Design, Construction and Characterization of Transport Current Properties of an HTS Coil

Abstract

The objective of this work was the design, the realization and the characterization of a superconducting coil, capable of generating a peak magnetic field of 100 mT. The measured degradation due to magnetic field and mechanical strain of the electrical properties of Bi-2223/Ag tapes has been taken into account in optimising the design. The resulting configuration consisted in a 10 double-pancakes coil realised with about 300 m of Bi-2223/Ag tape. The real degradation of each double pancake has been investigated by measuring the DC characteristic and the AC losses. The stacking configuration was finally defined by the measured differences among the critical current of each double-pancake. To minimise the effect of the perpendicular magnetic field degradation on the electrical properties of the whole coil, the pancakes with higher I c were mounted at the top and at the bottom. The DC electrical properties as well as the AC losses of the elementary components and of the whole coil have been measured and the results are presented and discussed in this paper.

AC loss in ReBCO pancake coils and stacks of them: modelling and measurement

“…Second, the anisotropic contribution, J c,ab in equation (1), is due to isotropic pinning of the elliptical anisotropic vortices. This is supported by: (i) the angular dependence is described by an elliptical function [equations (6), (7)] and (ii) the experimental anisotropy factor, u=5.5, is close to the mass anisotropy of YBCO, 5.3 [46,47]. The deviation of the ab peak from the ab direction is because of the tilt in the ab planes [34,35].…”

“…For the simulations, we use the same dimensions as the measured pancake coils (table 1) and a separation between pancakes or gap between Roebel strands of 200µm. We take the anisotropic field-dependent J c from equations (1)- (7). The simulations show that a Roebel cable does not reduce the AC loss in a single pancake coil ( figure 18).…”

“…The (black) chain lines in both graphs are directly calculated from the fit of Jc, equations (1)-(7), therefore that line represents the critical current if the self-field would not be present. The simulations, (red) solid lines, use the same Jc but taking into account the self-field.…”

Numerical Analysis of Hysteretic Losses in Bscco/Ag Tapes Due to Transport Current and External Magnetic Field

“…Experimental activity has been carried on at CESI [3] by measuring with the lock-in technique a.c. losses on small size tape specimens in the self-field case and with a sinusoidal transport current waveform. The tape dimensions are 3.99 mm large and 0.204 mm height; the value of the fill factor is 0.28, the critical current at 77K in the self-field case is 32.7 A and the best fit value of the n-power coefficient is 23.6.…”

“…Different models can be found in the literature to solve the 2D simplified problem; they are based on the current vector (T) and the magnetic scalar (Q) potential approach [1] or on the magnetic vector (A) and electric scalar (cp) potential approach [2]. In this paper a model based on the magnetic vector potential as in [2] is described and the results of the simulations are compared with the experimental data which were obtained at CESI [3]. The model has been developed in the framework of a research project on SMES at the University of Bologna [4] in cooperation with the superconductivity group of CESI.…”