  This study presents an HTS electromagnetic model combining the thin-strip,
homogeneous and multi-scale methods using T-A formulation. In particular, we
build the thin strips as both the analyzed HTS tapes and the boundaries of the
homogeneous bulks where the non-analyzed tapes are merged. Thus, the coil
geometry is re-constructed with several bulks, but the bulks boundaries and
domains are tackled with different electromagnetic properties, and solved by T
and A formulations, respectively. Firstly, we introduce the modeling process
and highlight the differences and advantages over the previous models. Then,
the accuracy of the proposed model is validated by comparing the results with
those from the reference model based on a 2000-turn coil. The distributions of
normalized current density, magnetic flux density and hysteresis losses from
the two models are highly consistent, and the error of the total loss is less
than 1%. Besides, the proposed model is the most time-saving among all the
advanced models. Furthermore, the model can be applied in 3D simulations, and
the high accuracy and efficiency are validated by simulating a 50-turn
racetrack coil. The proposed method provides a feasible approach to simulating
coils with many stacked tapes, and we will continue exploring more applications
in solving HTS systems with complex geometries.
