Circuit Module Documentation

Module: src/circuit (belfem::electronics) Date: 2026-06-28

A lumped-element circuit simulator embedded in BELFEM. It supplies/receives terminal current and voltage to/from the Maxwell FEM problem (h-φ), and models the external power supply, dump resistors, charge/dump inductors, filter capacitors, switches, diodes and lumped HTS branches around a superconducting magnet.

Documents

Document	Contents
circuit_usage_guide.md	Full usage guide: driving the circuit from belfem, the circuit{} input format, every available component, FEM coupling via terminal pairs/curves, source functions, the MNA + Newton + BDF numerics, a worked example, and pitfalls

Quick reference

Topic	Where
Entry point from the executable	src/executables/belfem.cpp:164 (ElectricalCircuitFactory)
Reads the circuit{} section	cl_ElectricalCircuitFactory.cpp
MNA / Jacobian / solve / timestep	cl_ElectricalCircuit.cpp
Abstract interface used by the FEM controller	src/numerics/sources/cl_Circuit.hpp
Time-dependent excitation	src/numerics/sources/cl_SourceFunction.hpp
Component list	Component_Enums.hpp

Available components

resistor, capacitor, inductor, voltage source, current source, switch, diode, superconductor, terminal pair (FEM-coupling). See the usage guide §4 for the per-component key tables.

Related

• src/circuit/doc/notes.md — refactoring notes (namespace, dependency inversion).
• todo/ngspice_parser_plan.md — the ngspice/SPICE netlist importer and a proposed standalone circuit-only runner. The parser shipped: cl_NetlistParser and cl_NgspiceCircuitFactory exist, and a deck reads a netlist through circuit { file : … }. No circuitrun executable exists, and that part remains deferred.