Magnet (unidirectional): linear approximation

Presentation

This model (Linear magnet described by the Br module) defines a B(H) dependence of linear demagnetization.

Main characteristics:

• the mathematical model and the direction of magnetization are dissociated
• a single material for description of several regions

Mathematical model

In the direction of magnetization the model is a straight line.

The corresponding mathematical formula is written as follows:

B_//(H)= μ₀μ_r//H_//+B_r

where:

• μ₀ is the permeability of vacuum, μ₀ = 4 π 10^-7 H/m
• μ_r// is the relative permeability (recoil line slope)
• B_r is the remanent flux density T

The shape of the B(H) dependence in the direction of magnetization is given in the following figure.

In transversal directions one can write:

B_⊥(H)= μ₀μ_r⊥H_⊥

where μ_r⊥ is the transverse relative permeability (μ_r⊥ = μ_r//)

Direction of magnetization

The direction of permanent magnet magnetization is “dissociated” from the model. In the software, it is defined separately.

The various possibilities available to the user are shown in the table below. (The basic plane is a plane XOY.)

Unidirectional	Radial positive	Radial negative	Orthoradial positive	Orthoradial negative

CR is the radiality center.