Magnetization and Demagnetization Studies of an HTS Bulk in an Iron Core

Abstract

High Temperature Superconductors (HTS) are promising materials in variety of practical applications due to their ability to act as powerful permanent magnets. Thus, in this paper, we have studied the influence of some pulsed and pulsating magnetic fields applied to a magnetized HTS bulk sample. The bulk sample, the iron core, the two inductors and the current sources used to magnetize and demagnetize the superconducting bulk in the iron core are presented. Then, we detail various magnetizing and demagnetizing processes, and their purposes. For the magnetization studies, we have shown that there is no significant difference between the Successive Process and the Direct Process of magnetization. The maximum Trapped Magnetic Field (TMF) is about 1 T, 10 min after the magnetization process. For the demagnetization studies, we propose many results as a hysteresis loop corresponding to the pulsed demagnetizing field influence. Various time evolutions of the TMF are also shown: when the demagnetizing AC field is applied a few minutes after or several days after the magnetization. This leads to completely different results, from 5 % / min to 1 % / (6 hours) of reduction of the TMF. The results presented here, give many practical information to users of superconducting bulk magnets. We assume that decreasing the temperature will increase the capabilities of trapping the magnetic field. We conclude that a strong interest must be kept on the applications of HTS bulks in Electrical Engineering, preferably at lower temperature than 77 K.

A new ring-shape high-temperature superconducting trapped-field magnet

“…For practical applications, the demagnetization rates of trapped field magnets need to be estimated to determine whether or not re-magnetization is required. The demagnetization of 2G HS bulks and stack of YBCO tapes have been studied extensively, with both perpendicular and parallel magnetic fields [39,40,41,42]. Strategies to suppress the demagnetization have been proposed using shielding rings [43,44].…”

Characterization of High-Temperature Superconductor Bulks for Electrical Machine Application

“…GREEN lab studied the magnetization of HTS bulk in an iron core (Figure 7), and they concluded that the trapped magnetic field in the HTS bulk increased and the current of the optimal pulse decreased. Therefore, iron around the HTS bulk improved the magnetization process [29,30] One of the issues with this kind of HTS motor is the choice of whether to magnetize the HTS bulks inside the machine (in situ) or outside of the machine (ex situ). The prototypes already made used ex situ magnetization because it is the simplest option in terms of magnetization.…”

“…A suitable magnetization method exists called pulse field magnetization (PFM). In this method, the HTS YBaCuO bulk is cooled down and then submitted to magnetic field pulses [ 28 , 29 , 30 ]. It traps less of the magnetic field than the ZFC method but it requires only a small copper magnetization coil.…”

“…The prototypes already made used ex situ magnetization because it is the simplest option in terms of magnetization. However, many teams [ 28 , 29 , 30 , 31 ] are working on in situ magnetization for future industrial applications because it should be simpler for the end user.…”

Stator Design and Performance of Superconducting Motors for Aerospace Electric Propulsion Systems

“…Conventional PM blocks with unity recoil permeability were used. Only the 'equivalent' remanent flux density of the blocks was varied to represent the high fields produced by the superconducting bulks [10], [18] or stacks of superconducting tapes [19].…”