AC losses of Roebel and CORC^® cables at higher AC magnetic fields and ramp rates

Abstract

We have measured ReBCO coated conductor-based CORC® and Roebel cables at 77 K in a Spinning Magnet Calorimeter which subjected the tapes in the samples to a radial magnetic field of 566 mT (peak) at frequencies up to 120 Hz (272 T/s, cyclic average) with an approximately sinusoidal waveform. The samples were oriented such that the field applied to the tapes within the cables was entirely radial, simplifying subsequent analysis. An expression for loss which included hysteretic, flux creep, and eddy current losses was fit to both the CORC® and the Roebel cables. This expression allowed easy comparison of the relative influence of eddy currents and flux creep (or power-law behavior) effects. The loss of both the CORC® and Roebel cables measured here were seen to be essentially the sum of the hysteretic loss, flux creep effects, and the normal metal eddy current losses of the individual tapes. The losses of these cables were measured at high B*dB/dt with no coupling current loss observed under the present preparation conditions. The influence of flux creep effects on loss were not negligible. The losses of the CORC® cable per meter of tape were seen to be reduced from the case of a flat tape because of the helical geometry of the tapes.

Measurement of AC loss down to 25 K in a REBCO racetrack coil for electrical aircraft motor

“…Apart from these works at low temperatures, the measurements in Refs. 26 , 27 at 77 K are highly remarkable. These experiments use a system that generates high magnetic inductions (more than 500 mT amplitude) at moderate frequencies, up to 200 Hz.…”

“…AC loss could be measured by two different techniques: calorimetric 6 , 15 , 21 , 26 , 27 or electric 12 – 16 , 18 , 19 , 21 – 25 . Electric measurements are more accurate than calorimetric, enabling to determine the AC loss also at low AC excitations.…”

HTS conductor coil by in-situ winding technology for large-scale high-field magnet

“…At present, there are various forms of HTS conductors, such as twisted stacked-tape cable [3,4], quasi-isotropic strand [5][6][7], ROEBEL Assembled Coated Conductors [8,9], conductors in tube [1], Cross Conductor [10], soldered stacked-square [11][12][13] and conductor on round core (CORC) [14]. The CORC has some advantages in higher current carrying capability [15,16] and lower AC loss [17][18][19][20][21].…”