A Slot Model for Loss Estimation in Superconducting AC Electrical Machine Windings

The use of superconducting AC windings in rotating electrical machines is usually avoided due to the non- negligible hysteresis losses of superconductors. However, if these AC losses are mitigated, their implementation may allow to further increase the power density of electrical machines. This paper proposes a methodology for evaluating the AC losses in superconducting tapes when applied to the realization of slotted stator windings in AC electrical machines. In particular, the approach allows to reduce the computational requirements when the geometrical nature of the considered superconducting electrical machine requires 3D finite-element models, as in the case of axial flux machines. The machine is first simulated with a 3D FEM model without superconductors. Then, using a 2D single-slot FEM model, the superconducting AC losses are computed. The methodology is applied to a case study of an axial flux permanent magnet machine with AC superconducting stator windings. The model is validated by comparing the magnetization and the transport current losses estimated in the superconductors by the FEM simulations with those by analytical formulations.