1、 g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58The European Standard EN 61788-1:2007 has the status of a British StandardICS 17.220; 29.050Superco
2、nductivity Part 1: Critical current measurement DC critical current of Nb-Ti composite superconductorsBRITISH STANDARDBS EN 61788-1:2007BS EN 61788-1:2007This British Standard was published under the authority of the Standards Policy and Strategy Committee on 28 February 2007 BSI 2007ISBN 978 0 580
3、50218 7Amendments issued since publicationAmd. No. Date CommentsThis 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 cannot confer immunity from legal obligations. National forewo
4、rdThis British Standard was published by BSI. It is the UK implementation of EN 61788-1:2007. It is identical with IEC 61788-1:2006. It supersedes BS EN 61788-1:1998 which is withdrawn.The UK participation in its preparation was entrusted to Technical Committee L/-/90, Superconductivity.A list of or
5、ganizations represented on L/-/90 can be obtained on request to its secretary.EUROPEAN STANDARD EN 61788-1 NORME EUROPENNE EUROPISCHE NORM January 2007 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechni
6、sche Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 2007 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 61788-1:2007 E ICS 17.220; 29.050 Supersedes EN 61788-1:1998English version Superconductivity Part 1: Cri
7、tical current measurement - DC critical current of Nb-Ti composite superconductors (IEC 61788-1:2006) Supraconductivit Partie 1: Mesure du courant critique - Courant critique continu de supraconducteurs en composite Nb-Ti (CEI 61788-1:2006) Supraleitfhigkeit Teil 1: Messen des kritischen Stromes - K
8、ritischer Strom (Gleichstrom) von Nb-Ti Verbundsupraleitern (IEC 61788-1:2006) This European Standard was approved by CENELEC on 2006-12-01. 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
9、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 versi
10、on 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, Cyprus, the Czech Re
11、public, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Foreword The text of document 90/196/FDIS, fu
12、ture edition 2 of IEC 61788-1, prepared by IEC TC 90, Superconductivity, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 61788-1 on 2006-12-01. This European Standard supersedes EN 61788-1:1998. It includes the following significant technical changes with respect to
13、EN 61788-1:1998: the addition of normative Annex C and informative Annex D; accuracy and precision statements were converted to uncertainty statements; the magnetic field uniformity statement was tightened from 2 % to be less than the larger of 0,5 % or 0,02 T. The following dates were fixed: latest
14、 date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2007-09-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2009-12-01 Annex ZA has been added by CENELEC. _ Endorsemen
15、t notice The text of the International Standard IEC 61788-1:2006 was approved by CENELEC as a European Standard without any modification. _ EN 61788-1:2007 2 EN 61788-1:2007 CONTENTS INTRODUCTION.4 1 Scope 5 2 Normative references .5 3 Terms and definitions .5 4 Principle.7 5 Requirements.7 6 Appara
16、tus.8 6.1 Measurement mandrel material 8 6.2 Mandrel construction .8 7 Specimen preparation.9 7.1 Specimen bonding .9 7.2 Specimen mounting .9 8 Measurement procedure .10 9 Uncertainty of the test method 11 9.1 Critical current.11 9.2 Temperature11 9.3 Magnetic field11 9.4 Specimen and mandrel suppo
17、rt structure .12 9.5 Specimen protection 12 10 Calculation of results 12 10.1 Critical current criteria .12 10.2 n-value (optional calculation, refer to A.7.2) .13 11 Test report .14 11.1 Identification of test specimen14 11.2 Report of Icvalues 14 11.3 Report of test conditions 14 Annex A (informat
18、ive) Additional information relating to the standard 15 Annex B (informative) Self-field effect 23 Annex C (normative) Test method for Cu/Cu-Ni/Nb-Ti composite superconductors 25 Annex D (informative) Guidance for estimating winding tensile force.26 Bibliography .28 Figure 1 Intrinsic U-I characteri
19、stic .13 Figure 2 U-I characteristic with a current transfer component 13 Figure A.1 Instrumentation of specimen with a null voltage tap pair.22 Table D.1 Typical values of E at room temperature for various materials .27 Annex ZA (normative) Normative references to international publications with th
20、eir corresponding European publications.29 3 EN 61788-1:2007 INTRODUCTION The critical currents of composite superconductors are used to establish design limits for applications of superconducting wires. The operating conditions of superconductors in these applications determine much of their behavi
21、our, and tests made with the method given in this part of IEC 61788 may be used to provide part of the information needed to determine the suitability of a specific superconductor. Results obtained from this method may also be used for detecting changes in the superconducting properties of a composi
22、te superconductor due to processing variables, handling, ageing or other applications or environmental conditions. This method is useful for quality control, acceptance or research testing, if the precautions given in this standard are observed. The critical current of composite superconductors depe
23、nds on many variables. These variables need to be considered in both the testing and the application of these materials. Test conditions such as magnetic field, temperature and relative orientation of the specimen, current and magnetic field are determined by the particular application. The test con
24、figuration may be determined by the particular conductor through certain tolerances. The specific critical current criterion may be determined by the particular application. It may be appropriate to measure a number of test specimens if there are irregularities in testing. 4 EN 61788-1:2007 SUPERCON
25、DUCTIVITY Part 1: Critical current measurement DC critical current of Nb-Ti composite superconductors 1 Scope This part of IEC 61788 covers a test method for the determination of the d.c. critical current of either Cu/Nb-Ti composite superconductors that have a copper/superconductor ratio larger tha
26、n 1 or Cu/Cu-Ni/Nb-Ti wires that have a copper/superconductor ratio larger than 0,9 and a copper alloy (Cu-Ni)/superconductor ratio larger than 0,2, where the diameter of Nb-Ti superconducting filaments is larger than 1 m. The changes for the Cu/Cu-Ni/Nb-Ti are described in Annex C. The Cu-Ni uses a
27、ll of the main part of the standard with the exceptions listed in Annex C that replace (and in some cases are counter to) some of the steps in the main text. This method is intended for use with superconductors that have critical currents less than 1 000 A and n-values larger than 12, under standard
28、 test conditions and at magnetic fields less than or equal to 0,7 of the upper critical magnetic field. The test specimen is immersed in a liquid helium bath at a known temperature during testing. The test conductor has a monolithic structure with a round or rectangular cross-sectional area that is
29、less than 2 mm2. The specimen geometry used in this test method is an inductively coiled specimen. Deviations from this test method that are allowed for routine tests and other specific restrictions are given in this standard. Test conductors with critical currents above 1 000 A or cross-sectional a
30、reas greater than 2 mm2could be measured with the present method with an anticipated increase in uncertainty and a more significant self-field effect (see Annex B). Other, more specialized, specimen test geometries may be more appropriate for larger conductor testing which have been omitted from thi
31、s present standard for simplicity and to retain a lower uncertainty. The test method given in this standard is expected to apply to other superconducting composite wires after some appropriate modifications. 2 Normative references The following referenced documents are indispensable for the applicat
32、ion 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 60050-815, International Electrotechnical Vocabulary (IEV) Part 815: Superconductivity 3 Terms and definitions For
33、 the purposes of this standard, the terms and definitions given in IEC 60050-815, some of which are repeated here for convenience, and the following apply. 5 EN 61788-1:2007 3.1 critical current Icmaximum direct current that can be regarded as flowing without resistance NOTE Icis a function of magne
34、tic field strength and temperature. IEV 815-03-01 3.2 critical current criterion Iccriterion criterion to determine the critical current, Ic, based on the electric field strength, E, or the resistivity, NOTE E = 10 V/m or E = 100 V/m is often used as the electric field strength criterion, and = 10-1
35、3m or = 10-14m is often used as the resistivity criterion. IEV 815-03-02, modified 3.3 n-value (of a superconductor) exponent obtained in a specific range of electric field strength or resistivity when the voltage/current U(I) curve is approximated by the equation U InIEV 815-03-10 3.4 quench uncont
36、rollable and irreversible transition of a superconductor or a superconducting device from the superconducting state to the normal conducting state NOTE A term usually applied to superconducting magnets. IEV 815-03-11 3.5 three-component superconducting wire composite superconducting wire composed of
37、 a superconducting component and two normal conducting materials NOTE This term is mostly used for Cu/Cu-Ni/Nb-Ti composite superconductors IEV 815-04-33 3.6 Lorentz force (on fluxons) force applied to fluxons by a current NOTE 1 The force per unit volume is given by J x B, where J is a current dens
38、ity, and B is a magnetic flux density. NOTE 2 “Lorentz force“ is defined in IEV 121-11-20.11). IEV 815-03-16 3.7 current transfer (of composite superconductor) phenomenon that a d.c. current transfers spatially from filament to filament in a composite superconductor, resulting in a voltage generatio
39、n along the conductor 1) Figures in square brackets refer to the Bibliography. 6 EN 61788-1:2007 NOTE In the Icmeasurement, this phenomenon appears typically near the current contacts where the injected current flows along the conductor from periphery to inside until uniform distribution among filam
40、ents is accomplished. 3.8 constant sweep rate method a U-I data acquisition method where a current is swept at a constant rate from zero to a current above Icwhile frequently and periodically acquiring U-I data 3.9 ramp-and-hold method a U-I data acquisition method where a current is ramped to a num
41、ber of appropriately distributed points along the U-I curve and held constant at each one of these points while acquiring a number of voltages and current readings 4 Principle The critical current of a composite superconductor is determined from a voltage (U) current (I) characteristic measured at a
42、 certain value of a static applied magnetic field strength (magnetic field) at a specified temperature in a liquid cryogen bath at a constant pressure. To get a U-I characteristic, a direct current is applied to the superconductor specimen and the voltage generated along a section of the specimen is
43、 measured. The current is increased from zero and the U-I characteristic generated is recorded. The critical current is determined as the current at which a specific electric field strength (electric field) criterion (Ec) or resistivity criterion (c) is reached. For either Ecor c, there is a corresp
44、onding voltage criterion (Uc) for a specified voltage tap separation. 5 Requirements The critical current of a superconductor shall be measured by applying a direct current (I) to the superconductor specimen and then measuring the voltage (U) generated along a section of the specimen. The current sh
45、all be increased from zero and the voltage-current (U-I) characteristic generated and recorded. The specimen shall be affixed to the measurement mandrel with sufficient tension or a low temperature adhesive. NOTE 1 Exception C.2.1 replaces this sentence for Cu/Cu-Ni/Nb-Ti specimens. The target uncer
46、tainty of this method is defined as a coefficient of variation (standard deviation divided by the average of the critical current determinations) that shall not exceed 3 % in an interlaboratory comparison. NOTE 2 Exception C.2.2 replaces this sentence for Cu/Cu-Ni/Nb-Ti specimens. The use of a commo
47、n current transfer correction is excluded from this test method. Furthermore, if a current transfer signature is pronounced in the measurement, then the measurement shall be considered invalid. It is the responsibility of the user of this standard to consult and establish appropriate safety and heal
48、th practices, and to determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given below. 7 EN 61788-1:2007 Hazards exist in this type of measurement. Very large direct currents with very low voltages do not necessarily provide a direct personal haza
49、rd, but accidental shorting of the leads with another conductor, such as tools or transfer lines, can release significant amounts of energy and cause arcs or burns. It is imperative to isolate and protect current leads from shorting. Also the stored energy in superconducting magnets commonly used for the background magnetic field can cause similar large current and/or voltage pulses or deposit large amounts of thermal energy in the cryo
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