IEC 60404-6:2018
(Main)Magnetic materials - Part 6: Methods of measurement of the magnetic properties of magnetically soft metallic and powder materials at frequencies in the range 20 Hz to 100 kHz by the use of ring specimens
Magnetic materials - Part 6: Methods of measurement of the magnetic properties of magnetically soft metallic and powder materials at frequencies in the range 20 Hz to 100 kHz by the use of ring specimens
IEC 60404-6:2018 specifies methods for the measurement of AC magnetic properties of soft magnetic materials, other than electrical steels and soft ferrites, in the frequency range 20 Hz to 100 kHz. The materials covered by this part of IEC 60404 include those speciality alloys listed in IEC 60404-8-6, amorphous and nano-crystalline soft magnetic materials, pressed and sintered and metal injection moulded parts such as are listed in IEC 60404-8-9, cast parts and magnetically soft composite materials. The object of this part is to define the general principles and the technical details of the measurement of the magnetic properties of magnetically soft materials by means of ring methods. For materials supplied in powder form, a ring test specimen is formed by the appropriate pressing method for that material. The measurement of the DC magnetic properties of soft magnetic materials is made in accordance with the ring method of IEC 60404-4. The determinations of the magnetic characteristics of magnetically soft components are made in accordance with IEC 62044-3. This edition includes the following significant technical changes with respect to the previous edition:
a) adaption to modern measurement and evaluation methods, in particular the introduction of the widely spread digital sampling method for the acquisition and evaluation of the measured data;
b) limitation of the frequency range up to 100 kHz;
c) deletion of Clause 7 of the second edition that specified the measurement of magnetic properties using a digital impedance bridge;
d) addition of a new Clause 7 on the measurement of the specific total loss by the wattmeter method, including an example of the application of the digital sampling method;
e) addition of an informative annex on the technical details of the digital sampling technique for the determination of magnetic properties.
The contents of the corrigendum of November 2018 have been included in this copy.
Matériaux magnétiques - Partie 6: Méthodes de mesure des propriétés magnétiques des matériaux métalliques et des matériaux en poudre magnétiquement doux, aux fréquences comprises entre 20 Hz et 100 kHz, sur des éprouvettes en forme de tore
IEC 60404-6:2018 spécifie les méthodes à utiliser pour mesurer les propriétés magnétiques en courant alternatif des matériaux magnétiques doux autres que les aciers électriques et les ferrites doux, aux fréquences comprises entre 20 Hz et 100 kHz. Les matériaux couverts par la présente partie de l'IEC 60404 incluent les alliages de spécialité répertoriés dans l'IEC 60404-8-6, les matériaux magnétiques doux amorphes et nanocristallins, les pièces compressées frittées et les pièces moulées par injection de métal répertoriées dans l'IEC 60404-8-9, ainsi que les pièces moulées et les matériaux composites magnétiquement doux. L'objet de la présente partie est de définir les principes généraux et les détails techniques de la mesure des propriétés magnétiques des matériaux magnétiquement doux au moyen des méthodes du tore. Pour les matériaux livrés sous forme de poudre, une éprouvette d'essai en forme d'anneau est réalisée à l'aide de la méthode de compression appropriée pour le matériau considéré. La mesure des propriétés magnétiques en courant continu des matériaux magnétiquement doux est réalisée selon la méthode du tore de l'IEC 60404-4. Les déterminations des propriétés magnétiques des composants magnétiquement doux sont réalisées selon l'IEC 62044-3. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) adaptation aux méthodes modernes de mesure et d'évaluation, notamment l'introduction de la méthode d'échantillonnage numérique largement répandue pour l'acquisition et l'évaluation des données mesurées;
b) limitation de la gamme de fréquences à 100 kHz;
c) suppression de l'Article 7 de la deuxième édition qui spécifiait la mesure des propriétés magnétiques à l'aide d'un pont d'impédance numérique;
d) ajout d'un nouvel Article 7 sur la mesure des pertes totales massiques par la méthode du wattmètre, y compris un exemple d'application de la méthode d'échantillonnage numérique;
e) ajout d'une annexe informative concernant les détails de la technique d'échantillonnage numérique pour déterminer les propriétés magnétiques du matériau.
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IEC 60404-6 ®
Edition 3.0 2018-05
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Magnetic materials –
Part 6: Methods of measurement of the magnetic properties of magnetically soft
metallic and powder materials at frequencies in the range 20 Hz to 200 100 kHz
by the use of ring specimens
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IEC 60404-6 ®
Edition 3.0 2018-05
REDLINE VERSION
INTERNATIONAL
STANDARD
colour
inside
Magnetic materials –
Part 6: Methods of measurement of the magnetic properties of magnetically soft
metallic and powder materials at frequencies in the range 20 Hz to 200 100 kHz
by the use of ring specimens
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.220.20; 29.030 ISBN 978-2-8322-5754-8
– 2 – IEC 60404-6:2018 RLV © IEC 2018
CONTENTS
FOREWORD . 4
INTRODUCTION .
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 8
4 General principles of measurement . 8
4.1 Principle of the ring method . 8
4.2 Test specimen . 8
4.3 Windings . 9
5 Temperature measurements . 10
6 Measurement of magnetic the relative amplitude permeability
and the AC magnetization curve using the voltmeter-ammeter method . 10
6.1 Introduction General . 10
6.2 Apparatus and connections . 10
6.3 Waveform of induced secondary voltage or magnetizing current . 11
6.4 Determination of characteristics . 12
6.4.1 Determination of the peak value of the magnetic field strength . 12
6.4.2 Determination of the peak value of the magnetic flux density . 13
6.4.3 Determination of the r.m.s. amplitude permeability and the relative
amplitude permeability . 13
6.4.4 Determination of the AC magnetization curve . 14
7 Measurement of the specific total loss by the wattmeter method . 14
7.1 Principle of measurement. 14
7.2 Voltage measurement . 16
7.2.1 Average type voltmeter, V . 16
7.2.2 R.M.S. type voltmeter, V . 16
7.3 Power measurement . 16
7.4 Procedure for the measurement of the specific total loss . 16
7.5 Determination of the specific total loss . 16
Measurement of magnetic properties using a digital impedance bridge .
Principle of measurement.
Apparatus .
Procedure .
Determination of the relative a.c. inductance permeability .
Determination of the specific total loss .
Measurement of magnetic properties using digital methods .
Introduction .
Apparatus and connections .
Magnetizing current waveform .
Magnetizing winding .
Determination of the magnetic field strength .
Determination of the magnetic flux density .
Determination of the relative a.c. permeability .
Determination of a.c. magnetization curve .
Determination of the specific total loss .
8 Uncertainties . 22
9 Test report . 22
Annex A (informative) Guidance on requirements for windings and instrumentation in
order to minimise additional losses . 24
A.1 Introduction General . 24
A.2 Reduction of additional losses . 24
Annex B (informative) Digital sampling technique for the determination of magnetic
properties and numerical air flux compensation . 25
B.1 General . 25
B.2 Technical details and requirements . 25
B.3 Calibration aspects . 29
B.4 Numerical air flux compensation . 29
Annex C (informative) Sinusoidal waveform control by digital means . 30
Bibliography . 31
Figure – Circuit of the digital impedance bridge method .
Figure – Circuit of the digital method .
Figure 1 – Circuit of the ring method measurement apparatus. 11
Figure 2 – Circuit of the conventional analogue wattmeter method (also representing
the metrological principle of the digital wattmeter method) . 15
Figure 3 – The wattmeter method when connected with the digital sampling technique
(example of circuit) . 15
– 4 – IEC 60404-6:2018 RLV © IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MAGNETIC MATERIALS –
Part 6: Methods of measurement of the magnetic properties of
magnetically soft metallic and powder materials at frequencies
in the range 20 Hz to 200 100 kHz by the use of ring specimens
FOREWORD
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This redline version of the official IEC Standard allows the user to identify the changes
made to the previous edition. A vertical bar appears in the margin wherever a change
has been made. Additions are in green text, deletions are in strikethrough red text.
International Standard IEC 60404-6 has been prepared by IEC technical committee 68:
Magnetic alloys and steels.
This third edition cancels and replaces the second published in 2003. This edition constitutes
a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) adaption to modern measurement and evaluation methods, in particular the introduction of
the widely spread digital sampling method for the acquisition and evaluation of the
measured data;
b) limitation of the frequency range up to 100 kHz;
c) deletion of Clause 7 of the second edition that specified the measurement of magnetic
properties using a digital impedance bridge;
d) addition of a new Clause 7 on the measurement of the specific total loss by the wattmeter
method, including an example of the application of the digital sampling method;
e) addition of an informative annex on the technical details of the digital sampling technique
for the determination of magnetic properties.
The text of this International Standard is based on the following documents:
FDIS Report on voting
68/595/FDIS 68/600/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 60404 series, published under the general title Magnetic materials,
can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
reconfirmed,
withdrawn,
replaced by a revised edition, or
amended.
The contents of the corrigendum of November 2018 have been included in this copy.
IMPORTANT – The “colour inside” logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this publication using a colour printer.
– 6 – IEC 60404-6:2018 RLV © IEC 2018
INTRODUCTION
This edition of IEC 60404-6 has been prepared by WG2 in the TC68 maintenance programme
of publications. The d.c. measurements in the first edition of this standard are now covered
in IEC 60404-4 and Amendment 1 to that standard. This edition of IEC 60404-6 includes
measurements on magnetically soft powder materials. Since measurements on these materials
at high frequencies employ some of the techniques used to measure magnetic components,
there has been active collaboration with IEC TC51. IEC TC51 recently started to publish the
new IEC 62044 series which will be composed of four parts. IEC 62044-3 presents methods of
measurement of magnetic properties at high excitation levels appropriate to various ferrite
core applications, whereas this edition of IEC 60404-6 covers the requirements of material
measurements excluding ferrites, so that the two standards do not overlap.
MAGNETIC MATERIALS –
Part 6: Methods of measurement of the magnetic properties of
magnetically soft metallic and powder materials at frequencies
in the range 20 Hz to 200 100 kHz by the use of ring specimens
1 Scope
This part of IEC 60404 specifies methods for the measurement of AC magnetic properties of
soft magnetic materials, other than electrical steels and soft ferrites, in the frequency range
20 Hz to 200 100 kHz. The materials covered by this part of IEC 60404 include those
speciality alloys listed in IEC 60404-8-6, amorphous and nano-crystalline soft magnetic
materials, pressed and sintered and metal injection moulded parts such as are listed in
IEC 60404-8-9, cast parts and magnetically soft composite materials.
The object of this part is to define the general principles and the technical details of the
measurement of the magnetic properties of magnetically soft materials by means of ring
methods. For materials supplied in powder form, a ring test specimen is formed by the
appropriate pressing method for that material.
DC magnetic measurements on magnetically soft materials shall be The measurement of the
DC magnetic properties of soft magnetic materials is made in accordance with the ring
method of IEC 60404-4. The determinations of the magnetic characteristics of magnetically
soft components shall be are made in accordance with IEC 62044-3.
NOTE IEC 62044-3:2000 specifies methods for the measurement of AC magnetic characteristics of magnetically
soft components in the frequency range up to 10 MHz.
Normally, the measurements shall be are made at an ambient temperature of (23 ± 5) °C on
ring test specimens which have first been magnetized, then demagnetized. Measurements
can be made over other temperature ranges by agreement between supplier and purchaser
parties concerned.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60050-121, International Electrotechnical Vocabulary – Part 121: Electromagnetism
IEC 60050-221, International Electrotechnical Vocabulary – Chapter 221: Magnetic materials
and components
IEC 60404-2:1996, Magnetic materials – Part 2: Methods of measurement of the magnetic
properties of electrical steel sheet and strip by means of an Epstein frame
IEC 60404-4:1995, Magnetic materials – Part 4: Methods of measurement of d.c. magnetic
properties of iron and steel
Amendment 1:2000
IEC 60404-8-6:1999, Magnetic materials – Part 8-6: Specifications for individual materials –
Soft magnetic metallic materials
– 8 – IEC 60404-6:2018 RLV © IEC 2018
IEC 60404-8-9:1994, Magnetic materials – Part 8: Specifications for individual materials −
Section 9: Standard specification for sintered soft magnetic materials
IEC 62044-3:2000, Cores made of soft magnetic materials – Measuring methods –
Part 3: Magnetic properties at high excitation levels
ISO/IEC Guide 98-3, Uncertainty of measurement – Part 3: Guide to the expression of
uncertainty in measurement, 1993 (GUM:1995)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-121 and
IEC 60050-221 apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
4 General principles of measurement
4.1 Principle of the ring method
The measurements are made on a closed magnetic circuit in the form of a ring test specimen
wound with one or two windings.
4.2 Test specimen
The test specimen shall be in the form of a ring of rectangular cross-section which may be
formed by
a) winding thin strip or wire to produce a clock-spring wound toroidal core; or
b) punching, laser cutting or photochemically etching a stack of punched, laser cut, wire cut
or photochemically etched ring laminations; or
c) pressing and sintering of powders, metal injection moulding, 3D printing or casting.
In the case of powder materials, the production of a ring test specimen by metal injection
moulding or by pressing (with heating if applicable) shall be carried out in accordance with the
material manufacturer's recommendations to achieve the optimum magnetic performance of
the powder material.
For all types of test specimen, burrs and sharp edges should be removed prior to heat
treatment. In the case of high permeability material, It is preferable to enclose the ring test
specimen in a two-part non-magnetic annular case. The case dimensions shall be such that it
closely fits without introducing stress into the material of the test specimen.
The ring shall have dimensions such that the ratio of the outer to inner diameter shall be no
greater than 1,4 and preferably less than 1,25 to achieve a sufficiently homogenous
magnetization of the test specimen.
For solid and pressed powder materials, the dimensions of the test specimen, that is the outer
and inner diameters and the height of the ring, shall be measured with suitable calibrated
measuring instruments. The respective dimensions shall be measured at several locations on
a test specimen and averaged. The cross-sectional area of the test specimen shall be
calculated from Formula (1).
( D − d )
A = h (1)
where
A is the cross-sectional area of the test specimen, in square metres;
D is the outer diameter of the test specimen, in metres;
d is the inner diameter of the test specimen, in metres;
h is the height of the test specimen, in metres.
For a stack of laminations or a toroidal wound core, the cross-sectional area of the test
specimen shall be calculated from the mass, density and the values of the inner and outer
diameter of the ring specimen. The mass and diameters shall be measured with suitable
calibrated instruments. The density shall be the conventional density for the material supplied
by the manufacturer. The cross-sectional area shall be calculated from Formula (2).
2 m
(2)
A =
ρπ (D + d )
where
m is the mass of the test specimen, in kilograms;
ρ is the density of the material, in kilograms per cubic metre.
For the calculation of the magnetic field strength use the mean magnetic path length of the
test specimen determined from Formula (3) shall be used.
(D + d )
l = π (3)
m
where
l is the mean magnetic path length of the test specimen, in metres.
m
NOTE For measurements of magnetically soft components, an effective core cross-sectional area and an effective
magnetic path length are used (described in IEC 62044-3:2000). The difference in results between material
measurements and component measurements is larger when the ratio of the outer to inner diameter is larger.
If the specific total loss is to be determined, then the mass of the test specimen shall be
measured with a suitable calibrated balance.
4.3 Windings
The test specimen shall be wound with a magnetizing winding and a secondary winding (see
Annex A).
The numbers of windings and turns depend upon the measuring equipment and method being
used. For specific total loss measurements, a magnetizing and a secondary winding are
normally required. In this case, The secondary winding shall be wound as closely as possible
to the test specimen to minimize the effect of air flux included in enclosed between the test
specimen and the secondary winding. All windings shall be wound uniformly over the whole
length of the test specimen.
For measurements at frequencies above power frequencies, care shall be taken to avoid
complications related to capacitance and other effects. These are introduced and discussed in
Annex A.
Care shall be taken to ensure that the wire insulation is not damaged during the winding
process causing a short circuit to the test specimen. An electrical check shall be made with a
– 10 – IEC 60404-6:2018 RLV © IEC 2018
suitable AC insulation resistance measuring device to ensure that there is no direct
connection between the windings and the test specimen.
5 Temperature measurements
When the temperature of the surface of the test specimen is required, it shall be measured by
affixing a calibrated non-magnetic thermocouple (for example a type T thermocouple) to the
test specimen. Where the test specimen is encapsulated enclosed in an annular case, a small
hole shall be made in the encapsulation case, taking care not to damage the material of the
test specimen, and the thermocouple fixed in contact with the core material test specimen. If
this is not possible, the thermocouple shall be affixed to the encapsulation case and this
procedure shall be reported in the test report. The thermocouple shall be connected to a
suitable calibrated digital voltmeter in order to measure its output voltage which can be
related to the corresponding temperature through the calibration tables for the thermocouple.
Where the temperature of the test specimen is found to vary with time after magnetization, the
measurements of the magnetic properties shall be carried out either when an agreed
temperature is reached or after a time agreed between the purchaser and supplier parties
concerned. If measurements are to be made at elevated temperatures, these may be carried
out with the test specimen placed in a suitable oven to produce the required temperature.
NOTE A second smaller time-dependent magnetic relaxation effect may can also affect the
magnetic properties. For the types of materials covered by this document, the effect is usually
masked by temperature changes. However, if such magnetic relaxation effects become
apparent, then the test specimen should be allowed to dwell at the prescribed magnetic flux
density or magnetic field strength for an agreed period of time before making the final
measurements.
6 Measurement of magnetic the relative amplitude permeability
and the AC magnetization curve using the voltmeter-ammeter method
6.1 Introduction General
The measurements are made using the ring method at frequencies normally from 20 Hz to
200 100 kHz, the upper frequency being limited by the performance of the instrumentation.
NOTE Where suitable calibrated instruments exist and careful winding to reduce interwinding
capacitance has been performed, this upper limit may be extended to 1 MHz (See Annex A).
NOTE DC measurements should be made in accordance with the ring method described in IEC 60404-4.
NOTE A selection of methods for the measurement of loss and effective permeability of cores, taken from current
production, at high excitation levels and at frequencies ranging from practically d.c. to 10 MHz and even higher, is
given in 6.2 and 6.3 of IEC 62044-3.
6.2 Apparatus and connections
The ring test specimen shall be wound with a magnetizing winding, N , and a secondary
winding, N (see 3.2 and Annex A).
The apparatus shall be connected as shown in Figure 1.
NOTE 1 Figure 3 can be used for the measurement of the relative amplitude permeability and the magnetization
curve using the digital sampling technique.
NOTE 2 For the application of digital sampling technique, see Annex B.
N N
1 2
A
Hz V V OSC
1 2
IEC
Key
~ power supply (usually an oscillator and a power amplifier)
A true r.m.s. or peak reading ammeter, or a true r.m.s. or peak reading voltmeter and a non-inductive
precision resistor to measure the magnetizing current
Hz frequency meter
N magnetizing winding
N secondary winding
OSC oscilloscope
V average type voltmeter
V r.m.s. voltmeter
Figure 1 – Circuit of the ring method measurement apparatus
NOTE When conducting sinusoidal current measurements, a non-inductive precision resistor
should be connected in series with the magnetizing winding N to guarantee that the
magnetizing circuit resistance is at least ten times greater than the impedance of the
magnetizing winding N on the test specimen.
The source of alternating current shall have a variation of voltage and frequency at its output
individually not exceeding ± 0,2 % of the adjusted value during the measurement. It shall be
connected to a true r.m.s. or peak reading ammeter, or a true r.m.s. or peak reading voltmeter
and a parallel non-inductive precision resistor, in series with the magnetizing winding N on
the ring test specimen, to measure the magnetizing current.
The secondary circuit comprises a secondary winding N connected to two voltmeters in
parallel. One voltmeter V measures the true r.m.s. value, the other voltmeter V measures
2 1
the average rectified value but is sometimes scaled in values 1,111 times the rectified value.
NOTE The waveform of the induced secondary voltage that is induced in the secondary
winding N should be checked with an oscilloscope to ensure that only the fundamental
component is present.
6.3 Waveform of induced secondary voltage or magnetizing current
In order to obtain comparable measurements, it shall be agreed prior to the measurements
that either the waveform of the induced secondary voltage or the waveform of the magnetizing
current shall be maintained sinusoidal with a form factor of 1,111 with a relative tolerance of
± 1 %. In the latter case, a non-inductive precision resistor connected in series with the
magnetizing circuit winding is required.
NOTE 1 The waveform of the induced secondary voltage and the magnetizing current can be measured by the
digital sampling technique. See Figure 3 and Annex B.
NOTE The time constant of the non-inductive precision resistor should be checked to be low to
ensure that the waveform is within the specified limits.
NOTE The non-inductive precision resistor can may be the same resistor as used for the
measurement of the magnetizing current.
NOTE 2 Sinusoidal waveform control may can be achieved by digital means (see Annex C).
– 12 – IEC 60404-6:2018 RLV © IEC 2018
At frequencies in the range 20 Hz to 50 kHz, the form factor of the induced secondary voltage
can be determined by connecting two voltmeters having a high impedance (typically > 1 MΩ in
parallel with 90 pF to 150 pF) across the secondary winding. One voltmeter shall be
responsive to the r.m.s. value of voltage and one the other shall be responsive to the average
rectified value of the secondary voltage. The form factor is then determined from the ratio of
the r.m.s. value to the average rectified value.
NOTE For optimum power transfer, it may be necessary to optimize the number of turns of the
magnetizing winding to match the output impedance of the power source supply. This can be
determined from Formula (4).
ZL= jw (4)
where
Z is the output impedance of the power source supply, in ohms;
j is the complex number sign;
w is the angular frequency of the output of the power source supply, in radians per
second;
L is the effective inductance of the magnetizing winding of the ring test specimen, in
henrys, calculated from Formula (5).
N Aµ µ
1 0 r
L = (5)
l
m
where
N is the number of turns of the magnetizing winding;
A is the cross-sectional area of the test specimen, in square metres;
−7
µ is the magnetic constant (4 π × 10 henrys per metre);
µ is the relative amplitude permeability of the test specimen;
r
l is the mean magnetic path length of the test specimen, in metres.
m
Where the relative magnetic amplitude permeability is not known, a preliminary measurement
may need to be made of the peak values of magnetic field strength and magnetic flux density
as described in 6.4.1 and 6.4.2 and the relative magnetic amplitude permeability calculated as
described in 6.4.3.
6.4 Determination of characteristics
6.4.1 Determination of the peak value of the magnetic field strength
The peak value of magnetic field strength at which the measurement is to be made is
calculated from Formula (6).
ˆ
N I
NI
ˆ 1
H = H = (6)
l
m m
where
ˆ
H
H is the peak value of the magnetic field strength, in amperes per metre;
N is the number of turns of the magnetizing winding on the test specimen;
ˆ
I
I is the peak value of the magnetizing current, in amperes;
l is the mean magnetic path length of the test specimen, in metres.
m
Normally the amplitude of the magnetic field strength is determined by measuring the r.m.s.
magnetizing current and multiplying by the square root of 2. For sinusoidal magnetizing
current, this defines the correct value of the peak value of magnetic field strength. For
sinusoidal magnetic flux density, this defines an equivalent peak value of magnetic field
strength, which is numerically lower for a given magnetizing current. As an alternative, the
peak value of magnetic field strength can be determined using a calibrated peak reading
ammeter or a peak reading voltmeter and a non-inductive precision resistor.
Prior to measurement, the test specimen shall be carefully demagnetized from a value of field
strength of not less than ten times the coercivity by slowly reducing the corresponding
magnitude of the magnetizing current to zero. Demagnetization shall be carried out at the
same or lower frequency as will be used for the measurements.
6.4.2 Determination of the peak value of the magnetic flux density
The average rectified value of the induced secondary voltage shall be measured using the a
calibrated average type voltmeter V or a digitizer (see Figure 3), and the peak value of the
magnetic flux density shall be calculated from Formula (7).
ˆ
ˆ
U = 4 f A B N B = U (7)
2 2
4 fN A
where
ˆ
B is the peak value of magnetic flux density, in teslas;
is the average rectified value of the induced secondary voltage, in volts;
U
f is the frequency, in hertz;
A is the cross-sectional area of the test specimen, in square metres.
N is the number of turns of the secondary winding.
NOTE For the application of the digital sampling technique, see Annex B.
Depending on the level of magnetic field strength and the ratio of the cross-sectional areas of
the test specimen and the secondary winding, it may be necessary to make a correction to the
magnetic flux density for the air flux enclosed between the test specimen and the secondary
winding. The corrected value B of the magnetic flux density is given by Formula (8).
(A′ − A)
(8)
′
B = B − µ H
A
where
B′ is the measured value of magnetic flux density, in teslas;
−7
µ is the magnetic constant (4 π × 10 henrys per metre);
H is the magnetic field strength, in amperes per metre;
A′ is the cross-sectional area enclosed by the secondary winding, in square metres;
A is the cross-sectional area of the test specimen, in square metres.
6.4.3 Determination of the r.m.s. amplitude permeability and the relative amplitude
permeability
For corresponding peak values of magnetic field strength and magnetic flux density, the r.m.s.
amplitude permeability shall be calculated from Formula (9).
– 14 – IEC 60404-6:2018 RLV © IEC 2018
ˆ
B
(9)
µ =
a, rms ~
µ 2 H
where
µ is the r.m.s. amplitude permeability (for sinusoidal magnetic flux density);
a,rms
µ is the relative amplitude permeability (for sinusoidal magnetic field strength);
a
−7
µ is the magnetic constant (4 π × 10 henrys per metre);
ˆ
is the peak value of magnetic flux density, in teslas;
B
~
H is the r.m.s. value of magnetic field strength, in amperes per metre.
NOTE The relative amplitude permeability, µ , can be conventionally expressed as:
r
ˆ
B
ˆ
B
(10)
µ =
a µ =
r
ˆ
ˆ
µ H
0 µ H
where
µ µ is the relative amplitude permeability (for sinusoidal magnetic field strength);
a r
−7
µ is the magnetic constant (4 π × 10 henrys per metre);
ˆ
B
is the peak value of magnetic flux density, in teslas;
ˆ
H is the peak value of magnetic field strength, in amperes per metre.
6.4.4 Determination of the AC magnetization curve
The test specimen shall be carefully demagnetized as described in 6.4.1. By successively
increasing the magnetizing current, corresponding peak values of magnetic field strength and
magnetic flux density can be obtained from which an AC magnetization curve can be plotted.
7 Measurement of the specific total loss by the wattmeter method
7.1 Principle of measurement
The principle of measurement is similar to that described in IEC 60404-2 except that the
Epstein frame is replaced by the ring test specimen and the instrumentation is capable of
making measurements at the required frequency. The measurement of specific total loss shall
be done under conditions of sinusoidal magnetic flux density. For some test specimens, this
may require the control of the magnetizing current induced secondary voltage waveform (see
Annex C) by means of analogue or digital techniques to ensure that sinusoidal magnetic flux
density is maintained.
NOTE A selection of methods for the measurement of specific total loss and amplitude permeability at high
excitation levels at frequencies ranging from practically d.c. to 10 MHz and even higher is given in 6.2 and 6.3 of
IEC 62044-3.
The apparatus and the windings of the test specimen shall be connected as shown in Figure 2.
N N
1 2
V V
Hz
OSC
1 2
W
IEC
Key
~ power supply (usually an oscillator and amplifier)
Hz frequency meter
N magnetizing winding
N secondary winding
OSC oscilloscope
W wattmeter
V average type voltmeter
V r.m.s. voltmeter
Figure 2 – Circuit of the conventional analogue wattmeter method (also representing
the metrological principle of the digital wattmeter method)
For the digital sampling technique, Figure 3 shows a possible circuit structure as an example.
In the latter case, a digitizer and supporting software adopt the functions of the oscilloscope,
the wattmeter and the voltmeters shown in Figure 2.
NOTE Figure 3 is not the only possible structure of digital sampling technique application, see Annex B.
N N
1 2
D
Hz
R
n
IEC
Key
R non-inductive precision resistor in series with the magnetizing winding to
n
determine the magnetizing current
D digitizer (usually a digital power analyser or a digital acquisition system with a computer)
Figure 3 – The wattmeter method when connected with
the digital sampling technique (example of circuit)
U (t) U (t)
1 2
– 16 – IEC 60404-6:2018 RLV © IEC 2018
7.2 Voltage measurement
7.2.1 Average type voltmeter, V
The average rectified value of the induced secondary voltage shall be measured using a
calibrated average type voltmeter or a calibrated digitizer (see Figures 2 and 3). The load on
the secondary circuit shall be as small low as possible (see Annex A). Consequently an
electronic a digital voltmeter or digitizer with a high input impedance is required.
NOTE 1 Instruments of this Average type voltmeters are usually graduated in average rectified value multiplied by
1,111.
NOTE 2 For the application of digital sampling technique, see Annex B.
7.2.2 R.M.S. type voltmeter, V
A calibrated voltmeter responsive to r.m.s. values shall be used. Again, the load on the
secondary circuit shall be as small as possible, an electronic voltmeter being preferred (see
Annex A).
The true r.m.s. value of the induced secondary voltage shall be measured using a calibrated
voltmeter responsive to r.m.s. values or a calibrated digitizer (see Figures 2 and 3). The load
on the secondary circuit shall be as low as possible (see Annex A). Consequently a digital
voltmeter or digitizer with high input impedance is required.
NOTE For the application of digital sampling technique, see Annex B.
7.3 Power measurement
The power shall be measured using a calibrated wattmeter suitable for circuits which may
have a low power factor (cosφ down to 0,1) or a calibrated digitizer (see Figures 2 and 3). The
input impedance of the voltage circuit shall be as high as possible (see Annex A).
NOTE For the application of digital sampling technique, see Annex B.
7.4 Procedure for the measurement of the specific total loss
The test specimen shall be carefully demagnetized as described in 6.4.1. The current in
the magnetizing winding N shall be increased until the voltage on voltmeter V (indicating the
1 1
average rectified voltage) corresponds to the required peak value of magnetic flux density
calculated from Formula (7).
The readings of the two voltmeters V and V The average rectified value and the r.m.s. value
1 2
of the induced secondary voltage shall be recorded and the form factor of the secondary
waveform shall be calculated and verified in accordance with 6.2. The wattmeter reading shall
then be recorded.
NOTE For the application of digitizing methods, see Annex B.
7.5 Determination of the specific total loss
The power P measured by the wattmeter includes the power consumed by the instruments in
m
~
U / R
the secondary circuit, which to a first approximation is equal to (1,111 U ) / R ,since
2 i
2 i
the induced secondary voltage is essentially sinusoidal.
Thus, the total loss P of the test specimen shall be calculated in accordance with
c
Formula (11).
...
IEC 60404-6 ®
Edition 3.0 2018-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Magnetic materials –
Part 6: Methods of measurement of the magnetic properties of magnetically soft
metallic and powder materials at frequencies in the range 20 Hz to 100 kHz by
the use of ring specimens
Matériaux magnétiques –
Partie 6: Méthodes de mesure des propriétés magnétiques des matériaux
métalliques et des matériaux en poudre magnétiquement doux, aux fréquences
comprises entre 20 Hz et 100 kHz, sur des éprouvettes en forme de tore
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IEC 60404-6 ®
Edition 3.0 2018-05
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Magnetic materials –
Part 6: Methods of measurement of the magnetic properties of magnetically soft
metallic and powder materials at frequencies in the range 20 Hz to 100 kHz by
the use of ring specimens
Matériaux magnétiques –
Partie 6: Méthodes de mesure des propriétés magnétiques des matériaux
métalliques et des matériaux en poudre magnétiquement doux, aux fréquences
comprises entre 20 Hz et 100 kHz, sur des éprouvettes en forme de tore
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.20; 29.030 ISBN 978-2-8322-5716-6
– 2 – IEC 60404-6:2018 © IEC 2018
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 General principles of measurement . 7
4.1 Principle of the ring method . 7
4.2 Test specimen . 7
4.3 Windings . 8
5 Temperature measurements . 9
6 Measurement of the relative amplitude permeability and the AC magnetization
curve . 9
6.1 General . 9
6.2 Apparatus and connections . 9
6.3 Waveform of induced secondary voltage or magnetizing current . 10
6.4 Determination of characteristics . 11
6.4.1 Determination of the peak value of the magnetic field strength . 11
6.4.2 Determination of the peak value of the magnetic flux density . 12
6.4.3 Determination of the r.m.s. amplitude permeability and the relative
amplitude permeability . 12
6.4.4 Determination of the AC magnetization curve . 13
7 Measurement of the specific total loss by the wattmeter method . 13
7.1 Principle of measurement. 13
7.2 Voltage measurement . 15
7.2.1 Average type voltmeter . 15
7.2.2 R.M.S. type voltmeter . 15
7.3 Power measurement . 15
7.4 Procedure for the measurement of the specific total loss . 15
7.5 Determination of the specific total loss . 15
8 Uncertainties . 16
9 Test report . 16
Annex A (informative) Guidance on requirements for windings and instrumentation in
order to minimise additional losses . 17
A.1 General . 17
A.2 Reduction of additional losses . 17
Annex B (informative) Digital sampling technique for the determination of magnetic
properties and numerical air flux compensation . 18
B.1 General . 18
B.2 Technical details and requirements . 18
B.3 Calibration aspects . 22
B.4 Numerical air flux compensation . 22
Annex C (informative) Sinusoidal waveform control by digital means . 23
Bibliography . 24
Figure 1 – Circuit of the measurement apparatus . 10
Figure 2 – Circuit of the conventional analogue wattmeter method (also representing
the metrological principle of the digital wattmeter method) . 14
Figure 3 – The wattmeter method when connected with the digital sampling technique
(example of circuit) . 14
– 4 – IEC 60404-6:2018 © IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MAGNETIC MATERIALS –
Part 6: Methods of measurement of the magnetic properties of
magnetically soft metallic and powder materials at frequencies
in the range 20 Hz to 100 kHz by the use of ring specimens
FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
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with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
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Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
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4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
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other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 60404-6 has been prepared by IEC technical committee 68:
Magnetic alloys and steels.
This third edition cancels and replaces the second published in 2003. This edition constitutes
a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) adaption to modern measurement and evaluation methods, in particular the introduction of
the widely spread digital sampling method for the acquisition and evaluation of the
measured data;
b) limitation of the frequency range up to 100 kHz;
c) deletion of Clause 7 of the second edition that specified the measurement of magnetic
properties using a digital impedance bridge;
d) addition of a new Clause 7 on the measurement of the specific total loss by the wattmeter
method, including an example of the application of the digital sampling method;
e) addition of an informative annex on the technical details of the digital sampling technique
for the determination of magnetic properties.
The text of this International Standard is based on the following documents:
FDIS Report on voting
68/595/FDIS 68/600/RVD
Full information on the voting for the approval of this International Standard can be found in
the report on voting indicated in the above table.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 60404 series, published under the general title Magnetic materials,
can be found on the IEC website.
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under "http://webstore.iec.ch" in the data related to
the specific document. At this date, the document will be
reconfirmed,
withdrawn,
replaced by a revised edition, or
amended.
The contents of the corrigendum of November 2018 have been included in this copy.
– 6 – IEC 60404-6:2018 © IEC 2018
MAGNETIC MATERIALS –
Part 6: Methods of measurement of the magnetic properties of
magnetically soft metallic and powder materials at frequencies
in the range 20 Hz to 100 kHz by the use of ring specimens
1 Scope
This part of IEC 60404 specifies methods for the measurement of AC magnetic properties of
soft magnetic materials, other than electrical steels and soft ferrites, in the frequency range
20 Hz to 100 kHz. The materials covered by this part of IEC 60404 include those speciality
alloys listed in IEC 60404-8-6, amorphous and nano-crystalline soft magnetic materials,
pressed and sintered and metal injection moulded parts such as are listed in IEC 60404-8-9,
cast parts and magnetically soft composite materials.
The object of this part is to define the general principles and the technical details of the
measurement of the magnetic properties of magnetically soft materials by means of ring
methods. For materials supplied in powder form, a ring test specimen is formed by the
appropriate pressing method for that material.
The measurement of the DC magnetic properties of soft magnetic materials is made in
accordance with the ring method of IEC 60404-4. The determinations of the magnetic
characteristics of magnetically soft components are made in accordance with IEC 62044-3.
NOTE IEC 62044-3:2000 specifies methods for the measurement of AC magnetic characteristics of magnetically
soft components in the frequency range up to 10 MHz.
Normally, the measurements are made at an ambient temperature of (23 ± 5) °C on test
specimens which have first been magnetized, then demagnetized. Measurements can be
made over other temperature ranges by agreement between parties concerned.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60050-121, International Electrotechnical Vocabulary – Part 121: Electromagnetism
IEC 60050-221, International Electrotechnical Vocabulary – Chapter 221: Magnetic materials
and components
IEC 60404-2, Magnetic materials – Part 2: Methods of measurement of the magnetic
properties of electrical steel sheet and strip by means of an Epstein frame
IEC 60404-4, Magnetic materials – Part 4: Methods of measurement of d.c. magnetic
properties of iron and steel
IEC 60404-8-6, Magnetic materials – Part 8-6: Specifications for individual materials – Soft
magnetic metallic materials
− Section 9:
IEC 60404-8-9, Magnetic materials – Part 8: Specifications for individual materials
Standard specification for sintered soft magnetic materials
IEC 62044-3, Cores made of soft magnetic materials – Measuring methods – Part 3: Magnetic
properties at high excitation level
ISO/IEC Guide 98-3, Uncertainty of measurement – Part 3: Guide to the expression of
uncertainty in measurement (GUM:1995)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-121 and
IEC 60050-221 apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
4 General principles of measurement
4.1 Principle of the ring method
The measurements are made on a closed magnetic circuit in the form of a ring test specimen
wound with two windings.
4.2 Test specimen
The test specimen shall be in the form of a ring of rectangular cross-section which may be
formed by
a) winding thin strip or wire to produce a clock-spring wound toroidal core; or
b) a stack of punched, laser cut, wire cut or photochemically etched ring laminations; or
c) pressing and sintering of powders, metal injection moulding, 3D printing or casting.
In the case of powder materials, the production of a ring test specimen by metal injection
moulding or by pressing (with heating if applicable) shall be carried out in accordance with the
material manufacturer's recommendations to achieve the optimum magnetic performance of
the powder material.
For all types of test specimen, burrs and sharp edges should be removed prior to heat
treatment. It is preferable to enclose the test specimen in a two-part non-magnetic annular
case. The case dimensions shall be such that it closely fits without introducing stress into the
material of the test specimen.
The ring shall have dimensions such that the ratio of the outer to inner diameter shall be no
greater than 1,4 and preferably less than 1,25 to achieve a sufficiently homogenous
magnetization of the test specimen.
For solid and pressed powder materials, the dimensions of the test specimen, that is the outer
and inner diameters and the height of the ring, shall be measured with suitable calibrated
instruments. The respective dimensions shall be measured at several locations on a test
specimen and averaged. The cross-sectional area of the test specimen shall be calculated
from Formula (1).
– 8 – IEC 60404-6:2018 © IEC 2018
( D− d )
A h (1)
=
where
A is the cross-sectional area of the test specimen, in square metres;
D is the outer diameter of the test specimen, in metres;
d is the inner diameter of the test specimen, in metres;
h is the height of the test specimen, in metres.
For a stack of laminations or a toroidal wound core, the cross-sectional area of the test
specimen shall be calculated from the mass, density and the values of the inner and outer
diameter of the ring specimen. The mass and diameters shall be measured with suitable
calibrated instruments. The density shall be the conventional density for the material supplied
by the manufacturer. The cross-sectional area shall be calculated from Formula (2).
2 m
(2)
A =
ρπ (D + d)
where
m is the mass of the test specimen, in kilograms;
ρ is the density of the material, in kilograms per cubic metre.
For the calculation of the magnetic field strength, the mean magnetic path length of the test
specimen determined from Formula (3) shall be used.
(D + d)
l = π (3)
m
where
l is the mean magnetic path length of the test specimen, in metres.
m
NOTE For measurements of magnetically soft components, an effective core cross-sectional area and an effective
magnetic path length are used (described in IEC 62044-3:2000). The difference in results between material
measurements and component measurements is larger when the ratio of the outer to inner diameter is larger.
If the specific total loss is to be determined, the mass of the test specimen shall be measured
with a suitable calibrated balance.
4.3 Windings
The test specimen shall be wound with a magnetizing winding and a secondary winding (see
Annex A).
The numbers of turns depend upon the measuring equipment and method being used. The
secondary winding shall be wound as closely as possible to the test specimen to minimize the
effect of air flux enclosed between the test specimen and the secondary winding. All windings
shall be wound uniformly over the whole length of the test specimen.
For measurements at frequencies above power frequencies, care shall be taken to avoid
complications related to capacitance and other effects. These are introduced and discussed in
Annex A.
Care shall be taken to ensure that the wire insulation is not damaged during the winding
process causing a short circuit to the test specimen. An electrical check shall be made with a
suitable AC insulation resistance measuring device to ensure that there is no direct
connection between the windings and the test specimen.
5 Temperature measurements
When the temperature of the surface of the test specimen is required, it shall be measured by
affixing a calibrated non-magnetic thermocouple (for example a type T thermocouple) to the
test specimen. Where the test specimen is enclosed in an annular case, a small hole shall be
made in the case, taking care not to damage the material of the test specimen, and the
thermocouple fixed in contact with the test specimen. If this is not possible, the thermocouple
shall be affixed to the case and this procedure shall be reported in the test report. The
thermocouple shall be connected to a suitable calibrated voltmeter in order to measure its
output voltage which can be related to the corresponding temperature through the calibration
tables for the thermocouple.
Where the temperature of the test specimen is found to vary with time after magnetization, the
measurements of the magnetic properties shall be carried out either when an agreed
temperature is reached or after a time agreed between the parties concerned. If
measurements are to be made at elevated temperatures, these may be carried out with the
test specimen placed in a suitable oven to produce the required temperature.
A second smaller time-dependent magnetic relaxation effect can also affect the magnetic
properties. For the types of materials covered by this document, the effect is usually masked
by temperature changes. However, if such magnetic relaxation effects become apparent, then
the test specimen should dwell at the prescribed magnetic flux density or magnetic field
strength for an agreed period of time before making the final measurements.
6 Measurement of the relative amplitude permeability and the
AC magnetization curve
6.1 General
The measurements are made using the ring method at frequencies normally from 20 Hz to
100 kHz, the upper frequency being limited by the performance of the instrumentation.
Where suitable calibrated instruments exist and careful winding to reduce interwinding
capacitance has been performed, this upper limit may be extended to 1 MHz (See Annex A).
6.2 Apparatus and connections
The apparatus shall be connected as shown in Figure 1.
NOTE 1 Figure 3 can be used for the measurement of the relative amplitude permeability and the magnetization
curve using the digital sampling technique.
NOTE 2 For the application of digital sampling technique, see Annex B.
– 10 – IEC 60404-6:2018 © IEC 2018
N N
1 2
A
Hz V V OSC
1 2
IEC
Key
~ power supply (usually an oscillator and a power amplifier)
A true r.m.s. or peak reading ammeter, or a true r.m.s. or peak reading voltmeter and a non-inductive
precision resistor to measure the magnetizing current
Hz frequency meter
N magnetizing winding
N secondary winding
OSC oscilloscope
V average type voltmeter
V r.m.s. voltmeter
Figure 1 – Circuit of the measurement apparatus
When conducting sinusoidal current measurements, a non-inductive precision resistor should
be connected in series with the magnetizing winding N to guarantee that the magnetizing
circuit resistance is at least ten times greater than the impedance of the magnetizing winding
N on the test specimen.
The source of alternating current shall have a variation of voltage and frequency at its output
individually not exceeding ± 0,2 % of the adjusted value during the measurement. It shall be
connected to a true r.m.s. or peak reading ammeter, or a true r.m.s. or peak reading voltmeter
and a parallel non-inductive precision resistor, in series with the magnetizing winding N on
the test specimen, to measure the magnetizing current.
The secondary circuit comprises a secondary winding N connected to two voltmeters in
parallel. One voltmeter V measures the true r.m.s. value, the other voltmeter V measures
2 1
the average rectified value but is sometimes scaled in values 1,111 times the rectified value.
The waveform of the induced secondary voltage that is induced in the secondary winding N
should be checked with an oscilloscope to ensure that only the fundamental component is
present.
6.3 Waveform of induced secondary voltage or magnetizing current
In order to obtain comparable measurements, it shall be agreed prior to the measurements
that either the waveform of the induced secondary voltage or the waveform of the magnetizing
current shall be maintained sinusoidal with a form factor of 1,111 with a relative tolerance of
± 1 %. In the latter case, a non-inductive precision resistor connected in series with the
magnetizing winding is required.
NOTE 1 The waveform of the induced secondary voltage and the magnetizing current can be measured by the
digital sampling technique. See Figure 3 and Annex B.
The time constant of the non-inductive precision resistor should be checked to be low to
ensure that the waveform is within the specified limits.
The non-inductive precision resistor may be the same resistor as used for the measurement
of the magnetizing current.
NOTE 2 Sinusoidal waveform control can be achieved by digital means (see Annex C).
At frequencies in the range 20 Hz to 50 kHz, the form factor of the induced secondary voltage
can be determined by connecting two voltmeters having a high impedance (typically > 1 MΩ in
parallel with 90 pF to 150 pF) across the secondary winding. One voltmeter shall be
responsive to the r.m.s. value of voltage and the other shall be responsive to the average
rectified value of the voltage. The form factor is then determined from the ratio of the r.m.s.
value to the average rectified value.
For optimum power transfer, it may be necessary to optimize the number of turns of the
magnetizing winding to match the output impedance of the power supply. This can be
determined from Formula (4).
ZL= jω (4)
where
Z is the output impedance of the power supply, in ohms;
j is the complex number sign;
ω is the angular frequency of the output of the power supply, in radians per second;
L is the effective inductance of the magnetizing winding of the test specimen, in henrys,
calculated from Formula (5).
N Amm
1 0 r
(5)
L=
l
m
where
N is the number of turns of the magnetizing winding;
A is the cross-sectional area of the test specimen, in square metres;
−7
m is the magnetic constant (4 π × 10 henrys per metre);
m is the relative amplitude permeability of the test specimen;
r
l is the mean magnetic path length of the test specimen, in metres.
m
Where the relative amplitude permeability is not known, a preliminary measurement may need
to be made of the peak values of magnetic field strength and magnetic flux density as
described in 6.4.1 and 6.4.2 and the relative amplitude permeability calculated as described in
6.4.3.
6.4 Determination of characteristics
6.4.1 Determination of the peak value of the magnetic field strength
The peak value of magnetic field strength at which the measurement is to be made is
calculated from Formula (6).
ˆ
NI
ˆ 1
H= (6)
l
m
where
ˆ
is the peak value of the magnetic field strength, in amperes per metre;
H
N is the number of turns of the magnetizing winding on the test specimen;
ˆ
I is the peak value of the magnetizing current, in amperes;
l is the mean magnetic path length of the test specimen, in metres.
m
– 12 – IEC 60404-6:2018 © IEC 2018
Normally the amplitude of the magnetic field strength is determined by measuring the r.m.s.
magnetizing current and multiplying by the square root of 2. For sinusoidal magnetizing
current, this defines the correct value of the peak value of magnetic field strength. For
sinusoidal magnetic flux density, this defines an equivalent peak value of magnetic field
strength, which is numerically lower for a given magnetizing current. As an alternative, the
peak value of magnetic field strength can be determined using a calibrated peak reading
ammeter or a peak reading voltmeter and a non-inductive precision resistor.
Prior to measurement, the test specimen shall be carefully demagnetized from a value of field
strength of not less than ten times the coercivity by slowly reducing the corresponding
magnitude of the magnetizing current to zero. Demagnetization shall be carried out at the
same or lower frequency as will be used for the measurements.
6.4.2 Determination of the peak value of the magnetic flux density
The average rectified value of the induced secondary voltage shall be measured using a
calibrated average type voltmeter or a digitizer (see Figure 3), and the peak value of the
magnetic flux density shall be calculated from Formula (7).
ˆ
B= U (7)
4 fN A
where
ˆ
B is the peak value of magnetic flux density, in teslas;
is the average rectified value of the induced secondary voltage, in volts;
U
f is the frequency, in hertz;
A is the cross-sectional area of the test specimen, in square metres.
N is the number of turns of the secondary winding.
NOTE For the application of the digital sampling technique, see Annex B.
Depending on the level of magnetic field strength and the ratio of the cross-sectional areas of
the test specimen and the secondary winding, it may be necessary to make a correction to the
magnetic flux density for the air flux enclosed between the test specimen and the secondary
winding. The corrected value B of the magnetic flux density is given by Formula (8).
(A′− A)
(8)
′
B = B−m H
A
where
′ is the measured value of magnetic flux density, in teslas;
B
−7
m is the magnetic constant (4 π × 10 henrys per metre);
H is the magnetic field strength, in amperes per metre;
A′ is the cross-sectional area enclosed by the secondary winding, in square metres;
A is the cross-sectional area of the test specimen, in square metres.
6.4.3 Determination of the r.m.s. amplitude permeability and the relative amplitude
permeability
For corresponding peak values of magnetic field strength and magnetic flux density, the r.m.s.
amplitude permeability shall be calculated from Formula (9).
ˆ
B
(9)
m =
a, rms ~
m 2 H
where
m is the r.m.s. amplitude permeability;
a,rms
−7
m is the magnetic constant (4 π × 10 henrys per metre);
ˆ
B is the peak value of magnetic flux density, in teslas;
~
is the r.m.s. value of magnetic field strength, in amperes per metre.
H
NOTE The relative amplitude permeability, µ , can be conventionally expressed as:
r
ˆ
B
(10)
µ =
r
ˆ
m H
where
m is the relative amplitude permeability;
r
−7
m is the magnetic constant (4 π × 10 henrys per metre);
ˆ
B is the peak value of magnetic flux density, in teslas;
ˆ
H is the peak value of magnetic field strength, in amperes per metre.
6.4.4 Determination of the AC magnetization curve
The test specimen shall be carefully demagnetized as described in 6.4.1. By successively
increasing the magnetizing current, corresponding peak values of magnetic field strength and
magnetic flux density can be obtained from which an AC magnetization curve can be plotted.
7 Measurement of the specific total loss by the wattmeter method
7.1 Principle of measurement
The principle of measurement is similar to that described in IEC 60404-2 except that the
Epstein frame is replaced by the ring test specimen and the instrumentation is capable of
making measurements at the required frequency. The measurement of specific total loss shall
be done under conditions of sinusoidal magnetic flux density. For some test specimens, this
may require the control of the induced secondary voltage waveform (see Annex C) by means
of analogue or digital techniques to ensure that sinusoidal magnetic flux density is maintained.
The apparatus and the windings of the test specimen shall be connected as shown in Figure 2.
– 14 – IEC 60404-6:2018 © IEC 2018
N N
1 2
V V
Hz
OSC
1 2
W
IEC
Key
~ power supply (usually an oscillator and amplifier)
Hz frequency meter
N magnetizing winding
N secondary winding
OSC oscilloscope
W wattmeter
V average type voltmeter
V r.m.s. voltmeter
Figure 2 – Circuit of the conventional analogue wattmeter method (also representing
the metrological principle of the digital wattmeter method)
For the digital sampling technique, Figure 3 shows a possible circuit structure as an example.
In the latter case, a digitizer and supporting software adopt the functions of the oscilloscope,
the wattmeter and the voltmeters shown in Figure 2.
NOTE Figure 3 is not the only possible structure of digital sampling technique application, see Annex B.
N N
1 2
D
Hz
R
n
IEC
Key
R non-inductive precision resistor in series with the magnetizing winding to
n
determine the magnetizing current
D digitizer (usually a digital power analyser or a digital acquisition system with a computer)
Figure 3 – The wattmeter method when connected with
the digital sampling technique (example of circuit)
U (t) U (t)
1 2
7.2 Voltage measurement
7.2.1 Average type voltmeter
The average rectified value of the induced secondary voltage shall be measured using a
calibrated average type voltmeter or a calibrated digitizer (see Figures 2 and 3). The load on
the secondary circuit shall be as low as possible (see Annex A). Consequently a digital
voltmeter or digitizer with high input impedance is required.
NOTE 1 Average type voltmeters are usually graduated in average rectified value multiplied by 1,111.
NOTE 2 For the application of digital sampling technique, see Annex B.
7.2.2 R.M.S. type voltmeter
The true r.m.s. value of the induced secondary voltage shall be measured using a calibrated
voltmeter responsive to r.m.s. values or a calibrated digitizer (see Figures 2 and 3). The load
on the secondary circuit shall be as low as possible (see Annex A). Consequently a digital
voltmeter or digitizer with high input impedance is required.
NOTE For the application of digital sampling technique, see Annex B.
7.3 Power measurement
The power shall be measured using a calibrated wattmeter suitable for circuits which may
have a low power factor (cosφ down to 0,1) or a calibrated digitizer (see Figures 2 and 3). The
input impedance of the voltage circuit shall be as high as possible (see Annex A).
NOTE For the application of digital sampling technique, see Annex B.
7.4 Procedure for the measurement of the specific total loss
The test specimen shall be carefully demagnetized as described in 6.4.1. The current in
the magnetizing winding shall be increased until the average rectified voltage corresponds to
the required peak value of magnetic flux density calculated from Formula (7).
The average rectified value and the r.m.s. value of the induced secondary voltage shall be
recorded and the form factor of the secondary waveform shall be calculated and verified in
accordance with 6.2. The wattmeter reading shall then be recorded.
NOTE For the application of digitizing methods, see Annex B.
7.5 Determination of the specific total loss
The power P measured by the wattmeter includes the power consumed by the instruments in
m
~
the secondary circuit, which to a first approximation is equal to U / R , since the induced
2 i
secondary voltage is essentially sinusoidal.
Thus, the total loss P of the test specimen shall be calculated in accordance with
c
Formula (11).
~
U
N
1 2
(11)
P = P −
c m
N 2 Ri
where
P is the calculated total loss of the test specimen, in watts;
c
P is the power measured by the wattmeter, in watts;
m
N is the number of turns of the magnetizing winding;
– 16 – IEC 60404-6:2018 © IEC 2018
N is the number of turns of the secondary winding;
~
is the r.m.s. value of the induced secondary voltage, in volts;
U
R is the combined equivalent resistance of the instruments connected to the secondary
i
winding, in ohms.
The specific total loss P shall be obtained by dividing P by the mass of the test specimen.
s c
Hence,
P
c
(12)
=
Ps
m
where
P is the specific total loss of the test specimen, in watts per kilogram;
s
m is the mass of the test specimen, in kilograms.
8 Uncertainties
The individual contributions to the uncertainty of a particular measurement shall be identified
and then combined in accordance with the guidelines set out in ISO/IEC Guide 98-3 to the
expression of uncertainty in measurement.
9 Test report
The test report shall contain as necessary
a) the type and serial number or mark of the test specimen;
b) the number of turns of the magnetizing winding and the secondary winding on the test
specimen;
c) the mass and dimensions of the test specimen and, for thin material, the density;
d) the frequency;
e) the test method used;
f) the ambient temperature;
g) the surface temperature of the test specimen;
h) the method for determining the peak value of the flux density;
i) the nature of the waveform: sinewave of induced secondary voltage or sinewave of
magnetizing current;
j) the method for determining the peak value of magnetizing current;
k) the quantities measured and their uncertainties.
Annex A
(informative)
Guidance on requirements for windings and instrumentation
in order to minimise additional losses
A.1 General
At frequencies above power frequencies, additional losses associated with the windings on
the test specimen can occur. These arise from
a) the interwinding capacitance between the magnetizing and secondary windings on the test
specimen;
b) the capacitance of the leads from the secondary winding to the instruments;
c) the capacitance and resistance of the input circuits of the instruments; and
d) the dielectric loss of the insulating material of the secondary winding.
A.2 Reduction of additional
...
IEC 60404-6 ®
Edition 3.1 2021-07
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Magnetic materials –
Part 6: Methods of measurement of the magnetic properties of magnetically soft
metallic and powder materials at frequencies in the range 20 Hz to 100 kHz by
the use of ring specimens
Matériaux magnétiques –
Partie 6: Méthodes de mesure des propriétés magnétiques des matériaux
métalliques et des matériaux en poudre magnétiquement doux, aux fréquences
comprises entre 20 Hz et 100 kHz, sur des éprouvettes en forme de tore
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IEC 60404-6 ®
Edition 3.1 2021-07
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Magnetic materials –
Part 6: Methods of measurement of the magnetic properties of magnetically soft
metallic and powder materials at frequencies in the range 20 Hz to 100 kHz by
the use of ring specimens
Matériaux magnétiques –
Partie 6: Méthodes de mesure des propriétés magnétiques des matériaux
métalliques et des matériaux en poudre magnétiquement doux, aux fréquences
comprises entre 20 Hz et 100 kHz, sur des éprouvettes en forme de tore
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.20; 29.030 ISBN 978-2-8322-4184-4
IEC 60404-6 ®
Edition 3.1 2021-07
CONSOLIDATED VERSION
REDLINE VERSION
VERSION REDLINE
colour
inside
Magnetic materials –
Part 6: Methods of measurement of the magnetic properties of magnetically soft
metallic and powder materials at frequencies in the range 20 Hz to 100 kHz by
the use of ring specimens
Matériaux magnétiques –
Partie 6: Méthodes de mesure des propriétés magnétiques des matériaux
métalliques et des matériaux en poudre magnétiquement doux, aux fréquences
comprises entre 20 Hz et 100 kHz, sur des éprouvettes en forme de tore
– 2 – IEC 60404-6:2018+AMD1:2021 CSV
© IEC 2021
CONTENTS
FOREWORD . 4
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 7
4 General principles of measurement . 7
4.1 Principle of the ring method . 7
4.2 Test specimen . 7
4.3 Windings . 8
5 Temperature measurements . 9
6 Measurement of the relative amplitude permeability and the AC magnetization
curve . 9
6.1 General . 9
6.2 Apparatus and connections . 9
6.3 Waveform of induced secondary voltage or magnetizing current . 10
6.4 Determination of characteristics . 11
6.4.1 Determination of the peak value of the magnetic field strength . 11
6.4.2 Determination of the peak value of the magnetic flux density . 12
6.4.3 Determination of the r.m.s. amplitude permeability and the relative
amplitude permeability . 12
6.4.4 Determination of the AC magnetization curve . 13
7 Measurement of the specific total loss by the wattmeter method . 13
7.1 Principle of measurement. 13
7.2 Voltage measurement . 15
7.2.1 Average type voltmeter . 15
7.2.2 R.M.S. type voltmeter . 15
7.3 Power measurement . 15
7.4 Procedure for the measurement of the specific total loss . 15
7.5 Determination of the specific total loss . 15
8 Uncertainties . 16
9 Test report . 16
Annex A (informative) Guidance on requirements for windings and instrumentation in
order to minimise additional losses . 17
A.1 General . 17
A.2 Reduction of additional losses . 17
Annex B (informative) Digital sampling technique for the determination of magnetic
properties and numerical air flux compensation . 18
B.1 General . 18
B.2 Technical details and requirements . 18
B.3 Calibration aspects . 22
B.4 Numerical air flux compensation . 22
Annex C (informative) Sinusoidal waveform control by digital means . 23
Bibliography . 24
Figure 1 – Circuit of the measurement apparatus . 10
© IEC 2021
Figure 2 – Circuit of the conventional analogue wattmeter method (also representing
the metrological principle of the digital wattmeter method) . 14
Figure 3 – The wattmeter method when connected with the digital sampling technique
(example of circuit) . 14
– 4 – IEC 60404-6:2018+AMD1:2021 CSV
© IEC 2021
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MAGNETIC MATERIALS –
Part 6: Methods of measurement of the magnetic properties of
magnetically soft metallic and powder materials at frequencies
in the range 20 Hz to 100 kHz by the use of ring specimens
FOREWORD
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indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
This consolidated version of the official IEC Standard and its amendment has been
prepared for user convenience.
IEC 60404-6 edition 3.1 contains the third edition (2018-05) [documents 68/595/FDIS and
68/600/RVD], its corrigendum 1 (2018-11) and its amendment 1 (2021-07) [documents
68/669/CDV and 68/684/RVC].
In this Redline version, a vertical line in the margin shows where the technical content
is modified by amendment 1. Additions are in green text, deletions are in strikethrough
red text. A separate Final version with all changes accepted is available in this
publication.
© IEC 2021
International Standard IEC 60404-6 has been prepared by IEC technical committee 68:
Magnetic alloys and steels.
This third edition constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) adaption to modern measurement and evaluation methods, in particular the introduction of
the widely spread digital sampling method for the acquisition and evaluation of the
measured data;
b) limitation of the frequency range up to 100 kHz;
c) deletion of Clause 7 of the second edition that specified the measurement of magnetic
properties using a digital impedance bridge;
d) addition of a new Clause 7 on the measurement of the specific total loss by the wattmeter
method, including an example of the application of the digital sampling method;
e) addition of an informative annex on the technical details of the digital sampling technique
for the determination of magnetic properties.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts in the IEC 60404 series, published under the general title Magnetic materials,
can be found on the IEC website.
The committee has decided that the contents of the base publication and its amendment will
remain unchanged until the stability date indicated on the IEC web site under
"http://webstore.iec.ch" in the data related to the specific publication. At this date, the
publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – IEC 60404-6:2018+AMD1:2021 CSV
© IEC 2021
MAGNETIC MATERIALS –
Part 6: Methods of measurement of the magnetic properties of
magnetically soft metallic and powder materials at frequencies
in the range 20 Hz to 100 kHz by the use of ring specimens
1 Scope
This part of IEC 60404 specifies methods for the measurement of AC magnetic properties of
soft magnetic materials, other than electrical steels and soft ferrites, in the frequency range
20 Hz to 100 kHz. The materials covered by this part of IEC 60404 include those speciality
alloys listed in IEC 60404-8-6, amorphous and nano-crystalline soft magnetic materials,
pressed and sintered and metal injection moulded parts such as are listed in IEC 60404-8-9,
cast parts and magnetically soft composite materials.
The object of this part is to define the general principles and the technical details of the
measurement of the magnetic properties of magnetically soft materials by means of ring
methods. For materials supplied in powder form, a ring test specimen is formed by the
appropriate pressing method for that material.
The measurement of the DC magnetic properties of soft magnetic materials is made in
accordance with the ring method of IEC 60404-4. The determinations of the magnetic
characteristics of magnetically soft components are made in accordance with IEC 62044-3.
NOTE IEC 62044-3:2000 specifies methods for the measurement of AC magnetic characteristics of magnetically
soft components in the frequency range up to 10 MHz.
Normally, the measurements are made at an ambient temperature of (23 ± 5) °C on test
specimens which have first been magnetized, then demagnetized. Measurements can be
made over other temperature ranges by agreement between parties concerned.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60050-121, International Electrotechnical Vocabulary – Part 121: Electromagnetism
IEC 60050-221, International Electrotechnical Vocabulary – Chapter 221: Magnetic materials
and components
IEC 60404-2, Magnetic materials – Part 2: Methods of measurement of the magnetic
properties of electrical steel sheet and strip by means of an Epstein frame
IEC 60404-4, Magnetic materials – Part 4: Methods of measurement of d.c. magnetic
properties of iron and steel
IEC 60404-8-6, Magnetic materials – Part 8-6: Specifications for individual materials – Soft
magnetic metallic materials
© IEC 2021
IEC 60404-8-9, Magnetic materials – Part 8: Specifications for individual materials − Section 9:
Standard specification for sintered soft magnetic materials
IEC 62044-3, Cores made of soft magnetic materials – Measuring methods – Part 3: Magnetic
properties at high excitation level
ISO/IEC Guide 98-3, Uncertainty of measurement – Part 3: Guide to the expression of
uncertainty in measurement (GUM:1995)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-121 and
IEC 60050-221 apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
4 General principles of measurement
4.1 Principle of the ring method
The measurements are made on a closed magnetic circuit in the form of a ring test specimen
wound with two windings.
4.2 Test specimen
The test specimen shall be in the form of a ring of rectangular cross-section which may be
formed by
a) winding thin strip or wire to produce a clock-spring wound toroidal core; or
b) a stack of punched, laser cut, wire cut or photochemically etched ring laminations; or
c) pressing and sintering of powders, metal injection moulding, 3D printing or casting.
In the case of powder materials, the production of a ring test specimen by metal injection
moulding or by pressing (with heating if applicable) shall be carried out in accordance with the
material manufacturer's recommendations to achieve the optimum magnetic performance of
the powder material.
For all types of test specimen, burrs and sharp edges should be removed prior to heat
treatment. It is preferable to enclose the test specimen in a two-part non-magnetic annular
case. The case dimensions shall be such that it closely fits without introducing stress into the
material of the test specimen.
The ring shall have dimensions such that the ratio of the outer to inner diameter shall be no
greater than 1,4 and preferably less than 1,25 to achieve a sufficiently homogenous
magnetization of the test specimen.
For solid and pressed powder materials, the dimensions of the test specimen, that is the outer
and inner diameters and the height of the ring, shall be measured with suitable calibrated
instruments. The respective dimensions shall be measured at several locations on a test
specimen and averaged. The cross-sectional area of the test specimen shall be calculated
from Formula (1).
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© IEC 2021
( D− d )
A h (1)
=
where
A is the cross-sectional area of the test specimen, in square metres;
D is the outer diameter of the test specimen, in metres;
d is the inner diameter of the test specimen, in metres;
h is the height of the test specimen, in metres.
For a stack of laminations or a toroidal wound core, the cross-sectional area of the test
specimen shall be calculated from the mass, density and the values of the inner and outer
diameter of the ring specimen. The mass and diameters shall be measured with suitable
calibrated instruments. The density shall be the conventional density for the material supplied
by the manufacturer. The cross-sectional area shall be calculated from Formula (2).
2 m
(2)
A =
ρπ (D + d)
where
m is the mass of the test specimen, in kilograms;
ρ is the density of the material, in kilograms per cubic metre.
For the calculation of the magnetic field strength, the mean magnetic path length of the test
specimen determined from Formula (3) shall be used.
(D + d)
l = π (3)
m
where
l is the mean magnetic path length of the test specimen, in metres.
m
NOTE For measurements of magnetically soft components, an effective core cross-sectional area and an effective
magnetic path length are used (described in IEC 62044-3:2000). The difference in results between material
measurements and component measurements is larger when the ratio of the outer to inner diameter is larger.
If the specific total loss is to be determined, the mass of the test specimen shall be measured
with a suitable calibrated balance.
4.3 Windings
The test specimen shall be wound with a magnetizing winding and a secondary winding (see
Annex A).
The numbers of turns depend upon the measuring equipment and method being used. The
secondary winding shall be wound as closely as possible to the test specimen to minimize the
effect of air flux enclosed between the test specimen and the secondary winding. All windings
shall be wound uniformly over the whole length of the test specimen.
For measurements at frequencies above power frequencies, care shall be taken to avoid
complications related to capacitance and other effects. These are introduced and discussed in
Annex A.
Care shall be taken to ensure that the wire insulation is not damaged during the winding
process causing a short circuit to the test specimen. An electrical check shall be made with a
suitable AC insulation resistance measuring device to ensure that there is no direct
connection between the windings and the test specimen.
© IEC 2021
5 Temperature measurements
When the temperature of the surface of the test specimen is required, it shall be measured by
affixing a calibrated non-magnetic thermocouple (for example a type T thermocouple) to the
test specimen. Where the test specimen is enclosed in an annular case, a small hole shall be
made in the case, taking care not to damage the material of the test specimen, and the
thermocouple fixed in contact with the test specimen. If this is not possible, the thermocouple
shall be affixed to the case and this procedure shall be reported in the test report. The
thermocouple shall be connected to a suitable calibrated voltmeter in order to measure its
output voltage which can be related to the corresponding temperature through the calibration
tables for the thermocouple.
Where the temperature of the test specimen is found to vary with time after magnetization, the
measurements of the magnetic properties shall be carried out either when an agreed
temperature is reached or after a time agreed between the parties concerned. If
measurements are to be made at elevated temperatures, these may be carried out with the
test specimen placed in a suitable oven to produce the required temperature.
A second smaller time-dependent magnetic relaxation effect can also affect the magnetic
properties. For the types of materials covered by this document, the effect is usually masked
by temperature changes. However, if such magnetic relaxation effects become apparent, then
the test specimen should dwell at the prescribed magnetic flux density or magnetic field
strength for an agreed period of time before making the final measurements.
6 Measurement of the relative amplitude permeability and the
AC magnetization curve
6.1 General
The measurements are made using the ring method at frequencies normally from 20 Hz to
100 kHz, the upper frequency being limited by the performance of the instrumentation.
Where suitable calibrated instruments exist and careful winding to reduce interwinding
capacitance has been performed, this upper limit may be extended to 1 MHz (See Annex A).
6.2 Apparatus and connections
The apparatus shall be connected as shown in Figure 1.
NOTE 1 Figure 3 can be used for the measurement of the relative amplitude permeability and the magnetization
curve using the digital sampling technique.
NOTE 2 For the application of digital sampling technique, see Annex B.
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© IEC 2021
N N
1 2
A
Hz V V OSC
1 2
IEC
Key
~ power supply (usually an oscillator and a power amplifier)
A true r.m.s. or peak reading ammeter, or a true r.m.s. or peak reading voltmeter and a non-inductive
precision resistor to measure the magnetizing current
Hz frequency meter
N magnetizing winding
N secondary winding
OSC oscilloscope
V average type voltmeter
V r.m.s. voltmeter
Figure 1 – Circuit of the measurement apparatus
When conducting sinusoidal current measurements, a non-inductive precision resistor should
be connected in series with the magnetizing winding N to guarantee that the magnetizing
circuit resistance is at least ten times greater than the impedance of the magnetizing winding
N on the test specimen.
The source of alternating current shall have a variation of voltage and frequency at its output
individually not exceeding ± 0,2 % of the adjusted value during the measurement. It shall be
connected to a true r.m.s. or peak reading ammeter, or a true r.m.s. or peak reading voltmeter
and a parallel non-inductive precision resistor, in series with the magnetizing winding N on
the test specimen, to measure the magnetizing current.
The secondary circuit comprises a secondary winding N connected to two voltmeters in
parallel. One voltmeter V measures the true r.m.s. value, the other voltmeter V measures
2 1
the average rectified value but is sometimes scaled in values 1,111 times the rectified value.
The waveform of the induced secondary voltage that is induced in the secondary winding N
should be checked with an oscilloscope to ensure that only the fundamental component is
present.
6.3 Waveform of induced secondary voltage or magnetizing current
In order to obtain comparable measurements, it shall be agreed prior to the measurements
that either the waveform of the induced secondary voltage or the waveform of the magnetizing
current shall be maintained sinusoidal with a form factor of 1,111 with a relative tolerance of
± 1 %. In the latter case, a non-inductive precision resistor connected in series with the
magnetizing winding is required.
NOTE 1 The waveform of the induced secondary voltage and the magnetizing current can be measured by the
digital sampling technique. See Figure 3 and Annex B.
The time constant of the non-inductive precision resistor should be checked to be low to
ensure that the waveform is within the specified limits.
The non-inductive precision resistor may be the same resistor as used for the measurement
of the magnetizing current.
NOTE 2 Sinusoidal waveform control can be achieved by digital means (see Annex C).
© IEC 2021
At frequencies in the range 20 Hz to 50 kHz, the form factor of the induced secondary voltage
can be determined by connecting two voltmeters having a high impedance (typically > 1 MΩ in
parallel with 90 pF to 150 pF) across the secondary winding. One voltmeter shall be
responsive to the r.m.s. value of voltage and the other shall be responsive to the average
rectified value of the voltage. The form factor is then determined from the ratio of the r.m.s.
value to the average rectified value.
For optimum power transfer, it may be necessary to optimize the number of turns of the
magnetizing winding to match the output impedance of the power supply. This can be
determined from Formula (4).
ZL= jω (4)
where
Z is the output impedance of the power supply, in ohms;
j is the complex number sign;
ω is the angular frequency of the output of the power supply, in radians per second;
L is the effective inductance of the magnetizing winding of the test specimen, in henrys,
calculated from Formula (5).
N Aµµ
1 0 r
L= (5)
l
m
where
N is the number of turns of the magnetizing winding;
A is the cross-sectional area of the test specimen, in square metres;
−7
µ is the magnetic constant (4 π × 10 henrys per metre);
µ is the relative amplitude permeability of the test specimen;
r
l is the mean magnetic path length of the test specimen, in metres.
m
Where the relative amplitude permeability is not known, a preliminary measurement may need
to be made of the peak values of magnetic field strength and magnetic flux density as
described in 6.4.1 and 6.4.2 and the relative amplitude permeability calculated as described in
6.4.3.
6.4 Determination of characteristics
6.4.1 Determination of the peak value of the magnetic field strength
The peak value of magnetic field strength at which the measurement is to be made is
calculated from Formula (6).
ˆ
NI
ˆ 1
H= (6)
l
m
where
ˆ
H is the peak value of the magnetic field strength, in amperes per metre;
N is the number of turns of the magnetizing winding on the test specimen;
ˆ
I is the peak value of the magnetizing current, in amperes;
l is the mean magnetic path length of the test specimen, in metres.
m
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© IEC 2021
Normally the amplitude of the magnetic field strength is determined by measuring the r.m.s.
magnetizing current and multiplying by the square root of 2. For sinusoidal magnetizing
current, this defines the correct value of the peak value of magnetic field strength. For
sinusoidal magnetic flux density, this defines an equivalent peak value of magnetic field
strength, which is numerically lower for a given magnetizing current. As an alternative, the
peak value of magnetic field strength can be determined using a calibrated peak reading
ammeter or a peak reading voltmeter and a non-inductive precision resistor.
Prior to measurement, the test specimen shall be carefully demagnetized from a value of field
strength of not less than ten times the coercivity by slowly reducing the corresponding
magnitude of the magnetizing current to zero. Demagnetization shall be carried out at the
same or lower frequency as will be used for the measurements.
6.4.2 Determination of the peak value of the magnetic flux density
The average rectified value of the induced secondary voltage shall be measured using a
calibrated average type voltmeter or a digitizer (see Figure 3), and the peak value of the
magnetic flux density shall be calculated from Formula (7).
ˆ
B= U (7)
4 fN A
where
ˆ
B is the peak value of magnetic flux density, in teslas;
is the average rectified value of the induced secondary voltage, in volts;
U
f is the frequency, in hertz;
A is the cross-sectional area of the test specimen, in square metres.
N is the number of turns of the secondary winding.
NOTE For the application of the digital sampling technique, see Annex B.
Depending on the level of magnetic field strength and the ratio of the cross-sectional areas of
the test specimen and the secondary winding, it may be necessary to make a correction to the
magnetic flux density for the air flux enclosed between the test specimen and the secondary
winding. The corrected value B of the magnetic flux density is given by Formula (8).
′
(A− A)
(8)
′
B = B−µ H
A
where
B′ is the measured value of magnetic flux density, in teslas;
−7
µ is the magnetic constant (4 π × 10 henrys per metre);
H is the magnetic field strength, in amperes per metre;
A′ is the cross-sectional area enclosed by the secondary winding, in square metres;
A is the cross-sectional area of the test specimen, in square metres.
6.4.3 Determination of the r.m.s. amplitude permeability and the relative amplitude
permeability
For corresponding peak values of magnetic field strength and magnetic flux density, the r.m.s.
amplitude permeability shall be calculated from Formula (9).
© IEC 2021
ˆ
B
(9)
µ =
a, rms ~
µ 2 H
where
µ is the r.m.s. amplitude permeability;
a,rms
−7
µ is the magnetic constant (4 π × 10 henrys per metre);
ˆ
B is the peak value of magnetic flux density, in teslas;
~
is the r.m.s. value of magnetic field strength, in amperes per metre.
H
NOTE The relative amplitude permeability, µ , can be conventionally expressed as:
r
ˆ
B
(10)
µ =
r
ˆ
µ H
where
µ is the relative amplitude permeability;
r
−7
µ is the magnetic constant (4 π × 10 henrys per metre);
ˆ
B is the peak value of magnetic flux density, in teslas;
ˆ
is the peak value of magnetic field strength, in amperes per metre.
H
6.4.4 Determination of the AC magnetization curve
The test specimen shall be carefully demagnetized as described in 6.4.1. By successively
increasing the magnetizing current, corresponding peak values of magnetic field strength and
magnetic flux density can be obtained from which an AC magnetization curve can be plotted.
7 Measurement of the specific total loss by the wattmeter method
7.1 Principle of measurement
The principle of measurement is similar to that described in IEC 60404-2 except that the
Epstein frame is replaced by the ring test specimen and the instrumentation is capable of
making measurements at the required frequency. The measurement of specific total loss shall
be done under conditions of sinusoidal magnetic flux density. For some test specimens, this
may require the control of the induced secondary voltage waveform (see Annex C) by means
of analogue or digital techniques to ensure that sinusoidal magnetic flux density is maintained.
The apparatus and the windings of the test specimen shall be connected as shown in Figure 2.
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© IEC 2021
N N
1 2
Hz V V
OSC
1 2
W
IEC
Key
~ power supply (usually an oscillator and amplifier)
Hz frequency meter
N magnetizing winding
N secondary winding
OSC oscilloscope
W wattmeter
V average type voltmeter
V r.m.s. voltmeter
Figure 2 – Circuit of the conventional analogue wattmeter method (also representing
the metrological principle of the digital wattmeter method)
For the digital sampling technique, Figure 3 shows a possible circuit structure as an example.
In the latter case, a digitizer and supporting software adopt the functions of the oscilloscope,
the wattmeter and the voltmeters shown in Figure 2.
NOTE Figure 3 is not the only possible structure of digital sampling technique application, see Annex B.
N N
1 2
D
Hz
R
n
IEC
Key
R non-inductive precision resistor in series with the magnetizing winding to
n
determine the magnetizing current
D digitizer (usually a digital power analyser or a digital acquisition system with a computer)
Figure 3 – The wattmeter method when connected with
the digital sampling technique (example of circuit)
U (t) U (t)
1 2
© IEC 2021
7.2 Voltage measurement
7.2.1 Average type voltmeter
The average rectified value of the induced secondary voltage shall be measured using a
calibrated average type voltmeter or a calibrated digitizer (see Figures 2 and 3). The load on
the secondary circuit shall be as low as possible (see Annex A). Consequently a digital
voltmeter or digitizer with high input impedance is required.
NOTE 1 Average type voltmeters are usually graduated in average rectified value multiplied by 1,111.
NOTE 2 For the application of digital sampling technique, see Annex B.
7.2.2 R.M.S. type voltmeter
The true r.m.s. value of the induced secondary voltage shall be measured using a calibrated
voltmeter responsive to r.m.s. values or a calibrated digitizer (see Figures 2 and 3). The load
on the secondary circuit shall be as low as possible (see Annex A). Consequently a digital
voltmeter or digitizer with high input impedance is required.
NOTE For the application of digital sampling technique, see Annex B.
7.3 Power measurement
The power shall be measured using a calibrated wattmeter suitable for circuits which may
have a low power factor (cosφ down to 0,1) or a calibrated digitizer (see Figures 2 and 3). The
input impedance of the voltage circuit shall be as high as possible (see Annex A).
NOTE For the application of digital sampling technique, see Annex B.
7.4 Procedure for the measurement of the specific total loss
The test specimen shall be carefully demagnetized as described in 6.4.1. The current in
the magnetizing winding shall be increased until the average rectified voltage corresponds to
the required peak value of magnetic flux density calculated from Formula (7).
The average rectified value and the r.m.s. value of the induced secondary voltage shall be
recorded and the form factor of the secondary waveform shall be calculated and verified in
accordance with 6.2. The wattmeter reading shall then be recorded.
NOTE For the application of digitizing methods, see Annex B.
7.5 Determination of the specific total loss
The power P measured by the wattmeter includes the power consumed by the instruments in
m
~
the secondary circuit, which to a first approximation is equal to U / R , since the induced
2 i
secondary voltage is essentially sinusoidal.
Thus, the total loss P of the test specimen shall be calculated in accordance with
c
Formula (11).
~
U
N
1 2
(11)
P = P −
c m
N 2 Ri
where
P is the calculated total loss of the test specimen, in watts;
c
P is the power measured by the wattmeter, in watts;
m
N is the number of turns of the magnetizing winding;
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© IEC 2021
N is the number of turns of the secondary winding;
~
is the r.m.s. value of the induced secondary voltage, in volts;
U
R is the combined equivalent resistance of the instruments connected to the secondary
i
winding, in ohms.
The specific total loss P shall be obtained by dividing P by the mass of the test specimen.
s c
Hence,
Pc
(12)
=
P
s
m
where
P is the specific total loss of the test specimen, in watts per kilogram;
s
m is the mass of the test specimen, in kilograms.
8 Uncertainties
The individual contributions to the uncertainty of a particular measurement shall be identified
and then combined in accordance with the guidelines set out in ISO/IEC Guide 98-3 to the
expression of uncertainty in measurement.
9 Test report
The test report shall contain as necessary
a) the type and serial number or mark of the test specimen;
b) the number of turns of the magnetizing winding and the secondary winding on the test
specimen;
c) the mass and dimensions of the test specimen and, for thin material, the density;
d) the frequency;
e) the test method used;
f) the ambient temperature;
g) the surface temperature of the test specimen;
h) the method for determining the peak value of the flux density;
i) the nature of the waveform: sinewave of induced secondary voltage or sinewave of
magnetizing current;
j) the method for determining the peak value of magnetizing current;
k) the quantities measured and their uncertainties.
© IEC 2021
Annex A
(informative)
...
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