Describing material media

Introduction

The material media are modeled by material regions:

  • mainly volume regions in 3D problems; surface regions and line regions are also possible in 3D
  • mainly surface regions in 2D problems; line regions and point regions are also possible in 2D

For additional information about the role of regions, see chapter Physics: principles.

Material regions: overview

Volume, surface or line material regions allow the modeling of the material media (with materials). The physical properties of the medium are those of the corresponding material region.

A region… enables the modeling…
Specific Magneto Static air or vacuum of the air or vacuum (permeability μr =1)

(soft material only)
magnetic non conducting

of a region:

magnetic (permeability μr)

non-conducting
coil conductor1

of a region:

conducting with source1

non-magnetic (permeability μr =1)

→ this region represents a coil
  • constituted of a number of turns
  • passed through by a current Js
A region… enables the modeling…

Specific

Transient /

Steady state AC Magnetic

solid conductor

of a region:

magnetic (permeability μr)

conducting (resistivity ρ )

(can be: passive/active)
A region… enables the modeling…

Specific Steady state AC Magnetic 2D and 3D

 coil conductor with losses

of a region:

conducting with source1

non-magnetic (permeability μr =1)
A region… enables the modeling…

Specific Steady state AC Magnetic 3D

 solid conductor

described as surface region in surface impedance formulation2

of a region:

magnetic (permeability μr)

conducting (resistivity ρ )

characterized by:

a very small skin depth with respect to the dimensions of the region

 (passive)
Note: 1 Cf. Describing the source
Note: 2 Cf. Surface impedance condition (3D).

Thin regions

The thin region item (condition) enables modeling volume regions of small thickness using surface regions.

  • The following region types are available for a 2D application:
    • Air-gap (= Air or vacuum ) region
    • Coil conductor region
    • Solid conductor region (passive or active)*
  • The following region types are available for a 3D application:
    • Air-gap (= Air or vacuum ) region
    • Magnetic region

    • Thin conducting region (= Passive solid conductor)

      (with hyperbolic variation of current density on the region thickness)*

Note: * The feature of thin conducting regions are detailed in the next chapter (see § Thin conducting regions).

Filiform regions

The filiform region item enables the modeling of small cross-section regions.

  • The following region type is available for a 2D application:
    • Coil conductor region
  • The following region type is available for a 3D application:
    • Magnetic region

Coil conductor region with losses and detailed geometrical description

The losses in the stranded type conductors due to skin effect and to the proximity effect can be difficult to model because of the big number of elementary wires composing the conductors. To obtain an accurate calculation of these losses in high frequency applications, it is preferable to have at least two meshes within the skin depth thickness of the elementary wires. Then, the number of nodes of finite element meshing should be very high, incompatible with the currently available computation resources, especially in 3D.

In order to be able to quantify these losses in an accurate manner with a reasonable computation time and memory resources, a homogenization technique has been implemented in the Flux software through the Coil Conductor region with losses and detailed geometrical description