IEC 61788-24:2018

IEC 61788-24 ®
Edition 1.0 2018-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Superconductivity –
Part 24: Critical current measurement – Retained critical current after double
bending at room temperature of Ag-sheathed Bi-2223 superconducting wires

Supraconductivité –
Partie 24: Mesurage du courant critique – Courant critique retenu après double
flexion à température ambiante des fils supraconducteurs Bi-2223 avec gaine Ag

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IEC 61788-24 ®
Edition 1.0 2018-06
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Superconductivity –
Part 24: Critical current measurement – Retained critical current after double

bending at room temperature of Ag-sheathed Bi-2223 superconducting wires

Supraconductivité –
Partie 24: Mesurage du courant critique – Courant critique retenu après double

flexion à température ambiante des fils supraconducteurs Bi-2223 avec gaine Ag

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.220; 29.050; 77.040.10 ISBN 978-2-8322-5801-9

– 2 – IEC 61788-24:2018 © IEC 2018
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Principle . 8
5 Apparatus . 8
5.1 General . 8
5.2 Bending mandrel . 8
5.3 Critical current measurement holder . 8
5.4 Critical current measuring system . 9
6 Specimen preparation and set up . 9
6.1 Length of specimen . 9
6.2 Mounting of the specimen . 10
7 Measurement procedures . 10
7.1 Critical current measurement . 10
7.2 Double bending . 10
7.3 Retained critical current after bending . 11
8 Calculation of results . 11
8.1 Critical current criteria. 11
8.2 n-value (optional) . 11
9 Test report . 11
9.1 Identification of test specimen . 11
9.2 Report of I values and/or retained I ratio . 12
c c
9.3 Report of I test conditions . 12
c
Annex A (informative) Additional information relating to Clauses 1 to 9 . 13
A.1 General . 13
A.2 Measurement condition . 13
A.3 Apparatus measurement holder material . 13
A.4 Specimen preparation . 16
A.5 Measurement procedures . 16
A.5.1 Critical current measurement . 16
A.5.2 Bending . 18
A.6 Calculation of results . 19
A.6.1 Critical current criteria . 19
A.6.2 n-value . 19
A.7 Relative standard uncertainty . 20
Annex B (informative) Evaluation of combined standard uncertainty for the retained I
c
after double bending . 22
B.1 Practice of critical current measurement . 22
B.2 Model equation . 22
B.3 Operation for the retained I measurement . 23
c
B.4 Combined standard uncertainty . 23

B.5 Evaluation of standard uncertainty (SU) for each measurand . 24
B.5.1 Voltage tap length (L) . 24
B.5.2 Voltage (U) . 24
B.5.3 Current (I) . 25
B.6 Evaluation of combined standard uncertainty . 26
Bibliography . 29

Figure 1 – Sample holder . 9
Figure 2 – Intrinsic U-I characteristic . 12
Figure 3 – U-I characteristic with a current transfer component . 12
Figure A.1 – Measurement configuration for a few hundred ampere class conductor . 15
Figure A.2 – Clips . 15
Figure A.3 – Additional strain caused by voltage tap wires and solders . 16
Figure A.4 – Boiling temperature of liquid nitrogen versus atmospheric pressure . 17
Figure A.5 – Critical current versus temperature for a typical Bi-2223 wire . 18
Figure A.6 – Bending process . 19
Figure B.1 – U-I diagram . 22
Figure B.2 – Bending diameter dependence of the retained I and , where the
c COV
calculated curve of I /I gives Equation (B.24). 28
c c0
Table A.1 – Thermal expansion data of Bi-2223 superconductors and selected
materials . 14
Table A.2 – Average of the degree of retained critical current (I /I ), their relative
c c0
standard uncertainty and coefficient
...