Electromagnetic and calorimetric measurements for AC losses of a YBa₂Cu₃O_7−δcoated conductor with Ni-alloy substrate

Abstract

The AC losses of a rolling-assisted-biaxially-textured-substrate (RABiTS™) processed YBa2Cu3O7−δ (YBCO) coated conductor (Goyal et al 1996 Appl. Supercond. 4 403–27) with Ni-alloy substrate and Cu stabilizer were measured at 77 K by both calorimetric (CM) and electromagnetic (EM) methods. In the CM method, improvements in the measurement were observed when a Cernox temperature sensor was used to measure the temperature rise on the sample instead of a differential thermocouple. The effect of heat transferred from current leads was taken into account to improve the accuracy of the CM results. In the EM method, the magnetization losses of the sample in a perpendicular applied field were measured by an in-plane pick-up coil. The calculation of the calibration factor C of the pick-up coil is discussed. Good agreement between AC loss results obtained from the CM and EM methods confirmed the validity of our measurements and calculations.

Design of a Race-Track Coil For Measurements of Ac Power Losses in High-Temperature Superconducting Tapes

“…" rms U is the loss voltage from the pick-up coil; and Hrms is the external magnetic field of the frequency f. The calibration factor C is a function of the ratio w/2a and goes to unity when w/2a→∞ [11,12]. In our case, for w/2a=3 the factor C is about 0.962.…”

“…In our case the width of the pick-up coil was about three times the sample strip's width (the width of the tape was 4 mm). Such geometry allows measuring magnetic losses within a few percent of the "true" loss [11,12].…”

Ac-loss measurement of coated conductors: The influence of the pick-up coil position

“…(19) in Ref. [9]), Comparing this result with the slab approach of Eq. (1) and using DU(t) = NoU(t)/ot, we find the relation…”

“…(18) in Ref. [9]). Integration of U(B 0 ) over one cycle yields the losses obtained by the magnetic flux measurement Q fm .…”

“…The hysteresis loop integral of magnetic flux penetrating the pick-up coil, R B dU, was calculated by Nguyen et al [9]. They used the magnetic field distribution within the tape, calculated by Brandt and Indenbom as a function of the external field B(t), see Eq.…”