ASTM A348/A348M-05(2021)
(Test Method)Standard Test Method for Alternating Current Magnetic Properties of Materials Using the Wattmeter-Ammeter-Voltmeter Method, 100 to 10 000 Hz and 25-cm Epstein Frame
Standard Test Method for Alternating Current Magnetic Properties of Materials Using the Wattmeter-Ammeter-Voltmeter Method, 100 to 10 000 Hz and 25-cm Epstein Frame
SIGNIFICANCE AND USE
4.1 This test method evaluates the performance of flat-rolled magnetic materials over a wide frequency range of ac excitation with and without incremental dc bias, as used on transformers, motors, and other laminated core devices.
4.2 This test method is suitable for design, specification acceptance, service evaluation, and research.
4.3 The application of test results obtained with this test method to the design or evaluation of a particular magnetic device must recognize the influence of the magnetic circuitry upon its performance. Some specific items to consider are size, shape, holes, welding, staking, bolting, bracketing, shorting between laminations, ac waveform, adjacent magnetic fields, and stress.
SCOPE
1.1 This test method covers the determination of the magnetic properties of flat-rolled magnetic materials using Epstein test specimens with double-lap joints in the 25-cm Epstein frame. It covers determination of core loss, rms and peak exciting current, exciting power, magnetic field strength, and permeability. This test method is commonly used to test grain-oriented and nonoriented electrical steels but may also be used to test nickel-iron, cobalt-iron, and other flat-rolled magnetic materials.
1.2 This test method shall be used in conjunction with Practice A34/A34M and Test Method A343/A343M.
1.3 Tests under this test method may be conducted with either normal ac magnetization or with ac magnetization and superimposed dc bias (incremental magnetization).
1.4 In general, this test method has the following limitations:
1.4.1 Frequency—The range of this test method normally covers frequencies from 100 to 10 000 Hz. With proper equipment, the test method may be extended above 10 000 Hz. When tests are limited to the use of power sources having frequencies below 100 Hz, they shall use the procedures of Test Method A343/A343M.
1.4.2 Magnetic Flux Density (may also be referred to as Flux Density)—The range of magnetic flux density for this test method is governed by the test specimen properties and by the available instruments and other equipment components. Normally, for many materials, the magnetic flux density range is from 1 to 15 kG [0.1 to 1.5 T].
1.4.3 Core Loss and Exciting Power—These measurements are normally limited to test conditions that do not cause a test specimen temperature rise in excess of 50°C or exceed 100 W/lb [220 W/kg].
1.4.4 Excitation—Either rms or peak values of exciting current may be measured at any test point that does not exceed the equipment limitations provided that the impedance of the ammeter shunt is low and its insertion into the test circuit does not cause appreciably increased voltage waveform distortion at the test magnetic flux density.
1.4.5 Incremental Properties—Measurement of incremental properties shall be limited to combinations of ac and dc excitations that do not cause secondary voltage waveform distortion, as determined by the form factor method, to exceed a shift of 10 % away from sine wave conditions.
1.5 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.
1.6 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.
1.7 This international standard was developed in accordance with internationally recognized princi...
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Standards Content (Sample)
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: A348/A348M − 05 (Reapproved 2021)
Standard Test Method for
Alternating Current Magnetic Properties of Materials Using
the Wattmeter-Ammeter-Voltmeter Method, 100 to 10 000 Hz
and 25-cm Epstein Frame
This standard is issued under the fixed designationA348/A348M; the number immediately following the designation indicates the year
of original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.
A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.4.4 Excitation—Either rms or peak values of exciting
current may be measured at any test point that does not exceed
1.1 This test method covers the determination of the mag-
the equipment limitations provided that the impedance of the
netic properties of flat-rolled magnetic materials using Epstein
ammeter shunt is low and its insertion into the test circuit does
test specimens with double-lap joints in the 25-cm Epstein
notcauseappreciablyincreasedvoltagewaveformdistortionat
frame. It covers determination of core loss, rms and peak
the test magnetic flux density.
exciting current, exciting power, magnetic field strength, and
1.4.5 Incremental Properties—Measurement of incremental
permeability. This test method is commonly used to test
properties shall be limited to combinations of ac and dc
grain-orientedandnonorientedelectricalsteelsbutmayalsobe
excitations that do not cause secondary voltage waveform
used to test nickel-iron, cobalt-iron, and other flat-rolled
distortion, as determined by the form factor method, to exceed
magnetic materials.
a shift of 10% away from sine wave conditions.
1.2 This test method shall be used in conjunction with
1.5 The values and equations stated in customary (cgs-emu
Practice A34/A34M and Test Method A343/A343M.
and inch-pound) or SI units are to be regarded separately as
1.3 Tests under this test method may be conducted with
standard. Within this standard, SI units are shown in brackets
either normal ac magnetization or with ac magnetization and
except for the sections concerning calculations where there are
superimposed dc bias (incremental magnetization).
separate sections for the respective unit systems. The values
1.4 In general, this test method has the following limita- stated in each system may not be exact equivalents; therefore,
each system shall be used independently of the other. Combin-
tions:
1.4.1 Frequency—The range of this test method normally ingvaluesfromthetwosystemsmayresultinnonconformance
covers frequencies from 100 to 10000 Hz. With proper with this standard.
equipment,thetestmethodmaybeextendedabove10000Hz.
1.6 This standard does not purport to address all of the
When tests are limited to the use of power sources having
safety concerns, if any, associated with its use. It is the
frequenciesbelow100Hz,theyshallusetheproceduresofTest
responsibility of the user of this standard to establish appro-
Method A343/A343M.
priate safety, health, and environmental practices and deter-
1.4.2 Magnetic Flux Density (may also be referred to as
mine the applicability of regulatory limitations prior to use.
Flux Density)—Therangeofmagneticfluxdensityforthistest
1.7 This international standard was developed in accor-
method is governed by the test specimen properties and by the
dance with internationally recognized principles on standard-
available instruments and other equipment components.
ization established in the Decision on Principles for the
Normally, for many materials, the magnetic flux density range
Development of International Standards, Guides and Recom-
is from 1 to 15 kG [0.1 to 1.5 T].
mendations issued by the World Trade Organization Technical
1.4.3 Core Loss and Exciting Power—These measurements
Barriers to Trade (TBT) Committee.
are normally limited to test conditions that do not cause a test
2. Referenced Documents
specimen temperature rise in excess of 50°C or exceed 100
W/lb [220 W/kg].
2.1 ASTM Standards:
A34/A34MPractice for Sampling and Procurement Testing
of Magnetic Materials
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
Current edition approved June 1, 2021. Published June 2021. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1960. Last previous edition approved in 2015 as A348/A348M–05 Standards volume information, refer to the standard’s Document Summary page on
(2015). DOI: 10.1520/A0348_A0348M-05R21. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A348/A348M − 05 (2021)
A340Terminology of Symbols and Definitions Relating to 5.4 Table 1 shows the number of Epstein strips that will
Magnetic Testing provide nominal weights of approximately 125, 250, 500, and
A343/A343MTest Method for Alternating-Current Mag- 1000 g for various strip thicknesses.
netic Properties of Materials at Power Frequencies Using
6. Basic Circuit (see Fig. 1)
Wattmeter-Ammeter-Voltmeter Method and 25-cm Ep-
stein Test Frame
6.1 Fig. 1 shows the essential apparatus and basic circuit
connections for this test. The ac source shall be capable of
3. Summary of Test Method
driving the test circuit with an ac sinusoidal waveform voltage
3.1 A representative sample of the magnetic material is cut
of desired amplitude and frequency. The series resistance
into Epstein strips and then annealed or otherwise treated in
components, randwattmetercurrentshunt,inconjunctionwith
accordance with the appropriate material specification or as
the ac source, shall be such as to provide a pure sine wave
agreed between producer and user. The strips are weighed and
voltage either at the test frame transformer primary, or if
loaded into the Epstein frame becoming the transformer core.
overall negative feedback is implemented, then the pure sine
The primary coil is then excited with ac voltage and current at
wave shall be at the test frame transformer secondary. The
the frequencies and magnetic flux densities of interest and
wiring and switches shall be selected to minimize current or
measurements taken. In some cases, a dc magnetic field
voltage reading errors, for example, the voltage connections
strength is superimposed (incremental dc bias). The magnetic
across rshallbemadepreciselyattheresistorterminalssothat
parameters are then calculated from the data.
no wire resistance is effectively added to that of the resistor.
Also, all voltage reading or negative feedback components
4. Significance and Use
across the secondary of the test frame transformer shall cause
4.1 Thistestmethodevaluatestheperformanceofflat-rolled
negligible loading, that is, shall draw sufficiently low currents
magnetic materials over a wide frequency range of ac excita-
to not appreciably affect power or current readings. When a
tion with and without incremental dc bias, as used on
common ground connection is made between primary and
transformers, motors, and other laminated core devices.
secondary of the test frame transformer, the ac source ground
connection must be isolated to eliminate ground loop current.
4.2 This test method is suitable for design, specification
acceptance, service evaluation, and research.
7. Apparatus
4.3 The application of test results obtained with this test
7.1 The test apparatus shall consist of as many of the
method to the design or evaluation of a particular magnetic
following components as required to perform the desired
device must recognize the influence of the magnetic circuitry
measurement functions:
uponitsperformance.Somespecificitemstoconsideraresize,
7.2 Balance or Scale—The balance or scales used for
shape, holes, welding, staking, bolting, bracketing, shorting
determining the mass of the test specimen shall weigh to an
between laminations, ac waveform, adjacent magnetic fields,
accuracy of 0.05%. The calculated test voltage E is directly
and stress.
f
proportional to specimen mass and magnetic flux density (see
5. Test Specimens
Note 2).
5.1 The test specimens shall consist of Epstein strips cut
from sheets or coiled strips of magnetic materials in accor-
TABLE 1 Number of Strips for Various Nominal Specimen Weight
dance with the test lot and sampling requirements of Practice
Epstein Frames (Minimum Strip Length is 28 cm [280 mm])
A34/A34M, Sections 5 and 7, and Test Method A343/A343M,
Number of Strips for Test Specimens of
Nominal Strip Thickness
Annex A3 (see Note 1).
Nominal Weight
Thick (cm) Thick (in.) 125 g 250 g 500 g 1000 g
NOTE1—Excessiveburrandnonflatnessofstripscanappreciablyaffect
0.079 0.0310 . . 12 20
test results.
0.071 0.0280 . . 12 24
5.1.1 If specimen is primarily isotropic, cut one half of the
0.064 0.0250 . . 12 24
0.056 0.0220 . . 16 28
stripswithgrainandone-halfcrossgrain.Ifanisotropic,cutall
0.047 0.0185 . 12 16 32
with grain. Other ratios of with and cross grain may be chosen
0.043 0.0170 . 12 20 36
by agreement.
0.039 0.0155 . 12 20 40
0.036 0.0140 . 12 24 44
5.2 The test specimen shall consist of multiples of four
0.032 0.0125 . 12 24 48
strips. The total number of strips shall be such as to: 0.028 0.0110 . 16 28 56
0.025 0.0100 . 16 32 60
5.2.1 Provide sufficient total losses to register within the
0.023 0.0090 . 16 36 68
range of required accuracy of the wattmeter.
0.020 0.0080 12 20 40 76
5.2.2 Fill the available vertical opening space in the test
0.018 0.0070 12 24 44 88
A
1 0.015 0.0060 12 24 52
frame to at least ⁄4 of its maximum height and
A
0.013 0.0050 16 32 60
5.2.3 Contain a minimum of twelve strips. A
0.010 0.0040 20 40 76
AA
0.0076 0.0030 24 52
5.3 Check each strip to assure its length and width are
AA
0.0051 0.0020 40 76
AAA
accurate to 60.04 cm [0.4 mm]. If the length is not 30.5 cm
0.0025 0.0010 76
[305 mm], use the actual length as described in Sections 9 and A
Not recommended.
10.
A348/A348M − 05 (2021)
NOTE 1—The ac source terminals must “float” to prevent ground loop currents. If the wattmeter has a common connection between its V and I
terminals, the rest of the circuit must be connected so as to prevent shorting.
NOTE 2—If, during demagnetization, current exceeds the wattmeter maximum rating, Switch S1 is required and is closed.
NOTE 3—A dc winding is required only if incremental properties are to be tested.
NOTE 4—The voltage and current monitoring oscilloscope may be a dual channel type and is optional equipment. Basic circuit-wattmeter-ammeter-
voltmeter method, 100 to 10000 Hz and 25-cm Epstein frame
FIG. 1 Basic Circuit-Wattmeter-Ammeter-Voltmeter Method, 100 to 10 000 Hz and 25–cm Epstein Frame
NOTE 2—Errors in the weight of a specimen will cause errors in 7.3.4 Air Flux Compensator—If the Epstein test frame has
magnetic flux density, core loss, and exciting power.
more than 200 turns, it shall contain an air flux compensator
7.3 Epstein Test Frame:
which opposes and balances out the air flux voltage induced in
7.3.1 Thedimensionsofthewindings,theirspacing,andthe
the secondary winding. Such compensation is necessary when-
general precautions and construction details of Test Method
ever the permeability of the test specimen is low under high
A343/A343M, Annex A1, shall apply. The Epstein test frame
magnetic field strength conditions to avoid serious errors in
should be selected to be compatible with the desired test
setting the flux voltage. The air flux compensator allows the
specimen size (see 5.4).
true intrinsic induction B to be measured. When tests are
i
7.3.2 The following numbers of total winding turns are
restricted to moderate magnetic flux density and field strength
usually commercially available and are suggested for testing at
where test specimen relative permeability remains high, the
various frequencies:
difference between B and B is small and air flux compensation
i
Frequency, Hz No. of Turns (Both Primary and Secondary)
is unnecessary.
Up to 400 700 or 352
7.4 Flux Voltmeter—A full wave true average responsive
400 to 1000 352
voltmeter calibrated so that its scale reads true average
1000 to 5000 200 (no air-flux compensator)
5000 to 10 000 100 (no air-flux compensator) 3π =2/4, and indicates the same value as an rms voltmeter
when measuring pure sine waves, shall be provided for
7.3.3 The primary winding is uniformly distributed along
measuring the peak value of the test induction. To meet the
the magnetic path and may be wound in multiple layers over
precision of this test method, meter error shall not exceed
the secondary winding. The secondary winding shall be the
0.25% (see Note 3). If the meter impedance is not sufficiently
innermost winding on the coil form and shall be a single layer
winding. The primary and secondary shall be wound in the high at the frequency of test, it is necessary to compensate for
its loading effect. To evaluate how much the meter loads the
samedirectionandtheirstartingendconnectionsshallbemade
at the same corner. circuit, read the rms ammeter and rms voltmeter before and
A348/A348M − 05 (2021)
after disconnecting the flux voltmeter. When dc bias is applied across the terminals of the current sensing resistor (r in Fig. 1)
tothetestframetransformer,thefluxvoltmetermustbeableto shall be provided to measure the peak value of the current
respond true average. waveform. Accuracy shall be 2%. Alternatively, an oscillo-
NOTE 3—Inaccuracies in setting the test voltage produce errors dispro- scope with voltage measurement capability can be used. An
portionately larger in core loss and exciting current. Evaluate meter error
oscilloscope,whenused,shallnotcauseshortingofanypartof
in accordance with the manufacturer’s information, for example, percent
the circuit through its dual input common ground.
of range, temperature, and frequency.
7.10 Oscilloscope Current Monitor (Optional)—Extreme
7.5 RMS Voltmeter—ARMSvoltmetershallbeprovidedfor
current wave peaking occurs as the magnetic core material
evaluating the exciting power and also the form factor of the
goes into saturation. This is readily observable on an oscillo-
voltage induced in the secondary winding of the test frame
scope connected across the current sensing resistor. An oscil-
transformer. The meter error shall not exceed 0.25% at the
loscope also makes it possible to recognize current waveform
frequency of test. The meter burden shall have no more than
non
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