple.5.8 Optional—Personal computer with appropriate I/O tocontrol equipment and collect data.6. Test Core Component6.1 The test core component can be of any magneticmaterial (soft ferrite, iron powder, and so forth). The effectivepermeability of the material must be sufficiently high so thatthe test core component can be driven to the desired fluxdensity with the available test equipment (within the poweramplifier limitations).6.2 When testing for material properties, the cross-sectionalarea of the test core component shall be uniform throughout itsentire magnetic path length. The core may be of any shape.Shapes with nonuniform cross-sectional areas within theirmagnetic path length can be tested for specific core shapeperformance comparisons; however, the core-loss density willnot be accurate, since the flux density and core loss varythroughout the magnetic path length and are not uniform.6.3 Mated core set assembled around a prewound coil canbe used, as well as toroidal cores.FIG. 1 Basic Circuit for VAW Meter Method Using Primary and Secondary WindingsFIG. 2 Optional Circuit for VAW Meter Method Using One Winding Only (See 7.1)A1013 − 00 (2013)´126.3.1 Mating surfaces must be ground smooth and flat tominimize air gaps. Air gaps cause reluctance in the flux pathand cause flux to fringe, both of which contribute to highermeasured losses.6.3.2 Clamping pressure for the mated core set needs to besufficient to hold the cores together with minimum air gaps butnot so strong that it affects the properties of the materialthrough the creation of stress-magnetostriction anisotropy. Apressure of 5 lb/in.2[35 kPa] is recommended where the areais the area of the mating surfaces.6.4 The length of test leads from the measuring instrumentsto the test core component should be minimized. The test leadsshould be twisted pairs to minimize magnetic pickup. The testlead capacitance can be significant at high frequencies andcontributes to inaccuracy in the measurements.7. Procedure7.1 Prepare the test core component in the form of atransformer by applying windings to a toroid or for a matedcore set by winding a bobbin and then assembling the magneticcores around it. In either case, the winding should be singlelayer, wound as a bifilar transformer, and distributed evenlyaround the winding length. The number of turns is based on themaximum voltage available from the power amplifier calcu-lated using Eq 6. If sufficient wire size (>600 circular mil/amp[0.30 mm2/amp]) is used, the winding losses are negligible;therefore, the secondary of Fig. 1 may be eliminated. Voltagescan then be measured across the primary as shown in theoptional circuit diagram (Fig. 2).7.2 Place the test core component in the temperature cham-ber and attach it to the test equipment.7.3 Set the chamber temperature. Sense the temperature ofthe core material by imbedding a platinum RTD or Type Tthermocouple into a block of material similar to the materialunder test and with a cross-sectional area equal to or larger thanthe test core component. Some materials, such as ferrite, arepoor thermal conductors and therefore may take considerabletime to reach the ambient temperature (20 min for a 0.5- by0.5-in. [12.7- by 12.7-mm] cross-sectional area is common).7.4 Use Eq 6 to calculate the flux voltage for the desired fluxdensity. Set the signal generator to the desired frequency thenadjust the output so that the flux voltmeter indicates the valueof voltage calculated to give the desired test induction. Thevoltage waveform must be sinusoidal to ensure that the powermeasurements are accurate. The simplest way to verify that thevoltage waveform is sinusoidal is to observe that the fluxvoltmeter and the RMS voltmeter indicate equal values within61 %, showing that the form factor of the voltage is 1.111.7.5 For core loss determinations, read and record the powerfrom the wattmeter. Core loss density can be calculated usingEq 7.8. Calculation (Customary Units)8.1 The effective dimensional core parameters of the testspecimen are computed by normalizing the core area (A)throughout the core’s magnetic path length (l). Core constantsC1and C2are calculated and used to calculate effectivemagnetic path length (l1), effective core cross-sectional area(Ae), and effective core volume (Ve), as follows:Core constant, C15(1n1nAncm21(1)Core constant, C25(1n1nAn2cm23(2)Effective magnetic path length, l15~C1!2C2cm (3)Effective core cross 2 sectional area, Ae5C1C2cm2(4)Effective core volume, Ve5~C1!3~C2!2cm3(5)8.2 Calculate flux voltage as follows:Ef5 =2 π BAeN2f 31028(6)where:Ef= flux voltage induced in winding N2,V;B = peak flux density, G;Ae= effective cross-sectional area of the test corecomponent, cm2;N2= number of turns of secondary winding; andf = frequency, Hz.8.3 Calculate specific core loss density as follows:Pcd5PCVe(7)where:Pcd= core loss density, mW/cm3;PC= core loss, mW; andVe= effective core volume, cm3.9. Calculation (SI Units)9.1 The effective dimensional core parameters of the testcore component are computed by normalizing the core area (A)throughout the core’s magnetic path length (l). Core constantsC1and C2are calculated and used to calculate effectivemagnetic path length (l1), effective core cross-sectional area(Ae), and effective core volume (Ve), as follows:Core constant, C15(1n1nAnm21(8)Core constant, C25(1n1nAn2m23(9)Effective magnetic path length, l15~C1!2C2m (10)Effective core cross 2 sectional area, Ae5C1C2m2(11)Effective core volume, Ve5~C1!3~C2!2m3(12)9.2 Calculate flux voltage as follows:Ef5 =2 π BAeN2f (13)where:Ef= flux voltage induced in winding N2,V;B = peak flux density, T;A1013 − 00 (2013)´13Ae= effective cross-sectional area of the test corecomponent, m2;N2= number of turns of secondary winding; andf = frequency, Hz.9.3 Calculate specific core loss density as follows:Pcd5 fPCVe(14)where:Pcd= core-loss density, [W/m3];PC= core loss, W; andVe= effective core volume, m3.10. Report10.1 Report the following information:10.1.1 Core component identification,10.1.2 Test frequencies,10.1.3 Test magnetic flux densities,10.1.4 Test temperature, and10.1.5 Test results (core loss density).11. Precision and Bias11.1 Test Program—Nine independent laboratories per-formed core-loss measurements on a common MnZn ferritetoroid using this test method. The core loss was measured at aninduction of 1 kG [0.1 T], a frequency of 25 kHz, and at 25°C.This data plus an experiment to determine repeatability at onelaboratory were used to develop the following precisioninformation.11.2 Precision—The precision is as follows:Core Loss, W Percent of ValueAverage test value: 0.246 . . .95 % repeatability limit (withinlaboratory)0.008 3.2595 % reproducibility limit(between laboratories)0.055 22.4The preceding terms (repeatability and reproducibility) areused as specified in Practice E177.These values are used for thecomparison of two test results, both of which are singlemeasurements. The respective standard deviations among testresults may be obtained by dividing the preceding values by2.8.11.3 Bias—Since there is no accepted reference material,method, or laboratory suitable for measuring the magneticproperties determined using this test method, there is nostatement of bias.12. Keywords12.1 alternating current; core; core loss; core test; ferritecore; high frequency; magnetic material; magnetic test; sinu-soidal; soft ferrite; volt-amp-wattAPPENDIX(Nonmandatory Information)X1. EQUIPMENT LIST FOR APPARATUS SHOWN IN FIGS. 1 AND 2X1.1 The following equipment list for the apparatus shownin Figs. 1 and 2 is included for information only and does notimply an endorsement of the particular equipment manufactur-ers nor limit the use of comparable equipment.X1.1.1 Signal Generator—HP 3225B or equivalent.X1.1.2 Broadband Power Amplifier —ENI 2100L orequivalent.X1.1.3 Volt-Amp-Watt Meter with Current Transformer—Clarke-Hess Model 258 or equivalent.X1.1.4 Flux Voltmeter—Fluke 8810A with ac converteroption 008 or equivalent.X1.1.5 Temperature Chamber—Delta Design Model 9064or equivalent.X1.1.6 Temperature Meter with Platinum RTD or Type TThermocouple—Newport 269 digital pyrometer or equivalent.X1.1.7 Optional—Personal computer with appropriate I/Oto control equipment and collect data.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. 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