ASTM A932 A932M-2001(2006) Standard Test Method for Alternating-Current Magnetic Properties of Amorphous Materials at Power Frequencies Using Wattmeter-Ammeter-Voltmeter Method wit.pdf

1、Designation: A 932/A932M 01 (Reapproved 2006)Standard Test Method forAlternating-Current Magnetic Properties of AmorphousMaterials at Power Frequencies Using Wattmeter-Ammeter-Voltmeter Method with Sheet Specimens1This standard is issued under the fixed designationA932/A932M; the number immediately

2、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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test m

3、ethod covers tests for various magneticproperties of flat-cast amorphous magnetic materials at powerfrequencies (50 and 60 Hz) using sheet-type specimens in ayoke-type test fixture. It provides for testing using eithersingle- or multiple-layer specimens.NOTE 1This test method has been applied only a

4、t frequencies of 50and 60 Hz, but with proper instrumentation and application of theprinciples of testing and calibration embodied in the test method, it isbelieved to be adaptable to testing at frequencies ranging from 25 to400 Hz.1.2 This test method provides a test for specific core loss,specific

5、 exciting power and ac peak permeability at moderateand high flux densities, but is restricted to very soft magneticmaterials with dc coercivities of 0.07 Oe 5.57 A/m or less.1.3 The test method also provides procedures for calculatingac peak permeability from measured peak values of totalexciting c

6、urrents at magnetic field strengths up to about 2 Oe159 A/m.1.4 Explanation of symbols and abbreviated definitionsappear in the text of this test method. The official symbols anddefinitions are listed in Terminology A 340.1.5 This test method shall be used in conjunction withPractice A 34/A 34M.1.6

7、The values stated in either customary (cgs-emu andinch-pound) or SI units are to be regarded separately asstandard. Within this standard, SI units are shown in brackets.The values stated in each system may not be exact equivalents;therefore, each system shall be used independently of the other.Combi

8、ning values from the two systems may result in noncon-formance with this standard.1.7 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 d

9、etermine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A 34/A 34M Practice for Sampling and Procurement Test-ing of Magnetic MaterialsA 340 Terminology of Symbols and Definitions Relating toMagnetic TestingA 343/A 343M Test Method for Alternatin

10、g-Current Mag-netic Properties of Materials at Power Frequencies UsingWattmeter-Ammeter-Voltmeter Method and 25-cm EpsteinTest FrameA 876 Specification for Flat-Rolled, Grain-Oriented,Silicon-Iron, Electrical Steel, Fully Processed TypesA 901 Specification for Amorphous Magnetic Core Alloys,Semi-Pro

11、cessed TypesA 912/A 912M Test Method for Alternating-Current Mag-netic Properties of Amorphous Materials at Power Fre-quencies Using Wattmeter-Ammeter-Voltmeter Methodwith Toroidal Specimens3. Terminology3.1 The definitions of terms, symbols, and conversion fac-tors relating to magnetic testing, use

12、d in this test method, arefound in Terminology A 340.3.2 Definitions of Terms Specific to This Standard:3.2.1 sheet specimena rectangular specimen comprisedof a single piece of material or parallel multiple strips ofmaterial arranged in a single layer.3.2.2 specimen stacktest specimens (as in 3.2.1)

13、 arrangedin a stack two or more layers high.4. Significance and Use4.1 This test method provides a satisfactory means ofdetermining various ac magnetic properties of amorphousmagnetic materials. It was developed to supplement the testingof toroidal and Epstein specimens. For testing toroidal speci-m

14、ens of amorphous materials, refer to Test Method A 912/A 912M.1This test method is under the jurisdiction of ASTM Committee A06 onMagnetic Properties and is the direct responsibility of SubcommitteeA06.01 on TestMethods.Current edition approved May 1, 2006. Published May 2006. Originallyapproved in

15、1995. Last previous edition approved in 2001 as A 932/A 932M 01.2For 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 websi

16、te.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.2 The procedures described herein are suitable for use bymanufacturers and users of amorphous magnetic materials formaterials specification acceptance and manufacturing control.NOT

17、E 2This test method has been principally applied to the magnetictesting of thermally, magnetically annealed, and flattened amorphous stripat 50 and 60 Hz. Specific core loss at 13 or 14 kG 1.3 or 1.4T, specificexciting power at 13 or 14 kG 1.3 or 1.4T, and the flux density, B,at1Oe 79.6 A/m are the

18、recommended parameters for evaluating powergrade amorphous materials.5. Interferences5.1 Because amorphous magnetic strip is commonly lessthan 0.0015 in. 0.04 mm thick, surface roughness tends tohave a large effect on the cross-sectional area and the crosssection in some areas can be less than the c

19、omputed average. Insuch cases, the test results using a single-strip specimen can besubstantially different from that measured with a stack ofseveral strips. One approach to minimize the error caused bysurface roughness is to use several strips in a stack to averageout the variations. The penalty fo

20、r stacking is that the activemagnetic path length of the specimen stack becomes poorlydefined. The variation of the active length increases with eachadditional strip in the stack. Moreover, the active length forstacked strips tends to vary from sample to sample. As thestack height increases, the err

21、or as a result of cross-sectionalvariations diminishes but that as a result of length variationsincreases with the overall optimum at about four to six layers.The accuracy for stacked strips is never as good as for a singlelayer of smooth strip.5.2 Some amorphous magnetic materials are highly magne-

22、tostrictive. This is an additional potential source of errorbecause even a small amount of surface loading, twisting, orflattening will cause a noticeable change in the measuredvalues.6. Basic Test Circuit6.1 Fig. 1 provides a schematic circuit diagram for the testmethod.Apower source of precisely c

23、ontrollable ac sinusoidalvoltage is used to energize the primary circuit. To minimizeflux-waveform distortion, current ratings of the power sourceand of the wiring and switches in the primary circuit shall besuch as to provide very low impedance relative to the imped-ance arising from the test fixtu

24、re and test specimen. Ratings ofswitches and wiring in the secondary circuit also shall be suchas to cause negligible voltage drop between the terminals of thesecondary test winding and the terminals of the measuringinstruments.7. Apparatus7.1 The test circuit shall incorporate as many of the follow

25、-ing components as are required to perform the desired mea-surements.7.2 Yoke Test FixtureFig. 2 shows a line drawing of ayoke fixture. Directions concerning the design, construction,and calibration of the fixture are given in 7.2.1, 7.2.2, AnnexA1, Annex A2, and Annex A3.7.2.1 Yoke StructureVarious

26、 dimensions and fabricationprocedures in construction are permissible. Since the recom-mended calibration procedure requires correlation with the25-cm Epstein test, the minimum inside dimension betweenpole faces must be at least 22 cm 220 mm. The thickness ofthe pole faces should be not less than 2.

27、5 cm 25 mm. Tominimize the influences of coil-end and pole-face effects, theyokes should be thicker than the recommended minimum. Forcalibration purposes, it is suggested that the width of the fixturebe at least 12.0 cm 120 mm which corresponds to thecombined width of four Epstein-type specimens.FIG

28、. 1 Basic Block Circuit Diagram of the Wattmeter MethodA 932/A932M 01 (2006)27.2.2 Test WindingsThe test windings, which shall consistof a primary (exciting) winding and a secondary (potential)winding, shall be uniformly and closely wound on a nonmag-netic, nonconducting coil form and each shall spa

29、n the greatestpossible distance between the pole faces of the yoke fixture. Itis recommended that the number of turns in the primary andsecondary windings be equal. The number of turns may bechosen to suit the instrumentation, mass of specimen, and testfrequency. The secondary winding shall be the i

30、nnermostwinding. The primary and secondary turns shall be wound inthe same direction from a common starting point at one end ofthe coil form. Also, to minimize self-impedances of thewindings, the opening in the coil form should be no greaterthan that required to allow easy insertion of the test spec

31、imen.Construction and mounting of the test coil assembly must besuch that the test specimen will be maintained without me-chanical distortion in the plane established by the pole faces ofthe yoke(s) of the test fixture.7.3 Air-Flux CompensatorTo provide a means of deter-mining intrinsic flux density

32、 in the test specimen, an air-coremutual inductor shall constitute part of the test-coil system.The respective primary and secondary windings of the air-coreinductor and the test-specimen coil shall be connected in seriesand the voltage polarities of the secondary windings shall be inopposition. By

33、proper adjustment of the mutual inductance ofthe air-core inductor, the average voltage developed across thecombined secondary windings is proportional to the intrinsicflux density in the test specimen. Directions for constructionand adjustment of the air-core mutual inductor for air flux arefound i

34、n Annex A3.7.4 Flux Voltmeter, VfA full-wave, true average respond-ing voltmeter, with scale readings in average volts times p.=2 /4 so that its indications will be identical with those ofa true rms voltmeter on a pure sinusoidal voltage, shall beprovided for evaluating the peak value of the test fl

35、ux density.To produce the estimated precision of test under this testmethod, the full-scale meter errors shall not exceed 0.25 %(Note 3). Either digital or analog flux voltmeters are permitted.Use of a digital flux voltmeter with high input impedance(typically, 10 MV) is recommended to minimize load

36、ingeffects and to reduce instrument loss compensation. If ananalog flux voltmeter is used, its input resistance shall begreater then 10 000 V/Vof full-scale indication.Voltage rangesand number of significant digits shall be consistent with theaccuracy specified above. Care shall be taken to avoid er

37、rorscaused by temperature and frequency effects in the instrument.NOTE 3Inaccuracies in setting the test voltage produce errors ap-proximately two times as large in the specific core loss.7.5 RMS Voltmeter, VrmsA true rms-indicating voltmetershall be provided for evaluating the form factor of the vo

38、ltageinduced in the secondary winding of the test fixture and forevaluating the instrument losses. The accuracy of the rmsvoltmeter shall be the same as specified for the flux voltmeter.Either digital or analog rms voltmeters are permitted. Thenormally high input impedance of digital rms voltmeters

39、isdesirable to minimize loading effects and to reduce the mag-nitude of instrument loss compensations. The input resistanceof an analog rms voltmeter shall not be less than 10 000 V/Vof full-scale indication.7.6 Wattmeter, WThe full-scale accuracy of the wattmetershall not be lower than 0.25 % at th

40、e test frequency and unitypower factor. The power factor encountered by a wattmeterduring a core loss test on a specimen is always less than unityand, at flux densities far above the knee of the magnetizationcurve, approaches zero. The wattmeter must maintain 1.0 %accuracy at the lowest power factor

41、 which is presented to it.Variable scaling devices may be used to cause the wattmeter toindicate directly in units of specific core loss if the combinationof basic instruments and scaling devices conforms to thespecifications stated here.7.6.1 Electronic Digital WattmeterAn electronic digitalwattmet

42、er is preferred in this test method because of its digitalreadout and its capability for direct interfacing with electronicdata acquisition systems. A combination true rms voltmeter-wattmeter-rms ammeter is acceptable to reduce the number ofinstruments connected in the test circuit.7.6.1.1 The volta

43、ge input circuitry of the electronic digitalwattmeter must have an input impedance sufficiently high sothat connection to the secondary winding of the test fixtureduring testing does not change the terminal voltage of thesecondary by more than 0.05 %. Also, the voltage inputcircuitry must be capable

44、 of accepting the maximum peakvoltage which is induced in the secondary winding duringtesting.7.6.1.2 The current input circuitry of the electronic digitalwattmeter should have as low an input impedance as possible,preferably no more than 0.1 V, otherwise the flux waveformdistortion tends to be exce

45、ssive. The effect of moderatewaveform distortion is addressed in 10.3. The current inputcircuitry must be capable of accepting the maximum rmscurrent and the maximum peak current drawn by the primarywinding of the test transformer when core loss tests are beingperformed. In particular, since the pri

46、mary current will be verynonsinusoidal (peaked) if core loss tests are performed on aspecimen at flux densities above the knee of the magnetizationcurve, the crest factor capability of the current input circuitryshould be 5 or more.7.6.2 Electrodynamometer WattmeterAreflecting-type as-tatic electrod

47、ynamometer wattmeter is permitted as an alterna-tive to an electronic wattmeter.7.6.2.1 The sensitivity of the electrodynamometer wattme-ter must be such that the connection of the potential circuit ofthe wattmeter, during testing, to the secondary winding of thetest fixture does not change the term

48、inal voltage of theFIG. 2 Single-Yoke Fixture (Exploded View)A 932/A932M 01 (2006)3secondary by more than 0.05 %. Also, the resistance of thepotential circuit of the wattmeter must be sufficiently high sothat the inductive reactance of the potential coil of thewattmeter in combination with the leaka

49、ge reactance of thesecondary circuit of the test fixture does not introduce anadditional phase angle error in the measurements. Should theimpedance of this combined reactance at the test frequencyexceed 1 V per 1000 V of resistance in the wattmeter-potentialcircuit, the potential circuit must be compensated for thisreactance.7.6.2.2 The impedance of the current coil of the electrody-namometer wattmeter should not exceed 2.0 V. If flux wave-form distortion tends to be excessive, this impedance should benot more than 0.1 V. The rated current carrying c