Characteristics of AC transport current losses in YBCO coated conductors and their dependence on distributions of critical current density in the conductors

We measured AC transport current losses in two kinds of thin film YBCO coated conductors with different critical current densities. The results show that the loss characteristics do not follow the Norris strip model. The loss in one of the samples follows the Norris elliptical model and the loss data of the other sample fall in between the elliptical and strip models. It is considered that the loss in a YBCO conductor of high quality, that is, high critical current density, follows the strip model. However, the measured losses of even high critical current density conductor (J_c ≈ 10⁶ A/cm²) does not follow the strip models. In the paper, an analytical model is presented to describe the AC transport current loss characteristics more generally than the Norris models and the model can well describe the experimental results.