1、Designation: A 804/A 804M 04Standard Test Methods forAlternating-Current Magnetic Properties of Materials atPower Frequencies Using Sheet-Type Test Specimens1This standard is issued under the fixed designation A 804/A 804M; the number immediately following the designation indicates the yearof origin
2、al 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 These test methods cover the determination of specificcore loss
3、and peak permeability of single layers of sheet-typespecimens tested with normal excitation at a frequency of 50 or60 Hz.NOTE 1These test methods have been applied only at the commercialpower frequencies, 50 and 60 Hz, but with proper instrumentation andapplication of the principles of testing and c
4、alibration embodied in the testmethods, they are believed to be adaptable to testing at frequenciesranging from 25 to 400 Hz.1.2 These test methods use calibration procedures thatprovide correlation with the 25-cm 250-mm Epstein test.1.3 The range of test magnetic flux densities is governed bythe pr
5、operties of the test specimen and by the availableinstruments and other equipment components. Normally, non-oriented electrical steels can be tested over a range from 8 to 16kG 0.8 to 1.6 T for core loss. For oriented electrical steels, thenormal range extends to 18 kG 1.8 T. Maximum magneticflux de
6、nsities in peak permeability testing are limited princi-pally by heating of the magnetizing winding and tests arelimited normally to a maximum ac magnetic field strength ofabout 150 Oe 12 000 A/m.1.4 These test methods cover two alternative procedures asfollows:Test Method 1Sections 6-12Test Method
7、2Sections 13-191.4.1 Test Method 1 uses a test fixture having (1) twowindings that encircle the test specimen, and (2) a ferromag-netic yoke structure that serves as the flux return path and haslow core loss and low magnetic reluctance.1.4.2 Test Method 2 uses a test fixture having (1) twowindings t
8、hat encircle the test specimen, (2) a third windinglocated inside the other two windings and immediately adja-cent to one surface of the test specimen, and (3) a ferromag-netic yoke structure which serves as the flux-return path andhas low magnetic reluctance.1.5 The values and equations stated in c
9、ustomary (cgs-emuand inch-pound) units or SI units are to be regarded separatelyas standard. Within this standard, 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 b
10、e 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.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility
11、 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:2A 34/A 34M Practice for Sampling and Procurement Test-ing of Magnetic MaterialsA 340 Terminology of S
12、ymbols and Definitions Relating toMagnetic TestingA 343/A 343M Test Method for Alternating-Current Mag-netic Properties of Materials at Power Frequencies UsingWattmeter-Ammeter-Voltmeter Method and 25-cm EpsteinTest FrameA 677/A 677M Specification for Nonoriented ElectricalSteel Fully Processed Type
13、sA 683/A 683M Specification for Nonoriented ElectricalSteel, Semiprocessed TypesA 876 Specification for Flat-Rolled, Grain-Oriented,Silicon-Iron Electrical Steel, Fully Processed Types3. Terminology3.1 Definitions:3.1.1 GeneralThe definitions of terms, symbols, and con-version factors relating to ma
14、gnetic testing found in DefinitionsA 340 are used in these methods.1These methods are under the jurisdiction of ASTM Committee A06 onMagnetic Properties and are the direct responsibility of Subcommittee A06.01 onTest Methods.Current edition approved May 1, 2004. Published May 2004. Originallyapprove
15、d in 1982. Last previous edition approved in 1999 as A 804/A 804M 99.2For 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
16、website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2 Definitions of Terms Specific to This Standard:3.2.1 sheet specimena rectangular specimen comprised ofa single piece of material or paralleled multiple strips ofmaterial arr
17、anged in a single layer.4. Significance and Use4.1 Materials EvaluationThese test methods were devel-oped to supplement the testing of Epstein specimens forapplications involving the use of flat, sheared laminationswhere the testing of Epstein specimens in either the as-shearedor stress-relief-annea
18、led condition fails to provide the mostsatisfactory method of predicting magnetic performance in theapplication. As a principal example, the methods have beenfound particularly applicable to the control and evaluation ofthe magnetic properties of thermally flattened, grain-orientedelectrical steel (
19、Condition F5, Specification A 876) used aslamination stock for cores of power transformers. Inasmuch asthe methods can only be reliably used to determine unidirec-tional magnetic properties, the methods have limited applica-bility to the testing of fully processed nonoriented electricalsteels as nor
20、mally practiced (Specification A 677/A 677M).4.2 Specification AcceptanceThe reproducibility of testresults and the accuracy relative to the 25-cm 250-mmEpstein method of test are considered such as to render themethods suitable for materials specification testing.4.3 Interpretation of Test ResultsB
21、ecause of specimensize, considerable variation in magnetic properties may bepresent within a single specimen or between specimens thatmay be combined for testing purposes. Also, variations mayexist in test values that are combined to represent a test lot ofmaterial. Test results reported will theref
22、ore, in general, repre-sent averages of magnetic quality and in certain applications,particularly those involving narrow widths of laminations,deviations in magnetic performance from those expected fromreported data may occur at times. Additionally, application oftest data to the design or evaluatio
23、n of a particular magneticdevice must recognize the influence of magnetic circuitry uponperformance and the possible deterioration in magnetic prop-erties arising from construction of the device.4.4 Recommended Standard TestsThese methods havebeen principally applied to the magnetic testing of therm
24、allyflattened, grain-oriented electrical steels at 50 and 60 Hz.Specific core loss at 15 or 17 kG 1.5 or 1.7 T and peakpermeability (if required) at 10 Oe 796 A/m are the recom-mended parameters for evaluating this class of material.5. Sampling5.1 Lot Size and SamplingUnless otherwise establishedby
25、mutual agreement between the manufacturer and the pur-chaser, determination of a lot size and the sampling of a lot toobtain sheets for specimen preparation shall follow the recom-mendations of Practice A 34, Sections 4 and 5.METHOD 1 TWO-WINDING YOKE-FIXTURE TESTMETHOD6. Basic Test Circuit6.1 Fig.
26、1 provides a schematic circuit diagram for the testmethod. A power source of precisely controllable 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
27、 as to provide very low impedance relative to the imped-ance arising from the test fixture 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 measu
28、ringinstruments.7. Apparatus7.1 The test circuit shall incorporate as many of the follow-ing components as are required to perform the desired mea-surements.7.2 Yoke Test FixtureFig. 2 and Fig. 3 show line drawingsof a single-yoke fixture and a double-yoke fixture, respectively.A double-yoke fixture
29、 is preferred in this method but asingle-yoke fixture is permitted. Directions concerning thedesign, construction, and calibration of the fixture are given in7.2.1, 7.2.2, Annex A1, and Annex A2.FIG. 1 Basic Circuit Diagram for Method 1A 804/A 804M 0427.2.1 Yoke StructureVarious dimensions and fabri
30、cationprocedures in construction are permissible. Since the recom-mended calibration procedure provides correlation with the25-cm 250-mm Epstein test, the minimum inside dimensionbetween pole faces must be at least 22 cm 220 mm. Thethickness of the pole faces should be not less than 2.5 cm 25mm. It
31、is recognized that pole faces as narrow as 1.9 cm 19mm are being used with nickel-iron yoke systems with goodresults. To minimize the influences of coil-end and pole-faceeffects, the yokes should be longer than the recommendedminimum. For calibration purposes, it is suggested that thewidth of the fi
32、xture be such as to accommodate a specimen ofat least 36-cm 360-mm width which corresponds to thecombined width of twelve Epstein-type specimens. Should thefixture width be less than 36 cm 360 mm, it will be necessaryto test each calibration specimen in two parts and average theresults.7.2.2 Test Wi
33、ndingsThe 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 span the greatestpracticable distance between the pole faces of the yoke fixture.It is recomm
34、ended 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 innermostwinding and, with instrumentation of suitably high inputresistance, normally may
35、 consist of a single layer. To reduceself-impedance and thereby minimize flux-waveform distor-tion, it is recommended that the primary winding consist ofmultiple layers of equal turns connected in parallel. Thenumber of such layers should be optimized based on consid-eration of a reduction in windin
36、g resistance versus an increasein inductive reactance at the third harmonic of the principal testfrequency used. The primary and secondary turns shall bewound in the same direction from a common starting point atone end of the coil form. Also, to minimize self-impedances ofthe windings, the opening
37、in the coil form should be no greaterthan required to allow easy insertion of the test specimen.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 tes
38、t fixture.7.3 Air-Flux CompensatorTo provide a means of deter-mining intrinsic induction 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
39、in seriesand the voltage polarities of the secondary windings shall be inopposition. By proper adjustment of the mutual inductance ofthe air-core inductor, the average of the voltage developedacross the combined secondary windings is proportional to theintrinsic induction in the test specimen. Direc
40、tions for con-struction and adjustment of the air-core mutual inductor forair-flux compensation are found in Annex A3.7.4 Flux Voltmeter, VfA full-wave, true-average voltme-ter, with scale reading in average voltage times 1.111 so that itsindications will be identical with those of a true rms voltme
41、teron a pure sinusoidal voltage, shall be provided for evaluatingthe peak value of the test magnetic flux density. To produce theestimated precision of test under this method, the full-scalemeter errors shall not exceed 0.25 % (Note 2). Meters of 0.5 %or more error may be used at reduced accuracy. E
42、ither digitalor analog flux voltmeters are permitted. The normally highinput impedance of digital voltmeters is desirable to minimizeloading effects and to reduce the magnitude of instrument losscompensations. The input resistance of an analog flux voltme-ter shall not be less than 1000 V/V of full-
43、scale indication. Aresistive voltage divider, a standard-ratio transformer, or othervariable scaling device may be used to cause the flux voltmeterto indicate directly in units of magnetic flux density if thecombination of basic instrument and scaling device conformsto the specifications stated abov
44、e.NOTE 2Inaccuracies in setting the test voltage produce percentageerrors approximately two times as large in the specific core loss. Careshould also be taken to avoid errors caused by temperature and frequencyeffects in the instrument.7.4.1 If used with a mutual inductor as a peak ammeter atmagneti
45、c flux densities well above the knee of the magnetiza-tion curve, the flux voltmeter must be capable of accuratelymeasuring the extremely nonsinusoidal (peaked) voltage that isinduced in the secondary winding of the mutual inductor.Additionally, if so used, an analog flux voltmeter should havean inp
46、ut resistance of 5000 to 10 000 V/V of full-scaleindication.7.5 RMS Voltmeter, VrmsA true rms-indicating voltmetershall be provided for evaluating the form factor of the voltageFIG. 2 Single-Yoke Fixture (Exploded View)FIG. 3 Double-Yoke Fixture (Exploded View)A 804/A 804M 043induced in the secondar
47、y winding of the test fixture and forevaluating the instrument losses. The accuracy of the rmsvoltmeter shall be the same as that specified for the fluxvoltmeter. Either digital or analog rms voltmeters are permit-ted. The normally high input impedance of digital voltmeters isdesirable to minimize l
48、oading effects and to reduce the mag-nitude of instrument loss compensations. The input resistanceof an analog rms voltmeter shall not be less than 500 V/V offull-scale indication.7.6 Wattmeter, WThe full-scale accuracy of the wattmetermust be better than 60.25 % at the frequency of test and atunity
49、 power factor. The power factor encountered by a watt-meter during a core loss test on a specimen is always less thanunity and, at magnetic flux densities far above the knee of themagnetization curve, approaches zero. The wattmeter mustmaintain adequate accuracy (better than 61 % of reading) evenat the most severe (lowest) power factor that 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 instrument and scaling devices conforms to t
