1、Designation: A 889/A 889M 03Standard Test Method forAlternating-Current Magnetic Properties of Materials at LowMagnetic Flux Density Using the Voltmeter-Ammeter-Wattmeter-Varmeter Method and 25-cm Epstein Frame1This standard is issued under the fixed designation A 889/A 889M; 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 the magnetic propertiesof basic flat-rolled magnetic materials at power frequencies (25to 400 Hz) using a 25-cm Epstein test frame and the 25-cmdouble-lap-jointed core.1.2 The magnetic properties of materials are determinedfrom measurements on Epstein core specimens with the c
4、oreand test coils treated as though they constituted a series-parallelequivalent circuit (Fig. A1.1) for the fundamental frequency ofexcitation where the apparent parallel inductance, L1, andresistance, R1, are attributable to the test specimen.1.3 This test method is suitable for the determination
5、of coreloss, rms volt-amperes, rms exciting current, reactive volt-amperes, and related properties of flat-rolled magnetic materi-als under ac magnetization.1.4 The frequency range of this test method is normally thatof the commercial power frequencies 50 to 60 Hz. It is alsoacceptable for measureme
6、nts at frequencies from 25 to 400 Hz.This test method is customarily used on nonoriented electricalsteels at inductions up to 10 kG 1.0 T and for grain-orientedelectrical steels at inductions up to 15 kG 1.5 T.1.5 For reactive properties, both flux and current waveformsintroduce limitations. Over it
7、s range of useful inductions, thevarmeter is valid for the measurement of reactive volt-amperes(vars) and inductance permeability. For the measurement ofthese properties, it is suggested that test inductions be limitedto values sufficiently low that the measured values of vars donot differ by more t
8、han 15 % (Note 1) from those calculatedfrom the measured values of exciting volt-amperes and coreloss.NOTE 1This limitation is placed on this test method in considerationof the nonlinear nature of the magnetic circuit, which leads to a differencebetween vars based on fundamental frequency components
9、 of voltage andcurrent and current after harmonic rejection and vars computed from rmscurrent, voltage, and watt values when one or more of these quantities arenonsinusoidal.1.6 This test method shall be used in conjunction withPractice A 34/A 34M.1.7 Explanation of terms, symbols, and definitions u
10、sed maybe found in the various sections of this test method. The officiallist of definitions and symbols may be found in TerminologyA 340.1.8 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
11、shown in brackets.The values 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.1.9 This standard does not purport to address all of thesafety concer
12、ns, 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 its use.2. Referenced Documents2.1 ASTM Standards:2A 34/A 34M Practice for Sampling and
13、Procurement Test-ing of Magnetic MaterialsA 340 Terminology of Symbols and Definitions Relating toMagnetic TestingA 343 Test Method for Alternating-Current Magnetic Prop-erties of Materials at Power Frequencies Using Wattmeter-Ammeter-Voltmeter Method and 25-cm Epstein TestFrame3. Significance and U
14、se3.1 This test method may be used to determine the specificcore loss, specific reactive power, specific exciting power,inductance permeability, and impedance permeability of flat-rolled magnetic materials over a wide range of inductions andat frequencies up to 400 Hz for symmetrically magnetized te
15、stsamples.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 Oct. 1, 2003. Published November 2003. Originallyapproved in 1988. Last previous edition approved in 1998
16、as A 889 93 (1998).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.1Copyright ASTM International, 100 Barr Ha
17、rbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2 These measurements are used by the producer and userof the flat-rolled material for quality control purposes. Thefundamental assumption inherent in these measurements is thatthey can be correlated with the electromagnetic c
18、haracteristicsof a core fabricated from the flat-rolled material.4. Test Specimen4.1 Select and prepare the specimens for this test in accor-dance with Practice A 34/A 34M.5. Basic Circuit5.1 Fig. 1 shows the essential apparatus and basic circuitconnections for this test. Terminals 1 and 2 are conne
19、cted to asource of adjustable ac voltage of sinusoidal waveform ofsufficient power rating to energize the primary circuit withoutappreciable voltage drop in the source impedance. All primarycircuit switches and all primary wiring should be capable ofcarrying much higher currents than are normally en
20、counteredto limit primary circuit resistance to values that will not causeappreciable distortion of the flux waveform in the specimenwhen relatively nonsinusoidal currents are drawn. The acsource may be an electronic amplifier which has a sine-waveoscillator connected to its input and may include th
21、e necessarycircuitry to maintain a sinusoidal flux waveform by usingnegative feedback of the induced secondary voltage. In thiscase, higher primary resistance can be tolerated since thissystem will maintain sinusoidal flux at much higher primaryresistance. Although the current drain in the secondary
22、 is quitesmall, especially when using modern high-input impedanceinstrumentation, the switches and wiring should be selected tominimize the lead resistance so that the voltage available at theterminals of the instruments is imperceptibly lower than thevoltage at the secondary terminals of the Epstei
23、n test frame.6. Apparatus6.1 The apparatus shall consist of as many of the followingcomponent parts as are required to perform the desiredmeasurement functions:6.2 Epstein Test Frame used for this test shall be inconformity with Annex A1.1 of Test Method A 343.6.3 Voltage and Current Signal Scaling
24、AmplifiersTheseamplifiers are used to amplify or attenuate the voltage inducedin the secondary winding of the test frame and the voltageappearing across the potential terminals of the current shunt,RS, to ranges that are suitable for electronic circuitry. The inputcircuitry of the voltage scaling am
25、plifier must have an inputimpedance sufficiently high that the connection of the circuitryto the secondary winding of the test fixture does not change theterminal voltage of the secondary by more than 0.05 %. Theinput circuitry of the current scaling amplifier must have aninput impedance sufficientl
26、y high that the connection of thecircuitry to the potential terminals of the current shunt does notchange the terminal voltage by more than 0.05 %. Theseamplifiers should have a linear frequency response up to about20 times the test frequency and a gain accuracy of 0.1 % orbetter since all instrumen
27、tation may be, and preferably will be,connected to the output of these amplifiers. Care should beexercised in the design of the amplifiers so that no phase shiftis introduced into either the current or the voltage signal.6.4 Flux VoltmeterThe flux voltmeter for this test shall bea true average-respo
28、nsive voltmeter calibrated to read averagevolts times=2 p/4, so that its indications will be identicalwith those of a true rms voltmeter on a pure sinusoidal voltage.A high-input-resistance, multirange electronic meter with afull-scale accuracy rating of 0.25 % or better is the preferredinstrument.6
29、.5 RMS VoltmeterA true rms-indicating voltmeter isneeded if measurements of exciting current are to be made bymeasuring the voltage drop across the potential terminals of thecurrent shunt. A high-input-resistance, multirange electronicinstrument with a full-scale accuracy of 0.25 % or better isrequi
30、red for this instrument. This voltmeter may also be used tomeasure the true rms voltage on the secondary of the Epsteintest frame.6.6 Wattmeter and VarmeterA wattmeter is required forthe measurement of core loss, and a varmeter is needed for themeasurement of reactive power. Since both are needed to
31、 makeall measurements, the preferred instrumentation is one high-accuracy watt converter and a 90 phase-shift circuit to be usedwith the watt converter to measure the reactive power byshifting the phase of the secondary voltage. Alternatively, awattmeter and a varmeter may be used as required to mak
32、e thedesired measurements. The rated accuracy of the wattmeter atthe test frequency and unity power factor should be less than0.25 % of full scale. The power factor encountered by thewattmeter during a core loss test on a specimen is always lessthan unity and, at inductions well above the knee of th
33、emagnetization curve, approaches zero. The wattmeter mustmaintain adequate accuracy (1 % of reading) even at the mostsevere (lowest) power factor which will be presented to it. Theaccuracy requirements for the varmeter are the same as for thewattmeter.6.6.1 Watt Converter and Phase ShifterAn electro
34、nic wattconverter that has two high impedance inputs and an outputthat is proportional to the product of the signals that are appliedto these inputs is the preferred instrument for the measurementof both power and reactive power. Such devices will probablyrequire the use of scaling amplifiers for th
35、e voltage and currentsignals. This device, which is used for the measurement ofpower, is also used for the measurement of reactive power byshifting the phase of the voltage signal by 90. This can bedone since the secondary voltage is essentially a pure sinusoidFIG. 1 Basic Circuit for Wattmeter-Varm
36、eter MethodA 889/A 889M 032at low-to-moderate inductions, especially if negative feedbackof the secondary voltage is used in the test power supplycircuitry. The phase shifter that is used for this purpose shouldbe a modern operational amplifier device which will accuratelyshift the phase of the inpu
37、t signal by exactly 90 (tolerance of0.1) without affecting the amplitude of the signal.6.6.2 WattmeterAn electronic wattmeter with appropriatevoltage and current ratings is the preferred instrument if theseparate scaling amplifiers and phase-shift circuits are notused. The voltage input circuitry of
38、 the electronic digitalwattmeter must have an input impedance sufficiently high thatthe connection of the circuitry to the secondary winding of thetest fixture does not change the terminal voltage of thesecondary by more than 0.05 %. The voltage circuit must alsobe capable of accepting the maximum p
39、eak voltage which isinduced in the secondary winding during testing. The currentinput circuitry of the electronic digital wattmeter must have aninput impedance of no more than 1 V, and preferably no morethan 0.1 V. The current input circuitry must also be capable ofhandling the maximum rms current a
40、nd the maximum peakcurrent drawn by the primary winding of the test fixture whencore loss tests are being performed.6.6.3 VarmeterAn electronic instrument with appropriatevoltage and current ratings is the preferred instrument if theseparate scaling amplifiers and phase-shift circuits are notused. T
41、he accuracy and impedance characteristics for thevarmeter should be the same as for the wattmeter described in6.6.2.6.7 Current ShuntThis should be a noninductive resistorwith an accuracy rating of 0.1 % or better. This resistor must becapable of handling the full exciting current of the test windin
42、gat the maximum test induction without destructive heating ormore than specified loss of accuracy as a result of self heating.To avoid intolerable levels of distortion, the value of theresistor should be reasonably low. However, a large value ofresistance is desirable to maximize the signal and redu
43、ce theeffects of noise. Fixed resistors of 100, 10, and 1 V are usefulvalues. The selection of shunt should be guided primarily bythe primary current and should be the lowest value whichretains an adequate signal-to-noise ratio.6.8 Power SupplyA source of sinusoidal test power oflow-internal impedan
44、ce and excellent voltage and frequencystability is required for this test. Voltage stability within 0.1 %and frequency accuracy within 0.1 % should be maintained.Electronic power sources using negative feedback from thesecondary winding of the test fixture to reduce flux waveformdistortion have been
45、 found to perform quite satisfactorily inthis test method.7. Procedure7.1 The first steps of procedure for this test method concernthe preparations for testing Epstein specimens which are thesame for this method as given in 6.1, 6.2, and 6.3 of TestMethod A 343.7.2 DemagnetizationConnect the require
46、d apparatus as inFig. 1 with the air-flux compensator in the test frame andTerminals 1 and 2 connected to a suitable power source. WithSwitch S1closed in the position to short RS, increase thevoltage supplied to the test frame from zero to a value in whichthe flux-voltmeter indicates an induction ab
47、ove the knee of themagnetization curve (where the exciting current increasessharply for a small increase in induction). At this point,decrease the voltage slowly and progressively during anelapsed time of 5 to 10 s so that the induction will be reducedsmoothly to a point below the lowest induction a
48、t which testsare to be performed and near zero induction. This willdemagnetize the specimen which is quite important, since mosthighly permeable materials become polarized by handling inthe earths magnetic field during loading of the specimens intothe test frame. After demagnetization, take care not
49、 to jar ormove the specimen in any way that will destroy the desiredreproducible (virgin) magnetic state of negligible flux density.Tests should be made immediately after demagnetization(within 2 to 3 min) for the desired test points.7.2.1 Core Loss, Exciting Current, and Reactive PowerWith an appropriate value for Rsinserted for the inductionrange to be tested (see 6.7), connect an appropriate test powersource to Terminals 1 and 2. Increase the voltage supplied tothe test frame until the flux voltmeter indicates that the desiredtest induction has been reached. R
