Review on thermal-related measurement methods for superconducting devices and prospect for high-speed maglev transportation application

High‐temperature superconducting(HTS)bulks can not only be self‐stable when levitated above a permanent magnet(PM)but also can be used as quasi PM with higher magnetic energy product due to their magnetic flux pinning characteristics.Therefore,HTS bulks have wide application potentials in maglev trains,maglev bearings,flywheel energy storage,drug delivery,and high field magnets.In the external magnetic field of common application scenarios,HTS bulks have no external input current,so it is difficult to achieve the overall quench.However,local quenching in the bulk is still possible in the harsh fluctuating external field environment.Although it is difficult to reach the total quench,its critical parameters like Jc will inevitably deteriorate,which may collapse the application system.Therefore,in contrast to superconducting wires and tapes that are more concerned with quench detection,HTS bulks with a 3D volume effect are more focused on internal sensitive temperature locations,the impacts of volume and scale,and the coupling influence on application parameters such as magnetism and force.Therefore,for efficient thermal‐related measurement of HTS bulk applications,this paper investigates and discusses 12 commonly‐used temperature measurement or quench detection methods in all superconducting application fields.These methods primarily refer to the current quench detection technologies used in HTS tapes and wires.From the standpoint of practical temperature measurement requirements of HTS bulks and technological limitations of maglev application scenarios,working characteristics and service conditions of the 12 methods,and 4 temperature detection methods are selected through a comprehensive understanding and comparison of basic principles.They are expected to be used in real‐time monitoring and early warning schemes for onboard superconducting levitation devices of HTS maglev transportation or other applications in the future.

Concept design of an HTS linear power generator for wave energy conversion

We show a conceptual structure for a wave energy converter,which features a direct‐drive linear power generator with REBaCuO high‐temperature superconducting(HTS)bulk field poles and driven by a heaving buoy.A dual translator power generation system of the proposed concept structure is a linear generator in which both the HTS bulks and armature copper coils move in opposite directions simultaneously.A performance analysis of our linear generator was conducted using a finite‐element electromagnetic field analysis method.The results of the analysis were compared between the HTS dual translator linear power generator and the HTS single translator linear power generator.The maximum electromagnetic force and the average output power of the HTS dual translator are around 5%and 11%higher than that of the HTS single translator.We further present the results of the analysis regarding the influence of reducing the stroke length of the linear generator translator on the output power,where the output power for the HTS dual translator system increased up to a factor of two,in comparison to the HTS single translator counterpart,for the same reduction of stroke length.