The Difficulty of Modeling Ripple Field Losses in Superconductors Using the Eddy Current Model

The eddy current (EC) model is a widely used tool for simulating hysteresis losses in superconductors. It is a reliable way to estimate losses in 50 Hz transport current, applied field or AC-AC cases. However, in some applications, such as synchronous electric motors with superconducting field windings, a small multifrequency external magnetic field is present while a superconducting coil carries a DC current. In such cases, the use of the EC model becomes challenging. In this paper, we investigate the challenges confronted in such cases by using the EC model in their simulation. It is observed that the EC model using the power law resistivity leads to current density profile homogenization even when no changes happen in the driving quantities. Also, modeling uncoupled cases in which a DC bias current flows in the conductor is troublesome.