14.5. Static (DC) Electric Circuit Analysis

In a static (DC) electric circuit analysis, you determine the voltage and current distribution in an electric circuit that is subjected to applied DC source voltages or currents. Static circuit analyses allow all circuit components.

14.5.1. Building a Circuit for Static Analysis

In a static analysis, the program treats capacitors as open circuits and inductors as short circuits. To represent a short circuit condition, couple the two nodes of the inductor in the VOLT degree of freedom, using one of the following:

Command(s): CP
GUI: Main Menu> Preprocessor> Coupling/Ceqn> Couple DOFs

Once you have built the circuit, you apply loads and obtain the solution, then view the results.

14.5.2. Applying Loads and Solving the Static Analysis

You need to define the analysis type and options, apply loads, and initiate the finite element solution. To accomplish these tasks, follow the steps listed below.

14.5.2.1. Enter the SOLUTION Processor

To enter the SOLUTION processor, use either of the following:

Command(s): /SOLU
GUI: Main Menu> Solution

14.5.2.2. Define the Analysis Type

To specify the analysis type, do either of the following:

  • In the GUI, choose menu path Main Menu> Solution> Analysis Type> New Analysis and choose a Static analysis.

  • If this is a new analysis, issue the command ANTYPE,STATIC,NEW.

Restarting an analysis usually is required only for continuing a transient circuit analysis.

14.5.2.3. Apply Loads on the Model

Normally, you specify source loads for circuits in the Circuit Builder, as element real constants. Besides the source loads, the only other "load" is a VOLT = 0 specification at the ground nodes. To specify VOLT = 0, use either of the following:

Command(s): D
GUI: Main Menu> Solution> Define Loads> Apply> Electric> Boundary> Voltage> On Nodes

Should you need to modify the source loads, use one of the following:

Command(s): R, RMODIF
GUI: Main Menu> Solution> Load Step Opts> Other> Real Constants> Add/Edit/Delete The RMODIF command has no GUI equivalent.

14.5.2.4. Copy the Database

Use either the SAVE command or the SAVE_DB button on the Toolbar to save a backup copy of the database.

14.5.2.5. Start the Solution

To start calculating the solution, use one of the following:

Command(s): SOLVE
GUI: Main Menu> Solution> Solve> Current LS

14.5.2.6. Apply Additional Loads

If you want to apply additional loads, repeat steps 3 and 4.

14.5.2.7. Finish the Solution

To leave the SOLUTION processor, use one of the following:

Command(s): FINISH
GUI: Main Menu> Finish

14.5.3. Reviewing Results from a Static Circuit Analysis

The program writes results from a static (DC) circuit analysis to the results file, Jobname.rth. The results are two types of primary data: nodal voltages (VOLT) and nodal currents (CURR). The following derived data calculated for each element also are available:

  • Element voltage drop (VOLTAGE)

  • Element current (CURRENT)

  • Element control voltage (CONTROL VOLT)

  • Element control current (CONTROL CURR)

  • Element power (POWER)

  • Element applied load (SOURCE)

For more information about the derived results, see the Element Reference.

You can review analysis results in POST1, the general postprocessor, by choosing either of the following:

Command(s): /POST1
GUI: Main Menu> General Postproc

To review results in POST1, the database must contain the same model for which the solution was calculated. Also, the results file (Jobname.rth) must be available.

To read the data from the results file into the database, use either of the following:

Command(s): SET
GUI: Utility Menu> List> Results> Load Step Summary

Once the database contains the desired set of results, use one of the following to list the primary nodal data (voltages and currents):

Command(s): PRNSOL
GUI: Main Menu> General Postproc> List Results> Nodal Solution

To list the derived element results, use one of the following:

Command(s): PRESOL
GUI: Main Menu> General Postproc> List Results> Element Solution