ASTM A772/A772M-00(2016)

Standard Test Method for AC Magnetic Permeability of Materials Using Sinusoidal Current

SIGNIFICANCE AND USE
4.1 The permeability determined by this method is the impedance permeability. Impedance permeability is the ratio of the peak value of flux density (Bmax) to the assumed peak magnetic field strength (Hz) without regard to phase. As compared to testing under sinusoidal flux (sinusoidal B) conditions, the permeabilities determined by this method are numerically lower since, for a given test signal frequency, the rate of flux change (dB/dt) is higher.  
4.2 This test method is suitable for impedance permeability measurements at very low magnetic inductions at power frequencies (50 to 60 Hz) to moderate inductions below the point of maximum permeability of the material (the knee of the magnetization curve) or until there is visible distortion of the current waveform. The lower limit is a function of sample area, secondary turns, and the sensitivity of the flux-reading voltmeter used. At higher inductions, measurements of flux-generated voltages that are appreciably distorted mean that the flux has appreciable harmonic frequency components. The upper limit is given by the availability of pure sinusoidal current, which is a function of the power source. In addition, a large ratio (≥10) of the total series resistance of the primary circuit to the primary coil impedance is required. With proper test apparatus, this test method is suitable for use at frequencies up to 1 MHz.  
4.3 This test method is suitable for design, specification acceptance, service evaluation, quality control, and research use.
SCOPE
1.1 This test method provides a means for determination of the impedance permeability (μz) of ferromagnetic materials under the condition of sinusoidal current (sinusoidal H) excitation. Test specimens in the form of laminated toroidal cores, tape-wound toroidal cores, and link-type laminated cores having uniform cross sections and closed flux paths (no air gaps) are used. The method is intended as a means for determining the magnetic performance of ferromagnetic strip having a thickness less than or equal to 0.025 in. [0.635 mm].  
1.2 This test method shall be used in conjunction with those applicable paragraphs in Practice A34/A34M.  
1.3 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.  
1.4 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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-Mar-2016
• ICS: 29.030 - Magnetic materials
• Technical Committee: A06 - Magnetic Properties
• Drafting Committee: A06.01 - Test Methods

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: A772/A772M − 00 (Reapproved 2016)
Standard Test Method for
AC Magnetic Permeability of Materials Using Sinusoidal
Current
This standard is issued under the fixed designationA772/A772M; 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 A340Terminology of Symbols and Definitions Relating to
Magnetic Testing
1.1 This test method provides a means for determination of
the impedance permeability (µ ) of ferromagnetic materials
z
3. Terminology
under the condition of sinusoidal current (sinusoidal H) exci-
3.1 Definitions—The terms and symbols used in this test
tation. Test specimens in the form of laminated toroidal cores,
tape-wound toroidal cores, and link-type laminated cores method are defined in Terminology A340.
having uniform cross sections and closed flux paths (no air
4. Significance and Use
gaps) are used. The method is intended as a means for
determining the magnetic performance of ferromagnetic strip
4.1 The permeability determined by this method is the
having a thickness less than or equal to 0.025 in. [0.635 mm].
impedancepermeability.Impedancepermeabilityistheratioof
the peak value of flux density (B ) to the assumed peak
1.2 This test method shall be used in conjunction with those
max
magnetic field strength (H ) without regard to phase. As
applicable paragraphs in Practice A34/A34M.
z
compared to testing under sinusoidal flux (sinusoidal B)
1.3 The values and equations stated in customary (cgs-emu
conditions, the permeabilities determined by this method are
and inch-pound) or SI units are to be regarded separately as
numerically lower since, for a given test signal frequency, the
standard. Within this standard, SI units are shown in brackets
rate of flux change (dB/dt) is higher.
except for the sections concerning calculations where there are
4.2 This test method is suitable for impedance permeability
separate sections for the respective unit systems. The values
measurements at very low magnetic inductions at power
stated in each system may not be exact equivalents; therefore,
frequencies (50 to 60 Hz) to moderate inductions below the
each system shall be used independently of the other. Combin-
pointofmaximumpermeabilityofthematerial(thekneeofthe
ingvaluesfromthetwosystemsmayresultinnonconformance
magnetization curve) or until there is visible distortion of the
with this standard.
currentwaveform.Thelowerlimitisafunctionofsamplearea,
1.4 This standard does not purport to address all of the
secondary turns, and the sensitivity of the flux-reading voltme-
safety concerns, if any, associated with its use. It is the
ter used.At higher inductions, measurements of flux-generated
responsibility of the user of this standard to establish appro-
voltages that are appreciably distorted mean that the flux has
priate safety and health practices and determine the applica-
appreciable harmonic frequency components. The upper limit
bility of regulatory limitations prior to use.
is given by the availability of pure sinusoidal current, which is
a function of the power source. In addition, a large ratio (≥10)
2. Referenced Documents
of the total series resistance of the primary circuit to the
2.1 ASTM Standards:
primarycoilimpedanceisrequired.Withpropertestapparatus,
A34/A34MPractice for Sampling and Procurement Testing
this test method is suitable for use at frequencies up to 1 MHz.
of Magnetic Materials
4.3 This test method is suitable for design, specification
acceptance, service evaluation, quality control, and research
use.
This test method is under the jurisdiction of ASTM Committee A06 on
MagneticPropertiesandisthedirectresponsibilityofSubcommitteeA06.01onTest
5. Apparatus
Methods.
Current edition approved April 1, 2016. Published April 2016. Originally
5.1 Thetestcircuit,whichisschematicallyillustratedinFig.
approved in 1980. Last previous edition approved in 2011 as A772/A772M–00
ɛ1
1, shall consist of the following components.
(2011) . DOI:10.1520/A0772_A0772M-00R16.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
5.2 Power Supply—For power frequency (50- or 60-Hz)
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
testing, a suitable power supply consists of two or three series
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. connected autotransformers of sufficient power rating. This
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A772/A772M − 00 (2016)
equations in 7.1 and 7.2 or 8.1 and 8.2. To obtain acceptable
uniformity of magnetic field strength throughout the specimen,
the following dimensional constraints shall be observed:
(1)foratoroidtheinsidediametertooutsidediameterratio
shall exceed 0.82, and
(2)forthelinkspecimenshowninFig.2,theseparation(s)
FIG. 1 Schematic Circuit for Sinusoidal Current Permeability Test
shall exceed nine times the radial width (w).
6.1.2 A secondary winding (N ) using insulated wire shall
be uniformly distributed over the test specimen using a
will provide a continuously variable current source to excite
sufficient number of turns so that a measurable voltage will be
thetestspecimen.Fortestingatotherthanpowerfrequency,an
obtained at the lowest flux density of interest. A uniformly
acpowersourceconsistingofalowdistortionsinusoidalsignal
distributed primary winding (N ) of insulated wire shall be
generatorandlinearamplifierarerequired.Theuseoffeedback
applied on top of the secondary winding and be of sufficient
control of the power amplifier is permitted.
diameter to conduct the highest intended magnetizing current
5.3 Isolation/Stepdown Transformer—The use of a low
safelywithoutsignificantheating.Twistedleadsorbiconductor
distortion isolation/stepdown transformer is highly recom-
cableshallbeusedtoconnectthespecimenwindingstothetest
mendedforoperatorsafetyandtoeliminateanydcbiascurrent
apparatus.
present when using electronic power supplies. A combined
6.2 Calculation of Test Signals—Testing is done either at
isolation/stepdown transformer can provide greater control
specified values of flux density (B ) or magnetic field
max
when testing is done at very low magnetizing currents.
strength (H ). Before testing, the rms magnetizing currents or
z
5.4 Primary Series Resistor (Z)—A noninductive resistor
voltages generated in the secondary shall be calculated using
having sufficiently high resistance to maintain sinusoidal cur-
the equations found in 7.3 and 7.4 or 8.3 and 8.4.
rent conditions at the highest magnetizing current and test
6.3 Demagnetization—After connecting the primary and
signalfrequencyofinterest.Inpractice,resistancevaluesof10
secondarywindingstotheapparatus,thetestspecimenshallbe
to 100 Ω are used. If this resistor is used to measure the
demagnetized by applying a magnetizing current sufficiently
magnetizing current, the resistance shall be known to better
large to create a magnetic field strength greater than ten times
than 0.5% and the resistance shall not increase by more than
the coercivity of the test specimen. The magnetizing current
0.5% at the rated maximum current of the power supply.
then shall be slowly and smoothly reduced to zero to demag-
5.5 True RMS Ammeter (A)—A true rms ammeter or a
netize the test specimen. The frequency used should be the
combination of a noninductive, precision current viewing
same as the test frequency.
resistor and true rms voltmeter shall be used to measure the
6.4 Measurement—The magnetizing current shall be care-
magnetizingcurrent.Themetershallhaveanaccuracyofbetter
fully increased until the lowest value of either magnetizing
than 0.5% full scale at the test frequency.The current viewing
current (if measuring at a specified value of magnetic field
resistor, if used, shall have an accuracy better than 0.5% and
strength) or flux density (if measuring at a speci
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: A772/A772M − 00 (Reapproved 2011) A772/A772M − 00 (Reapproved 2016)
Standard Test Method for
AC Magnetic Permeability of Materials Using Sinusoidal
Current
This standard is issued under the fixed designation A772/A772M; 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.
ε NOTE—Updated 6.2 and 7.3 editorially in August 2011.
1. Scope
1.1 This test method provides a means for determination of the impedance permeability (μ ) of ferromagnetic materials under
z
the condition of sinusoidal current (sinusoidal H) excitation. Test specimens in the form of laminated toroidal cores, tape-wound
toroidal cores, and link-type laminated cores having uniform cross sections and closed flux paths (no air gaps) are used. The
method is intended as a means for determining the magnetic performance of ferromagnetic strip having a thickness less than or
equal to 0.025 in. [0.635 mm].
1.2 This test method shall be used in conjunction with those applicable paragraphs in Practice A34/A34M.
1.3 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.
1.4 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 and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
A34/A34M Practice for Sampling and Procurement Testing of Magnetic Materials
A340 Terminology of Symbols and Definitions Relating to Magnetic Testing
3. Terminology
3.1 Definitions—The terms and symbols used in this test method are defined in Terminology A340.
4. Significance and Use
4.1 The permeability determined by this method is the impedance permeability. Impedance permeability is the ratio of the peak
value of flux density (B ) to the assumed peak magnetic field strength (H ) without regard to phase. As compared to testing under
max z
sinusoidal flux (sinusoidal B) conditions, the permeabilities determined by this method are numerically lower since, for a given
test signal frequency, the rate of flux change (dB/dt) is higher.
4.2 This test method is suitable for impedance permeability measurements at very low magnetic inductions at power frequencies
(50 to 60 Hz) to moderate inductions below the point of maximum permeability of the material (the knee of the magnetization
curve) or until there is visible distortion of the current waveform. The lower limit is a function of sample area, secondary turns,
and the sensitivity of the flux-reading voltmeter used. At higher inductions, measurements of flux-generated voltages that are
appreciably distorted mean that the flux has appreciable harmonic frequency components. The upper limit is given by the
This test method is under the jurisdiction of ASTM Committee A06 on Magnetic Properties and is the direct responsibility of Subcommittee A06.01 on Test Methods.
Current edition approved May 1, 2011April 1, 2016. Published May 2011April 2016. Originally approved in 1980. Last previous edition approved in 20052011 as
ɛ1
A772/A772M–00(2005).A772/A772M – 00 (2011) DOI:10.1520/A0772_A0772M-00R11E01. DOI:10.1520/A0772_A0772M-00R16.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A772/A772M − 00 (2016)
availability of pure sinusoidal current, which is a function of the power source. In addition, a large ratio (≥10) of the total series
resistance of the primary circuit to the primary coil impedance is required. With proper test apparatus, this test method is suitable
for use at frequencies up to 1 MHz.
4.3 This test method is suitable for design, specification acceptance, service evaluation, quality control, and research use.
5. Apparatus
5.1 The test circuit, which is schematically illustrated in Fig. 1, shall consist of the following components.
5.2 Power Supply—For power frequency (50- or 60-Hz) testing, a suitable power supply consists of two or three series
connected autotransformers of sufficient power rating. This will provide a continuously variable current source to excite the test
specimen. For testing at other than power frequency, an ac power source consisting of a low distortion sinosoidalsinusoidal signal
generator and linear amplifier are required. The use of feedback control of the power amplifier is permitted.
5.3 Isolation/Stepdown Transformer—The use of a low distortion isolation/stepdown transformer is highly recommended for
operator safety and to eliminate any dc bias current present when using electronic power supplies. A combined isolation/stepdown
transformer can provide greater control when testing is done at very low magnetizing currents.
5.4 Primary Series Resistor (Z)—A noninductive resistor having sufficiently high resistance to maintain sinusoidal current
conditions at the highest magnetizing current and test signal frequency of interest. In practice, resistance values of 10 to 100 Ω
are used. If this resistor is used to measure the magnetizing current, the resistance shall be known to better than 0.5 % and the
resistance shall not increase by more than 0.5 % at the rated maximum current of the power supply.
5.5 True RMS Ammeter (A)—A true rms ammeter or a combination of a noninductive, precision current viewing resistor and
true rms voltmeter shall be used to measure the magnetizing current. The meter shall have an accuracy of better than 0.5 % full
scale at the test frequency. The current viewing resistor, if used, shall have an accuracy better than 0.5 % and shall have sufficient
power rating such that the resistance shall not vary by more than 0.5 % at the rated maximum current of the power supply.
5.6 Flux Measuring Voltmeter (V)—The flux shall be determined from the voltage induced in the secondary winding using one
of the following type of voltmeter:
(1) an average responding digital voltmeter calibrated to read rms volts for a sine wave or
(1) an average responding digital voltmeter calibrated to read rms volts for a sine wave, or
(2) a true average responding digital voltmeter.
The voltmeter shall have input impedance greater than 1 MΩ, a full-scale accuracy of better than 0.5 % at the test frequency, and
a crest factor capability of 3 or greater.
(2) a true average responding digital voltmeter.
The voltmeter shall have input impedance greater than 1 MΩ, a full-scale accuracy of better than 0.5 % at the test frequency, and
a crest factor capability of 3 or greater.
6. Procedure
6.1 Specimen Preparation—After determining the mass and dimensions of the test specimen, it should be enclosed in a suitable
insulating case to prevent intimate contact between it and the primary and secondary windings. This will also minimize the stress
introduced by winding. The case shape and size shall approximate that of the test specimen so that the secondary winding encloses
minimal air flux. All test specimens shall have a uniform rectangular cross section.
6.1.1 The cross-sectional area and mean magnetic path length of the test specimen shall be calculated using the equations in
7.1 and 7.2 or 8.1 and 8.2. To obtain acceptable uniformity of magnetic field strength throughout the specimen, the following
dimensional constraints shall be observed:
(1) for a toroid the inside diameter to outside diameter ratio shall exceed 0.82 and
(1) for a toroid the inside diameter to outside diameter ratio shall exceed 0.82, and
(2) for the link specimen shown in Fig. 2, the separation (s) shall exceed nine times the radial width (w).
(2) for the link specimen shown in Fig. 2, t
...