If-Equation

1 Electrical units

type Voltage = Real(unit = "V");
type Current = Real(unit = "A");

2 Electrical Connectors

connector Pin Voltage v; flow Current i; end Pin;

3 Electrical Components

TwoPin is a partial class, which means that it is not possible to make instances of it but it can be extended.

partial class TwoPin "Superclass of elements with two electrical pins" Pin p, n; Voltage v; Current i; equation v = p.v - n.v; p.i + n.i = 0; i = p.i; end TwoPin;

4 Diode

Conditional expressions or equations describe discontinuous and conditional models. When writing conditional expressions no end if is needed. If the condition has more than two options then it is not enough with an else-statement to express this, so we have to add one or more elseif-statements.

model Diode "Ideal diode" extends TwoPin; Real s; Boolean off; equation off = s < 0; if off then v = s; else v = 0; // Conditional equations end if; i = if off then 0 else s; // Conditional expression end Diode;

Load the Modelica Standard Library in order to be able to import as below.

loadModel(Modelica)

We construct a circuit with a diode.

model Circuit import Modelica.Electrical.Analog.Basic.*; import Modelica.Electrical.Analog.Sources.*; Diode d(s(start = 0)); Resistor R1 (R = 2.0); Ground G; SineVoltage src (V = 3.0, freqHz = 5.0); equation connect(G.p,src.n); connect(src.p,R1.n); connect(R1.p,d.n); connect(d.p,src.n); end Circuit;

4.1 Simulation of circuit

simulate( Circuit, stopTime=10 )
plot(d.off)