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Parameters & units ​

Every component's behaviour is set by its parameters: a resistance, a source voltage, a controller gain. This page covers the properties dialog for one component, units and per-unit bases, and the Parameter Editor for changing many components at once.

The properties dialog ​

Double-click a component (double-tap on a touch device), or right-click it and choose Properties…, to open its properties dialog. The dialog is titled after the component, for example "Resistor Properties".

  • Parameters are grouped into tabs when the component has many.
  • Some fields only appear when they matter: switch a source from DC to AC and the frequency and phase fields appear.
  • Hover or tap the info icon next to a field for what it does. The Components reference describes every parameter too.

Click OK (or press Enter) to apply your changes, or Cancel to throw them away. Nothing changes on the canvas until you click OK, and all the changes from one visit to the dialog are a single step you can undo.

If you aren't signed in, the dialog opens read-only: the buttons read Close and Sign in to edit.

Units ​

Many numeric fields have a unit dropdown right next to the number. A resistance, for example, can be entered in Ω, kΩ, pu or S (siemens, i.e. a conductance). Pick the unit the number is in:

  • Switching the unit doesn't rescale the number. 10 with kΩ selected means 10 kΩ; change the unit to Ω and it means 10 Ω.
  • NumaSim converts to the simulator's base units when you run, so you can mix units freely across a circuit.

Per-unit bases ​

When you pick pu (or another unit that needs a base) in any field, a Units tab appears in the dialog with the bases for that component:

FieldDefault
S_base (MVA)100
V_base (kV)230
Frequency (Hz)60

Each component has its own bases, so set them to match the equipment. A per-unit impedance is converted with (Z_\text{base} = V_\text{base}^2 / S_\text{base}) (kV and MVA in, Ω out). The tab disappears again when no field on the component uses a unit that needs it.

Parameters are numbers, not formulas: there are no expressions or circuit-wide variables to reference.

Copying parameters between components ​

Right-click a component and choose Copy data, then right-click another component of the same type and choose Paste data. Every parameter is copied, including signal names, so rename those afterwards if both components measure something — duplicate names stop a run.

Editing many components at once ​

Click Parameters in the status bar to open the Parameter Editor. It lists the components on the canvas:

  1. Narrow the list with the type filter (All types shows everything) and Filter by name....
  2. Tick the components you want to change, or use Select all and Invert.
  3. Choose how to edit them:
    • Per type — edit the parameters of one component type, for every selected component of that type.
    • Common parameters — edit the parameters that all the selected components share, across types.
  4. Tick the box next to each parameter you want to change, and set its value. An unticked parameter whose values differ across the selection is marked mixed; unticked parameters keep each component's own value.
  5. Click Apply to n, where n is the number of components that will change.

The Parameter Editor can also pop out into its own window, which is handy on a second screen.

Editing during a run ​

You can change parameters while a simulation is running; the change takes effect on the next run. The Time Step and Duration fields are locked until the run ends, and clicking a Switch on the canvas to change its position is disabled while running.

On a free account, a circuit over the size limit still lets you change parameter values; only structural edits are paused. See Plans & limits.

See also ​