Solving

The problem physics lives under Solver. The Magnetic field node is created with the project; the + next to Model creates other physics, such as an external circuit. The ▶ button solves (generating the mesh first if needed), and messages explain what is missing: a region without a material, no boundary with a prescribed A, an invalid B-H curve…

Currents

Each physics has its own Currents section, with the current of each circuit and of each region with its own current. The values apply to that physics only: a static, an AC and a transient study can have different currents in the same project. In the console: s.current("n2", "Coil", "10*sin(2*pi*60*t)").

Analysis types

In the physics properties, choose the analysis:

Analysis	What it solves	Parameters
Magnetostatic	fields from DC currents and magnets	—
Harmonic (AC)	sinusoidal steady state, with phasors	frequency (Hz)
Transient	time evolution, with eddy currents	time step Δt and end time

Magnetostatic

Solves −∇·(ν∇A) = J (plus the magnet term) with A_z in planar problems or ψ = r·A_φ in axisymmetric ones. If any material has a B-H curve, the problem is nonlinear and solved by Newton-Raphson with a line search; the number of iterations is shown with the results.

Harmonic (AC)

Currents are peak amplitudes at the given frequency. Conductors with σ > 0 and no source carry eddy currents. Materials with a B-H curve use the effective permeability (as in FEMM), iterated until it converges. Results can be viewed over one period, A(t) = Re(Â e^{jωt}), and surface integrals give eddy-current losses and iron losses (Steinmetz, with the material coefficients).

Transient

Implicit Euler with time step Δt up to the end time. Currents can be functions of t, for example 10*sin(2*pi*60*t) or 5*min(1, t/0.002) (a 2 ms ramp up to 5 A); conductors without a source carry eddy currents; steel is nonlinear at every step. In the results, the view gets a time bar and table items become curves over time.

External circuit

With the Circuit physics, coils of the model join a schematic with sources, resistors, inductors and capacitors, solved together with the field (strong coupling). See External circuit.

Performance

The solver runs in a Web Worker, in WebAssembly, without freezing the interface. Problems with tens of thousands of elements solve in seconds in linear magnetostatics. The matrix is sparse, solved by LDLᵀ (static) or LU (AC and circuit). See the formulation for details.