Circuit Elements Reference

Circuit elements are ideal representations of electric components. A circuit element has two or more terminals, through which electric current flows in or out of the element. A terminal can be grounded or connected to the terminal of another circuit element.

Circuit Elements Node Right-Click Actions

New Circuit Element

Adds a circuit element to the circuit. The available options are:

Battery Circuit Element
Available only when the Battery model is activated in the physics continuum.
Multicontact Circuit Element
Diode Circuit Element
Program Circuit Element
Available only when the Battery model is activated in the physics continuum.
Scalar Circuit Element
Creates a Resistance, Inductance, Capacitance, Current, Voltage, or Power element, according to the Load Type property setting.
Table Circuit Element
Excitation Coil Circuit Element
Available only when the Excitation Coil model is active in the physics continuum.

See Circuit Elements.

Circuit Element Properties

The Circuit model supports the following circuit elements:

Resistance

Defines an ideal resistor with resistance

R

The voltage-current relationship for a resistor is: $V (t) = R I (t)$

Resistance element properties:

Load Type: Specifies the method for defining the circuit element. Set to Resistance.
Load: Defines the load resistance (ohm). The resistance can be a constant value or a scalar expression.

Capacitance

Defines an ideal capacitor with capacitance

C > 0

The voltage-current relationship for a capacitor is: $I (t) = C (d V (t) / d t)$ .

Capacitance element properties and nodes:

Load Type: Specifies the method for defining the circuit element. Set to Capacitance.
Load: Defines the load capacitance (farad). The capacitance can be a constant value or a scalar expression, but must be positive.
Initial Condition: Lets you set the initial value of the voltage across the element using a constant or a scalar expression.

Inductance

Defines an ideal inductor with inductance

L > 0

The voltage-current relationship for an inductor is: $V (t) = L (d I (t) / d t)$ .

Inductance element properties and nodes:

Load Type: Specifies the method for defining the circuit element. Set to Inductance.
Load: Defines the load inductance (H). The inductance can be a constant value or a scalar expression, but must be positive.
Initial Condition: Lets you set the initial value of the electric current through the element using a constant or a scalar expression.

Current

Defines an electric current through the element.

Current element properties:

Load Type: Specifies the method for defining the circuit element. Set to Current.
Load: Defines the load current (A). The current can be a constant value or a scalar expression.

Voltage

Defines the voltage across the element.

Voltage element properties:

Load Type: Specifies the method for defining the circuit element. Set to Voltage.
Load: Defines the load voltage (V). The voltage can be a constant value or a scalar expression. For the voltage load element to act as a voltage source, specify a negative value.

Power

Defines the power demand of the element. Use the power element only when the current or voltage stays either positive or negative throughout the simulation. If one of these two quantities (either current or voltage) crosses zero, the other quantity (voltage if current crosses zero) diverges until it reaches the bounds set in the initial conditions.

The power element is defined by a first-order delay due to the discretization scheme. This means the desired power is not applied instantaneously. Instead, the power is applied with respect to the transient effects of the circuit.

The current-voltage relationship for a power element is: $P = I V$

Power element properties and nodes:

Load Type

Specifies the method for defining the circuit element. Set to Power.

Load

Defines the power. The power can be a constant value or a scalar expression. For a power load, specify a positive value.

Relaxation Parameter

Defines the lag time for the element (that is, how quickly the element applies a power change from external conditions to the rest of the circuit). The parameter must be a positive constant value.

Initial Conditions

Depending on the selected Causality Type, you can specify the initial current or voltage values as well as their maximum and minimum values.

Current (fixed current sources or inductive components)—allows you to specify the initial current value as well as the maximum and minimum values of voltage.
Voltage (fixed voltage sources or capacitive components, such as a battery)—allows you to specify the initial voltage value as well as the maximum and minimum values of current.

Depending on how you define the external circuit, the current and voltage solution can be different for the same power specified. The solution provided by the simulation depends on the initial conditions specified.

Diode

Defines a diode component. Diodes have low resistance in one direction (the forward direction) and high resistance in the other direction (the reverse direction), causing electric current to flow mainly in the forward direction.

Diode element properties:

Forward Voltage: Specifies the voltage value above which the diode conducts current. If the voltage across the diode exceeds the specified value, the diode behaves like a linear resistor plus a series voltage source. If the voltage across the diode is less than the specified value, the diode behaves like a linear resistor with low conductance.
On Resistance: Specifies the resistance of the diode when the voltage exceeds the specified Forward Voltage.
Off Conductance: Specifies the conductance of the diode when the voltage is less than the specified Forward Voltage. For a forced current in the reverse direction, you should expect a large voltage jump in accordance with the specified Off Conductance.

Joint

Allows multiple connections, so that many terminals can act together as a single terminal. Joints are removed when the circuit is passed to the solver.

Table

Defines a circuit load as a function of time using tabular data.

Table element properties and nodes:

Load Type: Specifies the method for defining the circuit load. The available types are Resistance, Capacitance, Inductance, Current, Voltage, and Power, as described above.
Table: Allows you to select the table that contains the data, from tables imported under the Tools > Tables node.
The input table must have a column with time values and a column with the load values. You can define the units in the column heading using parentheses, for example, Time (min). Simcenter STAR-CCM+ converts these units to the default SI units. If you do not specify any units, Simcenter STAR-CCM+ imports the values in the default units.
Time Data: Specifies the column that contains the time values.
Load Data: Specifies the column that contains the load values.
The values are linearly interpolated to provide data at all time-steps.
Initial Condition: If the element has an inductance load, you set the initial value of the electric current through the element. If the element has a capacitance load, you set the initial value of the voltage across the element.

Multicontact

Defines a group of connected contacts with known resistance and inductance (representing, for example, a group of connected coils).

Multicontact element properties and nodes:

Number of Contacts: Defines the number of contacts $n$ . One negative contact represents the voltage reference; $n - 1$ positive contacts represent the connected group of coils.
Resistance Matrix, Inductance Matrix: These nodes allow you to define the resistance and inductance of the connected contacts as $(n - 1) \times (n - 1)$ symmetric matrices, where n is the number of contacts. The diagonal components represent the resistance or inductance from each positive contact to the negative contact. The off-diagonal components represent the mutual resistance or mutual inductance between pairs of positive contacts.
Initial Condition: These nodes lets you set the initial value of the electric current for each terminal using a constant or a scalar expression.

Excitation Coil

Connects a coil region, or group of regions, from a 2D or 3D electromagnetic analysis to the circuit. You can define the coil element using either the electromotive force or the lumped parameters (resistance and inductance) computed for the coil region. This element type is available only when a magnetic vector potential model and an excitation coil model are active in one or more physics continua.

The Excitation Coil circuit element has the following properties and nodes:

Regions

Allows you to select the regions that represent the excitation coil, or group of coils. The physics continuum associated with the coil regions requires either the Excitation Coil model or the Finite Element Excitation Coil model, and one of the magnetic vector potential models. Optionally, you can activate the Excitation Coil Lumped Parameters model, which calculates the resistance and inductance of the coil region.

Load Type

Specifies the quantity that defines the coil element. The available methods are:

Voltage Source	Defines the coil element using the electromotive force computed in the selected coil regions.
Compound	Defines the coil element using the lumped parameters (resistance and inductance) computed in the selected coil regions. Requires the Excitation Coil Lumped Parameters model.

Periodicity Factor

In some cases, the associated regions represent only a sector of the full model, that is, the full domain is geometrically reduced using symmetry conditions. For these cases, the periodicity factor scales the values of resistance and inductance, extracted for the associated regions, to reconstruct the values for the full domain.

For axisymmetric models, you typically set the periodicity factor to <1 rev> or <360 deg>. For sectors of domains with repeating geometries, you set the periodicity factor to the number of copies of the sector that are required to replicate the full domain.

Initial Condition

Lets you set the initial value of the electric current through the element using a constant or a scalar expression.

Voltage Source Option

Available for excitation coil elements with a Compound load. When you set this option to Motion Induced, Simcenter STAR-CCM+ accounts for any voltage that is induced in the coil region by motion.

Battery

Allows you to connect a battery module from a battery simulation to the circuit. This element type is available only when the Battery model is active in one or more physics continua.

Battery element properties:

Battery Assembly: Specifies the appropriate battery module.

Program

Allows you to define a load using a program file (.prg) prepared in Simcenter Battery Design Studio. These program files define charging, discharging, and resting procedures for batteries (see Preparing Files in Simcenter Battery Design Studio). This element type is available only when the Battery model is active in one or more physics continua.

Program element properties:

Program Data: Specifies the .prg file that defines the electrical load. The program file contains one or more lines of input that specify the load type (voltage, current, resistance, or power), the numerical value of the load, and the time duration for the load.

Circuit Element Terminal Properties

Each circuit element has two or more terminals, through which electric current flows in or out of the element. A terminal can be grounded or connected to the terminal of another circuit element.

[circuit element terminal or contact]

Terminals and contacts connect different circuit elements or are grounded. All circuit elements other than multicontact circuit elements have a positive and a negative terminal. Multicontact elements with n contacts have one negative contact and

n - 1

positive contacts.

Each terminal and contact node has the following properties:

Connection: Displays the name of the connection to which the terminal is assigned.
Grounded: When activated, the terminal is grounded, or earthed.
The maximum number of grounded terminal in a circuit is specified in the Number of Allowed Groundings property of the circuit. By default, this value is 1.

[circuit element] Right-click Actions

The following right-click action is available for excitation coil elements when the Excitation Coil Lumped Parameter model is activated.

Create Reports

Creates the following reports for the coil element under the Reports node:

[circuit element] Excitation Coil Conductor Resistance
[circuit element] Magnetic Flux Linkage
[circuit element] Magnetic Inductance
[circuit element] Magnetic Motion Induced Voltage

For a description of each report, see Excitation Coil Model Reference and Excitation Coil Lumped Parameter Model Reference.