Self-field losses in 1Â m HTS conductor consisted of YBCO tapes

The self-field losses of 1 m HTS conductor consisted of YBCO tapes are calculated by the electric-circuit (EC) model. The conductor has two superconducting layers using 32 tapes, which is fabricated by Furukawa Electric Corporation (FEC). The current-dependent resistance of HTS layers in EC model is estimated on the base of Norris expressions for ellipse and thin strip, respectively. Numerically calculated losses are compared with experimental results measured by 4-terminal method by FEC. The calculations based on the Norris expression for thin strip are almost equal to the measurements at wide transport-current range below the IC of conductor. The calculation of layer-currents indicates that the currents passing through inner and outer layers are slightly different. Uniform layer's current distribution causes the minimum self-field loss of HTS conductor. Minimization of self-field loss at transporting 1 kArms is numerically executed by adjustment of helical pitches of HTS layers. As a result, the difference of layer currents is improved. However, the obtained minimum loss is 0.30 W/m that is not so different from the original loss of 0.32 W/m in HTS conductor on the FEC's design of helical pitches.