About orientation of magnets

Definition

Before discussing the magnet orientation, the concept of magnet in Flux must be defined specifying the point of view it is related to.

for magnet manufacturers:
- a material for an isotropic magnet is a material with identical magnetic characteristics in all directions; the magnetization process of the magnet will lead to the same result in any direction
- a material for an anisotropic magnet has a preferred direction of magnetization; it will be magnetized in this direction
in the Flux software:
a material of the magnet type is a magnetized magnet ; it has a preferred direction - its direction of magnetization

Consequence

A magnet must be oriented in the region it is affected in.

Various models

The various types (models) provided for the magnets are presented in chapter Materials: principles (§B(H) law: models for hard materials).

The distinction between the unidirectional model and the vector model is explained in the two tables below:


In a model of the “unidirectional” type the mathematical model and the direction of magnetization are dissociated
Definition		Use
Module of Br	Direction (in a plane XOY) unidirectional radial orthoradial	A single material can be used for definition of several regions (with different directions of magnetization)


In a model of the “vector” type (linear approximation only) the mathematical model and the direction of magnetization are associated
Definition	Use
Components of Br in a cartesian coordinate system Components of Br in a cylindrical coordinate system Components of Br in a spherical coordinate system	It is necessary to create the same number of materials and/or coordinate systems as the regions

Orientation of unidirectional magnets: principle

For a unidirectional magnet, there is no information (at the level of the definition of the material) on the direction of magnetization.

To “orient a unidirectional magnet in a region”, one must:

choose the type of orientation
define the characteristics of this type

The principle of orientation for a unidirectional magnet in a region is presented in the figure below. (The basic plane is a XOY plane)


Type of orientation	Scheme		Description characteristics
Unidirectional			Coordinate system θ angle
Radial positive / negative			Coordinate system Coordinates of the center of radiality (CR)
Orthoradial positive / negative			Coordinate system Coordinates of the center of radiality (CR)

Orientation of vector magnets: principle

For a vector magnet, the direction of magnetization is defined in a virtual coordinate system.

To “orient a (cartesian, cylindrical, spherical) vector magnet in a region”, one must choose a coordinate system for orientation (real coordinate system).

The principle of orientation for a vector magnet (cartesian) in a region is presented in the figure below:

!!! Magnets and thin or filiform region

Everything that was previously stated concerns the massive regions (volume regions in 3D / face regions in 2D).

Generally speaking, the models for magnets cannot be used in thin or filiform regions (3D exception: see next block).

3D exception

In 3D, it is possible to use the magnet models in thin regions (face regions).

Attention: When we use a magnet model for a thin region, the user must verify the coherence between the direction of magnetic field and the direction of magnetization. This problem of coherence is presented in the table below:


During …	the user chooses …
the creation of thin region	the direction of magnetic flux: no restriction quasi normal quasi tangential
the orientation of magnet	the direction of magnetization: see previous block

In order to avoid any problem of coherence on the direction of the magnetic flux, it is advised to use the option “no restriction on the direction of the magnetic flux”.