The relative permeability mu_r as a function of flux density B for all soft magnetic materials currently included in this library is approximated with the following function [Ro00]:
Two of the five parameters of this equation have a physical meaning, namely the initial relative permeability mu_i at B=0 and the magnetic flux density at maximum permeability B_myMax. B_N is the flux density normalized to latter parameter.
function mu_rApprox extends Modelica.Icons.Function; input SI.MagneticFluxDensity B "Flux density in ferromagnetic flux tube element"; input SI.RelativePermeability mu_i "Initial relative permeability at B=0"; input SI.MagneticFluxDensity B_myMax "Flux density at maximum relative permeability"; input Real c_a "Coefficient of approximation function"; input Real c_b "Coefficient of approximation function"; input Real n "Exponent of approximation function"; output SI.RelativePermeability mu_r "Relative magnetic permeability of ferromagnetic flux tube element"; end mu_rApprox;