  Numerical models based on the finite-element method (FEM) are popular tools
for investigating the macroscopic electromagnetic behavior of high-temperature
superconductor (HTS) applications. This article explains how to use the $T$-$A$
formulation for modeling HTS coils in 2D with different coupling scenarios
between the turns. First we consider a racetrack coil wound from one piece of
superconducting tape. Then we consider a coil obtained by winding a cable
composed of different HTS tapes. In the latter case, the tape turns are either
electrically connected along their entire length or just at the two ends of the
coil: in the model, these two different types of electrical connection are
implemented with the help of the electrical circuit module. The current density
distributions and the AC losses of the coils in the different coupling
scenarios are compared and discussed. The limits of applicability of the
presented approach are pointed out. The model is developed for the straight
section of racetrack coils, but can be easily adapted to axisymmetric
geometries.
