When a non-magnetic armour is present, $R_s$ is replaced by $R_e$ in the following formulas.

Symbol
$M_{\mathrm{e}}$
Unit
-
Formulae
$\frac{R_{\mathrm{s}}}{X_{\mathrm{s}}}$trefoil arrangement
$\frac{R_{\mathrm{s}}}{X_{\mathrm{m}} + X_{\mathrm{s}}}$flat arrangement
Related
$R_{\mathrm{e}}$
$X_{\mathrm{m}}$
$X_{\mathrm{s}}$
Used in
$F_{\mathrm{e}}$