systems.cfg - [ELECTRICAL]

This section controls everything related to the aircraft electrical systems. An electrical system is defined by its components, of which there are 5 types:

• circuits: A circuit consumes power, requiring current to function (see Circuits for governing SimVars).
• batteries: A battery is a power source with a set capacity in ampere hours (see Batteries for governing SimVars).
• alternators: The alternator is a power source dependent on an engine/APU's RPM (see Alternators for governing SimVars).
• external power: This is an external power source which delivers power as long as it is available (see External Power for governing SimVars).
• buses: a bus is what creates connections between systems and sub-systems (see General / Buses for governing SimVars).
  IMPORTANT! A system only exists if at least one bus is defined.

Each of these components can be defined multiple times as parameters within the [ELECTRICAL] configuration header. For how to access the information that these parameters add to an aircraft, please see the section on SimVars And Keys.

circuit.N

Circuits are the most used electrical components, and the circuit hash map is comprised of the following multiple key:value pairs, separated by the # symbol. This hash map takes the following form:

circuit.N = Type:<circuit_type>:<index>#Connections:<bus:max_amp>#Power:<table>#Name:<debug_name>

Note that you may have more than one circuit of the same type, in which case you would increment the <index> parameter, starting from 1. A full example of a single circuit definition would be like this:

circuit.1 = Type:CIRCUIT_GENERAL_PANEL:1#Connections:bus.1#Power:0.5,1,20.0#Name:General_Panel_Main

circuit.15 = Type:CIRCUIT_FUEL_PUMP:1#Connections:bus.2#Power:3,5,20#Name:Fuel_P_L1
circuit.16 = Type:CIRCUIT_FUEL_PUMP:2#Connections:bus.2#Power:3,5,20#Name:Fuel_P_L2
circuit.17 = Type:CIRCUIT_FUEL_PUMP:3#Connections:bus.2#Power:3,5,20#Name:Fuel_P_R1
circuit.18 = Type:CIRCUIT_FUEL_PUMP:4#Connections:bus.2#Power:3,5,20#Name:Fuel_P_R2

Power:10.0, 15.0, 20.0

circuit.N - Type

When defining circuits for the electrical system, the first parameter of the hash-map that is a variable that defines the type of circuit. The table below shows all the variables that correspond to each of the available types as well as a brief description of what that circuit controls.

circuit.N - Power

This parameter takes a table of three values to define the power consumption, where:

• 1st value: A minimum Watt consumption
• 2nd value: A maximum/ideal Watt consumption
• 3rd value: A minimum voltage

These wattage values and minimum voltage let us define a range for the resistance (Ohm) used for interpolation when selecting a power setting for a circuit. By default a circuit aims for the maximum power setting (maximum/ideal Watt consumption).

In the simulation, an aircraft circuit functions in a similar way as they do in real life. The load (in amps) drawn by a circuit is defined by the received voltage divided by it's internal resistance. Below is an example of how this key/value pair is structured:

#Power:10.0, 15.0, 20.0

Here the values represent: MinW=10W, MaxW=15W, MinV=20.0V.

Generated values for resistance are:

• ResMin(Ohm) = 20.0/(10.0/20.0) # MinV / (MinW/MinV) -> resistance for min power setting
• ResMax(Ohm) = 20.0/(15.0/20.0) # MinV / (MaxW/MinV) -> resistance for max power setting

Which means (using Ohm's law) that the circuit will consume:

• I(Amps) = (Voltage / Resistance)
• I(Amps) = 20.0 / ResMax(Ohm) = 0.75A (at 20.0V and max power setting)
• I(Amps) = 28.0 / ResMax(Ohm) = 1.05A (at 28.0V and max power setting)
• I(Amps) = 20.0 / ResMin(Ohm) = 0.5A (at 20.0V and min power setting)
• I(Amps) = 28.0 / ResMin(Ohm) = 0.7A (at 28.0V and min power setting)

The power setting lets us have a variable resistance which can be used for any purposes. For example interior lights use this power setting for dimming. Moreover, in some situations, power might be limited. If the whole system is working using alternators then the power generated might not be enough to sustain every circuit. The power allocated to each circuit is then balanced as a proportion of the circuit MaxW value. A circuit will stay powered as long as the received power is higher than the MinW value and voltage is higher than MinV. This let us define priority in which system gets turned off first by lack of power. Reducing a circuit power setting will give more energy to the other circuits.

battery.N

A battery is a power supplier with a set capacity that decreases over time depending on the load it must sustain. The battery hash map is comprised of a set of key:value pairs, separated by the # symbol and takes the following form:

battery.N = Connections:<buses>#Capacity:<value>#Voltage:<curve_ref>#Name:<debug_name>

A full example of a single battery definition would be like this:

battery.1 = Connections:bus.3#Capacity:13.6#Voltage:curve.1#Name:Main_Battery

alternator.N

This defines an alternator power source dependent on an engine/APU's RPM, and the appended number corresponds to its unique ID (N, starting at 1). The alternator hash map is comprised of key:value pairs, separated by the # symbol, and takes the following form:

alternator.N = Connections:<buses>#iEng:<value>#Voltage:<curve_ref>#load:<curve_ref>#Name:<debug_name>

or:

alternator.N = Connections:<buses>#iEng:<value>#RatedVoltage:<value>#load:<curve_ref>#Name:<debug_name>

A full example of a single alternator definition would be like this:

alternator.1 = Connections:bus.3#iEng:0#RatedVoltage:28#Load:curve.3#Name:LH_Alternator

externalpower.N

An external power source is a power supplier with a constant and infinite power output, and the appended number corresponds to its unique ID (N, starting at 1). The external power hash map is comprised of key:value pairs, separated by the # symbol, and takes the following form:

externalpower.N = Connections:<buses>#RatedVoltage:<value>#Load:<value>#Name:<debug_name>

A full example of a single external power source definition would be like this:

externalpower.1 = Connections:bus.8#RatedVoltage:28.5#Load:400

bus.N

A bus is a hub for connecting different components (and other buses) to each other, and the appended number corresponds to its unique ID (N, starting at 1). The bus hash map is comprised of key:value pairs, separated by the # symbol, and takes the following form:

bus.N = Connections:<buses>#Name:<debug_name>

A full example of a single bus definition would be like this:

bus.3 = Connections:bus.1, bus.2#Name:Hot_Battery_BUS

curve.N

The curve parameter is defined as a 1D table of paired values, and the parameter is appended with a number that corresponds to its unique ID (N, starting at 1). The exact number of paired values that are in the curve will depend on the use the curve is going to get, since curves are used by other parameters to store information. For example, you may have defined a battery like this:

battery.1 = Connections:bus.3,bus.5#Capacity:15.5#Voltage:curve.1#Name:Battery_Main

In this case, curve.1 references the battery voltage capacity, and would have been defined like this:

curve.1 = 0:21, 0.1:10.5, 0.5:12, 0.9:13, 1:13.4

procedure.N

Procedures are a set of actions that can either be manually triggered or triggered when entering a given context. Procedures are created one at a time and appended with a number that corresponds to its unique ID (N, starting at 1). They consist of a context and then a series of paired values telling the simulation what procedures (actions) to carry out within that context. The general structure for a procedure is as follow:

procedure.1 = <Context>#<action:id>,<value>#<action:id>,<value>#<action:id>,<value>#...

When creating the procedure, the context can only be one of the following three constants:

Once you have the given context, you can add in the actions to be performed when the procedure is triggered (either manually or automatically) with each action separated by a #. Every action takes a given number of arguments and will manipulate the state of the system, and the actions themselves can only be one of the following constants:

To see how this works in practice, let's look at the following example: 

procedure.1 = None#SetCir:5,0#SetBat:1,1#SetBus2Bus_Con:1,4,1

In this example, the procedure will perform the following three actions when it is manually triggered (the context None will only work with manual triggers):

• SetCir:5,0: Turn off the circuit with ID 5
• SetBat:3,1: Turn on the battery with ID 3
• SetBus2Bus_Con:1,4,1: Sets the bus with ID 1 to transfer electricity to the bus with ID 4  

Triggering Procedures

As mentioned above, procedures can be manually triggered and/or auto triggered. Auto triggering is performed on engine start or shutdown - assuming the correct context is used - but manual triggering requires using the key event ELECTRICAL_EXECUTE_PROCEDURE (in WebAssembly or RPN or any other source). This key event requires 2 arguments to be passed with it, although the second one is optional:

• [0] = Procedure ID: This is the ID of the procedure to be triggered, for example to to trigger procedure.3 the index would be 3.
• [1] = bInverse: This is a boolean value that, if omitted, will default to 0 (FALSE). If it is set to 1 (TRUE) then the procedure boolean values will be inverted when executing the procedure. For example, if the procedure has the action SetCir:5,0, it will then become SetCir:5,1.

Connections

Connections define links between buses and power suppliers/consumers, and they are used in the circuit.N, battery.N, alternator.N, externalpower.N and bus.N parameters within the electrical system.

When defining a connection you need to give at least one target bus, specifying the ID value, eg:

Connections:bus.1, bus.3

You may also, optionally, give a maximum amp value for the bus, separating it from the bus ID using a ":". For example:

Connections:bus.1:3.25, bus.3:2.66

This amp value is the amperage above which the breaker will automatically trigger, cutting the power flow through the bus. If this amp value is not defined, then the default behaviour is for the connection to sustain an infinite current.

Keys

The table below shows the different key event IDs that can be used to modify things within the electrical system of an aircraft. These would be used along with the Aircraft Electrics Variables (as explained in the section SimVars And Keys):