The magnetic force components generate a reluctance force. They may be used to model position-dependent air-gaps and permanent magnet sections of translatory actuators. The position coordinate, $s$, of the mechanical actuator coincides with the variable $\ell$, which is the dimension that changes with the armature motion.

The derivative of the permeance of a component with respect to armature position is calculated as

$\frac{{\mathrm{dG}}_m}{\mathrm{dx}}\=\frac{{\mathrm{dG}}_m}{d\ell }\frac{d\ell }{\mathrm{dx}}\cdot$

The parameter $\frac{d\ell }{\mathrm{dx}}$ must be set in each component to +1 or -1, according to the definition of the armature coordinate and the position of the element in the device's magnetic circuit.

The reluctance force, $F_m$, is computed from the change in the magnetic coenergy, $W_m$, with respect to the armature position:

$F_m\=\frac{\partial }{\partial x}{W}_m\=\frac{\partial }{\partial x}\left(\frac{1}{2}{G}_m{V}_m^2\right)\=\frac{1}{2}{V}_m^2\frac{{\mathrm{dG}}_m}{\mathrm{dx}}\cdot$

Cuboid Orthogonal Flux

Cuboid Parallel Flux

Hollow Cylinder Axial Flux

Hollow Cylinder Radial Flux

Leakage Around Poles