${\displaystyle {\alpha }_{\text{F}}=\frac{{\alpha }_{\mu }}{{\mu }_{\Theta }}=\frac{{\mu }_{\Theta }-{\mu }_{\text{ref}}}{{\mu }_{\Theta }{\mu }_{\text{ref}}\left(\Theta -{\Theta }_{\text{ref}}\right)}}$

or

${\displaystyle {\alpha }_{\text{F}}=\frac{{\alpha }_{\mu }}{{\mu }_{\text{ref}}}=\frac{{\mu }_{\Theta }-{\mu }_{\text{ref}}}{{\mu }_{\text{ref}}^2\left(\Theta -{\Theta }_{\text{ref}}\right)}}$

when µ_Θ and µ_ref differ insignificantly

Note – The temperature factor of permeability is a material property which enables to calculate the temperature coefficient of effective permeability α_µe by multiplying α_F by µ_e:

${\displaystyle {\alpha }_{\mu \text{e}}={\alpha }_{\text{F}}\cdot {\mu }_{{\text{e}}^{\cdot }}}$

${\displaystyle {\alpha }_{\text{F}}=\frac{{\alpha }_{\mu }}{{\mu }_{\Theta }}=\frac{{\mu }_{\Theta }-{\mu }_{\text{ref}}}{{\mu }_{\Theta }{\mu }_{\text{ref}}\left(\Theta -{\Theta }_{\text{ref}}\right)}}$

ou

${\displaystyle {\alpha }_{\text{F}}=\frac{{\alpha }_{\mu }}{{\mu }_{\text{ref}}}=\frac{{\mu }_{\Theta }-{\mu }_{\text{ref}}}{{\mu }_{\text{ref}}^2\left(\Theta -{\Theta }_{\text{ref}}\right)}}$

si µ_Θ et µ_ref diffèrent de manière insignifiante

Note – Le facteur de température de la perméabilité est une propriété du matériau qui permet de calculer le coefficient de température de la perméabilité effective α_µe en multipliant α_F par µ_e:

${\displaystyle {\alpha }_{\mu \text{e}}={\alpha }_{\text{F}}\cdot {\mu }_{{\text{e}}^{\cdot }}}$