1、BRITISH STANDARDBS EN 61788-3:2006Superconductivity Part 3: Critical current measurement DC critical current of Ag- and/or Ag alloy-sheathed Bi-2212 and Bi-2223 oxide superconductorsThe European Standard EN 61788-3:2006 has the status of a British StandardICS 17.220; 29.050g49g50g3g38g50g51g60g44g49
2、g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN 61788-3:2006This British Standard was published under the authority of the Standards Policy and Strategy Committee on 29
3、 September 2006 BSI 2006ISBN 0 580 49146 3National forewordThis British Standard was published by BSI. It is the UK implementation of EN 61788-3:2006. It is identical with IEC 61788-3:2006. It supersedes BS EN 61788-3:2001 which is withdrawn.The UK participation in its preparation was entrusted to T
4、echnical Committee L/-/90, Super Conductivity.A list of organizations represented on L/-/90 can be obtained on request to its secretary.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
5、 Standard cannot confer immunity from legal obligations.Amendments issued since publicationAmd. No. Date CommentsEUROPEAN STANDARD EN 61788-3 NORME EUROPENNE EUROPISCHE NORM August 2006 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Eu
6、ropisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 2006 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 61788-3:2006 E ICS 17.220; 29.050 Supersedes EN 61788-3:2001English ver
7、sion Superconductivity Part 3: Critical current measurement - DC critical current of Ag- and/or Ag alloy-sheathed Bi-2212 and Bi-2223 oxide superconductors (IEC 61788-3:2006) Supraconductivit Partie 3: Mesure du courant critique - Courant critique continu des oxydes supraconducteurs Bi-2212 et Bi-22
8、23 avec gaine Ag et/ou en alliage dAg (CEI 61788-3:2006) Supraleitfhigkeit Teil 3: Messen des kritischen Stromes -Kritischer Strom (Gleichstrom) von Ag- und/oder Ag-Legierung ummantelten oxidischen Bi-2212 und Bi-2223-Supraleitern (IEC 61788-3:2006) This European Standard was approved by CENELEC on
9、2006-06-01. 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
10、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 t
11、he Central Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malt
12、a, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. Foreword The text of document 90/184/FDIS, future edition 2 of IEC 61788-3, prepared by IEC TC 90, Superconductivity, was submitted to the IEC-CENELEC parallel vote and was a
13、pproved by CENELEC as EN 61788-3 on 2006-06-01. This European Standard supersedes EN 61788-3:2001. Modifications made to EN 61788-3:2001 mostly involve wording and essentially include no technical changes. Examples of technical changes introduced include the voltage lead diameter being smaller than
14、0,21 mm and the mode of expression for magnetic field accuracy being 1 % and 0,02 T instead of 1 %. The expression for magnetic field precision has been changed in the same way. The following dates were fixed: latest date by which the EN has to be implemented at national level by publication of an i
15、dentical national standard or by endorsement (dop) 2007-03-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2009-06-01 Annex ZA has been added by CENELEC. _ Endorsement notice The text of the International Standard IEC 61788-3:2006 was approved by CEN
16、ELEC as a European Standard without any modification. _ 2 EN 61788-3:2006CONTENTS 1 2 3 4 5 6 7 8 9 Annex B (informative) Magnetic hysteresis of the critical current of high-temperature Figure A.1 Illustration of a measurement configuration for a short specimen of a few 3 EN 61788-3:2006INTRODUCTION
17、.4 Scope.5 Normative reference .5 Terms and definitions .5 Principle .7 Requirements .7 Apparatus.7 Specimen preparation.8 Measurement procedure .9 Precision and accuracy of the test method10 10 Calculation of results11 11 Test report12 Annex A (informative) Additional information relating to Clause
18、s 1 to 1014 oxide superconductors20 Bibliography22 Figure 1 Intrinsic U-I characteristic 13 Figure 2 U-I characteristic with a current transfer component.13 hundred A class conductors19 Figure A.2 Illustration of superconductor simulator circuit 19 Table A.1 Thermal expansion data of Bi-oxide superc
19、onductor and selected materials 18 Annex ZA (normative) Normative references to international publications with their corresponding European publications 23 INTRODUCTION In 1986 J.G. Bednorz and K.A. Mueller discovered that some Perovskite type Cu-containing oxides show superconductivity at temperat
20、ures far above those which metallic superconductors have shown. Since then, extensive R L1is the length of a specimen to be measured; L2is the length of the soldered part of the current contact; L3 is the shortest distance from a current contact to a voltage tap; W is the width or diameter of a spec
21、imen to be measured. For a specimen with a large current-carrying capacity, narrow tape, or round wire, L2shall be larger. L shall be larger for a measurement that needs high sensitivity and L3shall be larger when current transfer voltage cannot be neglected. In the case of a specimen that has a sta
22、inless steel or other high-resistivity material backing or jacket, L2 shall be longer than 3 W. In the case of the wire specimen the angle between the specimen axis and the magnetic field shall be (90 9). This angle shall be determined with an accuracy of 2. In the case of tape specimens, there are
23、two options in addition to the requirement that the angle between the longitudinal specimen axis and the magnetic field shall be (90 9). In one option, the magnetic field shall be perpendicular to the specimen surface, the angle deviation being within 7. In the second option, the magnetic field shal
24、l be parallel to the specimen surface, the angle deviation being within 3. The voltage taps shall be placed in the central part along both the specimen length and the specimen width. All soldering shall be conducted as quickly as possible so as not to cause thermal damage to the specimen. Voltage le
25、ads with a diameter less than 0,21 mm shall be used and twisted together before soldering. The distance between the voltage taps, L, shall be measured to an accuracy of 5 %. 8 Measurement procedure The specimen shall be immersed in cryogen for the data acquisition phase. The specimen may be cooled s
26、lowly in cryogen vapour and then inserted into the cryogen bath, or inserted slowly into the cryogen bath, or, in the case of cooling to the 4,2 K range, first slowly immersed in liquid nitrogen and then liquid helium. The specimen shall be cooled from room temperature to liquid helium (or liquid ni
27、trogen) temperature over a time period of at least 5 min. When measuring at more than one temperature or magnetic field angle, between each measuring temperature and/or each magnetic-field angle, the specimen shall be cooled in zero field, from a temperature above the critical temperature down to th
28、e measuring temperature, and then the field angle with respect to the conductor cross-section shall be fixed while the field is still zero. This procedural step can only be omitted if one of the following two conditions is met: 9 EN 61788-3:2006only zero applied field measurements will be made with
29、monotonically increasing temperatures or the specimen has a demonstrated magnetic hysteresis of less than 2 % at the magnetic fields where Icis to be reported (see Annex B). The temperature of the cryogen bath shall be measured during each determination of Ic. Unless a quench protection circuit or r
30、esistive shunt is used to protect the specimen from damage, the specimen current shall be kept low enough so that the specimen does not enter the normal state. When using the constant sweep rate method, the time for the ramp from zero current to Icshall be more than 30 s. When using the ramp-and-hol
31、d method, the current sweep rate between current set points shall be lower than the equivalent of ramping from zero current to Icin 3 s. Data acquisition at each set point shall be started as soon as the flow/creep voltage generated by the current ramp can be disregarded. The current drift during ea
32、ch current set point shall be less than 1 % of Ic. The relation between the magnetic field and the magnet current shall be measured beforehand. The magnet current shall be measured before each determination of Ic. If the magnetic field is parallel to the surface of the measurement holder, the relati
33、ve direction of the current to the applied magnetic field shall result in the Lorentz force which pushes the specimen against the surface of the measurement holder. In the case of the applied magnetic field perpendicular to the measurement holder surface, either direction of the current relative to
34、the field is possible, with the condition that the specimen is rigidly mounted to the measurement holder with appropriate adhesive. Record the U-I characteristic with increasing current and at monotonically increasing magnetic fields (see Annex B). The baseline voltage of the U-I characteristic shal
35、l be taken as the recorded voltage at zero current for the ramp-and-hold method or the average voltage at approximately 0,1 Icfor the constant sweep rate method. 9 Precision and accuracy of the test method 9.1 Critical current The current source shall provide a dc current having a maximum periodic a
36、nd random deviation of less than 2 % at Ic, within the bandwidth 10 Hz to 10 MHz. A four-terminal standard resistor, with an accuracy of at least 0,5 %, shall be used to determine the specimen current. A recorder and the necessary preamplifiers, filters or voltmeters, or a combination thereof, shall
37、 be used to record the U-I characteristic. The record of the U-I characteristic shall allow the determination of Ucto a precision of 10 % and the corresponding current to an accuracy of 1 % and with a precision of 1 %. 9.2 Temperature A cryostat shall provide the necessary environment for measuring
38、Icand the specimen shall be measured while immersed in liquid helium or liquid nitrogen. The liquid temperature shall be reported to an accuracy of 0,1 K, measured by means of a pressure sensor or an appropriate temperature sensor. 10 EN 61788-3:2006The difference between the specimen temperature an
39、d the bath temperature shall be minimized. To convert the pressure observed in the cryostat into a temperature value, the phase diagram of helium or nitrogen shall be used. The pressure measurement shall be accurate enough to obtain the required accuracy of the temperature measurement. 9.3 Magnetic
40、field A magnet system shall provide the magnetic field to an accuracy better than the larger of 1 % and 0,02 T and a precision better than the larger of 0,5 % and 0,02 T. When testing without a magnet, the background magnetic field shall be measured to an accuracy of 0,0002 T and a precision of 0,00
41、01 T. The magnetic field shall have a uniformity better than the larger of 0,5 % and 0,02 T over the length of the specimen between the voltage contacts. The maximum periodic and random deviation of the magnetic field shall be less than the larger of 1 % and 0,02 T. For critical current measurements
42、 at zero or very low magnetic field, the residual magnetic field in a superconducting magnet shall be minimized. 9.4 Specimen and holder support structure The support structure shall provide adequate support for the specimen and the orientation of the specimen with respect to the magnetic field. The
43、 specimen support is adequate if it allows additional determinations of critical current with a precision of 2 %. 9.5 Specimen protection If a resistive shunt or a quench protection circuit is used in parallel with the specimen, then the current through the shunt or the circuit shall be less than 1
44、% of the total current at Ic. 10 Calculation of results 10.1 Critical current criteria The critical current Icshall be determined by using an electric field criterion Ecor a resistivity criterion cwhere the total cross-sectional area S of the composite superconductor is preferred for the estimation
45、of the resistivity (see Figures 1 and 2). In the case of the electric field criterion, two values of Icshall be determined at criteria of 100 V/m and 500 V/m. In the other case, two values of Icshall be determined at the resistivity criteria of 2 1013m and 1012m. When it is difficult to measure the
46、Icproperly at a criterion of 500 V/m, an Eccriterion of less than 500 V/m shall be substituted. Otherwise, measurements using the resistivity criterion are recommended. The Icshall be determined as the current corresponding to the point on the U-I curve where the voltage is Ucmeasured relative to th
47、e baseline voltage (see Figures 1 and 2): Uc= L Ec(3) 11 EN 61788-3:2006where Ucis the voltage criterion in microvolts (V); L is the voltage tap separation in meters (m); Ecis the electric field criterion in microvolts/meter (V/m); or, when using a resistivity criterion: Uc= IccL/S (4) where Uc, Ica
48、nd care the corresponding voltage, current and resistivity to the intersecting point of a straight line with the U-I curve as shown in Figure 1, and S is the total cross-sectional area in square meters. A straight line shall be drawn from the baseline voltage to the average voltage near 0,5 Ic(see F
49、igures 1 and 2). A finite slope of this line may be due to current transfer and/or local sample damage. A valid determination of Icrequires that the slope of the line be less than 0,3 Uc/Ic, where Ucand Icare determined at a criterion of 100 V/m or 2 1013m. 10.2 n-value (optional) The n-value shall be calculated as the slope of the plot of log U versus log I in the region where the Icis determined. The range of the criteria used to determine n shall be reported. 11 Test report 11.1 Iden
