IEC 60404-4:1995

IEC 60404-4 ®
Edition 2.2 2008-11
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Magnetic materials –
Part 4: Methods of measurement of d.c. magnetic properties of magnetically soft
materials
Matériaux magnétiques –
Partie 4: Méthodes de mesure en courant continu des propriétés magnétiques
des matériaux magnétiquement doux

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form
or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from
either IEC or IEC's member National Committee in the country of the requester. If you have any questions about IEC
copyright or have an enquiry about obtaining additional rights to this publication, please contact the address below or
your local IEC member National Committee for further information.

Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de l'IEC ou du Comité national de l'IEC du pays du demandeur. Si vous avez des
questions sur le copyright de l'IEC ou si vous désirez obtenir des droits supplémentaires sur cette publication, utilisez
les coordonnées ci-après ou contactez le Comité national de l'IEC de votre pays de résidence.

IEC Central Office Tel.: +41 22 919 02 11
3, rue de Varembé Fax: +41 22 919 03 00
CH-1211 Geneva 20 info@iec.ch
Switzerland www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.

About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.

IEC Catalogue - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
The stand-alone application for consulting the entire The world's leading online dictionary of electronic and
bibliographical information on IEC International Standards, electrical terms containing 20 000 terms and definitions in
Technical Specifications, Technical Reports and other English and French, with equivalent terms in 15 additional
documents. Available for PC, Mac OS, Android Tablets and languages. Also known as the International Electrotechnical
iPad. Vocabulary (IEV) online.

IEC publications search - www.iec.ch/searchpub IEC Glossary - std.iec.ch/glossary
The advanced search enables to find IEC publications by a 65 000 electrotechnical terminology entries in English and
variety of criteria (reference number, text, technical French extracted from the Terms and Definitions clause of
committee,…). It also gives information on projects, replaced IEC publications issued since 2002. Some entries have been
and withdrawn publications. collected from earlier publications of IEC TC 37, 77, 86 and

CISPR.
IEC Just Published - webstore.iec.ch/justpublished

Stay up to date on all new IEC publications. Just Published IEC Customer Service Centre - webstore.iec.ch/csc
details all new publications released. Available online and If you wish to give us your feedback on this publication or
also once a month by email. need further assistance, please contact the Customer Service
Centre: csc@iec.ch.
A propos de l'IEC
La Commission Electrotechnique Internationale (IEC) est la première organisation mondiale qui élabore et publie des
Normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.

A propos des publications IEC
Le contenu technique des publications IEC est constamment revu. Veuillez vous assurer que vous possédez l’édition la
plus récente, un corrigendum ou amendement peut avoir été publié.

Catalogue IEC - webstore.iec.ch/catalogue Electropedia - www.electropedia.org
Application autonome pour consulter tous les renseignements
Le premier dictionnaire en ligne de termes électroniques et
bibliographiques sur les Normes internationales,
électriques. Il contient 20 000 termes et définitions en anglais
Spécifications techniques, Rapports techniques et autres
et en français, ainsi que les termes équivalents dans 15
documents de l'IEC. Disponible pour PC, Mac OS, tablettes
langues additionnelles. Egalement appelé Vocabulaire
Android et iPad.
Electrotechnique International (IEV) en ligne.

Recherche de publications IEC - www.iec.ch/searchpub
Glossaire IEC - std.iec.ch/glossary
La recherche avancée permet de trouver des publications IEC
65 000 entrées terminologiques électrotechniques, en anglais
en utilisant différents critères (numéro de référence, texte,
et en français, extraites des articles Termes et Définitions des
comité d’études,…). Elle donne aussi des informations sur les
publications IEC parues depuis 2002. Plus certaines entrées
projets et les publications remplacées ou retirées.
antérieures extraites des publications des CE 37, 77, 86 et

CISPR de l'IEC.
IEC Just Published - webstore.iec.ch/justpublished

Restez informé sur les nouvelles publications IEC. Just Service Clients - webstore.iec.ch/csc
Published détaille les nouvelles publications parues. Si vous désirez nous donner des commentaires sur cette
Disponible en ligne et aussi une fois par mois par email. publication ou si vous avez des questions contactez-nous:
csc@iec.ch.
IEC 60404-4 ®
Edition 2.2 2008-11
CONSOLIDATED VERSION
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Magnetic materials –
Part 4: Methods of measurement of d.c. magnetic properties of magnetically

soft materials
Matériaux magnétiques –
Partie 4: Méthodes de mesure en courant continu des propriétés magnétiques

des matériaux magnétiquement doux

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220.20; 29.030 ISBN 978-2-8891-0188-7

– 2 – 60404-4 © IEC:1995+A1:2000
+A2:2008
CONTENTS
FOREWORD.4
1 Scope and object.6
2 Normative references.6
3 Determination of the magnetic characteristics by the ring method.7
3.1 Object.7
3.2 General.7
3.3 Effect of temperature on the measurements .7
3.4 Test specimen.7
3.5 Windings.8
3.6 Methods of measurement by the ring method .9
3.6.1 Magnetic field strength .9
3.6.2 Magnetic flux density.9
3.6.3 Connection of apparatus.10
3.6.4 Determination of normal magnetization curve .10
3.6.5 Determination of a complete hysteresis loop.11
3.6.6 Determination of remanent flux density.12
3.6.7 Determination of coercive field strength.12
3.7 Uncertainty by the ring method.12
4 Determination of the magnetic characteristics by the permeameter method .13
4.1 Object.13
4.2 Principle of the permeameter.13
4.3 Test specimen.14
4.4 Methods of measurement by the permeameter method.14
4.4.1 Measurement of magnetic field strength .14
4.4.2 Measurement of magnetic flux density .15
4.4.3 Connection of apparatus.16
4.4.4 Determination of the normal magnetization curve .17
4.4.5 Determination of a complete hysteresis loop.17
4.4.6 Determination of remanent flux density.18
4.4.7 Determination of coercive field strength.18
4.5 Uncertainty by the permeameter method .18
5 Test report.19

Annex A (normative) Calibration of search coils .25
Annex B (informative) Methods of calibrating the flux integrator.27
Annex C (informative) Requirements for the J-compensated coil system.30

60404-4 © IEC:1995+A1:2000 – 3 –
+A2:2008
Figure 1 – Circuit for the determination of the magnetic characteristics
by the ring method .20
Figure 2 – Hysteresis loop .20
Figure 3 – Typical arrangement of a type A permeameter .21
Figure 4 – Typical arrangement of a type B permeameter .22
Figure 5 – Arrangement of search coils.24
Figure 6 – Circuit for the determination of the normal magnetization curve and
hysteresis loop of bar specimens using a double yoke permeameter.24
Figure A.1 – Circuit for the calibration of search-coils .26
Figure B.1 – Circuit for calibration the flux integrator by the capacitor
discharge method .29
Table 1 – Switching sequence to maintain the test specimen in a steady cyclic state.12

– 4 – 60404-4 © IEC:1995+A1:2000
+A2:2008
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MAGNETIC MATERIALS –
Part 4: Methods of measurement of d.c.
magnetic properties of magnetically soft materials
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,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
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
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
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 provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
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
m of its technical committees and IEC National Committees for any personal injury, property damage or
embers
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.
This consolidated version of the official IEC Standard and its amendments has been
prepared for user convenience.
IEC 60404-4 edition 2.2 contains the second edition (1995) [documents 68(CO)95 and
68/117/RVD], its amendment 1 (2000) [documents 68/215/FDIS and 68/217/RVD] and its
amendment 2 (2008) [documents 68/363/CDV and 68/375/RVC].
A vertical line in the margin shows where the base publication has been modified by
amendments 1 and 2.
International Standard IEC 60404-4 has been prepared by IEC technical committee 68:
Magnetic alloys and steels.
60404-4 © IEC:1995+A1:2000 – 5 –
+A2:2008
Annex A forms an integral part of this standard.
Annexes B and C are for information only.
The committee has decided that the contents of the base publication and its amendments will
remain unchanged until the maintenance result 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.
– 6 – 60404-4 © IEC:1995+A1:2000
+A2:2008
MAGNETIC MATERIALS –
Part 4: Methods of measurement of d.c.
magnetic properties of magnetically soft materials

1 Scope and object
This part of IEC 60404 specifies the methods of measuring the d.c. magnetic properties of
magnetically soft materials in a closed magnetic circuit using either the ring or the permea-
meter methods. The ring method is suitable for use with laminated or solid ring specimens as
well as ring specimens produced by sintering.
Two methods are used:
a) the ring method, particularly for magnetic field strengths of up to 10 kA/m;
b) the permeameter method for magnetic field strengths in the range 1 kA/m to 200 kA/m.
NOTE The measurement of coercivity in an open magnetic circuit is specified in IEC 60404-7.
2 Normative references
The following referenced documents are indispensable for the application 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 60404-7:1982, Magnetic materials – Part 7: Method of measurement of the coercivity of
magnetic materials in an open magnetic circuit
IEC 60404-8-2:1985, Magnetic materials – Part 8: Specifications for individual materials –
Section Two: Specification for cold-rolled magnetic alloyed steel strip delivered in the semi-
processed state
IEC 60404-8-3:1985, Magnetic materials – Part 8: Specifications for individual materials –
Section Three: Specification for cold-rolled magnetic non-alloyed steel strip delivered in the
semi-processed state
IEC 60404-8-4:1986, Magnetic materials – Part 8: Specifications for individual materials –
Section Four: Specification for cold-rolled non-oriented magnetic steel sheet and strip
IEC 60404-8-6:1986, Magnetic materials – Part 8: Specifications for individual materials –
Section Six: Soft magnetic metallic materials
Amendment 1 (1992)
IEC 60404-8-7:1988, Magnetic materials – Part 8: Specifications for individual materials –
Section Seven: Specification for grain-oriented magnetic steel sheet and strip
Amendment 1 (1991)
IEC 60404-8-8:1991, Magnetic materials – Part 8: Specifications for individual materials –
Section 8: Specification for thin magnetic steel strip for use at medium frequencies

60404-4 © IEC:1995+A1:2000 – 7 –
+A2:2008
3 Determination of the magnetic characteristics by the ring method
3.1 Object
This clause describes the ring method used to obtain the normal magnetization curve and the
hysteresis loop.
3.2 General
This method is used particularly for magnetic field strengths of up to 10 kA/m. However, if
care is taken to avoid heating the test specimen, this method may be used at higher magnetic
field strengths.
3.3 Effect of temperature on the measurements
Care shall be taken to avoid unduly heating the test specimen. The measurements shall be
made at an ambient temperature of (23 ± 5) °C. The temperature of the test specimen shall
not exceed 50 °C which shall be monitored by means of a temperature sensor.
For materials which are particularly temperature sensitive, product standards may define
lower or higher test specimen temperatures.
3.4 Test specimen
The test specimen is a homogeneous unwelded ring of rectangular or circular cross-section.
The cross-sectional area of the ring is determined by the product dimensions, uniformity of
magnetic properties, instrumentation sensitivity and space required for the test windings.
2 2
Usually the cross-sectional area is in the range of 10 mm to 200 mm .
Care shall be taken in the preparation of the test specimen to avoid work hardening or heating
of the material which might affect the magnetic characteristics. The test specimen can be
prepared by turning and finished by light grinding with sufficient coolant to prevent heating the
material. The edges of the rings shall be deburred.
To reduce the effect of radial variation of the magnetic field strength, 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. If the ratio approaches the value 1,4, there will be a greater radial
variation in the magnetic field strength.
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 value of the inner and outer
diameter of the ring. The density can be the conventional density for the material supplied by
the manufacturer. The cross-sectional area shall be calculated from the following equation:
2m
A = (1)
ρ π(D + d)
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;
m is the mass of the test specimen, in kilograms;
ρ is the density of the material, in kilograms per cubic metre.

– 8 – 60404-4 © IEC:1995+A1:2000
+A2:2008
The dimensions of the test specimen shall be determined by measuring the outside and inside
diameters of the ring together with the height or diameter using a suitable micrometer
or vernier gauge. The mean cross-sectional area shall be calculated with an uncertainty
of ±0,5 % or better.
The mean magnetic path length of the test specimen shall also be calculated with an
uncertainty of ±0,5 % or better from the relationship:
D + d
l = π (2)
where
l is the mean magnetic path length of test specimen, in metres.
3.5 Windings
Before winding, a connection shall be made to the core in order to check subsequently the
insulation of the windings, a temperature sensor shall be attached to the test specimen and
then the ring shall be overlaid with a thin layer of insulating material.
Firstly, a secondary winding of insulated copper wire shall be wound evenly round the core.
The dimensions of the secondary winding shall be determined and the mean cross-sectional
area, A , of the secondary winding shall be calculated.
c
A magnetizing winding of wire capable of carrying the maximum magnetizing current and of a
sufficient number of turns to produce the maximum required magnetic field strength shall be
evenly wound in one or more layers on the core. The magnetizing winding can consist of:
a) a large number of turns of a single conductor applied closely and uniformly round the
whole ring, or
b) a smaller number of turns of a multicore cable applied closely and uniformly round the
whole ring, the ends of the conductor in the individual cores being interconnected to give
the effect of one multilayer winding, or
c) an arrangement of rigid, or part rigid and part flexible, conductors which can be opened to
admit the ring (carrying the secondary winding and insulation) and then closed to form a
uniformly wound toroid round the ring.
If necessary, the wound ring is immersed in an oil bath or subjected to an air blast in order to
cool it.
NOTE If the above arrangements are used with a uniformly distributed secondary winding, an error, which may be
present in any ring test, is liable to be magnified and to become of considerable importance. This error arises
because, in winding a ring specimen toroidally, an effective circular turn of diameter equal to the mean diameter of
the ring is produced.
The flux between the effective mutually inductive circular turns of the magnetizing winding and secondary winding,
associated with flux parallel to the axis of the ring, is added to, or subtracted from the circumferential flux. When a
multiconductor cable is used for the magnetizing winding, the number of turns in the primary of the supplementary
mutual inductance is increased in proportion to the number of cores, and the error from this source, particularly at
high field-strengths where the permeability of the test specimen is reduced, may amount to several per cent. To
eliminate this error a turn should be wound back on the secondary winding along the mean circumference of the
ring, or, preferably, the magnetizing cable should be wound in pairs of layers, alternate layers being wound
clockwise and anti-clockwise around the ring.

60404-4 © IEC:1995+A1:2000 – 9 –
+A2:2008
3.6 Methods of measurement by the ring method
3.6.1 Magnetic field strength
The magnetizing current shall be measured with an uncertainty of ±0,5 % or better. The
magnetic field strength shall be calculated from the following relationship:
N I
H = (3)
l
where
H is the magnetic field strength, in amperes per metre;
N is the number of turns of magnetizing winding of the ring;
l is the mean magnetic path length, in metres;
I is the magnetizing current, in amperes.
3.6.2 Magnetic flux density
The secondary winding N (B coil) shall be connected to a flux integrator (electronic
integrator, ballistic galvanometer or fluxmeter) the calibration of which shall be established in
accordance with one of the procedures given in annex B with an uncertainty of ±1 % or better.
The changes of the magnetic flux density shall be calculated from the following relationship:
K α
b b
ΔB = (4)
N A
where
ΔB is the measured change of the magnetic flux density, in teslas;
K is the flux integrator calibration constant, in volts seconds;
B
α is the reading of the flux integrator;
B
N is the number of turns on the secondary winding of the ring;
A is the cross-sectional area of the ring, in square metres.
For direct reading of the ΔB, the flux integrator may be adjusted so that K /(N A) becomes a
B 2
power of 10.
Provided that the secondary winding is wound closely on the test specimen, the air flux
included in the secondary winding over the range of magnetic field strength 0 to 4 kA/m will
be insignificant and no correction need be applied. At higher values of magnetic field strength,
an air flux correction shall be applied in accordance with equation (8).

– 10 – 60404-4 © IEC:1995+A1:2000
+A2:2008
3.6.3 Connection of apparatus
The apparatus is connected as shown in figure 1.
A source of direct current E (stabilized d.c. supply with a ripple content of less than 0,1 %, or
a battery) is connected through a current-measuring device A and a reversing switch S to the
magnetizing winding N on the ring specimen. If a bipolar current source is used, reversing
switch S is not required. With switch S closed, the current in the magnetizing circuit is
1 2
controlled by resistor R . If a stabilized supply with a continuously controllable output is used,
resistor R is not required. This is the arrangement of the magnetizing circuit for the
determination of the normal magnetization curve and for the measurement of the tip points of
hysteresis loops. Switch S , together with resistor R are necessary in some arrangements for
2 2
the determination of the complete hysteresis loop. The secondary circuit comprises the
secondary winding N (B coil) connected to the flux integrator.
3.6.4 Determination of normal magnetization curve
The test specimen shall be carefully demagnetized from a magnetic field strength of not less
than 5 kA/m by the repeated reversals of a gradually reducing demagnetizing field. Test
specimens which have been subjected to a higher magnetic field strength shall be
demagnetized from a suitably high field before test (for example, when machined using a
magnetic chuck).
NOTE In order that the magnetic field may completely penetrate the test specimen, the dwell time after each
reversal should be greater than 2 s for a cross-section 10 mm × 10 mm, and 10 s for a cross-section 20 mm × 20 mm.
The flux integrator shall be calibrated by one of the methods described in annex B. With S
closed, the normal magnetization curve shall then be determined by one of the following
methods.
Method A: continuous recording method
To utilize this method, the output from the flux integrator shall be connected to the Y axis of
an X-Y recorder, plotter or computer interface. A low value (e.g. 0,1 Ω or 1 Ω) calibrated
resistor with two current and two voltage terminals shall be connected in series with the
magnetizing winding. The potential terminals of this resistor shall be connected to the X axis
of the recorder, plotter or computer interface. The system can be calibrated overall to give
direct readings of magnetic flux density and magnetic field strength on the recorder, plotter or
computer interface.
The magnetizing current shall be steadily increased from zero to the value to produce the
required maximum magnetic field strength. The magnetization curve is then produced on the
X-Y recorder, plotter or computer interface.
Method B: point-by-point method
A low current corresponding to a low magnetic field strength (see equation 3) shall be passed
through the magnetizing winding N . The current shall be reversed about 10 times by means
of reversing switch S to bring the material into a steady cyclic state. Switch S shall be
1 3
closed during this operation to maintain the flux integrator at zero. With switch S open, the
flux integrator reading corresponding to the reversal of the magnetizing field shall be recorded
and the corresponding magnetic flux density calculated.
By successively increasing the magnetizing current and repeating this procedure,
corresponding values of magnetic field strength and magnetic flux density are obtained from
which the normal magnetization curve can be plotted.

60404-4 © IEC:1995+A1:2000 – 11 –
+A2:2008
The magnetizing current shall never be decreased during the measurements, otherwise the
test specimen shall be demagnetized before resuming measurements.
3.6.5 Determination of a complete hysteresis loop
The test specimen shall be demagnetized in accordance with 3.6.4 and the hysteresis loop
shall be determined by one of the following methods.
Method A: continuous recording method
The additional equipment specified in method A of 3.6.4 is required. The flux integrator shall
be zeroed and then a current of value sufficient to produce the maximum magnetic field
strength required shall be passed through the magnetizing winding N . This current shall be
slowly reduced to zero, reversed, increased to its maximum negative value, reduced to zero,
reversed again and increased to its maximum positive value.
NOTE The cycle should be completed in a time between 30 s to 60 s, although some materials, e.g. pure iron,
may require longer, in order to allow time for the magnetization of the test specimen to follow the applied magnetic
field and yet avoid significant drift of the flux integrator zero with time.
Method B: point-by-point method
The test specimen shall be demagnetized and a current sufficient to produce the maximum
magnetic field strength required shall be passed through the magnetizing winding N . The tip
points of the hysteresis loop shall be determined by measuring the corresponding values of
magnetic field strength and magnetic flux density in accordance with method B of 3.6.4.
Portion PQ of the hysteresis loop (see figure 2) is then determined with switch S closed in
position 1, by opening switch S , and measuring the corresponding magnetic field strength
and change in magnetic flux density. By adjusting resistor R a number of points on the curve
PQ can be obtained. The point Q is obtained with switch S closed and measuring the change
in magnetic flux density when opening switch S .
The value of the magnetic field strength at each point is calculated from the corresponding
measured value of current flowing (see equation (3)).
The value of the magnetic flux density at each point is calculated from the following relation-
ship:
B = B – ΔB (5)
P′ P
where
B is the flux density at the point P′ of curve PQ, in teslas;
P′
B is the magnetic flux density at tip of hysteresis loop, in teslas;
P
ΔB is the change in magnetic flux density measured when switch S is opened, switch S
2 1
being closed in position 1, in teslas.
Portion QS of the hysteresis loop is determined, with switch S open, by closing switch S .
2 1
Changes in magnetic field strength and magnetic flux density are measured starting with
switch S in the open position and closing it to position 2.
The value of the magnetic field strength at each point is calculated from the measured value
of the current flowing when S is closed in position 2 (see equation (3)).
– 12 – 60404-4 © IEC:1995+A1:2000
+A2:2008
The value of the magnetic flux density at each point is calculated from the following
relationship:
B = B – ΔB (6)
Q′ Q
where
B is the magnetic flux density at the point Q′ on curve QS, in teslas;
Q′
B is the magnetic flux density at the point Q, in teslas;
Q
ΔB is the change in magnetic flux density measured when switch S is closed in position 2
with the switch S open, in teslas.
To obtain the complete hysteresis loop, the switching sequence shall be in accordance with
the arrangement given in table 1 to maintain the test specimen in a steady cyclic state.
Table 1 – Switching sequence to maintain the test specimen
in a steady cyclic state
Switch- Switch Point on loop
S S
1 2
Closed P
1 Closed (1)
Open P′
2 Closed (1)
Open Open Q
Closed (2) Open Q′
Closed (2) Closed S
Closed (2) Open S′
Open Open T
Closed (1) Open T′
Closed (1) Closed P
Resistors R and R respectively are adjusted to obtain:
1 2
– resistor R : values of magnetic field strength +H or –H, that is point P or point S on the
loop (figure 2);
– resistor R : values of magnetic field strength +H′ or –H′, that is points P′ and T′ or points
Q′ and S′ on the loop (figure 2).
It is desirable to make measurements on the complete hysteresis loop, to eliminate drift errors
in the flux integrator. However, since portion STUP of the loop is symmetrical with portion
PQRS, measurements may be made for only one-half of the hysteresis loop.
3.6.6 Determination of remanent flux density
For a given hysteresis loop, the remanent flux density of the material is the value of the
magnetic flux density, in teslas, when the magnetic field strength is zero. It shall be
determined from the position of point Q on the hysteresis loop or the symmetrical point T.
3.6.7 Determination of coercive field strength
For a given hysteresis loop, the coercive field strength of the material is the value of the
magnetic field strength, in amperes per metre, when the magnetic flux density is zero. It shall
be determined from point R on the hysteresis loop or the symmetrical point U.
3.7 Uncertainty by the ring method
The total uncertainty in the measurement of the magnetic flux density or the magnetic field
strength normally expected is less than or equal to, ±2 % when using measuring instruments

60404-4 © IEC:1995+A1:2000 – 13 –
+A2:2008
whose estimated uncertainty is less than, or equal to, ±1 % for measurements by the point by
point method. Where a complete magnetization curve or hysteresis loop is determined by the
continuous recording method, the overall uncertainty may be increased by the uncertainty and
resolution of the recorder system or computer interface.
As the result of the measurements is affected by changes in temperature, precautions must
be taken to avoid heating the test specimen (see 3.3).
4 Determination of the magnetic characteristics by the permeameter method
4.1 Object
Clause 4 describes the permeameter method for determining the normal magnetization curve
and the hysteresis loop.
4.2 Principle of the permeameter
The principle of the instrument is illustrated in figures 3 and 4. The test specimen is clamped
between two massive steel yokes which provide a flux closure path for the test specimen. The
yokes are formed from either:
a) two strip-wound C-cores of grain-oriented steel as specified in IEC 60404-8-7, or
b) two strip-wound C-cores of nickel iron as specified in IEC 60404-8-6, or
c) two stacks of laminations cut from electrical steel as specified in IEC 60404-8-2,
IEC 60404-8-3, IEC 60404-8-4, IEC 60404-8-7 or IEC 60404-8-8, or
d) two yokes machined from solid low carbon steel or soft iron.
For tests on round or square bars, pole pieces shall be fabricated from two pairs of low
carbon steel or soft iron blocks, each pair being machined to accommodate the test specimen
to provide as close a fit as possible (see figures 3c and 3d). The pole pieces should have a
permeability sufficiently high to produce a low reluctance path for the magnetic flux passing
between the test specimen and yokes.
Two types of permeameter are shown in figures 3 and 4 having the following properties:
Type A: range of magnetic field strength: 1 kA/m to 200 kA/m;
magnetizing coil: on former around test specimen;
minimum length of test specimen: 250 mm;
H measuring systems: search coil or Hall probe.

Type B: range of magnetic field strength: 1 kA/m to 50 kA/m;
magnetizing coil: wound around yoke;
minimum length of test specimen: 100 mm;
H measuring system: Rogowski-Chattock potentiometer.
The requirements of 3.3 shall also apply to the permeameter methods.

– 14 – 60404-4 © IEC:1995+A1:2000
+A2:2008
4.3 Test specimen
Unless otherwise specified in the product standards, the test specimen shall have a minimum
length of 250 mm for the type A permeameter, or 100 mm for the type B permeameter, a
2 2
minimum cross-sectional area of 10 mm and a maximum cross-sectional area of 500 mm . It
shall consist of either:
a) a round, square, rectangular or hexagonal bar of uniform cross-section.
Where it is necessary to machine the test specimen to minimize the air gap between the
sample and the pole pieces, the surface of the test specimen in contact with the pole
pieces shall be turned or ground using sufficient coolant to prevent heating the material; or
b) for material cut from sheet or coil, one strip of width 30 mm shall be cut parallel to the
direction of rolling and one strip cut at right angles to the direction of rolling, and
measured separately.
The cross-sectional area of the test specimen shall be determined from a number of measure-
ments of each necessary dimension, equally spaced over the test length. The transverse
dimensions shall be measured by means of a micrometer at approximately every 10 mm along
the test length. The mean cross-sectional area shall be computed as the mean of the areas
determined from these measurements with an uncertainty of ±0,5 %. The difference between
the greatest and smallest of the cross-sectional areas shall not exceed 0,5 % of the mean
area.
4.4 Methods of measurement by the permeameter method
4.4.1 Measurement of magnetic field strength
The magnetic field strength shall be measured with an uncertainty of ±1 % or better by one of
the following methods:
Type A permeameters:
a) a search-coil of length between 10 mm and 50 mm (see figure 5c) connected to a
magnetic flux integrator which shall be calibrated in accordance with one of the methods
given in annex B.
The search-coil usually comprises two coils connected in series addition and mounted one
coil on each of two opposite sides of the test specimen or two coils coaxial with the test
specimen wound in series opposition. The coils shall be wound on non-magnetic, non-
conducting formers. The effective area-turns product of the search-coil shall be
determined with an uncertainty of ±0,5 % by one of the methods in annex A;
NOTE  The number of turns on the search-coils depends upon the sensitivity of the flux integrator used, and
also upon the range of magnetic field strength to be measured.
b) a Hall effect device or other passive means of directly sensing a magnetic field having an
uncertainty of ±0,5 % or better. These devices can be calibrated either in a suitable
solenoid of known field to current constant or in a uniform magnetic field using an
appropriate nuclear magnetic resonance probe.
Type B permeameters:
c) Using one of the methods described for type A permeameters, provided the variation of
the magnetic field strength in the radial direction can be demonstrated to be insignificant,
or
d) a Rogowski-Chattock potentiometer (a C-shape H-potentiometer coil, see figure 5e) con-
nected to a magnetic flux integrator.

60404-4 © IEC:1995+A1:2000 – 15 –
+A2:2008
The H-potentiometer coil shall comprise a continuously wound coil whose axis lies on a
semicircle of 40 mm maximum diameter or a combination of discrete series connected
coils with their axes arranged similarly but not so as to introduce significant discontinuities
in the integration of the magnetic potential. The end faces of the coil system shall lie
within 0,5 mm of the surface of the test specimen.
The effective area-turns product of the H-coils shall be determined with an uncertainty of
±0,5 % by one of the methods given in annex A.
Using one of the coil arrangements described in a) or d) above, the changes of the magnetic
field strength shall be calculated from the relationship:
K α
H H
ΔH = (7)
μ (NA)
where
ΔH is the change of magnetic field strength, in amperes per metre;
K is the calibration constant of the flux integrator (H), in volts seconds;
H
α is the reading of the flux integrator (H);
H
–7
μ is the magnetic constant (4 π 10 henrys per metre);
(NA) is the effective area turns product of the H-coil, in square metres.
For direct reading of the values, the flux integrator may be adjusted so that K /[μ (NA)]
H 0
becomes a power of 10.
4.4.2 Measurement of magnetic flux density
The magnetic flux density shall be measured with an uncertainty of ±1 % or better by one of
the following methods:
a) a flux-sensing coil (B-coil, see figure 5a), of length between 10 mm and 50 mm, shall be
connected to a flux integrator. The calibration of the flux integrator shall be established by
the method given in annex B.
Depending on the level of the magnetic field strength and the relative cross-sectional
areas of the test specimen and flux-sensing coil, it may be necessary to make a correction
to the magnetic flux density for the air flux enclosed by the flux-sensing coil.
The corrected value of the magnetic flux density is given by the following relationship:

A − A
c
B = B – μ H (8)
corrected 0
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 of the flux-sensing coil, in square metres;
c
A is the cross-sectional area of test specimen, in square metres.
Alternatively, a compensating coil of effective area equivalent to that of the air section
between the winding and the test specimen may be connected in series opposition with the
flux-sensing coil.
– 16 – 60404-4 © IEC:1995+A1:2000
+A2:2008
The changes in magnetic flux density shall be calculated from the relationship:
K α
B B
ΔB = (9)
(N A)
where
ΔB is the change of the magnetic flux density, in teslas;
K is the calibration constant of the flux integrator (B), in volts seconds;
B
α is the reading of the flux integrator (B);
B
N is the number of turns of the flux-sensing coil;
A is the cross-sectional area of the test specimen, in square metres,
b) by measuring the magnetic polarization with an uncertainty of ±1 % or better and
calculating the magnetic flux density from this value and the magnetic field strength from
the
...