1、Designation: A 348/A 348M 05Standard Test Method forAlternating Current Magnetic Properties of Materials Usingthe Wattmeter-Ammeter-Voltmeter Method, 100 to 10 000 Hzand 25-cm Epstein Frame1This standard is issued under the fixed designationA348/A 348M; the number immediately following the designati
2、on 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 method covers the determ
3、ination of the mag-netic properties of flat-rolled magnetic materials using Epsteintest specimens with double-lap joints in the 25-cm Epsteinframe. It covers determination of core loss, rms and peakexciting current, exciting power, magnetic field strength, andpermeability. This test method is common
4、ly used to testgrain-oriented and nonoriented electrical steels but may also beused to test nickel-iron, cobalt-iron, and other flat-rolledmagnetic materials.1.2 This test method shall be used in conjunction withPractice A 34/A 34M and Test Method A 343/A 343M.1.3 Tests under this test method may be
5、 conducted witheither normal ac magnetization or with ac magnetization andsuperimposed dc bias (incremental magnetization).1.4 In general, this test method has the following limita-tions:1.4.1 FrequencyThe range of this test method normallycovers frequencies from 100 to 10 000 Hz. With properequipme
6、nt, the test method may be extended above 10 000 Hz.When tests are limited to the use of power sources havingfrequencies below 100 Hz, they shall use the procedures ofTestMethod A 343/A 343M.1.4.2 Magnetic Flux Density (may also be referred to asFlux Density)The range of magnetic flux density for th
7、is testmethod is governed by the test specimen properties and by theavailable instruments and other equipment components. Nor-mally, for many materials, the magnetic flux density range isfrom 1 to 15 kG 0.1 to 1.5 T.1.4.3 Core Loss and Exciting PowerThese measurementsare normally limited to test con
8、ditions that do not cause a testspecimen temperature rise in excess of 50C or exceed 100W/lb 220 W/kg.1.4.4 ExcitationEither rms or peak values of excitingcurrent may be measured at any test point that does not exceedthe equipment limitations provided that the impedance of theammeter shunt is low an
9、d its insertion into the test circuit doesnot cause appreciably increased voltage waveform distortion atthe test magnetic flux density.1.4.5 Incremental PropertiesMeasurement of incrementalproperties shall be limited to combinations of ac and dcexcitations that do not cause secondary voltage wavefor
10、mdistortion, as determined by the form factor method, to exceeda shift of 10 % away from sine wave conditions.1.5 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
11、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
12、 this standard.1.6 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.
13、2. Referenced Documents2.1 ASTM Standards:2A 34/A 34M Practice for Sampling and ProcurementTestingof Magnetic MaterialsA 340 Terminology of Symbols and Definitions Relating toMagnetic TestingA 343/A 343M Test Method for Alternating-Current Mag-netic Properties of Materials at Power Frequencies Using
14、Wattmeter-Ammeter-Voltmeter Method and 25-cm EpsteinTest Frame3. Summary of Test Method3.1 A representative sample of the magnetic material is cutinto Epstein strips and then annealed or otherwise treated in1This test method is under the jurisdiction of ASTM Committee A06 onMagnetic Properties and i
15、s the direct responsibility of SubcommitteeA06.01 on TestMethods.Current edition approved Nov. 1, 2005. Published December 2005. Originallyapproved in 1960. Last previous edition approved in 2000 as A 348/A 348M 00.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM
16、Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.accordance with the appropriate
17、 material specification or asagreed between producer and user. The strips are weighed andloaded into the Epstein frame becoming the transformer core.The primary coil is then excited with ac voltage and current atthe frequencies and magnetic flux densities of interest andmeasurements taken. In some c
18、ases, a dc magnetic fieldstrength is superimposed (incremental dc bias). The magneticparameters are then calculated from the data.4. Significance and Use4.1 This test method evaluates the performance of flat-rolledmagnetic materials over a wide frequency range of ac excita-tion with and without incr
19、emental dc bias, as used on trans-formers, motors, and other laminated core devices.4.2 This test method is suitable for design, specificationacceptance, service evaluation, and research.4.3 The application of test results obtained with this testmethod to the design or evaluation of a particular mag
20、neticdevice must recognize the influence of the magnetic circuitryupon its performance. Some specific items to consider are size,shape, holes, welding, staking, bolting, bracketing, shortingbetween laminations, ac waveform, adjacent magnetic fields,and stress.5. Test Specimens5.1 The test specimens
21、shall consist of Epstein strips cutfrom sheets or coiled strips of magnetic materials in accor-dance with the test lot and sampling requirements of PracticeA 34/A 34M, Sections 5 and 7, and Test Method A 343/A343M, Annex A3 (see Note 1).NOTE 1Excessive burr and nonflatness of strips can appreciably
22、affecttest results.5.1.1 If specimen is primarily isotropic, cut one half of thestrips with grain and one-half cross grain. If anisotropic, cut allwith grain. Other ratios of with and cross grain may be chosenby agreement.5.2 The test specimen shall consist of multiples of fourstrips. The total numb
23、er of strips shall be such as to:5.2.1 Provide sufficient total losses to register within therange of required accuracy of the wattmeter.5.2.2 Fill the available vertical opening space in the testframe to at least14 of its maximum height and5.2.3 Contain a minimum of twelve strips.5.3 Check each str
24、ip to assure its length and width areaccurate to 60.04 cm 0.4 mm. If the length is not 30.5 cm305 mm, use the actual length as described in Sections 9 and10.5.4 Table 1 shows the number of Epstein strips that willprovide nominal weights of approximately 125, 250, 500, and1000 g for various strip thi
25、cknesses.6. Basic Circuit (see Fig. 1)6.1 Fig. 1 shows the essential apparatus and basic circuitconnections for this test. The ac source shall be capable ofdriving the test circuit with an ac sinusoidal waveform voltageof desired amplitude and frequency. The series resistancecomponents, r and wattme
26、ter current shunt, in conjunction withthe ac source, shall be such as to provide a pure sine wavevoltage either at the test frame transformer primary, or ifoverall negative feedback is implemented, then the pure sinewave shall be at the test frame transformer secondary. Thewiring and switches shall
27、be selected to minimize current orvoltage reading errors, for example, the voltage connectionsacross r shall be made precisely at the resistor terminals so thatno wire resistance is effectively added to that of the resistor.Also, all voltage reading or negative feedback componentsacross the secondar
28、y of the test frame transformer shall causenegligible loading, that is, shall draw sufficiently low currentsto not appreciably affect power or current readings. When acommon ground connection is made between primary andsecondary of the test frame transformer, the ac source groundconnection must be i
29、solated to eliminate ground loop current.7. Apparatus7.1 The test apparatus shall consist of as many of thefollowing components as required to perform the desiredmeasurement functions:7.2 Balance or ScaleThe balance or scales used fordetermining the mass of the test specimen shall weigh to anaccurac
30、y of 0.05 %. The calculated test voltage Efis directlyproportional to specimen mass and magnetic flux density (seeNote 2).NOTE 2Errors in the weight of a specimen will cause errors inmagnetic flux density, core loss, and exciting power.7.3 Epstein Test Frame:7.3.1 The dimensions of the windings, the
31、ir spacing, and thegeneral precautions and construction details of Test MethodA 343/A 343M, Annex A1, shall apply. The Epstein test frameshould be selected to be compatible with the desired testspecimen size (see 5.4).7.3.2 The following numbers of total winding turns areusually commercially availab
32、le and are suggested for testing atvarious frequencies:TABLE 1 Number of Strips for Various Nominal SpecimenWeight Epstein Frames (Minimum Strip Length is 28 cm 280mm)Nominal Strip ThicknessNumber of Strips for Test Specimens ofNominal WeightThick (cm) Thick (in.) 125 g 250 g 500 g 1000 g0.079 0.031
33、0 . . 12 200.071 0.0280 . . 12 240.064 0.0250 . . 12 240.056 0.0220 . . 16 280.047 0.0185 . 12 16 320.043 0.0170 . 12 20 360.039 0.0155 . 12 20 400.036 0.0140 . 12 24 440.032 0.0125 . 12 24 480.028 0.0110 . 16 28 560.025 0.0100 . 16 32 600.023 0.0090 . 16 36 680.020 0.0080 12 20 40 760.018 0.0070 12
34、 24 44 880.015 0.0060 12 24 52A0.013 0.0050 16 32 60A0.010 0.0040 20 40 76A0.0076 0.0030 24 52AA0.0051 0.0020 40 760.0025 0.0010 76AAAANot recommended.A 348/A 348M 052Frequency, Hz No. of Turns (Both Primary and Secondary)Up to 400 700 or 352400 to 1000 3521000 to 5000 200 (no air-flux compensator)5
35、000 to 10 000 100 (no air-flux compensator)7.3.3 The primary winding is uniformly distributed alongthe magnetic path and may be wound in multiple layers overthe secondary winding. The secondary winding shall be theinnermost winding on the coil form and shall be a single layerwinding. The primary and
36、 secondary shall be wound in thesame direction and their starting end connections shall be madeat the same corner.7.3.4 Air Flux CompensatorIf the Epstein test frame hasmore than 200 turns, it shall contain an air flux compensatorwhich opposes and balances out the air flux voltage induced inthe seco
37、ndary winding. Such compensation is necessary when-ever the permeability of the test specimen is low under highmagnetic field strength conditions to avoid serious errors insetting the flux voltage. The air flux compensator allows thetrue intrinsic induction Bito be measured. When tests arerestricted
38、 to moderate magnetic flux density and field strengthwhere test specimen relative permeability remains high, thedifference between B and Biis small and air flux compensationis unnecessary.7.4 Flux VoltmeterA full wave true average responsivevoltmeter calibrated so that its scale reads true average 3
39、p=2 /4, and indicates the same value as an rms voltmeter whenmeasuring pure sine waves, shall be provided for measuringthe peak value of the test induction. To meet the precision ofthis test method, meter error shall not exceed 0.25 % (see Note3). If the meter impedance is not sufficiently high at t
40、hefrequency of test, it is necessary to compensate for its loadingeffect. To evaluate how much the meter loads the circuit, readthe rms ammeter and rms voltmeter before and after discon-necting the flux voltmeter. When dc bias is applied to the testframe transformer, the flux voltmeter must be able
41、to respondtrue average.NOTE 3Inaccuracies in setting the test voltage produce errors dispro-portionately larger in core loss and exciting current. Evaluate meter errorin accordance with the manufacturers information, for example, percentof range, temperature, and frequency.NOTE 1The ac source termin
42、als must “float” to prevent ground loop currents. If the wattmeter has a common connection between its V and Iterminals, the rest of the circuit must be connected so as to prevent shorting.NOTE 2If, during demagnetization, current exceeds the wattmeter maximum rating, Switch S1 is required and is cl
43、osed.NOTE 3A dc winding is required only if incremental properties are to be tested.NOTE 4The voltage and current monitoring oscilloscope may be a dual channel type and is optional equipment. Basic circuit-wattmeter-ammeter-voltmeter method, 100 to 10 000 Hz and 25-cm Epstein frameFIG. 1 Basic Circu
44、it-Wattmeter-Ammeter-Voltmeter Method, 100 to 10 000 Hz and 25cm Epstein FrameA 348/A 348M 0537.5 RMS VoltmeterARMS voltmeter shall be provided forevaluating the exciting power and also the form factor of thevoltage induced in the secondary winding of the test frametransformer. The meter error shall
45、 not exceed 0.25 % at thefrequency of test. The meter burden shall have no more than0.05 % effect on the test frame transformer voltage or current.To evaluate how much the meter loads the circuit, read theRMS ammeter and flux voltmeter before and after disconnect-ing the RMS voltmeter. When dc bias
46、is applied to the testframe transformer, the RMS meter must be able to indicate trueRMS ac voltage.7.6 Oscilloscope Voltage Monitor (Optional)An oscillo-scope may be provided to monitor the waveshape of thesecondary voltage. Connection of the oscilloscope shall notaffect the voltage or current more
47、than 0.05 %.7.6.1 The oscilloscope dual input common ground connec-tions shall not cause ground loop currents in any part of thecircuit.7.7 WattmeterThe wattmeter error shall not exceed0.25 % at unity power factor at the frequency of test. Errorshall not exceed 1 % of reading at the lowest power fac
48、torencountered. If desired, the reactive power may also bemeasured or calculated.7.7.1 The voltage sensing terminals of the wattmeter shallhave an input impedance sufficiently high that the voltage orcurrent is changed no more than 0.05 %.7.7.2 The current sensing terminals of the wattmeter shallhav
49、e a low impedance so as to not change the test fixturetransformer primary current waveshape appreciably. An inputimpedance of 0.1 V is preferred. The wattmeter shall becapable of accepting the maximum peak current encounteredwithout exceeding its crest factor rating.7.8 RMS AmmeterA RMS ammeter consisting of a RMSvoltmeter connected across the terminals of the current sensingresistor (r in Fig. 1) shall be provided. The RMS voltmetershall have an error no greater than 0.25 % considering themaximum crest factor and all frequencies and amplitudesencou
