Connectors

The Modelica standard library defines the most important elementary connectors in various domains. If any possible, a user should utilize these connectors in order that components from the Modelica Standard Library and from other libraries can be combined without problems. The following elementary connectors are defined (potential variables are connector variables without the flow attribute, flow variables are connector variables that have the flow attribute):

domain	pot. variables	flow variables	connector definition	icons
electrical analog	electrical potential	electrical current	Modelica.Electrical.Analog.Interfaces Pin, PositivePin, NegativePin
electrical multi-phase	vector of electrical pins		Modelica.Electrical.MultiPhase.Interfaces Plug, PositivePlug, NegativePlug
electrical sphace phasor	2 electrical potentials	2 electrical currents	Modelica.Electrical.Machines.Interfaces SpacePhasor
magnetic	magnetic potential	magnetic flux	Modelica.Magnetic.FluxTubes.Interfaces MagneticPort, PositiveMagneticPort, NegativeMagneticPort
translational	distance	cut-force	Modelica.Mechanics.Translational.Interfaces Flange_a, Flange_b
rotational	angle	cut-torque	Modelica.Mechanics.Rotational.Interfaces Flange_a, Flange_b
3-dim. mechanics	position vector orientation object	cut-force vector cut-torque vector	Modelica.Mechanics.MultiBody.Interfaces Frame, Frame_a, Frame_b, Frame_resolve
simple fluid flow	pressure specific enthalpy	mass flow rate enthalpy flow rate	Modelica.Thermal.FluidHeatFlow.Interfaces FlowPort, FlowPort_a, FlowPort_b
heat transfer	temperature	heat flow rate	Modelica.Thermal.HeatTransfer.Interfaces HeatPort, HeatPort_a, HeatPort_b
block diagram	Real variable Integer variable Boolean variable	---	Modelica.Blocks.Interfaces RealSignal, RealInput, RealOutput IntegerSignal, IntegerInput, IntegerOutput BooleanSignal, BooleanInput, BooleanOutput
state machine	Boolean variables (occupied, set, available, reset)	---	Modelica.StateGraph.Interfaces Step_in, Step_out, Transition_in, Transition_out
Connectors from other libraries
hydraulic	pressure	volume flow rate	HyLibLight.Interfaces Port_A, Port_b
pneumatic	pressure	mass flow rate	PneuLibLight.Interfaces Port_1, Port_2

In all domains, usually 2 connectors are defined. The variable declarations are identical, only the icons are different in order that it is easy to distinguish connectors of the same domain that are attached at the same component.

Modelica supports also hierarchical connectors, in a similar way as hierarchical models. As a result, it is, e.g., possible, to collect elementary connectors together. For example, an electrical plug consisting of two electrical pins can be defined as:

   connector Plug
   import Modelica.Electrical.Analog.Interfaces;
   Interfaces.PositivePin phase;
   Interfaces.NegativePin ground;
end Plug;

With one connect(..) equation, either two plugs can be connected (and therefore implicitly also the phase and ground pins) or a Pin connector can be directly connected to the phase or ground of a Plug connector, such as "connect(resistor.p, plug.phase)".