What is BS EN IEC 61788-24- Critical current measurement about?
BS EN IEC 61788-24 is a safety standard on critical current measurement.
BS EN IEC 61788-24 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 monoor 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.
Who is BS EN IEC 61788-24- Critical current measurement for?
BS EN IEC 61788-24 on critical current measurement is relevant to:
- Electrical engineers
- Mechanical engineers
- Electricians
- Manufacturers of superconducting wires and superconductivity materials
- Testing authorities
Why should you use BS EN IEC 61788-24- Critical current measurement?
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. The 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. BS EN IEC 61788-24 assists with the critical current measurement. After a wire is made into a coil or a cable, the critical current is often measured under bending conditions or a more complex deformation state. In these cases, changes in critical current include both reversible and irreversible contributions depending on the amount of deformation. Irreversible degradation usually originates from a fracture in the superconducting component. The critical bending diameter below which wire performance degrades significantly is typically specified for use of commercial superconducting wire. BS EN IEC 61788-24 advises standardized measurement methods for the retained critical current after double bending. BS EN IEC 61788-24 can be applied to other similar bending tests such as single bending, cyclic bending, etc. BS EN IEC 61788-24 consists of two fundamental technologies of the critical current measurement and the double bending process. Critical current at 77 K under self-field is measured in a straight configuration with no mechanical strain. After measurement, the specimen is warmed up to room temperature.
Overall, BS EN IEC 61788-24 is useful as it provides guidance on a new class of high critical temperature (Tc) copper oxide superconductors, Bi-Sr-Ca-Cu-O, which was discovered in 1988. After nearly three decades, (Bi,Pb)2Sr2Ca2Cu3Ox (Bi-2223) is now being utilized as a commercial high-Tc superconducting wire. BS EN IEC 61788-24 helps in evaluating irreversible contributions, measuring the retained critical current.
