ASTM A889/A889M-14(2020)
(Test Method)Standard Test Method for Alternating-Current Magnetic Properties of Materials at Low Magnetic Flux Density Using the Voltmeter-Ammeter-Wattmeter-Varmeter Method and 25-cm Epstein Frame
Standard Test Method for Alternating-Current Magnetic Properties of Materials at Low Magnetic Flux Density Using the Voltmeter-Ammeter-Wattmeter-Varmeter Method and 25-cm Epstein Frame
SIGNIFICANCE AND USE
3.1 This test method may be used to determine the specific core loss, specific reactive power, specific exciting power, inductance permeability, and impedance permeability of flat-rolled magnetic materials over a wide range of inductions and at frequencies up to 400 Hz for symmetrically magnetized test samples.
3.2 These measurements are used by the producer and user of the flat-rolled material for quality control purposes. The fundamental assumption inherent in these measurements is that they can be correlated with the electromagnetic characteristics of a core fabricated from the flat-rolled material.
SCOPE
1.1 This test method covers tests for the magnetic properties of basic flat-rolled magnetic materials at power frequencies (25 to 400 Hz) using a 25-cm Epstein test frame and the 25-cm double-lap-jointed core.
1.2 The magnetic properties of materials are determined from measurements on Epstein core specimens with the core and test coils treated as though they constituted a series-parallel equivalent circuit (Fig. A1.1) for the fundamental frequency of excitation where the apparent parallel inductance, L1, and resistance, R1, are attributable to the test specimen.
1.3 This test method is suitable for the determination of core loss, rms volt-amperes, rms exciting current, reactive volt-amperes, and related properties of flat-rolled magnetic materials under ac magnetization.
1.4 The frequency range of this test method is normally that of the commercial power frequencies 50 to 60 Hz. It is also acceptable for measurements at frequencies from 25 to 400 Hz. This test method is customarily used on nonoriented electrical steels at inductions up to 10 kG [1.0 T] and for grain-oriented electrical steels at inductions up to 15 kG [1.5 T].
1.5 For reactive properties, both flux and current waveforms introduce limitations. Over its range of useful inductions, the varmeter is valid for the measurement of reactive volt-amperes (vars) and inductance permeability. For the measurement of these properties, it is suggested that test inductions be limited to values sufficiently low that the measured values of vars do not differ by more than 15 % (Note 1) from those calculated from the measured values of exciting volt-amperes and core loss.
Note 1: This limitation is placed on this test method in consideration of the nonlinear nature of the magnetic circuit, which leads to a difference between vars based on fundamental frequency components of voltage and current and current after harmonic rejection and vars computed from rms current, voltage, and watt values when one or more of these quantities are nonsinusoidal.
1.6 This test method shall be used in conjunction with Practice A34/A34M.
1.7 Explanation of terms, symbols, and definitions used may be found in the various sections of this test method. The official list of definitions and symbols may be found in Terminology A340.
1.8 The values and equations stated in customary (cgs-emu and inch-pound) or SI units are to be regarded separately as standard. Within this standard, SI units are shown in brackets except for the sections concerning calculations where there are separate sections for the respective unit systems. 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 nonconformance with this standard.
1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.10 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Stand...
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This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: A889/A889M − 14 (Reapproved 2020)
Standard Test Method for
Alternating-Current Magnetic Properties of Materials at Low
Magnetic Flux Density Using the Voltmeter-Ammeter-
Wattmeter-Varmeter Method and 25-cm Epstein Frame
This standard is issued under the fixed designationA889/A889M; the number immediately following the designation indicates the year
of 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 (´) indicates an editorial change since the last revision or reapproval.
current and current after harmonic rejection and vars computed from rms
1. Scope
current, voltage, and watt values when one or more of these quantities are
1.1 This test method covers tests for the magnetic properties
nonsinusoidal.
ofbasicflat-rolledmagneticmaterialsatpowerfrequencies(25
1.6 This test method shall be used in conjunction with
to 400 Hz) using a 25-cm Epstein test frame and the 25-cm
Practice A34/A34M.
double-lap-jointed core.
1.7 Explanationofterms,symbols,anddefinitionsusedmay
1.2 The magnetic properties of materials are determined
befoundinthevarioussectionsofthistestmethod.Theofficial
from measurements on Epstein core specimens with the core
list of definitions and symbols may be found in Terminology
andtestcoilstreatedasthoughtheyconstitutedaseries-parallel
A340.
equivalent circuit (Fig.A1.1) for the fundamental frequency of
1.8 The values and equations stated in customary (cgs-emu
excitation where the apparent parallel inductance, L , and
and inch-pound) or SI units are to be regarded separately as
resistance, R , are attributable to the test specimen.
standard. Within this standard, SI units are shown in brackets
1.3 Thistestmethodissuitableforthedeterminationofcore
except for the sections concerning calculations where there are
loss, rms volt-amperes, rms exciting current, reactive volt-
separate sections for the respective unit systems. The values
amperes, and related properties of flat-rolled magnetic materi-
stated in each system may not be exact equivalents; therefore,
als under ac magnetization.
each system shall be used independently of the other. Combin-
1.4 The frequency range of this test method is normally that
ingvaluesfromthetwosystemsmayresultinnonconformance
of the commercial power frequencies 50 to 60 Hz. It is also
with this standard.
acceptable for measurements at frequencies from 25 to 400 Hz.
1.9 This standard does not purport to address all of the
This test method is customarily used on nonoriented electrical
safety concerns, if any, associated with its use. It is the
steels at inductions up to 10 kG [1.0 T] and for grain-oriented
responsibility of the user of this standard to establish appro-
electrical steels at inductions up to 15 kG [1.5 T].
priate safety, health, and environmental practices and deter-
1.5 Forreactiveproperties,bothfluxandcurrentwaveforms mine the applicability of regulatory limitations prior to use.
introduce limitations. Over its range of useful inductions, the
1.10 This international standard was developed in accor-
varmeter is valid for the measurement of reactive volt-amperes dance with internationally recognized principles on standard-
(vars) and inductance permeability. For the measurement of
ization established in the Decision on Principles for the
these properties, it is suggested that test inductions be limited Development of International Standards, Guides and Recom-
to values sufficiently low that the measured values of vars do
mendations issued by the World Trade Organization Technical
not differ by more than 15 % (Note 1) from those calculated Barriers to Trade (TBT) Committee.
from the measured values of exciting volt-amperes and core
2. Referenced Documents
loss.
2.1 ASTM Standards:
NOTE 1—This limitation is placed on this test method in consideration
A34/A34M Practice for Sampling and Procurement Testing
of the nonlinear nature of the magnetic circuit, which leads to a difference
between vars based on fundamental frequency components of voltage and of Magnetic Materials
A340 Terminology of Symbols and Definitions Relating to
Magnetic Testing
This test method is under the jurisdiction of ASTM Committee A06 on
MagneticPropertiesandisthedirectresponsibilityofSubcommitteeA06.01onTest
Methods. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
CurrenteditionapprovedJune1,2020.PublishedJuly2020.Originallyapproved contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
in 1988. Last previous edition approved in 2014 as A889/A889M – 14. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/A0889_A0889M-14R20. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A889/A889M − 14 (2020)
A343/A343M Test Method for Alternating-Current Mag- terminals of the instruments is imperceptibly lower than the
netic Properties of Materials at Power Frequencies Using voltage at the secondary terminals of the Epstein test frame.
Wattmeter-Ammeter-Voltmeter Method and 25-cm Ep-
6. Apparatus
stein Test Frame
6.1 The apparatus shall consist of as many of the following
3. Significance and Use
component parts as are required to perform the desired
measurement functions:
3.1 This test method may be used to determine the specific
core loss, specific reactive power, specific exciting power,
6.2 Epstein Test Frame used for this test shall be in
inductance permeability, and impedance permeability of flat-
conformity with Annex A1.1 of Test Method A343/A343M.
rolled magnetic materials over a wide range of inductions and
6.3 Voltage and Current Signal Scaling Amplifiers—These
at frequencies up to 400 Hz for symmetrically magnetized test
amplifiers are used to amplify or attenuate the voltage induced
samples.
in the secondary winding of the test frame and the voltage
3.2 These measurements are used by the producer and user
appearing across the potential terminals of the current shunt,
of the flat-rolled material for quality control purposes. The
R , to ranges that are suitable for electronic circuitry.The input
S
fundamentalassumptioninherentinthesemeasurementsisthat
circuitry of the voltage scaling amplifier must have an input
they can be correlated with the electromagnetic characteristics
impedance sufficiently high that the connection of the circuitry
of a core fabricated from the flat-rolled material.
to the secondary winding of the test fixture does not change the
terminal voltage of the secondary by more than 0.05 %. The
4. Test Specimen
input circuitry of the current scaling amplifier must have an
4.1 Select and prepare the specimens for this test in accor-
input impedance sufficiently high that the connection of the
dance with Practice A34/A34M.
circuitry to the potential terminals of the current shunt does not
change the terminal voltage by more than 0.05 %. These
5. Basic Circuit
amplifiers should have a linear frequency response up to about
5.1 Fig. 1 shows the essential apparatus and basic circuit 20 times the test frequency and a gain accuracy of 0.1 % or
connections for this test. Terminals 1 and 2 are connected to a better since all instrumentation may be, and preferably will be,
source of adjustable ac voltage of sinusoidal waveform of connected to the output of these amplifiers. Care should be
exercised in the design of the amplifiers so that no phase shift
sufficient power rating to energize the primary circuit without
appreciable voltage drop in the source impedance.All primary is introduced into either the current or the voltage signal.
circuit switches and all primary wiring should be capable of
6.4 Flux Voltmeter—The flux voltmeter for this test shall be
carrying much higher currents than are normally encountered
a true average-responsive voltmeter calibrated to read average
to limit primary circuit resistance to values that will not cause
volts times =2π/4, so that its indications will be identical with
appreciable distortion of the flux waveform in the specimen
those of a true rms voltmeter on a pure sinusoidal voltage. A
when relatively nonsinusoidal currents are drawn. The ac
high-input-resistance, multirange electronic meter with a full-
source may be an electronic amplifier which has a sine-wave
scale accuracy rating of 0.25 % or better is the preferred
oscillator connected to its input and may include the necessary
instrument.
circuitry to maintain a sinusoidal flux waveform by using
6.5 RMS Voltmeter—A true rms-indicating voltmeter is
negative feedback of the induced secondary voltage. In this
needed if measurements of exciting current are to be made by
case, higher primary resistance can be tolerated since this
measuringthevoltagedropacrossthepotentialterminalsofthe
system will maintain sinusoidal flux at much higher primary
current shunt. A high-input-resistance, multirange electronic
resistance.Although the current drain in the secondary is quite
instrument with a full-scale accuracy of 0.25 % or better is
small, especially when using modern high-input impedance
requiredforthisinstrument.Thisvoltmetermayalsobeusedto
instrumentation, the switches and wiring should be selected to
measure the true rms voltage on the secondary of the Epstein
minimize the lead resistance so that the voltage available at the
test frame.
6.6 Wattmeter and Varmeter—A wattmeter is required for
the measurement of core loss, and a varmeter is needed for the
measurement of reactive power. Since both are needed to make
all measurements, the preferred instrumentation is one high-
accuracy watt converter and a 90° phase-shift circuit to be used
with the watt converter to measure the reactive power by
shifting the phase of the secondary voltage. Alternatively, a
wattmeter and a varmeter may be used as required to make the
desired measurements. The rated accuracy of the wattmeter at
the test frequency and unity power factor should be less than
0.25 % of full scale. The power factor encountered by the
wattmeter during a core loss test on a specimen is always less
than unity and, at inductions well above the knee of the
FIG. 1 Basic Circuit for Wattmeter-Varmeter Method magnetization curve, approaches zero. The wattmeter must
A889/A889M − 14 (2020)
maintain adequate accuracy (1 % of reading) even at the most Electronic power sources using negative feedback from the
severe (lowest) power factor which will be presented to it. The secondary winding of the test fixture to reduce flux waveform
accuracy requirements for the varmeter are the same as for the distortion have been found to perform quite satisfactorily in
wattmeter. this test method.
6.6.1 Watt Converter and Phase Shifter—An electronic watt
converter that has two high impedance inputs and an output 7. Procedure
thatisproportionaltotheproductofthesignalsthatareapplied
7.1 The first steps of procedure for this test method concern
to these inputs is the preferred instrument for the measurement
the preparations for testing Epstein specimens which are the
of both power and reactive power. Such devices will probably
same for this method as given in 6.1, 6.2, and 6.3 of Test
require the use of scaling amplifiers for the voltage and current
Method A343/A343M.
signals. This device, which is used for the measurement of
7.2 Demagnetization—Connect the required apparatus as in
power, is also used for the measurement of reactive power by
Fig. 1 with the air-flux compensator in the test frame and
shifting the phase of the voltage signal by 90°. This can be
Terminals 1 and 2 connected to a suitable power source. With
done since the secondary voltage is essentially a pure sinusoid
Switch S closed in the position to short R , increase the
at low-to-moderate inductions, especially if negative feedback 1 S
voltage supplied to the test frame from zero to a value in which
of the secondary voltage is used in the test power supply
the flux-voltmeter indicates an induction above the knee of the
circuitry. The phase shifter that is used for this purpose should
magnetization curve (where the exciting current increases
be a modern operational amplifier device which will accurately
sharply for a small increase in induction). At this point,
shift the phase of the input signal by exactly 90° (tolerance of
decrease the voltage slowly and progressively during an
0.1°) without affecting the amplitude of the signal.
elapsed time of 5 to 10 s so that the induction will be reduced
6.6.2 Wattmeter—An electronic wattmeter with appropriate
smoothly to a point below the lowest induction at which tests
voltage and current ratings is the preferred instrument if the
are to be performed and near zero induction. This will
separate scaling amplifiers and phase-shift circuits are not
demagnetize the specimen which is quite important, since most
used. The voltage input circuitry of the electronic digital
highly permeable materials become polarized by handling in
wattmeter must have an input impedance sufficiently high that
the earth’s magnetic field during loading of the specimens into
the connection of the circuitry to the secondary winding of the
the test frame. After demagnetization, take care not to jar or
test fixture does not change the terminal voltage of the
move the specimen in any way that will destroy the desired
secondary by more than 0.05 %. The voltage circuit must also
reproducible (virgin) magnetic state of negligible flux density.
be capable of accepting the maximum peak voltage which is
Tests should be made immediately after demagnetization
induced in the secondary winding during testing. The current
(within 2 to 3 min) for the desired test points.
input circuitry of the electronic digital wattmeter must have an
7.2.1 Core Loss, Exciting Current, and Reactive Power—
input impedance of no more than 1Ω, and preferably no more
With an appropriate value for R inserted for the induction
than 0.1Ω. The current input circuitry must also be capable of
s
range to be tested (see 6.7), connect an appropriate test power
handling the maximum rms current and the maximum peak
source to Terminals 1 and 2. Increase the voltage supplied to
current drawn by the primary winding of the test fixture when
the test frame until the flux voltmeter indicates that the desired
core loss tests are being performed.
test induction has been reached. Read the wattmeter to deter-
6.6.3 Varmeter—An electronic instrument with appropriate
mine core loss and the rms voltmeter to determine the rms
voltage and current ratings is the prefe
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