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 of variance. 21
Table B.1 – Precondition for evaluating standard uncertainty . 22
Table B.2 – Partial sum (Equation (B.17) of standard uncertainty as related to the
current measurement) . 26
Table B.3 – Budget table of standard uncertainty for each component . 27
Table B.4 – Combined standard uncertainty . 27

– 4 – IEC 61788-24:2018 © IEC 2018
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SUPERCONDUCTIVITY –
Part 24: Critical current measurement –
Retained critical current after double bending at room
temperature of Ag-sheathed Bi-2223 superconducting wires

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
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patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61788-24 has been prepared by IEC technical committee 90:
Superconductivity:
The text of this standard is based on the following documents:
FDIS Report on voting
90/402/FDIS 90/406/RVD
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.

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.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – IEC 61788-24:2018 © IEC 2018
INTRODUCTION
In 1988, a new class of high critical temperature (T ) copper oxide superconductors,
c
Bi-Sr-Ca-Cu-O, was discovered. After nearly three decades, (Bi,Pb) Sr Ca Cu O (Bi-2223)
2 2 2 3 x
is now being utilized as a commercial high-T superconducting wire.
c
Superconducting wires are often subjected to bending deformation during production and
application, e.g. during wire processing, magnet construction, cable fabrication, etc. The wire
is bent towards both the upper and lower directions as it passes through several pulleys.
These production processes are carried out at room temperature. Critical current of the wire is
likely influenced through such bending, and may be accompanied by irreversible degradation
in case of large deformation. The easiest way to evaluate the influence of bending on critical
current is to carry out comparative measurement with the wire in the straight form before and
after bending to a specific diameter.
After a wire is made into a coil or a cable, critical current is often measured under bending
conditions or a more complex deformation state. In these cases, change in critical current
may include both reversible and irreversible contributions depending on the amount of
deformation. Irreversible degradation usually originates from a fracture in the superconducting
component. In order to evaluate only irreversible contributions, measuring the retained critical
current after the wire is straightened back from its deformed shape is necessary.
The critical bending diameter below which wire performance degrades significantly is typically
specified for use of commercial superconducting wire. Thus, it is important to standardize
measurement methods for the retained critical current after double bending. This document
can be applied to other similar bending tests such as single bending, cyclic bending, etc.
This document consists of two fundamental technologies of the critical current measurement
and the double bending process.

SUPERCONDUCTIVITY –
Part 24: Critical current measurement –
Retained critical current after double bending at room
temperature of Ag-sheathed Bi-2223 superconducting wires

1 Scope
This part of IEC 61788 describes a test method for determining the retained critical current
after double bending at room temperature of short and straight Ag- and/or Ag alloy-sheathed
Bi-2223 superconducting wires that have the shape of a flat or square tape containing mono-
or multicores of oxides. The wires can be laminated with copper alloy, stainless steel or Ni
alloy tapes.
The test method is intended for use with superconductors that have a critical current less than
300 A and an n-value larger than 5. The test to determine the retained critical current is
carried out without an applied magnetic field, with the test specimen immersed in a liquid
nitrogen open bath.
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 60050-815:2015, International Electrotechnical Vocabulary – Part 815: Superconductivity
(available at http://www.electropedia.org/)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in IEC 60050-815 and the
following 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
3.1
double bending
bending in one direction to a certain diameter followed by the subsequent bending in the
opposite direction to the same diameter
Note 1 to entry: Bending diameter is defined as the diameter of the bending mandrel.
Note 2 to entry: The definition of bending diameter is in principle the sum of the mandrel diameter and
superconductor thickness. In the engineering process, however, the minimum diameter of the pulleys through
which the wire is passed should also be considered.

– 8 – IEC 61788-24:2018 © IEC 2018
3.2
constant sweep rate method
voltage-current data (U-I data) acquisition method where a current is swept at a constant rate
from zero to a value above critical current (I ) while continuously or frequently and
c
periodically acquiring U-I data
3.3
ramp-and-hold method
U-I data acquisition method where a current is ramped to a number of appropriately
distributed points along the U-I curve and held constant at each of these points while
acquiring a number of voltages and current readings
4 Principle
The principle of the double bending method is described as follows. Critical current at 77 K
under self-field shall be measured in a straight configuration with no mechanical strain. After
measurement the specimen shall be warmed up to room temperature.
Hereafter, the specimen shall be bent in one direction to the specified diameter and then
returned to the straight configuration. Successively, the specimen shall be bent in the
opposite direction to the same diameter and returned to the straight configuration again.
Critical current of the specimen at 77 K under self-field shall be measured after double
bending and straightening. The time interval between critical current measurements before
and after bending should be as short as possible.
Critical current is determined from voltage-current (U-I) characteristic measured in a liquid
nitrogen open bath under a constant pressure. Critical current is determined as the current at
a specific electric field strength criterion (electric field criterion) (E ), which corresponds to the
c
voltage criterion (U ) for a specified voltage tap separation.
c
5 Apparatus
5.1 General
The apparatuses required for the present test methods include the following:
• mandrels with necessary bending diameters;
• critical current measuring system.
5.2 Bending mandrel
Bending diameter shall be defined as the diameter of the bending mandrel. Bendable length
shall be longer than the distance between the voltage taps.
5.3 Critical current measurement holder
The measurement holder is constructed from an insulating material.
Critical current may inevitably depend on the measurement holder material due to specimen
strain induced by the difference of thermal contraction between specimen and holder.
The structure of the measurement holder shall be one which does not induce a local excess
strain. The specimen strain induced by the difference of thermal contraction between
specimen and holder during cooling from room temperature to 77 K shall be minimized to
within ± 0,1 %. This thermal strain can be evaluated in cases where the thermal expansion

coefficients of constituent materials are known. To minimize the thermal strain, the holder
shall be constructed from material which has a thermal contraction similar to the specimen.
NOTE Recommended measurement holder materials are described in A.3.
5.4 Critical current measuring system
The apparatus to measure U-I characteristics consists of a specimen probe, an open bath of
liquid nitrogen and a U-I measurement system.
The specimen probe, which consists of a specimen, a measurement holder and a specimen
support structure, is inserted in the open bath filled with liquid nitrogen. The U-I measurement
system consists of a direct current source, a recorder and necessary preamplifiers, filters or
voltmeters, or a combination thereof.
A computer-assisted data acquisition system is recommended.
6 Specimen preparation and set up
6.1 Length of specimen
The length (L) of the specimen to be measured shall be determined as follows (see Figure 1):
L = 2 × L + 2 × L + L + 2 × L > 5 × W (1)
2 4 1 3
L ≥ W, L ≥ W, L ≥ W (2)
1 2 3
where
L is the distance between the voltage taps;
L is the length of the current contact;
L is the shortest distance from the current contact to the voltage tap;
L is the width of the voltage tap;
W is the width of the specimen to be measured.
L L L L L L L
2 3 4 1 4 3 2
Current
Current Voltage
Voltage
IEC
Figure 1 – Sample holder
For a specimen with a larger current-carrying capacity/width, L shall be longer than 3W. In
cases where the specimen is laminated with stainless steel or laminated with another highly
resistive material, L shall be larger. For measurement which requires higher voltage
sensitivity, L shall be larger. In cases where current transfer voltage cannot be ignored, L shall
1 3
be larger.
– 10 – IEC 61788-24:2018 © IEC 2018
In Table 2 of [1] , five successful double bend test conditions are shown. Typically, specimen
length L ranges from 90 mm to 150 mm, L from 18,25 mm to 50 mm, L from 10 mm to
1 2
20 mm, L from 12,5 mm to 20 mm, and L from 1,75 mm to 11 mm. When testing Bi-2223
3 4
wire with a stainless steel or nickel alloy laminate, L should be sufficiently large to avoid
local heating.
6.2 Mounting of the specimen
The specimen shall be mounted on the flat surface of the holder and both ends shall be
fastened to the current contact blocks without solder, as described in A.3. As long as the
current pad areas of the wire are not located within the area to be bent, they can also be
soldered, if desired.
Voltage taps shall be placed in the central section of the specimen, without any material
which cannot be removed.
NOTE The recommended voltage tap method is described in A.3.
The voltage leads shall be twisted as close to the voltage taps as possible.
7 Measurement procedures
7.1 Critical current measurement
Critical current shall be measured under conditions that avoid any extra mechanical strain.
The specimen shall be slowly immersed in the liquid nitrogen bath. The specimen shall be
cooled from room temperature to the temperature of the liquid nitrogen over a time period of
at least a few tens of seconds.
When using the constant sweep rate method, ramp rate shall be set so that I and n-value are
c
not ramp rate dependent.
When using the ramp-and-hold method, current sweep rate between current set points shall
be set lower than the equivalent ramping from zero current to I in 3 s. Data acquisition at
c
each set point shall begin as soon as the flow/creep voltage generated by the current ramp
can be disregarded. Current drift during each current set point shall be less than 1 % of I .
c
U-I characteristics are measured and recorded at increasing current values.
Baseline voltage of the U-I characteristic shall be determined as the recorded voltage at zero
current for the ramp-and-hold method or the average voltage at approximately 0,1 I for the
c
constant sweep rate method.
After measurement, the specimen shall be warmed up to room temperature.
7.2 Double bending
At room temperature, one end of the specimen shall be affixed to a mandrel of a specific
diameter and the specimen bent along the mandrel from the fixed end to the free end, as
shown in A.5.2. The bending section shall include the entire length between the voltage taps.
Hereafter, the specimen shall be free of bending.
___________
Numbers in square brackets refer to the Bibliography.

The specimen shall be turned over and reaffixed to the mandrel with the same diameter and
bent along the mandrel from the fixed end to the free end of specimen.
Finally, the specimen shall be straightened.
7.3 Retained critical current after bending
Critical current shall be measured in a straight configuration with no mechanical strain other
than straightening from the plastic deformation caused by the previous bending.
Critical current measurement shall be carried out using the same procedure as in 7.1.
Measurement shall be carried out in a liquid nitrogen open bath with a time interval between
critical current measurements before and after bending treatment as short as possible. Since
critical current is strongly dependent on temperature, attention shall be given to avoid
variation in temperature before and after bending. A detailed discussion is provided in A.5.1.
8 Calculation of results
8.1 Critical current criteria
Critical current I shall be determined using electric field criterion E .
c c
The value of I shall be determined under criteria of 100 μV/m and/or 10 μV/m.
c
I shall be determined to be the current corresponding to the point on the U-I curve where
c
voltage U is measured relative to the baseline voltage (see Figure 2 and Figure 3):
c
U = L E (3)
c 1 c
where
U is the voltage criterion in microvolts (μV);
c
L is the voltage tap separation in metres (m);
E is the electric field criterion in microvolts per metre (μV/m);
c
where U and I are the corresponding voltage and current values at the intersecting point of
c c
the straight lines with the U-I curve as shown in Figure 2.
A straight line shall be drawn from the baseline voltage to the average voltage near 0,5 I
c
(see Figure 3). The finite slope of this line shall be due to current transfer and/or local sample
damage. Valid determination of I requires that the slope of the line be less than 0,3 U /I ,
c c c
where U and I are determined under the criteria of 100 μV/m and/or 10 μV/m.
c c
8.2 n-value (optional)
n-value shall be calculated as the slope of the plot of log U versus log I in the region between
100 μV/m and 10 μV/m.
9 Test report
9.1 Identification of test specimen
The test specimen shall be identified by the following:
a) name of the manufacturer of the specimen;

– 12 – IEC 61788-24:2018 © IEC 2018
b) classification and/or symbol;
c) lot number.
9.2 Report of I values and/or retained I ratio
c c
I values before and after bending and/or the retained I ratio, together with their
c c
corresponding criteria and n-values (optional), shall be reported.
9.3 Report of I test conditions
c
The following test conditions shall be reported as needed:
a) bending diameter (D);
b) fixing method of the current and voltage taps (for example, clip, crimping using Cu block,
solder (for currents) or another connecting method);
c) length of specimen (L);
d) distance between voltage taps (L );
e) the shortest distance from a current contact to a voltage tap (L );
f) length of the current contacts (L );
g) sweep rate when using the constant sweep rate method;
h) ramp pitch, ramping time and holding time when using the ramp-and-hold method.
U = LE
c
0 I
c
DC current, I (arbitrary units)
IEC
Figure 2 – Intrinsic U-I characteristic
U = LE
c
Current transfer line
I
c
DC current, I (arbitrary units)
IEC
Figure 3 – U-I characteristic with a current transfer component

Voltage U (arbitrary units) Voltage U (arbitrary units)
U = LE
U = LE c c
c c
Annex A
(informative)
Additional information relating to Clauses 1 to 9
A.1 General
Many different variables have a significant effect on the critical current measurement value for
Ag- and/or Ag alloy-sheathed Bi-2223 superconductor wires. However, significant portions of
the test method covered in this document are common or similar to those for Bi-based oxide
superconductors (IEC 61788-3 [2]). Only some of these variables are addressed in Annex A.
For variables that are not mentioned here, refer to IEC 61788-3.
Special features of oxide superconductors can be classified into two groups. The first group is
specific to oxide composite superconductors, including mechanical fragility, electromagnetic
weak links, cryogen gas bubble formation, aging degradation, magnetic flux flow and creep,
large anisotropy, hysteresis in critical current with magnetic field sweep, etc. The second
group is related to the short length of the specimen used in the standard. Critical current
measurement of such a specimen may easily pick up varying voltage signals due to thermal
electromotive force, inductive voltage, thermal noise, current redistribution, specimen motion
relative to the holder, etc. Current transfer voltages may be present due to the short distance
from a current contact to the voltage tap.
Superconductors with critical currents above 300 A can be measured using this document
with an anticipated reduction both in accuracy and precision and a more significant self-field
effect.
Restrictions in this test method have been added in order to obtain the required precision in
the final definitive phase of long conductor qualification.
A.2 Measurement condition
The minimum total length of the tape specimen is five times the tape width (W) plus two times
the voltage tap width (L ), which represents the sum of the following:
– the minimum voltage tap separation (L ≥ W);
– the length of the current contacts (L ≥ W);
– the shortest distance between the current and voltage contacts (L ≥ W).
A.3 Apparatus measurement holder material
In this method, the specimen strain is kept to a minimum (less than 0,1 %). A thermal
contraction of less than 0,1 % does not result in an appreciable deviation of I at 0 T, near
c
77 K. One significant source of strain is the mismatch of thermal contraction rates between
the measurement holder and the specimen when cooled to liquid nitrogen temperature.
Based on the typical thermal contractions shown in Table A.1, the following materials are
recommended for the measurement holder material. For alternative holder materials, a
carefully prepared qualification study should precede routine tests.
The recommended holder material is fibreglass epoxy composite, with the specimen lying in
the plane of the fabric warp.
– 14 – IEC 61788-24:2018 © IEC 2018
Table A.1 – Thermal expansion data of Bi-2223 superconductors
and selected materials
Material ∆L/L [%]
293K-77K
Ag-sheathed Bi-2223 [3] 0,274
Ag,Au-sheathed Bi-2223 [3] 0,293
Copper alloy laminated Bi-2223 0,275
Stainless steel laminated Bi-2223 0,265
Nickel alloy laminated Bi-2223 0,227
Silver [4] 0,370
Copper [5] 0,302
GFRP G10, warp [6][7] 0,21
GFRP G10, normal [6][7] 0,64
An example of a measurement holder is shown in Figure A.1.
As shown in Figure A.1 (a), the sample holder is constructed by four contact blocks made of
silver tape (2) attached to the fibreglass epoxy base (1). The braided wires (3) are soldered to
the silver tapes in the opposite surface as current and voltage taps.
As shown in Figure A.1 (b), the tape specimen (4) is set on the sample holder by contacting
the silver tapes and lapped by the braided wires. The lapped surface is then tightly gripped
with the clips ((5) in Figure A.1 (c)). Examples of the clips are shown in Figure A.2.

L L
2 4
L
L
3 1
3 4
(4)
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(a) Measurement holder (b) Specimen laid on the holder
(5)
1 2 4
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(d) All contacts clipped on to the specimen
(c) Current contact clipped on to the specimen

Key
 current contacts
 voltage taps
Figure A.1 – Measurement configuration for a few hundred ampere class conductor

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Figure A.2 – Clips
– 16 – IEC 61788-24:2018 © IEC 2018
Additional strain
Solder
Wire
Wire
Solder
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Bending in one direction Bending in the opposite direction
Figure A.3 – Additional strain caused by voltage tap wires and solders
A critical current measurement standard (IEC 61788-3) exists for BSCCO wire. IEC 61788-3
uses soldering to affix the voltage taps. However, if IEC 61788-3 is used, additional strain is
induced on the wire at the soldered position, when the wire is bent and the solder and voltage
taps are caught between the wire and the bending mandrel. This document for critical current
measurement is an exception in order to avoid additional strain-induced degradation of the
wire.
A.4 Specimen preparation
The distance between the voltage taps is defined as the smallest distance between the
voltage contacts, irrespective of size.
A.5 Measurement procedures
A.5.1 Critical current measurement
To reduce thermoelectric potential on the specimen voltage leads, copper voltage leads are
used continuously from the cryogen bath until room temperature, where an isothermal
environment for all room temperature joints or connections is provided. It should be noted that
the joints or connections immersed in the cryogen bath are isothermal.
The rate of cooling may affect the results of critical current measurement due to differential
cooling rates and differential thermal contraction causing excessive strain of the specimen.
Atmospheric pressure causes variation in the boiling temperature of liquid nitrogen filled in the
open bath. Figure A.4 shows the correlation between boiling temperature (T ) and
b
atmospheric pressure (P).
78,5
77,5
y = 0,084 8x + 68,745
R = 0,999 4
76,5
85 90 95 100 105 110 115
P (kPa)
IEC
Figure A.4 – Boiling temperature of liquid nitrogen
versus atmospheric pressure
The critical current of Bi-2223 wires depends on temperature as shown in Figure A.5.
In this document, the objective is to obtain the ratio of critical currents before and after the
bending treatment. In order to avoid a significant temperature change from atmospheric
pressure variation over time, the duration between two critical current measurements shall be
as short as possible.
If system noise is significant compared to the prescribed value of voltage, i.e. U , increasing
c
the time for the ramp progress from zero current to I to more than 150 s is desirable. In this
c
case, care should be taken to sufficiently increase the heat capacity and/or to sufficiently cool
the surface of the current contacts to suppress the influence of heat generation due to the
longer time required for measurement. It should be noted that the ramp-and-hold method
allows for averaging data which can be appropriately distributed along the U-I characteristics.
T (K)
b
– 18 – IEC 61788-24:2018 © IEC 2018
y = –9,131 8x + 885,58
77 77,2 77,4 77,6 77,8
Temperature (K)
IEC
Figure A.5 – Critical current versus temperature for a typical Bi-2223 wire
Ramping the specimen current can induce a positive or negative voltage on the voltage taps
over time. This source of interference voltage during ramping can be identified by its
proportional dependence on ramp rate. If this voltage is significant compared to U , then
c
decreasing the ramp rate, decreasing the area of the loop formed by the voltage taps and the
specimen in between, or using the ramp-and-hold method is recommended.
Faster current ramp rates can be used for the ramp-and-hold method if the measurement
system proves to yield consistent results with a specific ramp rate equivalent to ramping from
zero to I in 3 s. It is possible to obtain consistent results with ramp rates as high as 500 A/s
c
on a conductor with critical current from 10 A to 200 A.
Baseline voltage may include thermoelectric, off-set, ground-loop and common-mode voltages.
It is assumed that these voltages remain relatively constant for the time it takes to record
each U-I characteristic. Small changes in thermoelectric and off-set voltages can be
approximately negated by measuring the baseline voltage before and after the U-I curve
measurement and assuming a linear change with time. If the change in the baseline voltage is
significant compared to U , then the experimental configuration should be corrected.
c
A.5.2 Bending
In these procedures, “double bending” re
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