# Meshed coils (2D/3D)

## Representation of a meshed coil in 2D

In a 2D application, a coil is represented by one surface region or by a group of surface regions of the coil conductor type.

By convention, the current is:

• positive, when it goes out the screen

• negative, when it goes into the screen

It is possible to modify the direction of the current by using the Orientation command.

## Examples (2D)

Examples of coil representation for axisymmetric 2D and plane 2D studies are shown below.

Study Real device Finite elements domain

2D axisymmetric study:

a circular coil is represented by a single region.

2D plane study:

a rectangular coil is represented by two regions:

• one for the in section
• the other for the out section

The model does not involve the forward and the backward parts of the coil.

## Representation of a meshed coil in 3D

In a 3D application, a coil is represented by a group of volume regions of the coil conductor type.

## Examples (3D)

Two examples of coil representation are presented below.

 “Open” coil “Closed” coil

## Geometric restrictions (3D)

Flux is unable to model all coil shapes.

The main rules to be observed are the following:

• generally, the changes of the section are allowed
• for open coils, the changes of the section are allowed, but the entering and the exiting faces of the current should have the same shape
• “parasite”points and lines are not allowed

A “parasite” point or line is a useless supplementary geometric entity (point or line), as presented in the right side figure (in bold)

Note: For a more complete discussion on the geometrical restrictions of 3D meshed coils, please refer to the following documentation page: Solving options and methods for estimating the current density in 3D coil conductor regions.

## Current orientation (3D)

The current orientation is set by:

• the entering and exiting faces of the current, for the open coils, and
• an orientation line for the closed coils
Note: For a more complete discussion on the current orientation of 3D meshed coils, please refer to the following documentation page: Current orientation of coil conductor regions in Flux 3D.

## Meshed coils and symmetries/ periodicities

In the presence of symmetries and/or periodicities, only the coils (or parts of coils) presented in the study domain are described. The coils (or parts of coils) symmetric and/or periodic are taken into account by means of the boundary conditions on the symmetry and/or periodicity planes.

Note: For a more complete discussion on symmeries and periodicities affecting meshed coils, please refer to the following documentation page: Coil entities in symmetrical or periodical domains.