
QuickField can solve both linear and nonlinear magnetic problems. Magnetic field may be induced by the concentrated or distributed currents, permanent magnets or external magnetic fields.
The magnetic problem is formulated as the Poisson's equation for vector magnetic potential A (B = curl A, B  magnetic flux density vector). The flux density is assumed to lie in the plane of model (xy or zr), while the vector of electric current density j and the vector potential A are orthogonal to it. Only j_{z} and A_{z} in planar or j_{θ} and A_{θ} in axisymmetric case are not equal to zero. We will denote them simply j and A. The equation for planar case is
and for axisymmetric case is
where components of magnetic permeability tensor μ_{x} and μ_{y} (μ_{z} and μ_{r}), components of coercive force vector H_{cx} and H_{cy} (H_{cz} and H_{cr}), and current density j are constants within each block of the model.
Note. Isotropic (μ_{x} = μ_{y} or μ_{z} = μ_{r}) but field dependent permeability is assumed in nonlinear case. Magnetization characteristic of material is described by the BH curve.