Too high loss levels can severely limit the efficiency and the safe operation of several high-temperature superconductor (HTS) AC applications. A reliable estimation of AC losses is therefore paramount. For this purpose, in the past decades, numerous numerical models have been proposed [1]. Those models can calculate the AC losses of superconductors with good accuracy in a variety of application scenarios. However, they are usually implemented in rather complex numerical models, which, for various reasons, are not always of easy access to the users: these reasons include the availability of the codes, the implementation in commercial software that sometimes require expensive licenses, and the intrinsic complexity of the models. For users not routinely working on numerical modeling of superconductors, analytical models would be a preferable tool, especially in situations where the precise calculation of AC loss values is not necessary and establishing general trends and dependences of AC losses on various parameters is sufficient.

Analytical models for computing AC losses in superconductors exist, but they mostly use the critical state model with constant values for the superconductor’s critical current density Jc, whereas in reality Jc exhibits a dependence on the magnetic field. In this contribution, we aim at evaluating the influence of the Jc(B) dependence on the AC losses of HTS coated conductors in different scenarios, ranging from individual tapes to stacks and arrays. For this purpose, we use an integral equation numerical model [2][3], which simulates the superconductor with a power-law resistivity that includes the Jc(B) dependence, as reference. Then, we compare the results with those obtained with analytical formulas. For the latter, the constant Jc value is recalculated by taking into account the approximate magnetic field experienced by the HTS wire in the various cases.

The results of this work allow assessing if and with what accuracy analytical models can be used for evaluating the AC losses of HTS applications in cases of practical interest.

References
[1]    F. Grilli et al. 2014 IEEE Trans. Appl. Supercond. 24 8200433
[2]    R. Brambilla et al. 2008 Supercond. Sci. Technol. 21 105008
[3]    R. Brambilla et al. 2009 Supercond. Sci. Technol. 22 075018

Keywords: AC losses, High-temperaure superconductors, Finite-element method, Numerical models