Calculations of AC current losses from the experimental field profiles in various types of coated conductors with applied currents

Abstract

We measured the field profiles, H(x,I), near the surface of a coated conductor (CC) using the scanning Hall probe method. The samples were SmBCO-CC tape fabricated by co-evaporation method and YBCO-CC tape fabricated by PLD method. The applied current, I, were decreased from Ipeak to -I peak stepwise. We calculated the current profiles, J(x, I), by the inversion method. From the values of J(x,I) and the corresponding flux densities, we calculated the hysteretic energy losses per cycle, Q, for various values of Ipeak. From the values of Q, we calculated the characteristic functions, f, which were ??Q/??0I2c. Here, Ic is the critical current. The f-value of SmBCO CC-tape was lager than the f-value of YBCO CC-tape. We also compared values of our f with the values of other f obtained by other research groups. Our values of f were basically similar to the values of Brandts theoretical f in the most range of Ipeak. We found that the area of J-B hysteretic curves of SmBCO CC-tape is larger than that of YBCO CC-tape. These differences are due to the difference of current profiles and flux density profiles. This feature might explain the difference of the Q- values of the two samples. ?? 2008 IOP Publishing Ltd.