SIST EN 60404-6:2004
(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 200 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 200 kHz by the use of ring specimens
Specifies methods for the measurement of a.c. magnetic properties of materials in the frequency range 20 Hz to 200 kHz other than electrical steels and soft ferrites. The materials covered by this part of EN 60404 include those speciality alloys listed in EN 60404-8-6, amorphous and nanocrystalline materials, pressed and sintered and metal injection moulded parts such as are listed in EN 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 made in accordance with the ring method of EN 60404-4. The determinations of the magnetic characteristics of magnetically soft components shall be made in accordance with EN 62044-3. Normally, the measurements shall be 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. The scope of the second edition has been extended to include all magnetically soft materials except ferrites.
Magnetische Werkstoffe -- Teil 6: Verfahren zur Messung der magnetischen Eigenschaften weichmagnetischer und pulverförmiger Werkstoffe bei Frequenzen im Bereich 20 Hz bis 200 kHz mit Hilfe von Ringproben
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 200 kHz, sur des éprouvettes en forme de tore
Spécifie des méthodes de mesure des propriétés magnétiques en courant alternatif, dans la gamme de fréquences comprise entre 20 Hz et 200 kHz, pour les matériaux autres que les aciers électriques et les ferrites doux. Les matériaux couverts par la présente partie de la EN 60404 incluent les alliages de spécialité énumérés dans la EN 60404-8-6, les matériaux amorphes et nanocristallins, les pièces compressées et frittées et les pièces moulées par injection de métal énumérées dans la EN 60404-8-9, 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 en forme d'anneau est réalisée par la méthode de compression appropriée pour ce matériau. Les mesures magnétiques en courant continu sur les matériaux magnétiquement doux doivent être réalisées selon la méthode du tore de la EN 60404-4. Les déterminations des caracté-ristiques magnétiques des composants magnétiquement doux doivent être réalisées selon la EN 62044-3. Normalement, les mesures doivent être réalisées à température ambiante de (23 ± 5) °C sur des éprouvettes en forme d'anneau qui ont été d'abord aimantées, puis désaimantées. Des mesures peuvent être faites pour d'autres gammes de températures, par accord entre le fournisseur et l'acheteur. Le domaine d'application de la deuxième édition a été étendu pour inclure tous les matériaux magnétiquement doux, à l'exception des ferrites.
Magnetic materials - Part 6: Methods of measurement of the magnetic properties of magnetically soft metallic and powder materials at frequencies in the range of 20 Hz to 200 kHz by the use of ring specimens (IEC 60404-6:2003)
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Standards Content (Sample)
SLOVENSKI SIST EN 60404-6:2004
STANDARD
julij 2004
Magnetic materials - Part 6: Methods of measurement of the magnetic properties of
magnetically soft metallic and powder materials at frequencies in the range of 20 Hz
to 200 kHz by the use of ring specimens (IEC 60404-6:2003)
ICS 17.220.20; 29.030 Referenčna številka
SIST EN 60404-6:2004(en)
© Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno
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EUROPEAN STANDARD EN 60404-6
NORME EUROPÉENNE
EUROPÄISCHE NORM September 2003
ICS 17.220.20; 29.030
English version
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 kHz
by the use of ring specimens
(IEC 60404-6:2003)
Matériaux magnétiques Magnetische Werkstoffe
Partie 6: Méthodes de mesure Teil 6: Verfahren zur Messung der
des propriétés magnétiques magnetischen Eigenschaften
des matériaux métalliques weichmagnetischer und pulverförmiger
et des matériaux en poudre, Werkstoffe bei Frequenzen im Bereich
magnétiquement doux, aux fréquences 20 Hz bis 200 kHz mit Hilfe von
comprises entre 20 Hz et 200 kHz, Ringproben
sur des éprouvettes en forme de tore (IEC 60404-6:2003)
(CEI 60404-6:2003)
This European Standard was approved by CENELEC on 2003-09-01. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2003 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 60404-6:2003 E
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EN 60404-6:2003 - 2 -
Foreword
The text of document 68/271/FDIS, future edition 2 of IEC 60404-6, prepared by IEC TC 68, Magnetic
alloys and steels, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC
as EN 60404-6 on 2003-09-01.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2004-06-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2006-09-01
Annexes designated "normative" are part of the body of the standard.
Annexes designated "informative" are given for information only.
In this standard, annex ZA is normative and annexes A and B are informative.
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 60404-6:2003 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated:
IEC 62044 NOTE Harmonized in the series EN 62044 (not modified).
__________
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- 3 - EN 60404-6:2003
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of any
of these publications apply to this European Standard only when incorporated in it by amendment or
revision. For undated references the latest edition of the publication referred to applies (including
amendments).
NOTE When an international publication has been modified by common modifications, indicated by (mod), the relevant
EN/HD applies.
Publication Year Title EN/HD Year
IEC 62044-3 2000 Cores made of soft magnetic materials - EN 62044-3 2001
Measuring methods
Part 3: Magnetic properties at high
excitation level
IEC 60404-2 1996 Magnetic materials EN 60404-2 1998
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 Part 4: Methods of measurement of d.c. EN 60404-4 1997
magnetic properties of magnetically soft
materials
A1 2000 A1 2002
IEC 60404-8-6 1999 Part 8-6: Specifications for individual - -
materials - Soft magnetic metallic
materials
IEC 60404-8-9 1994 Part 8: Specification for individual - -
materials
Section 9: Standard specification for
sintered soft magnetic materials
ISO/IEC 1993 Guide to the expression of uncertainty - -
in measurement
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NORME CEI
INTERNATIONALE IEC
60404-6
INTERNATIONAL
Deuxième édition
STANDARD
Second edition
2003-06
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 200 kHz, sur des
éprouvettes en forme de tore
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 kHz by the use of ring specimens
© IEC 2003 Droits de reproduction réservés ⎯ Copyright - all rights reserved
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utilisée sous quelque forme que ce soit et par aucun procédé, form or by any means, electronic or mechanical, including
électronique ou mécanique, y compris la photocopie et les photocopying and microfilm, without permission in writing from
microfilms, sans l'accord écrit de l'éditeur. the publisher.
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Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
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Pour prix, voir catalogue en vigueur
For price, see current catalogue
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60404-6 © IEC:2003 – 3 –
CONTENTS
FOREWORD . 5
INTRODUCTION .9
1 Scope .11
2 Normative references.11
3 General principles of measurement .13
3.1 Test specimen .13
3.2 Windings .15
4 Temperature measurements .15
5 Measurement of magnetic permeability and magnetization curve using the
voltmeter-ammeter method .17
5.1 Introduction.17
5.2 Apparatus and connections .17
5.3 Determination of magnetic field strength.19
5.4 Determination of the magnetic flux density .21
5.5 Determination of the r.m.s. amplitude permeability and the relative
amplitude permeability .21
5.6 Determination of magnetization curve.23
6 Measurement of specific total loss by the wattmeter method.23
6.1 Principle of measurement.23
7 Measurement of magnetic properties using a digital impedance bridge .25
7.1 Principle of measurement.25
7.2 Apparatus .27
7.3 Procedure.27
7.4 Determination of the relative a.c. inductance permeability.29
7.5 Determination of the specific total loss .29
8 Measurement of magnetic properties using digital methods .29
8.1 Introduction.29
8.2 Apparatus and connections .31
8.3 Magnetizing current waveform.31
8.4 Magnetizing winding.31
8.5 Determination of the magnetic field strength.31
8.6 Determination of the magnetic flux density .33
8.7 Determination of the relative a.c. permeability .33
8.8 Determination of a.c. magnetization curve .33
8.9 Determination of the specific total loss .33
9 Uncertainties.35
10 Test report .35
Annex A (informative) Guidance on requirements for windings and instrumentation
in order to minimise additional losses .41
Annex B (informative) Sinusoidal waveform control by digital means .43
Bibliography .45
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60404-6 © IEC:2003 – 5 –
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 kHz by the use of ring specimens
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical specifications, technical reports or guides and they are accepted by the National
Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The 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 second edition cancels and replaces the first edition published in 1986 and constitutes
a technical revision.
The scope of the first edition has been extended to include all magnetically soft materials
except ferrites. Chapter 1 of the first edition relating to d.c. measurements is covered by
IEC 60404-4 (1995) and its amendment 1 (2000).
The text of this standard is based on the following documents:
FDIS Report on voting
68/271/FDIS 68/275/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
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60404-6 © IEC:2003 – 7 –
The committee has decided that the contents of this publication will remain unchanged until 2007.
At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
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60404-6 © IEC:2003 – 9 –
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.
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60404-6 © IEC:2003 – 11 –
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 kHz by the use of ring specimens
1 Scope
This part of IEC 60404 specifies methods for the measurement of a.c. magnetic properties of
materials in the frequency range 20 Hz to 200 kHz other than electrical steels and soft ferrites.
The materials covered by this part of IEC 60404 include those speciality alloys listed in
IEC 60404-8-6, amorphous and nanocrystalline 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 made in accordance with
the ring method of IEC 60404-4. The determinations of the magnetic characteristics of
magnetically soft components shall be made in accordance with IEC 62044-3.
Normally, the measurements shall be 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.
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 62044-3:2000, Cores made of soft magnetic materials – Measuring methods –
Part 3: Magnetic properties at high excitation levels
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
IEC 60404-8-9:1994, Magnetic materials – Part 8: Specifications for individual materials −
Section 9: Standard specification for sintered soft magnetic materials
ISO/IEC Guide to the expression of uncertainty in measurement, 1993
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60404-6 © IEC:2003 – 13 –
3 General principles of measurement
The measurements are made on a closed magnetic circuit in the form of a ring test specimen
wound with one or two windings.
3.1 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 ring laminations; or
c) pressing and sintering of powders, metal injection moulding 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 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.
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
(D − d)
A = h (1)
2
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. 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
2 m
A = (2)
ρπ()D + d
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60404-6 © IEC:2003 – 15 –
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
()D + d
= π (3)
"
m
2
where " is the mean magnetic path length of the test specimen, in metres.
m
If the specific total loss is to be determined, then the mass of the test specimen shall be
measured.
3.2 Windings
The number of windings and the number of 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 the 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 a.c. insulation resistance measuring device to ensure that there is no direct connection
between the winding and the test specimen.
4 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, a small hole shall be made in
the encapsulation, taking care not to damage the material of the test specimen, and the
thermocouple fixed in contact with the core material. If this is not possible, the thermocouple
shall be affixed to the encapsulation 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. 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 also affect the magnetic properties. For
the types of materials covered by this standard, 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.
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60404-6 © IEC:2003 – 17 –
5 Measurement of magnetic permeability and magnetization curve
using the voltmeter-ammeter method
5.1 Introduction
The measurements are made using the ring method at frequencies normally from 20 Hz to
200 kHz, the upper frequency being limited by the performance of the instrumentation.
NOTE 1 Where suitable calibrated instruments exist, this upper limit may be extended to 1 MHz.
NOTE 2 DC measurements should be made in accordance with the ring method described in IEC 60404-4.
NOTE 3 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.
5.2 Apparatus and connections
The ring test specimen shall be wound with a magnetizing winding, N , and a secondary
1
winding, N (see 3.2 and Annex A).
2
The apparatus shall be connected as shown in Figure 1.
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 voltmeter and a precision resistor, in series with
the magnetizing winding N on the ring test specimen, to measure the magnetizing current.
1
The secondary circuit comprises a secondary winding N connected to two voltmeters in
2
parallel. One voltmeter (V ) measures the true r.m.s. value, the other (V ) measures the
2 1
average rectified value but is sometimes scaled in values 1,111 times the rectified value.
NOTE The waveform of the secondary voltage should be checked with an oscilloscope to ensure that only the
fundamental component is present.
5.2.1 Waveform of 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 secondary voltage or the waveform of the magnetizing current shall
be maintained sinusoidal with a form factor of 1,111 ± 1 %. In the latter case, a non-inductive
resistor connected in series with the magnetizing circuit is required.
NOTE 1 The time constant of the non-inductive resistor should be low to ensure that the waveform is within the
specified limits.
NOTE 2 The non-inductive resistor can be the same resistor as used for the measurement of the magnetizing
current.
NOTE 3 Sinusoidal waveform control may be achieved by digital means (see Annex B).
At frequencies in the range 20 Hz to 50 kHz, the form factor of the 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 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.
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60404-6 © IEC:2003 – 19 –
NOTE 4 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. This can be determined from
Z = jωL (4)
where
Z is the output impedance of the power source, in ohms;
ω is the angular frequency of the output of the power source, in radians per second;
L is the effective inductance of the magnetizing winding of the ring test specimen, in henrys, calculated from
2
N Aµ µ
1 0 r
L = (5)
"
m
where
N is the number of turns of the magnetizing winding;
1
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);
0
µ is the relative permeability of the test specimen;
r
" is the mean magnetic path length of the test specimen, in metres.
m
Where the relative magnetic permeability is not known, a preliminary measurement may need to be made of the
magnetic field strength and magnetic flux density as described in 5.3 and 5.4 and the relative magnetic permeability
calculated as described in 5.5.
5.3 Determination of magnetic field strength
The magnetic field strength at which the measurement is to be made is calculated from the
following relationship:
N I
1
H = (6)
"
m
where
H is the magnetic field strength, in amperes per metre;
N is the number of turns of the magnetizing winding on the test specimen;
1
I is the magnetizing current, in amperes;
" is the mean magnetic path length, 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 magnetic field strength. For sinusoidal magnetic flux
density, this defines an equivalent peak magnetic field strength, which is numerically lower for
a given magnetiz
...
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