Coil Groups
The Coil nodes, in 2D and 2D axisymmetry, present an additional Coil Group check box that allows to easily model one or more coil features connected in series. Each domain in the coil feature selection is considered a separate turn of the coil. Use this feature in 2D and 2D axisymmetric models for coils that cross the modeling plane more than once.
The Coil Group mode automatically sets up the relations between the variables associated to each domain. Current and voltage variables for each domain (or turn) are computed the same as for the base coil feature, while the total variables for the coil are computed using the rules for series-connection — the total voltage is the sum of the voltages, while the total current is equal to the current flowing in each domain.
Special subnodes can be added to the Coil nodes once the Coil Group check box has been selected in order to better control the setup of the connections:
Domain Group
When the Coil Group mode is active, each domain in the selection will be considered individually as a series-connected entity. The Domain Group subnode can be used to mark a group of domains which should be treated as one domain for the purpose of the coil set up. Multiple instances of this subnodes can be added to mark different groups. Domains that do not belong to a group are connected individually in series.
Reversed Current Direction
Use this subnode to mark a geometrical entity where the current flows in the opposite direction, that is antiparallel to the out-of-plane direction (z or azimuthal direction). This feature can be applied to any entity in the coil’s selection, regardless of the group (if any) it belongs to.
In COMSOL Multiphysics version 4.3a and earlier, a separate Coil Group Domain node was available. This is replaced in the current version by a Single-Turn Coil domain node with the Coil Group check box selected.