IEC 61788-26-2020 Superconductivity – Part 26: Critical current measurement – DC critical current of RE-Ba-Cu-O composite superconductors.
This part of IEC 61 788 specifies a test method for determining the DC critical current of short RE (rare earth)-Ba-Cu-O (REBCO) composite superconductor specimens that have a shape of straight flat tape. This document applies to test specimens shorter than 300 mm and having a rectangular cross section with an area of 0,03 mm 2 to 7,2 mm 2 , which corresponds to tapes with width ranging from 1 ,0 mm to 1 2,0 mm and thickness from 0,03 mm to 0,6 mm. This method is intended for use with superconductor specimens that have critical current less than 300 A and n-values larger than 5 under standard test conditions: the test specimen is immersed in liquid nitrogen bath at ambient pressure without external magnetic field during the testing. Deviations from this test method that are allowed for routine tests and other specific restrictions are given in this document.
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 60050-81 5, International Electrotechnical Vocabulary (IEV) – Part 815: Superconductivity 3 Terms and definitions For the purposes of this document, the terms and definitions given in IEC 60050-81 5 and the following apply. ISO and IEC maintain terminological databases for use in standardization at the following URLs:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp/
3.1 constant sweep rate method U-I data acquisition method where a current is swept at a constant rate from zero to a current above I c , and where the U-I data are acquired continuously or frequently
3.2 ramp-and-hold method U-I data acquisition method where a current is swept in stages from zero to a current above I c , where the current is held for an appropriate amount of time at each stage, and where the U-I data are acquired continuously or frequently
4 Principle The critical current of a composite superconductor specimen shall be determined from a voltage–current (U-I) characteristic measured in a liquid nitrogen bath at ambient pressure. To get a U-I characteristic, a direct current is applied to the superconductor specimen and the voltage generated along the specimen is measured. The current is increased from zero and the U-I characteristic is recorded. The critical current shall be determined as the current at which a specific electric field strength criterion (electric field criterion) (E c ) is reached. For any selected E c , there shall be a corresponding voltage criterion (U c ) for a specified voltage tap separation.IEC 61788-26 pdf download.