ASTM A804/A804M-99
(Test Method)Standard Test Methods for Alternating-Current Magnetic Properties of Materials at Power Frequencies Using Sheet-Type Test Specimens
Standard Test Methods for Alternating-Current Magnetic Properties of Materials at Power Frequencies Using Sheet-Type Test Specimens
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1.1 These test methods cover the determination of specific core loss and peak permeability of single layers of sheet-type specimens tested with normal excitation at a frequency of 50 or 60 Hz. Note 1-These test methods have been applied only at the commercial power frequencies, 50 and 60 Hz, but with proper instrumentation and application of the principles of testing and calibration embodied in the test methods, they are believed to be adaptable to testing at frequencies ranging from 25 to 400 Hz.
1.2 These test methods employ calibration procedures that provide correlation with the 25-cm [250-mm] Epstein test.
1.3 The range of test inductions is governed by the properties of the test specimen and by the available instruments and other equipment components. Normally, nonoriented electrical steels can be tested over a range from 8 to 16 kG [0.8 to 1.6 T] for core loss. For oriented electrical steels, the normal range extends to 18 kG [1.8 T]. Maximum inductions in peak permeability testing are limited principally by heating of the magnetizing winding and tests are limited normally to a maximum a-c magnetizing force of about 150 Oe [12 000 A/m].
1.4 These test methods cover two alternative procedures as follows: Test Method 1-Sections 6 to 12 Test Method 2-Sections 13 to 19
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Designation: A 804/A804M – 99
Standard Test Methods for
Alternating-Current Magnetic Properties of Materials at
Power Frequencies Using Sheet-Type Test Specimens
This standard is issued under the fixed designation A 804/A804M; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
1.1 These test methods cover the determination of specific
bility of regulatory limitations prior to use.
core loss and peak permeability of single layers of sheet-type
1.6 The values stated in either customary (cgs-emu and
specimens tested with normal excitation at a frequency of 50 or
inch-pound) units or SI units are to be regarded separately as
60 Hz.
standard. Within the text, the SI units are shown in brackets
NOTE 1—These test methods have been applied only at the commercial
except for the sections concerning calculations where there are
power frequencies, 50 and 60 Hz, but with proper instrumentation and
separate sections for the respective unit systems. The values
application of the principles of testing and calibration embodied in the test
stated in each system are not exact equivalents; therefore, each
methods, they are believed to be adaptable to testing at frequencies
system shall be used independently of the other. Combining
ranging from 25 to 400 Hz.
values from the systems may result in nonconformance with
1.2 These test methods use calibration procedures that
the specification.
provide correlation with the 25-cm [250-mm] Epstein test.
1.3 The range of test inductions is governed by the proper-
2. Referenced Documents
ties of the test specimen and by the available instruments and
2.1 ASTM Standards:
other equipment components. Normally, nonoriented electrical
A 34/A 34M Practice for Sampling and Procurement Test-
steels can be tested over a range from 8 to 16 kG [0.8 to 1.6 T]
ing of Magnetic Materials
for core loss. For oriented electrical steels, the normal range
A 340 Terminology of Symbols and Definitions Relating to
extends to 18 kG [1.8 T]. Maximum inductions in peak
Magnetic Testing
permeability testing are limited principally by heating of the
A 343 Test Method for Alternating-Current Magnetic Prop-
magnetizing winding and tests are limited normally to a
erties of Materials at Power Frequencies Using Wattmeter-
maximum ac magnetizing force of about 150 Oe [12 000 A/m].
Ammeter-Voltmeter Method and 25-cm Epstein Test
1.4 These test methods cover two alternative procedures as
Frame
follows:
A 677 Specification for Nonoriented Electrical Steel Fully
Test Method 1—Sections 6-12
Processed Types
Test Method 2—Sections 13-19
A 677M Specification for Nonoriented Electrical Steel,
1.4.1 Test Method 1 uses a test fixture having (1) two
Fully Processed Types (Metric)
windings that encircle the test specimen, and (2) a ferromag-
A 683 Specification for Nonoriented Electrical Steel, Semi-
netic yoke structure that serves as the flux return path and has
processed Types
low core loss and low magnetic reluctance.
A 683M Specification for Nonoriented Electrical Steel,
1.4.2 Test Method 2 uses a test fixture having (1) two
Semiprocessed Types [Metric]
windings that encircle the test specimen, (2) a third winding
A 876/A 876M Specification for Flat-Rolled, Grain-
located inside the other two windings and immediately adja-
Oriented, Silicon-Iron Electrical Steel, Fully Processed
cent to one surface of the test specimen, and (3) a ferromag-
Types
netic yoke structure which serves as the flux-return path and
has low magnetic reluctance.
3. Terminology
1.5 This standard does not purport to address all of the
3.1 Definitions:
safety concerns, if any, associated with its use. It is the
3.1.1 General—The definitions of terms, symbols, and con-
version factors relating to magnetic testing found in Definitions
A 340 are used in these methods.
These methods are under the jurisdiction of ASTM Committee A-6 on
3.2 Definitions of Terms Specific to This Standard:
Magnetic Properties and are the direct responsibility of Subcommittee A06.01 on
Test Methods.
Current edition approved May 10, 1999. Published August 1999. Originally
published as A 804 – 82. Last previous edition A 804/A 804M – 94. Annual Book of ASTM Standards, Vol 03.04.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
A 804/A804M
3.2.1 sheet specimen—a rectangular specimen comprised of flattened, grain-oriented electrical steels at 50 and 60 Hz.
a single piece of material or paralleled multiple strips of Specific core loss at 15 or 17 kG [1.5 or 1.7 T] and peak
material arranged in a single layer. permeability (if required) at 10 Oe [796 A/m] are the recom-
mended parameters for evaluating this class of material.
4. Significance and Use
5. Sampling
4.1 Materials Evaluation—These test methods were devel-
5.1 Lot Size and Sampling—Unless otherwise established
oped to supplement the testing of Epstein specimens for
by mutual agreement between the manufacturer and the pur-
applications involving the use of flat, sheared laminations
chaser, determination of a lot size and the sampling of a lot to
where the testing of Epstein specimens in either the as-sheared
obtain sheets for specimen preparation shall follow the recom-
or stress-relief-annealed condition fails to provide the most
mendations of Practice A 34, Sections 4 and 5.
satisfactory method of predicting magnetic performance in the
application. As a principal example, the methods have been
METHOD 1 TWO-WINDING YOKE-FIXTURE TEST
found particularly applicable to the control and evaluation of
METHOD
the magnetic properties of thermally flattened, grain-oriented
6. Basic Test Circuit
electrical steel (Condition F5, Specification A 876) used as
lamination stock for cores of power transformers. Inasmuch as
6.1 Fig. 1 provides a schematic circuit diagram for the test
the methods can only be reliably used to determine unidirec-
method. A power source of precisely controllable ac sinusoidal
tional magnetic properties, the methods have limited applica-
voltage is used to energize the primary circuit. To minimize
bility to the testing of fully processed nonoriented electrical
flux-waveform distortion, current ratings of the power source
steels as normally practiced (Specification A 677).
and of the wiring and switches in the primary circuit shall be
4.2 Specification Acceptance—The reproducibility of test
such as to provide very low impedance relative to the imped-
results and the accuracy relative to the 25-cm [250-mm]
ance arising from the test fixture and test specimen. Ratings of
Epstein method of test are considered such as to render the
switches and wiring in the secondary circuit also shall be such
methods suitable for materials specification testing.
as to cause negligible voltage drop between the terminals of the
4.3 Interpretation of Test Results—Because of specimen
secondary test winding and the terminals of the measuring
size, considerable variation in magnetic properties may be
instruments.
present within a single specimen or between specimens that
7. Apparatus
may be combined for testing purposes. Also, variations may
exist in test values that are combined to represent a test lot of 7.1 The test circuit shall incorporate as many of the follow-
material. Test results reported will therefore, in general, repre- ing components as are required to perform the desired mea-
sent averages of magnetic quality and in certain applications, surements.
particularly those involving narrow widths of laminations, 7.2 Yoke Test Fixture—Fig. 2 and Fig. 3 show line drawings
deviations in magnetic performance from those expected from of a single-yoke fixture and a double-yoke fixture, respectively.
reported data may occur at times. Additionally, application of A double-yoke fixture is preferred in this method but a
test data to the design or evaluation of a particular magnetic single-yoke fixture is permitted. Directions concerning the
device must recognize the influence of magnetic circuitry upon design, construction, and calibration of the fixture are given in
performance and the possible deterioration in magnetic prop- 7.2.1, 7.2.2, Annex A1, and Annex A2.
erties arising from construction of the device. 7.2.1 Yoke Structure—Various dimensions and fabrication
4.4 Recommended Standard Tests—These methods have procedures in construction are permissible. Since the recom-
been principally applied to the magnetic testing of thermally mended calibration procedure provides correlation with the
FIG. 1 Basic Circuit Diagram for Method 1
A 804/A804M
eration of a reduction in winding resistance versus an increase
in inductive reactance at the third harmonic of the principal test
frequency used. The primary and secondary turns shall be
wound in the same direction from a common starting point at
one end of the coil form. Also, to minimize self-impedances of
the windings, the opening in the coil form should be no greater
than required to allow easy insertion of the test specimen.
Construction and mounting of the test coil assembly must be
such that the test specimen will be maintained without me-
chanical distortion in the plane established by the pole faces of
the yoke(s) of the test fixture.
FIG. 2 Single-Yoke Fixture (Exploded View)
7.3 Air-Flux Compensator—To provide a means of deter-
mining intrinsic induction in the test specimen, an air-core
mutual inductor shall constitute part of the test-coil system.
The respective primary and secondary windings of the air-core
inductor and the test-specimen coil shall be connected in series
and the voltage polarities of the secondary windings shall be in
opposition. By proper adjustment of the mutual inductance of
the air-core inductor, the average of the voltage developed
across the combined secondary windings is proportional to the
intrinsic induction in the test specimen. Directions for con-
struction and adjustment of the air-core mutual inductor for
air-flux compensation are found in Annex A3.
7.4 Flux Voltmeter, V —A full-wave, true-average voltme-
f
ter, with scale reading in average volts times 1.111 so that its
indications will be identical with those of a true rms voltmeter
on a pure sinusoidal voltage, shall be provided for evaluating
the peak value of the test induction. To produce the estimated
FIG. 3 Double-Yoke Fixture (Exploded View)
precision of test under this method, the full-scale meter errors
shall not exceed 0.25 % (Note 2). Meters of 0.5 % or more
25-cm [250-mm] Epstein test, the minimum inside dimension
error may be used at reduced accuracy. Either digital or analog
between pole faces must be at least 22 cm [220 mm]. The
flux voltmeters are permitted. The normally high-input imped-
thickness of the pole faces should be not less than 2.5 cm [25
ance of digital flux voltmeters is desirable to minimize loading
mm]. It is recognized that pole faces as narrow as 1.9 cm [19
effects and to reduce the magnitude of instrument loss com-
mm] are being used with nickel-iron yoke systems with good
pensations. The input resistance of an analog flux voltmeter
results. To minimize the influences of coil-end and pole-face
shall not be less than 1000 V/V of full-scale indication. A
effects, the yokes should be longer than the recommended
resistive voltage divider, a standard-ratio transformer, or other
minimum. For calibration purposes, it is suggested that the
variable scaling device may be used to cause the flux voltmeter
width of the fixture be such as to accommodate a specimen of
to indicate directly in units of induction if the combination of
at least 36-cm [360-mm] width which corresponds to the
basic instrument and scaling device conforms to the specifica-
combined width and twelve Epstein-type specimens. Should
tions stated above.
the fixture width be less than 36 cm [360 mm], it will be
necessary to test each calibration specimen in two parts and NOTE 2—Inaccuracies in setting the test voltage produce errors ap-
proximately two times as large in the specific core loss. Voltage scales
average the results.
should be such that the instrument is not used at less than half-scale. Care
7.2.2 Test Windings—The test windings, which shall consist
should also be taken to avoid errors caused by temperature and frequency
of a primary (exciting) winding and a secondary (potential)
effects in the instrument.
winding, shall be uniformly and closely wound on a nonmag-
7.4.1 If used with a mutual inductor as a peak ammeter at
netic, nonconducting coil form and each shall span the greatest
inductions well above the knee of the magnetization curve, the
practicable distance between the pole faces of the yoke fixture.
flux voltmeter must be capable of accurately measuring the
It is recommended that the number of turns in the primary and
extremely nonsinusoidal (peaked) voltage that is induced in the
secondary windings be equal. The number of turns may be
secondary winding of the mutual inductor. Additionally, if so
chosen to suit the instrumentation, mass of specimen and test
used, an analog flux voltmeter should have an input resistance
frequency. The secondary winding shall be the innermost
of 5000 to 10 000 V/V of full-scale indication.
winding and, with instrumentation of suitably high-input resis-
tance, normally may consist of a single layer. To reduce 7.5 RMS Voltmeter, V —A true rms-indicating voltmeter
rms
self-impedance and thereby minimize flux-waveform distor- shall be provided for evaluating the form factor of the voltage
tion, it is recommended that the primary winding consist of induced in the secondary winding of the test fixture and for
multiple layers of equal turns connected in parallel. The evaluating the instrument losses. The accuracy of the rms
number of such layers should be optimized based on consid- voltmeter shall be the same as that specified for the flux
A 804/A804M
voltmeter. Either digital or analog rms voltmeters are permit- circuitry must be capable of accepting the maximum peak
ted. The normally high-input impedance of digital rms voltme- voltage that is induced in the secondary winding during testing.
ters is desirable to minimize loading effects and to reduce the
7.6.2.2 The current input circuitry of the electronic digital
magnitude of instrument loss compensations. The input resis-
wattmeter must have an input impedance of no more th
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