IEC 61788-8:2010 pdf – Superconductivity – Part 8: AC loss measurements-Total AC loss measurement of roundsuperconducting wires exposed to a transverse alternating magnetic fieldat liquid helium temperature by a pickup coil method.
uncertainties evaluated in Annex G are 3,8 % for the hysteresis loss and 5,4 % (5,5 %) for the coupling loss (the coupling time constant) as a typical example for NbTi conductors under the condition that the ratio of the hysteresis loss to the total AC loss is 0.5 on an average at the upper limit in the measurement frequency region. The target relative combined standard uncertainty of this method is defined as an expanded uncertainty with a coverage factor k of 2, which does not exceed 7.6 % and 10,8 % (11,0 %) respectively in the above example.
9.2 Uncertainty of measurement apparatus
Measurement apparatus with relative standard uncertainty not to exceed 0.5 % shall be used.
The dimension measuring apparatus shall have a relative standard uncertainty not to exceed
0.5 %.
9.3 Uncertainty of applied field
An applied magnetic field system shall provide the magnetic field with a relative standard uncertainty not to exceed 0,5 %. The applied field shall have a uniformity given in 7.1.5.
9.4 Uncertainty of measurement temperature
A cryostat shall provide the necessary environment for measuring AC loss and the specimen shall be measured while immersed in liquid helium. The specimen temperature is assumed to be the same as the temperature of the liquid. The liquid temperature shall be reported with a standard uncertainty not to exceed 0.05 K. For converting the observed atmospheric pressure in the cryostat to a temperature value, the phase diagram of helium shall be used. The atmospheric pressure measurement shall have low enough uncertainty to obtain the required uncertainty of the temperature measurement, For liquid helium depths greater than I m. a head correction may be necessary.
10 Test report
10.1 Identification of specimen
The specimen shall be identified, if possible, by the following:
a) name of manufacturer;
b) classification
C) lot number;
d) matrix material;
e) dimension of the wire;
f) filament diameter;
g) number of filaments;
h) interfilamentary spacing;
I) twist pitch;
k) residual resistance ratio IRRR);
I) thickness of insulation layer.
10.2 Configuration of coiled specimen
The following configuration of the coiled specimen shall be reported;
a) inner diameter:
b) outer diameter;
c) height;
d) number of turns:
e) eflectiva cross-sectional area of coiled specimen;
f) volume ratio of coiled specimen volume within the height of the pickup coils to the volume of the space between the pickup coils.
10.3 Testing condItions
The following testing conditions shall be reported:
a) amplitude of applied field;
b) waveform of applied field;
c) frequency of applied field;
d) uniformities of applied field over the coil length of the specimen and the length of pickup coils:
e) measurement temperature;
I) measurement method of temperature;
g) sampling time of Induced voltage of pickup coils:
h) magnitude of background loss.
10.4 Results
The following results shall be reported. In repeated measurements of the total AC loss, the hysteresis loss and the coupling loss (the coupling time constant), the average value and the relative expanded uncertainty for the coverage factor k of 2 shall be reported with the repeated number of times ci:
a) total AC loss including a hysteresis loss and a coupling loss;
b) hysteresis loss;
C) coupling time constant or coupling loss;
d) magnetization curve.
In the measurements where the AC losses are not divided into the hysteresis loss and the coupling loss, the results only of a) and d) shall be reported.
It is recommended that the following results be reported, even in the case where controllable errors, such as the geometrical error of the pickup coil system mentioned in 5.2 and Annex C, can be reduced:
e) hysteresis loss and magnetization curve of the Pb standard specimen;
f) maximum and minimum values of magnetization value in Pb standard specimen under external magnebc field with the amplitude of 0,1 T;
g) critical field strength ot Pb standard specimen.
10.5 Measurement apparatus
The test report shall contain the following information.