SIST EN IEC 60404-16:2018
(Main)Magnetic materials - Part 16: Methods of measurement of the magnetic properties of Fe-based amorphous strip by means of a single sheet tester (IEC 60404-16:2018)
Magnetic materials - Part 16: Methods of measurement of the magnetic properties of Fe-based amorphous strip by means of a single sheet tester (IEC 60404-16:2018)
This part of IEC 60404 is applicable to Fe-based amorphous strips specified in IEC 60404-8-
11 for the measurement of AC magnetic properties at frequencies up to 400 Hz.
The object of this part is to define the general principles and technical details of the
measurement of the magnetic properties of Fe-based amorphous strips by means of a single
sheet tester.
The single sheet tester is applicable to test specimens obtained from Fe-based amorphous
strips of any quality. The AC magnetic characteristics are determined for a sinusoidal induced
voltage, for specified peak values of magnetic polarization and for a specified frequency.
The measurements are made at an ambient temperature of (23 ± 5) °C on test specimens
which have first been demagnetized.
NOTE 1 The single sheet tester specified in this document is appropriate for other materials which have magnetic
properties and physical characteristics similar to those of Fe-based amorphous strip, such as nano-crystalline soft
magnetic strip. The single sheet tester for electrical steel sheets is specified in IEC 60404-3.
NOTE 2 Throughout this document the term “magnetic polarization” is used as described in IEC 60050-121. In
some standards of the IEC 60404 series, the term “magnetic flux density” is used.
Magnetische Werkstoffe - Teil 16 : Verfahren zur Messung der magnetischen Eigenschaften von eisenbasiertem, amorphem Band unter Verwendung eines Tafelmessgerätes
Matériaux magnétiques - Partie 16: Méthodes de mesure des propriétés magnétiques des bandes en alliage amorphe à base de fer à l'aide de l'essai sur tôle unique
L'IEC 60404-16:2018 s'applique aux bandes en alliage amorphe à base de fer spécifiées dans l'IEC 60404-8-11 pour la mesure des propriétés magnétiques en courant alternatif, avec des fréquences allant jusqu'à 400 Hz.
L'objet de la présente partie est de définir les principes généraux et les détails techniques sur la mesure des propriétés magnétiques des bandes en alliage amorphe à base de fer à l'aide de l'essai sur tôle unique.
Magnetni materiali - 16. del: Metode merjenja magnetnih lastnosti amorfnega traku na osnovi železa z uporabo enolistnega preskuševalnika (IEC 60404-16:2018)
Ta del standarda IEC 60404 se uporablja za amorfne trakove na osnovi železa, ki so določeni v standardu IEC 60404-8-11, za merjenje magnetnih lastnosti AC pri frekvencah do 400 Hz.
Namen tega dela je opredeliti splošna načela in tehnične podrobnosti za merjenje magnetnih lastnosti amorfnih trakov na osnovi železa z uporabo enolistnega preskuševalnika.
Enolistni preskuševalnik se uporablja za preskušanje vzorcev, pridobljenih iz amorfnih trakov na osnovi železa poljubne kakovosti. Magnetne lastnosti AC se določijo za sinusoidno inducirano napetost za določene najvišje vrednosti magnetne polarizacije in za določeno frekvenco. Meritve se opravijo pri sobni temperaturi (23 ± 5) °C na preskusnih vzorcih, ki so bili pred tem razmagneteni.
OPOMBA 1: Enolistni preskuševalnik, določen v tem dokumentu, je primeren za druge materiale, ki imajo podobne magnetne lastnosti in fizikalne značilnosti kot amorfni trak na osnovi želena, na primer nano-kristalni mehkomagnetni trak. Enolistni preskuševalnik za elektropločevino je določen v standardu IEC 60404-3.
OPOMBA 2: V tem dokumentu je izraz »magnetna polarizacija« uporabljen tako, kot je opisan v standardu IEC 60050-121. V nekaterih standardih iz skupine standardov IEC 60404 je uporabljen izraz »gostota magnetnega pretoka«.
General Information
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Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Magnetni materiali - 16. del: Metode merjenja magnetnih lastnosti amorfnega traku na osnovi železa z uporabo enolistnega preskuševalnika (IEC 60404-16:2018)Magnetic materials - Part 16: Methods of measurement of the magnetic properties of Fe-based amorphous strip by means of a single sheet tester (IEC 60404-16:2018)29.030Magnetni materialiMagnetic materials17.220.20Measurement of electrical and magnetic quantitiesICS:Ta slovenski standard je istoveten z:EN IEC 60404-16:2018SIST EN IEC 60404-16:2018en01-september-2018SIST EN IEC 60404-16:2018SLOVENSKI
STANDARD
SIST EN IEC 60404-16:2018
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN IEC 60404-16
July 2018 ICS 17.220.20; 29.030
English Version
Magnetic materials - Part 16: Methods of measurement of the magnetic properties of Fe-based amorphous strip by means of a single sheet tester (IEC 60404-16:2018)
Matériaux magnétiques - Partie 16: Méthodes de mesure des propriétés magnétiques des bandes en alliage amorphe à base de fer à l'aide de l'essai sur tôle unique (IEC 60404-16:2018)
Magnetische Werkstoffe - Teil 16 : Verfahren zur Messung der magnetischen Eigenschaften von eisenbasiertem, amorphem Band unter Verwendung eines Tafelmessgerätes (IEC 60404-16:2018) This European Standard was approved by CENELEC on 2018-04-12. 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 CEN-CENELEC Management Centre 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 CEN-CENELEC Management Centre has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung CEN-CENELEC Management Centre: Rue de la Science 23,
B-1040 Brussels © 2018 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 60404-16:2018 E SIST EN IEC 60404-16:2018
EN IEC 60404-16:2018 2 European foreword The text of document 68/570/CDV, future edition 1 of IEC 60404-16, prepared by IEC/TC 68 "Magnetic alloys and steels" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as EN IEC 60404-16:2018. The following dates are fixed: • latest date by which the document has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2019-01-12 • latest date by which the national standards conflicting with the document have to be withdrawn (dow) 2021-04-12
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights. Endorsement notice The text of the International Standard IEC 60404-16:2018 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 60404-6:2003 NOTE Harmonized as EN 60404-6:2003 (not modified). SIST EN IEC 60404-16:2018
EN IEC 60404-16:2018 3 Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
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.
NOTE 1
Where an International Publication has been modified by common modifications, indicated by (mod), the relevant EN/HD applies.
NOTE 2
Up-to-date information on the latest versions of the European Standards listed in this annex is available here: www.cenelec.eu.
Publication Year Title EN/HD Year IEC 60050-121 -
International Electrotechnical Vocabulary (IEV) -
Part 121: Electromagnetism - -
IEC 60050-221 -
International Electrotechnical Vocabulary (IEV) -
Chapter 221: Magnetic materials and components - -
IEC 60404-8-11 -
Magnetic materials -
Part 8-11: Specifications for individual materials - Fe-based amorphous strip delivered in the semi-processed state EN IEC 60404-8-11 -
SIST EN IEC 60404-16:2018
SIST EN IEC 60404-16:2018
IEC 60404-16 Edition 1.0 2018-03 INTERNATIONAL STANDARD NORME INTERNATIONALE Magnetic materials –
Part 16: Methods of measurement of the magnetic properties of Fe-based amorphous strip by means of a single sheet tester
Matériaux magnétiques –
Partie 16: Méthodes de mesure des propriétés magnétiques des bandes en alliage amorphe à base de fer à l'aide de l'essai sur tôle unique
INTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION ELECTROTECHNIQUE INTERNATIONALE
ICS 17.220.20; 29.030
ISBN 978-2-8322-5426-4
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale ®
Warning! Make sure that you obtained this publication from an authorized distributor.
Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé. SIST EN IEC 60404-16:2018
– 2 – IEC 60404-16:2018 © IEC 2018 CONTENTS FOREWORD . 4 INTRODUCTION . 6 1 Scope . 7 2 Normative references . 7 3 Terms and definitions . 7 4 General principles . 8 4.1 Principle of the method . 8 4.2 Test specimen . 9 4.3 Test apparatus . 9 4.3.1 General . 9 4.3.2 Yoke . 10 4.3.3 Windings . 10 4.3.4 Air flux compensation . 11 4.3.5 Magnetic shielding . 11 4.4 Power supply . 11 4.5 Measuring instruments . 12 4.6 Digital sampling technique . 12 5 Measurement procedure . 13 5.1 Principle of measurement. 13 5.2 Preparation of measurement . 13 5.3 Adjustment of power supply . 14 6 Determination of characteristics . 14 6.1 Determination of the magnetic polarization . 14 6.2 Determination of the magnetic field strength . 15 6.3 Determination of the specific total loss . 15 6.4 Determination of the specific apparent power . 16 7 Reproducibility . 16 Annex A (informative)
Requirements of the single sheet tester for Fe-based amorphous strip . 17 A.1 Shape of test specimen . 17 A.2 H coil method . 17 A.3 Yoke . 17 A.4 Wirings . 17 A.5 Non-inductive precision resistor . 18 A.6 Magnetic shielding . 18 A.7 Method for checking the stability of the installed H coil from time to time . 18 Annex B (informative)
Digital sampling technique for the determination
of the magnetic properties and numerical air flux compensation . 19 B.1 General . 19 B.2 Technical details and requirements . 19 B.3 Calibration aspects . 22 B.4 Numerical air flux compensation . 22 Annex C (informative)
Sinusoidal waveform control of the magnetic polarization by digital means . 24 Bibliography . 26
SIST EN IEC 60404-16:2018
IEC 60404-16:2018 © IEC 2018 – 3 –
Figure 1 – Schematic diagram of the test apparatus. 8 Figure 2 – Circuit of the wattmeter method with H coil mode . 9 Figure 3 – Yoke dimensions . 10 Figure 4 – Circuit of the wattmeter method with H coil mode adopting the digital sampling technique . 12
SIST EN IEC 60404-16:2018
– 4 – IEC 60404-16:2018 © IEC 2018 INTERNATIONAL ELECTROTECHNICAL COMMISSION ____________
MAGNETIC MATERIALS –
Part 16: Methods of measurement of the magnetic properties of
Fe-based amorphous strip by means of a single sheet tester
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 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 members of its technical committees and IEC National Committees for any personal injury, property damage or 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 60404-16 has been prepared by IEC technical committee 68: Magnetic alloys and steels. The text of this International Standard is based on the following documents: CDV Report on voting 68/570/CDV 68/583A/RVC
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. SIST EN IEC 60404-16:2018
IEC 60404-16:2018 © IEC 2018 – 5 –
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.
SIST EN IEC 60404-16:2018
– 6 – IEC 60404-16:2018 © IEC 2018 INTRODUCTION A method of measuring the magnetic properties of Fe-based amorphous strip is required to grade what is regarded as a promising material to reduce energy loss in transformer cores and, consequently, to reduce global warming. Fe-based amorphous strip is produced by a rapidly-solidifying, direct-casting process. The strip is intended primarily for the construction of wound cores of distribution transformers for commercial power frequency (50 Hz and 60 Hz) applications. After appropriate heat treatment, the strip exhibits a significantly lower value of specific total loss compared to grain-oriented electrical steel strip. It is associated with low hysteresis loss due to low magnetic anisotropy and low eddy current loss due to high resistivity and reduced thickness. However, significant deterioration can occur by applying stress on the strip due to the large magnetostriction and low magnetic anisotropy characteristics of the material. Therefore, a method of measurement of the magnetic properties of Fe-based amorphous strip by means of a single sheet tester (SST) is required, independent of IEC 60404-3 [1]1, which is specified for electrical steel sheets. The almost exclusively applied wattmeter method is used also in this standard. However, the widely used version with the determination of the magnetic field strength from the magnetizing current (“MC method”) is not applicable to this kind of material, because the influence of the yokes on the loss measurement is significantly greater for the thinner and magnetically softer test specimen of this material. Thus, the wattmeter method with H coil mode (“H coil method”) has been included for the magnetic field determination. International round robin tests of SST and Fe-based amorphous test specimens have been carried out, resulting in a suitable configuration of the SST for amorphous material. The single-yoke concept was adopted in order to avoid the effect of the impact of the upper yoke caused by the high magneto-elastic sensitivity of the material.
___________ 1 Numbers in square brackets refer to the Bibliography. SIST EN IEC 60404-16:2018
IEC 60404-16:2018 © IEC 2018 – 7 –
MAGNETIC MATERIALS –
Part 16: Methods of measurement of the magnetic properties of
Fe-based amorphous strip by means of a single sheet tester
1 Scope This part of IEC 60404 is applicable to Fe-based amorphous strips specified in IEC 60404-8-11 for the measurement of AC magnetic properties at frequencies up to 400 Hz. The object of this part is to define the general principles and technical details of the measurement of the magnetic properties of Fe-based amorphous strips by means of a single sheet tester. The single sheet tester is applicable to test specimens obtained from Fe-based amorphous strips of any quality. The AC magnetic characteristics are determined for a sinusoidal induced voltage, for specified peak values of magnetic polarization and for a specified frequency. The measurements are made at an ambient temperature of (23 ± 5) °C on test specimens which have first been demagnetized. NOTE 1 The single sheet tester specified in this document is appropriate for other materials which have magnetic properties and physical characteristics similar to those of Fe-based amorphous strip, such as nano-crystalline soft magnetic strip. The single sheet tester for electrical steel sheets is specified in IEC 60404-3.
NOTE 2 Throughout this document the term “magnetic polarization” is used as described in IEC 60050-121. In some standards of the IEC 60404 series, the term “magnetic flux density” is used. 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 60404-8-11, Magnetic materials – Part 8-11: Specifications for individual materials – Fe-based amorphous strip delivered in the semi-processed state 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 SIST EN IEC 60404-16:2018
– 8 – IEC 60404-16:2018 © IEC 2018 4 General principles 4.1 Principle of the method This document applies the wattmeter method with H coil mode for the determination of the magnetic field strength (“H coil method”). The flux closure is made by a single “U”-shaped yoke. The test specimen comprises a Fe-based amorphous strip, which is placed inside the following two windings: – an exterior primary winding (magnetizing winding); – an interior secondary winding (induced voltage winding). A H coil that detects the magnetic field strength at the surface of the test specimen is placed under the test specimen. The flux closure is made by a single vertical “U” shaped yoke, the cross-section of which is very large compared with that of the test specimen (see Figure 1).
Figure 1 – Schematic diagram of the test apparatus NOTE 1 Double yokes are unsuitable because the influence of the loading of an upper yoke on the test specimen is significant due to the large magnetostriction of the material. However, the upper yoke can be placed on the lower yoke in the absence of the test specimen to demagnetize yokes and to measure the power loss in the yokes. The circuit diagram of Figure 2 illustrates the principle of the wattmeter method with H coil mode. The single sheet tester and the measuring instruments shall be connected as shown in Figure 2. NOTE 2 Figure 2 also sets out the fundamentals of the widely used digital sampling technique, where the instrument functions are realised partly, or fully, through evaluating software. For the application of the digital sampling technique, see 4.6 and Annex B. Figure 2 does not show the feed-back circuit for the waveform control of the induced secondary voltage (see 4.4 and Annex C).
IEC Windings Yoke Test specimen SIST EN IEC 60404-16:2018
IEC 60404-16:2018 © IEC 2018 – 9 –
Key ~
power supply Hz
frequency meter N1 primary winding N2 secondary winding H H coil V voltmeter
integrator W wattmeter Figure 2 – Circuit of the wattmeter method with H coil mode NOTE 3 The voltage induced in the H coil, UH(t), can be used for the air flux compensation in different ways (see 4.3.4 and Clause B.4) and for the digital sinusoidal waveform control of the induced secondary voltage, U2(t) (see 5.3 and Annex C) . 4.2 Test specimen The test specimen shall be sampled in accordance with IEC 60404-8-11. NOTE Nominal widths of Fe-based amorphous strip are 142,2 mm, 170,2 mm and 213,4 mm (see IEC 60404-8-11). The length of the test specimen shall be no less than 280 mm, which is the outside dimension of the distance across the pole faces of the yoke. Although the part of the specimen situated outside the pole faces has no great influence on the measurement, this part shall not be longer than is necessary to facilitate insertion and removal of the test specimen. The test specimen shall be cut to length from Fe-based amorphous strip without the formation of excessive burrs or mechanical distortion. The test specimen shall be plane and rectangular. The test specimen shall be prepared by a magnetic anneal in a DC magnetic field directed parallel to the casting direction according to the instructions of the manufacturer. The test specimen shall be flat during the treatment. Care shall be taken in handling the test specimen after the treatment in order to avoid raising fragments of the strip or creating mechanical stresses in the test specimen because the material is usually brittle after heat treatment. 4.3 Test apparatus 4.3.1 General The test apparatus comprises the windings and the yoke (see Figure 1). IEC Hz H N1 W V N2
HttH⇒∫dddSIST EN IEC 60404-16:2018
– 10 – IEC 60404-16:2018 © IEC 2018 Care shall be taken to ensure that temperature changes are kept below a level likely to produce stress in the test specimen due to the distribution of thermal expansion or contraction. 4.3.2 Yoke The yoke is in the form of a letter U built by using soft ferrite (see Figure 3). It should have a low magnetic remanence, a low reluctance and a specific total loss as low as possible. NOTE 1 Lower quality of yoke materials can lead to poor measurement quality and to misleading results of the magnetic properties of the test specimen accordingly (see Annex A).
Dimensions in millimetres
Figure 3 – Yoke dimensions The yoke shall have pole faces having a width of 20 mm ± 1 mm. The two pole faces of the yoke shall be as flat as possible and coplanar to within 0,1 mm. Also, the yoke shall be rigid in order to avoid creating mechanical stresses in the test specimen. The height of the yoke shall be between 80 mm and 120 mm. The yoke shall have a width of 220 mm ± 1 mm and an inside length of 240 mm ±=1 mm (see Figure 3). Other yoke dimensions may be used provided that comparability of the results can be demonstrated. NOTE 2 The power loss dissipated in the yoke can be measured by making a magnetic closure circuit consisting of the yoke and a matching upper yoke that are wound with primary and secondary windings; 25 turns are sufficient for each winding. There shall be a specimen support, which is made of non-conductive and non-magnetic materials, between the vertical limbs of the yokes. The surface of the support, on which the test specimen is supported, shall be in the same plane with the pole faces so that the test specimen can contact the pole faces with minimum air gaps. NOTE 3 If there are steps between the surface of the test support plane and the pole faces, deteriorated magnetic properties are measured. 4.3.3 Windings The primary winding shall be at least 230 mm in length. The secondary winding shall be 120 mm ± 1 mm in length and centred in the primary winding. The primary and secondary windings shall be wound on a non-conducting, non-magnetic and rectangular former. The dimensions of the former shall be as follows: – length for winding: 235 mm ± 5 mm; – internal height: 3 mm ± 1 mm; – external height: ≤ 15 mm; the value of 12 mm is recommended. IEC <0,1 20 120 80 220 20 240 SIST EN IEC 60404-16:2018
IEC 60404-16:2018 © IEC 2018 – 11 –
The primary winding can be made up of a single continuous and uniform winding taking up the whole length. One example of the winding is made up of 220 turns of copper wire 1 mm in diameter taking up the whole length, wound in one or more layers. The secondary winding shall be made up of a single continuous and uniform winding taking up the length of 120 mm ± 1 mm, wound in one layer. The number of turns on the secondary winding depends on the characteristics of the measuring instruments. The H coil shall have the same length as the secondary winding and be centred in the primary winding. The H coil shall be wound on a non-conducting, non-magnetic and rectangular plate. The width of the plate shall be 120 mm ± 1 mm and the height of the plate shall be 3 mm ± 0,2 mm.
The H coil shall be embedded in the specimen support plate and the distance between the upper surface of the support plate and the upper surface of the H coil shall be 1 mm ± 0,2 mm.
The area-turns of the H coil shall be calibrated in a uniform field using a solenoid coil of a diameter and length large enough to obtain a uniform field over the volume of the H coil. 4.3.4 Air flux compensation Compensation of the effect of air flux on the induced secondary voltage shall be made. This can be achieved, for example, by the numerical air flux compensation method (see Clause B.4). 4.3.5 Magnetic shielding A simple magnetic shielding of the single sheet tester is recommended to weaken sufficiently the effects of geomagnetic and other external magnetic fields in order to avoid unexpected magnetization of the test apparatus (see Annex A). 4.4 Power supply The power supply should consist of a computer-controlled arbitrary signal generator and a power amplifier, or an instrument integrating both of these functions (see Figure 4). The arbitrary signal generator shall synthesize a signal of magnetizing waveform, amplitude and frequency data, which are programmed externally. A low pass filter should be inserted between the arbitrary signal generator and the power amplifier to prevent aliasing at the measuring instruments. The frequency shall be measured with an accuracy of ±0,1 % or better. The waveform of the induced secondary voltage shall be maintained as sinusoidal as possible. It is preferable not only to maintain the form factor of the induced secondary voltage to within 1,111 with a relative tolerance of ±1 %, but also to suppress harmonic contents in the induced secondary voltage to as low as possible. This can be achieved by various means, using analogue feedback control or by digital means described in Annex C. The power amplifier shall be of low internal i
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