# 2D plane / axisymmetric study, 3D study

## Preliminary consideration

Before starting the description of a device, it is necessary to answer the following questions:

• What type of study is possible to carry out on this device?
• What application should be used: 2D or 3D?

## Different study types

It is possible to distinguish the following different study types.

Study type Device characteristics Geometric representation
2D plane device supposed infinitely long in one direction in a cross section plane

2D axi

symmetric

device having a revolution symmetry around an axis in a cross section plane
3D unspecified complete

## 2D plane study: characteristics

It is possible to carry out a 2D plane study if the device is supposed infinitely long in one direction.

The geometric representation of the device is carried out in a cross section plane (perpendicular to this direction).

The device depth is taken into account (at physical level) to compute the global quantities (force, energy…)

Example

## 2D plane study: working assumptions

Working assumptions:

The device is supposed infinitely long along a direction (depth).

The magnetic flux is concentrated on the cross section plane, there is no extremity effect (magnetic flux leakage) in the 3 rd direction (depth).

Possible interpretations of these working assumptions:

• The air gap thickness is reduced with respect to the device depth.
• There is no leakage in the third direction.

## Example: 2D plane study or 3D study?

Two devices are represented in the figure below. These two devices are built on the same support (from the geometric point of view), but they do not function in the same way (from physical point of view).

 Device consisting of: two magnets in opposition two magnetic cores (2 yokes) Device consisting of: two inductors (in opposition) a magnetic circuit Long device, but important 3D effect (leakage at extremities) Long device and magnetic flux concentrated in the magnetic circuit

Discussion on the 2D / 3D choice:

• From geometric point of view:

These two devices can be described on cross section planes. Thus, a 2D study can be considered in both situations.

• From physical point of view:
• a 3D study is recommended in the 1st situation, because there is an important magnetic flux leakage at the back and in the front of the device (due to the magnets in opposition).
• a 2D study is recommended in the 2nd situation, because the magnetic fluxes, created by the inductors, have the same orientation. Thus, the magnetic flux is strongly confined in the magnetic circuit, and therefore in the cross section plane.

## 3D study

In this type of study any geometry can be represented, but within the software possibilities limits.

## 2D axisymmetric study: characteristics

It is possible to carry out a 2D axisymmetric study if the device has revolution symmetry around one of the axis.

The geometric representation of the device is carried out on a cross section plane.

Pay attention, the revolution axis of the geometry should be obligatorily vertical and should pass through the origin of the coordinate system.

Although we speak about a 2D study (plane geometric representation), we deal in fact with a 3D study. The device is entirely modeled, the global results being provided for the whole volume of the device.

Example

## Choice of the application

The choice of the application (2D or 3D) is carried out at supervisor level (Flux 2D or Flux 3D tabs).