BS-EN-10330-2003.pdf

BRITISH STANDARD BS EN 10330:2003 Magnetic materials Method of measurement of the coercivity of magnetic materials in an open circuit The European Standard EN 10330:2003 has the status of a British Standard ICS 29.030 ? Licensed Copy: sheffieldun sheffieldun, na, Thu Oct 26 04:40:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS EN 10330:2003 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 2 May 2003 © BSI 2 May 2003 ISBN 0 580 41785 9 National foreword This British Standard is the official English language version of EN 10330:2003. It supersedes BS 6404-7:1986 which is withdrawn. The UK participation in its preparation was entrusted to Technical Committee ISE/NFE/5, Magnetic alloys and steels, which has the responsibility to: A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 10, an inside back cover and a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since publication Amd. No. DateComments Licensed Copy: sheffieldun sheffieldun, na, Thu Oct 26 04:40:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM EN 10330 April 2003 ICS 29.030 English version Magnetic materials - Method of measurement of the coercivity of magnetic materials in an open circuit Matériaux magnétiques - Méthode de mesure du champ coercitif des matériaux magnétiques en circuit magnétique ouvert Magnetische Werkstoffe - Verfahren zur Messung der Koerzivität magnetischer Werkstoffe im offenen Magnetkreis This European Standard was approved by CEN on 21 February 2003. CEN 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 Management Centre or to any CEN 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 CEN member into its own language and notified to the Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG Management Centre: rue de Stassart, 36 B-1050 Brussels © 2003 CENAll rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 10330:2003 E Licensed Copy: sheffieldun sheffieldun, na, Thu Oct 26 04:40:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 10330:2003 (E) 2 Contents page Foreword3 1Scope 4 2Normative references 4 3Terms and definitions4 4Principle4 5Test specimen5 6Measurement5 6.1Magnetization.5 6.2Measuring devices.5 6.2.1General5 6.2.2Method A.5 6.2.3Method B.6 6.3Determination of coercivity.6 6.4Reproducibility.6 7Test report 7 Annex A (normative) Precautions to be taken for measurements of coercivity below 40 A/m and above 160 kA/m .10 Licensed Copy: sheffieldun sheffieldun, na, Thu Oct 26 04:40:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 10330:2003 (E) 3 Foreword This document (EN 10330:2003) has been prepared by Technical Committee ECISS/TC 24, “Electrical steel sheet and strip qualities - Qualities dimensions, tolerances and specific tests“, the secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by October 2003, and conflicting national standards shall be withdrawn at the latest by October 2003. This document is equivalent to IEC 60404-7. Annex A is normative. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. Licensed Copy: sheffieldun sheffieldun, na, Thu Oct 26 04:40:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 10330:2003 (E) 4 1 Scope This European Standard specifies the method of measurement of the coercivity of magnetic materials in an open magnetic circuit. It applies to magnetic materials having a coercivity up to 500 kA/m. Special precautions to take in measuring coercivities below 40 A/m and above 160 kA/m are given in annex A. 2 Normative references 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). IEC 60050-121:1998, International Electrotechnical Vocabulary (IEV) Chapter 121: Electromagnetism. IEC 60050-221:1990, International Electrotechnical Vocabulary (IEV) Chapter 221: Magnetic materials and components. 3 Terms and definitions For the purposes of this European Standard, the terms and definitions given in IEC 60050-121:1998 and IEC 60050-221:1990 and the following apply 3.1 coercivity, HcJ magnetic field strength required to reduce the magnetic polarization to zero in a magnetic specimen which has previously been magnetized to saturation NOTEThe coercivities HcB and HcJ are respectively discriminated depending on the hysteresis loop being defined in the B = f(H), or J = f(H) system (see Figure 1). It can be shown that, for materials of high-incremental permeability in the region B = 0, the difference between the intrinsic coercivity HcJ and the coercivity HcB is negligible since : µ= B H HH 0cJcB 1 where HcBis the induction coercivity, in amperes per metre ; HcJis the polarization coercivity, in amperes per metre ; Bis the incremental change in magnetic flux density, in teslas (for B = 0) ; His the corresponding change in magnetic field strength, in amperes per metre ; µ0is the magnetic constant = 4 x 10-7 H/m (henrys per metre). 4 Principle If a magnetic specimen is placed in a uniform magnetic field then it will distort this magnetic field unless no flux (additional to that previously carried by the air space it now occupies) enters or emerges from it. This condition represents a state of complete demagnetization which occurs when a demagnetizing coercive magnetic field strength is applied to the specimen such that the magnetic polarization is zero. Licensed Copy: sheffieldun sheffieldun, na, Thu Oct 26 04:40:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 10330:2003 (E) 5 A magnetic flux detector allows detection of the condition of no distortion of a uniform magnetic field by the specimen and provides the means for determining the coercive field strength. The method is first to magnetise the specimen to saturation, then to apply a demagnetizing field until no field distortion due to the specimen is apparent. The applied magnetic field strength required to achieve this condition is measured and defined as the coercivity of that specimen. For this measurement, the specimen is placed in an open magnetic circuit at the centre of a solenoid. The detector may be placed : a) close to the end of the specimen (method A, Figure 2) or b) outside the solenoid (method B, Figure 3). 5 Test specimen The shape and the dimensions of the specimen can be varied provided that they meet the following conditions: a) the specimen can be placed inside the solenoid so that its major axis is coincident with the axis of the solenoid ; b) the specimen shall have a generally elongated shape so that its self-demagnetizing factor is such that the specimen can be saturated and the shape effects do not produce a significant error in coercivity. (For example, in the case of cylindrical test specimens, it is recommended to have a ratio of length to diameter greater than 5:1). 6 Measurement 6.1 Magnetization The test specimen is magnetized to saturation in either: a) the solenoid of the coercivity measuring device, or b) a separate device which can be, for example, a system with a permanent magnet or an electromagnet, or a pulsed magnetizing coil. Saturation is considered to be achieved when an increase of 50 % in the magnetizing field strength gives an increase in the coercive field strength of less than 1 %. For magnetic materials having a low coercivity and a high electrical conductivity, the application of the magnetizing field shall be made smoothly without interruption ; the duration of the saturation field shall be long enough to ensure complete penetration of the material. (Depending on the magnetic permeability, electrical conductivity and thickness of the material, this duration will usually be between 2 s and 20 s). NOTESee also item a) in clause A.2. 6.2 Measuring devices 6.2.1 General Two methods can be used for the detection of zero magnetic polarization of the test specimen during the demagnetisation: 6.2.2 Method A This method is based on the use of: Licensed Copy: sheffieldun sheffieldun, na, Thu Oct 26 04:40:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 10330:2003 (E) 6 c) either an axially vibrating search coil placed near the end of the test specimen (Figure 2). The point at which zero alternating voltage, induced in the search coil by the polarization of the test specimen, is detected (e.g. on an oscilloscope) ; d) or a magnetic flux sensing probe (e.g. Hall or fluxgate probe) placed near the test specimen with its measurement axis normal to the axis of the solenoid (Figure 2). The probe shall be positioned off the axis of the solenoid to give good sensitivity. 6.2.3 Method B This method is based on the use of two differential magnetic flux sensing probes (e.g. Hall or fluxgate probes) placed outside the solenoid (Figure 3). By this differential method, the influence of uniform external magnetic fields is amply compensated. 6.3 Determination of coercivity The solenoid, in which the test specimen is placed, shall be connected to a d.c. supply. The demagnetizing current through the solenoid shall be increased continuously and slowly to the point at which zero polarization of the test specimen is detected. The value of this demagnetizing current shall be measured with an ammeter of accuracy class 0.5 or by means of a digital voltmeter connected across a standard resistor (Figure 4) giving an equivalent accuracy. The magnetic field strength in the solenoid over the volume of the sample shall not vary by more than ± 0.5 %. The current shall be measured for each of the two directions of the demagnetizing field of the solenoid. The value of the coercivity shall be calculated from the relationship: HcJ = k I where HcJis the coercivity, in amperes per metre; Iis the mean value of the two currents of opposite polarity, in amperes; kis the magnetic field strength to current ratio for the solenoid, in reciprocal metre. When method A is used, the measurement shall be made for each end of the specimen, the value of the coercivity being taken as the mean of the two measurements. For materials having a coercivity greater than 500 A/m, it is not necessary to make measurements for two directions of the magnetic field. NOTEMethod A is a localised measurement whereas method B is an integrated measurement. Therefore, the results may not be the same for an inhomogeneous test specimen. 6.4 Reproducibility Provided the foregoing procedures are carried out and the material has a uniform magnetic polarization, the reproducibility (agreement between different laboratories) of the determination of the coercivity normally expected is less than or equal to ± 5 % for coercivities less than 40 A/m and ± 2 % for coercivities greater than 40 A/m. However, this reproducibility may be affected by non-uniform properties and shape of the test specimen. Licensed Copy: sheffieldun sheffieldun, na, Thu Oct 26 04:40:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 10330:2003 (E) 7 7 Test report The test report shall contain, as necessary: type and condition of the material ; shape and dimensions of the test specimen ; method of magnetization to saturation ; measuring method and device used ; calculated value of the coercivity HcJ ; test temperature. Figure 1 Hysteresis loop Licensed Copy: sheffieldun sheffieldun, na, Thu Oct 26 04:40:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 10330:2003 (E) 8 Key 1Solenoid 2Test specimen 3Flux sensing probe (e.g. Hall or fluxgate probe) mounted off the axis 4Vibrating search coil Figure 2 Method A Key 1Solenoid 2Test specimen 3Differential probes (e.g. Hall or fluxgate probes) Figure 3 Method B Licensed Copy: sheffieldun sheffieldun, na, Thu Oct 26 04:40:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 10330:2003 (E) 9 Key 1Solenoid 2Magnetizing current source EVariable d.c. supply ACurrent measuring device S1Changeover switch S2Reversing switch Figure 4 Magnetizing and demagnetizing circuit Licensed Copy: sheffieldun sheffieldun, na, Thu Oct 26 04:40:01 GMT+00:00 2006, Uncontrolled Copy, (c) BSI EN 10330:2003 (E) 10 Annex A (normative) Precautions to be taken for measurements of coercivity below 40 A/m and above 160 kA/m A.1Coercivities below 40 A/m For materials having a coercivity below 40 A/m, the following preca