FAQ

How to choose a value for dt and Tscreen?
It depends on the type of application. As a general rule of thumb, dt is selected such that it is 10 to 100 times smaller than the smallest time transient occurring in your simulation. For example, if the switching frequency equals 20kHz, the period equals 50μs. To have at least an accuracy of 1% in the dutycycle, time steps of 50μs/100=500ns should be considered. Therefore a timestep of at least dt=500ns or even more accurate dt=100ns should be selected. Tscreen can be chosen such to have at least 1000 simulation steps on your screen. In the 20kHz example, you could choose 1000*500ns=500μs. Practical time steps are:

SMPS(100kHz)
dt=(1/100)(1/Fs), for Fs=100kHz choose dt=100ns
Tscreen=1ms

SMPS(500kHz)
dt=(1/100)(1/Fs), for Fs=500kHz choose dt=20ns
Tscreen=200μs

AC grid
dt=(1/100)(1/50Hz)=200μ, choose dt=100μs
Tscreen=1s for overview and Tscreen=100ms for detailed view of waveforms.

AC machines(N=1500-3000rpm)
dt=(1/100)(1/50Hz)=200μ, choose dt=100μs
Tscreen=1s for overview and Tscreen=100ms for detailed view of waveforms.

AC machines(N=9000rpm)
dt=(1/100)(1/150Hz)=65μ, choose dt=20μs
Tscreen=200ms for overview and Tscreen=20ms for detailed view of waveforms.

Analog control systems with Bandwidth in Hz
dt=(1/100)(1/Bandwidth), for Bandwidth=1kHz choose dt=10μs
Tscreen=100ms for overview and Tscreen=10ms for detailed view of waveforms.

Digital control systems with sampling time Ts
Choose at least dt<=Ts
Tscreen=10000*Ts for overview and Tscreen=1000*Ts for detailed view of waveforms.

Rerunning the simulation with half or even less time step dt gives insight in the accuracy of the results. Always perform a second simulation with dt=dt/2 or with dt=dt/5 to see if the simulations results differ.

How can I add some notes in the scope?
Export the png and open in Paint or any other graphics program, or export the data in a matlab file and open in matlab to add anything, or export to text file and open in excel.

I do not see any numerical voltage values at the nodes?
Give the node a label (right mouse click and add label) and during animation, the voltage will be shown

How to get nice scope graphs in my document?
Export the png inside the scope [File/Export png]

The characters are so small I can hardly see them?
Increase the size of the font [Options/Font]

My scope does not have a white background?
Select [Options/Options] and mark the SaveInk option

I want my graphs to be black and white ?
Select [Options/Options] and mark the Black/White option

Sometimes I see dots on the nodes and sometimes I cannot see them?
You can toggle the display of nodal dots by selecting [Options/Options] and mark the Show Nodes option

I want to hide the label and value for each component?
Select [Edit/Toggle display of label and value] and the display toggles between hidden and shown

How to add some text to my schematic?
Add a [Insert/Note] and select the display style

Can I place some frame around a group of components?
Add a [Insert/Note] and change the line display style from default to any other form. The text is displayed as header of the frame

The results in the scope are not visible by using a larger screen projector?
Increase the line thickness in the scope by selecting [Option/Line Thickness] inside the scope and choose 3 or 5 pixels for display

When I start building the schematic, a ground reference label is always inserted at the wrong node?
When you start build a new schematic from scratch, first place a ground label on the schematic by clicking the button with the ground symbol at the bottom button bar and insert the symbol

While editing I created some small wires around a node and I cannot delete them?
Select the node with the right mouse button and select [Delete Node]

I am simulating an induction motor drive, but have no idea about the parameters?
Use the model where only the amount of power and nominal speed are the main parameters, everything else is scaled automatically according the the size of the machine

What numerical algorithm does Caspoc use for the circuit analysis?
The algorithm uses nodal analysis with the euler/trapezoidal/gear rule integration. More important solves all equations simultaneously and does not generate state-space matrices which are common in other system level simulators. These state space matrices introduce convergence problems when there are large derivatives.

What are the main differences between Caspoc and SPICE?
Caspoc is designed specifically for power electronics and motor control, whereas SPICE-based programs are designed for general electronic circuits. The main differences between PSIM and SPICE relate to speed of simulation and simulation convergence or "robustness". Typically a Caspoc simulation will be significantly faster without any convergence or solve problems. Caspoc includes many building blocks unique to power electronics and motor drives and also allows for mixed domain simulation, with simulations containing the following: analog control, digital control, thermal, motor, magnetic and c code

Can Caspoc import a SPICE netlist?
A spice netlist for R L C K V I E F G H can be added in the schematic and is connected via nodes. The component NETLIST is found under Components/Circuit/Miscellaneous.

Can Caspoc import SPICE models?
The way that a circuit mode is set up and solved is different from the spice models. Therefore the complicated netlist models that some manufacturers provide do not work in Caspoc. The build in models do accept the same type of parameters (BJT, Diode and Msofet) and are preferred regarding absence convergence issues and secondly include a thermal node to simulate the combine electrical-thermal behavior

Can Caspoc simulate a digital control?
A digital control in Caspoc can be added just like any othe r block diagram and includes a number of function blocks, such as zero-order hold, unit delay, z-domain transfer function blocks, digital FIR and IIR filters, circular buffer, quantization block, and other blocks, which can be used to implement a digital control scheme. Further, an AC sweep with digital elements can be performed of a topology to determine the impacts of digital delay on the phase of plant response. This information is invaluable when implementing a control scheme in the z-domain. With Caspoc you can study the effect of different sampling rates, investigate the quantization effect of the A/D conversion with different number of bits, and evaluate the performance of a digital filter.

Can Caspoc include a digital control as source code?
You can either use the code block to write a basic C function that is simulated, or you can include a compiled code (*.dll) from any compiler using the LibML or FromML and ToML blocks.

How are the semiconductors modelled in Caspoc?
Models in Caspoc have different levels of complexity, models start with behavior or ideal characteristics and progress to non-ideal device level characteristics. The ideal circuit models are best suited for fast simulations while the models from the library can be used as a device level simulation with results comparable to a SPICE level simulation. For example multiple model levels exist for:MOSFET - ideal, conduction loss only, thermal, behavioral, IGBT - ideal, conduction loss only, thermal, behavioral, Diode - ideal, conduction loss only, thermal, behavioral, OpAmp/comparator - ideal, non-ideal, PWM control ICs - ideal, non-ideal. Ideal models are faster to solve and are best suited for simulations over multiple switching cycles, where non-ideal models should only be used when a few cycles are needed for the simulation.

How do I determine the input impedance of a power converter?
Make use of the smsg function block to inject frequencies into the converter while monitoring the input current. Once the simulation is done you can apply Ohms law to determine the impedance.

Can Caspoc simulate saturation or other nonlinear functions?
The professional version of Caspoc includes; a saturable inductor, a magnetics core model that includes saturation of the iron core, a IPM/PMSM model with non-linear Ld and Lq (look up table and/or function), induction machine models with saturating magnetizing inductance, behavioral MOSFET, IGBT, diode models. Caspoc provides lookup table function blocks which can be used to implement any non-linear function, along with a full suite of voltage and current sources that can be controlled with mathematical expressions.

Can Caspoc simulate switching losses?
Caspoc can simulate the switching losses of semiconductors with several methods. Using the combined electro-thermal models you can simulate thermally dependant switching losses of a MOSFET, IGBT and diode, When using the combined electro-thermal models the thermally dependant conduction losses are also calculated. The junction temperature of the device is determined and this is used inside the model to adapt the loss characteristics. Additionally, with the behavioral models from the library it is possible to simulate switching losses of a MOSFET and the reverse recovery of a diode. Integrating the voltage across a device with the current flowing through it will give you the switching losses.

Can I include Mathematical expressions in the block diagram?
Using the Components/Blocks/Cscript&Expression components ExpressionXX you can include any algebraic relation * /%+-(). Use the ^ symbol for for sqr and square root, like a^2, a^3 or a^0.5

Everything You Always Wanted to Know About Caspoc, But Were Afraid to Ask

1	What is new in CASPOC, A Simulation Experience!

2	What are the advantages of CASPOC to other simulation programs

3	Is everything in one window?

4	I changed the color of the waveform, but he did not change it in the scope?

5	How can I change the time scale in the scope?

6	What extensions to use for include files?

7	Where to store the include *.mod files?

8	Can I store Scope-data, HTML-data, commands, options or include files in an exported *.LIB file?

9	Where can I store my library (*.lib) files

10	Can I zoom the schematic with the cursor keys?

11	Can I scroll the schematic with the keyboard?

12	The animated object has a distorted color?

13	It seems that the arrows in the SCOPE and some animated objects are not nicely redrawn, when I continue the simulation?

14	How can I speed-up the animation?

15	Are there any shortcuts?

16	The schematic in the exported HTML or EMF file is not looking so nice?

17	Is there a variable time step?

18	Why are there no Spice models?

19	Why is not every nodal voltage and component current stored in data-files during simulation?

20	Are there standard models for semiconductors?

21	Can parameters for semiconductors be defined?

22	Can .Model parameters be used for any type of model?

23	How to model mechanical systems like drive-chains?

24	Are there models for State Machines?

25	Can State-Space equations be included as the model?

26	Why is there no script language for definition of functions?

27	Is there a replay function of the simulation results?

28	What if the step size is not matching with the switch intervals, such as with PFM?

29	Is there some post processing in the Scope?

30	Can I rotate a component while dragging it on the screen?

31	Get help on the buttons in the button bar?

32	Get help on the menu items?

33	Switch the language of the user interface to German?

34	Start Caspoc from the desktop?

35	Rotate a circuit component?

36	Perform auto scaling at the end of the screen?

37	Zoom in a Scope window?

38	Open the dialog box for scope input properties?

39	Open the dialog box for scale properties?

40	Connect the input of a scope?

41	Move a selected part of the schematic?

42	Make special purpose components?

43	Export a library block?

44	Importing a library block?

45	View simulation results numerically?

46	Open a Caspoc file (*.csi) from the explorer?

47	Make a voltage source dependent on a block-diagram value?

48	Connect a switch?

49	Define constant values for inputs of a block-diagram component?

50	Couple inductors?

51	Connect nodes without wires?

52	When I create my own library block, can I add some help notes?

53	Is there a coupling to Field solvers like FEM and BEM?

54	Can I include magnetic couplings from packaging in my model?

55	Are there any other probes than the Voltage and Current blocks?

56	Is there a model for the synchronous generator?

57	Is there a dynamic model for the Mosfet?

58	Are there models for modeling heatsinks?

59	Are the scopes storing the auto-co-ordinate values?

60	Can I label the scopes?

61	Can I use the K element for coupling inductors inside a library block?

62	Are there any formulas for modeling non-linear capacitance?

63	Is there a block for weighted summing of inputs?

64	Can I use Library blocks inside another library block?

65	Are there multidimensional lookup tables?

66	Can I evaluate expressions in a block?

67	After the analysis the cursors do not stay on the waveforms?

68	How do I get a log representation for the frequency and dB representation for the amplitude?

69	How do I modify the frequency range of the small-signal representation?

70	How can I see what my circuit is doing during the small-signal analysis?

71	I performed a small signal analysis, but I do not see the transfer function in my tiny scopes?

72	Can I have more than one input per scope during the small signal analysis?

73	If I change the number of harmonics to be displayed, do I have to perform another small-signal analysis?

74	Is current measurement through controlled sources possible?

75	How to change the gain in a controlled source?

76	How to include a Spice netlist, Spice options or a Spice .Model?

77	How long can file names be?

78	What is the format of numerical data files for the Lookup Tables and the Scope?

79	What are the restrictions when using the Simulink coupling?

80	I make changes in a sample or library block, but it looks like it has no effect or gives only errors.

Q	Is everything in one window?
A	All the components, circuit and/or block diagram and the scopes for viewing the simulation results during the simulation are edited in one window.

Q	I changed the color of the waveform, but he did not change it in the scope?
A	If you have only 256 color selected for your display driver, Windows will round the color to the nearest available color. Change the display settings to High Color (16 bit) or higher. Select "Settings/Control Panel", click on the icon "Display" and select the tab "Settings". Change the "Color Palette" to "High Color (16 bit)" or better.

Q	How can I change the time scale in the scope?
A	Select "Simulation/Simulation Parameters". The parameter "Tscreen" defines the length of the x-axis in the scope.

Q	What extensions to use for include files?
A	Use the .mod extension to indicate that the file has to be included during simulation. In Spice the include-files are indicated with .lib In Caspoc the .lib are used for library files. Rename the spice files into .mod files, when used by Caspoc.

Q	Where to store the include *.mod files?
A	You can store these files in the same directory where the example is stored, or store them in the directory [Path Caspoc]\include\, where [Path Caspoc] is the directory for Caspoc.exe

Q	Can I store Scope-data, HTML-data, commands, options or include files in an exported *.LIB file?
A	Only commands, edited in the commands editor can be stored in a *.Lib file. To keep .Model data in a library block, include the .Model data in the commands editor.

Q	Where can I store my library (*.lib) files
A	Library files can be stored on different locations. [Caspoc]\library Use this directory for the libraries supplied by the caspoc program The three directories defended in the dialog box Options In the same directory where the Caspoc (*.csi) file is stored

Q	Can I zoom the schematic with the cursor keys?
A	Use the + and - key on the numerical keypad to zoom out or zoom in.

Q	The animated object has a distorted color?
A	If you are using a colored background or a bitmap as background, the animated object can be distorted, because Caspoc makes an XOR-display. The advantage is a fast simulation where no special graphic-accelerators are necessary. Use a solid color in the background, where the animated object is moving.

Q	It seems that the arrows in the SCOPE and some animated objects are not nicely redrawn, when I continue the simulation?
A	Set the Zoom to a round value, such as 100%. In this case he is not making any round-off errors, when displaying the arrows or the animated objects.

Q	How can I speed-up the animation?
A	In the Animation dialog box, set the radiobutton [Each i timestep], in order to skip i simulation timesteps before the screen is updated. Although the animation looks less smooth, the simulation is using the original timestep dt, simulation results are displayed each timestep dt in the Scopes, but the animation is only shown after i timesteps of dt.

Q	The schematic in the exported HTML or EMF file is not looking so nice?
A	Set the zoom to 100% before exporting the EMF or HTML file.

Q	Why is not every nodal voltage and component current stored in data-files during simulation?
A	Storing all this information during simulation requires a lot of time, slowing the simulation down. Instead only data in 'Scopes' is stored during the simulation. You can add as many 'Scopes' as you want to view nodal voltages and component currents.

Q	Are there standard models for semiconductors?
A	For the Diode, SCR, GTO, DIAC, TRIAC, ZENER, SCHOTTKY, MOSFET and IGBT there are ideal models, which are very fast and robust. They can be found in the standard library.

Q	Can .Model parameters be used for any type of model?
A	Using the blocks 'Mname' and 'MPar', parameters in .Model lines can be used for any block in the block diagram. Using the block 'ChangeE', also circuit components can be made dependent on model parameters in .Model lines.Only changing the name of the model in the block 'MName', changes the parameter set.

Q	How to model mechanical systems like drive-chains?
A	There are special block� for modeling shafts, gearboxes, machines, mechanical loads, etc., in the library. They can be combined in any possible order.

Q	Are there models for State Machines?
A	A State Machine has to be modeled in the modeling language. In the modeling language variables can be defined f�r storing values and states. The model in the modeling language is then used as Multi-Input / Multi-Output block in the block diagram.

Q	Can State-Space equations be included as the model?
A	In the modeling language State-Space equations can be added. Any type of differential equation of the type dx/dt=f(x,t,y) can be added.

Q	Why is there no script language for definition of functions?
A	There is no faster code than compiled code. Therefore it is suggested to model as much as possible (only applicable in large models) in the modeling language, since the compiler generates optimized code, compared to slow running interpreted scripts.

Q	Is there a replay function of the simulation results?
A	In the 'Scope' the simulation results are stored, which can be examined using the cursor or mouse pointer.

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Q	What if the step size is not matching with the switch intervals, such as with PFM?
A	Using a state-event block 'STE' you can resize the step size during simulation, to let it exactly match with the variable switch intervals.

Q	Is there some post processing in the Scope?
A	Using the block-diagram you can define any type of signal, such as for example, RMS, average, harmonics, THD, etc., signals, which can be displayed in a 'Scope'

Q	Can I rotate a component while dragging it on the screen?
A	If you select a component from the list-box or if you are moving a component, you can rotate it during dragging by pressing the right mouse button. Note that if you are moving a component, keep the left mouse button pressed. Note that rotation only applies to circuit components.

Q	Get help on the buttons in the button bar?
A	A button bar is included for easy and fast operation of the program. A help flag will pop-up if the mouse is dragged over a button in the button bar.

Q	Get help on the menu items?
A	While browsing the menu, a brief help notification is displayed in the status bar.

Q	Switch the language of the user interface to German?
A	Select 'Options/Language' and select the German language.

Q	Start Caspoc from the desktop?
A	Dropping a caspoc file (*.csi) to the caspoc shortcut on your desktop, or the worksheet, will start the simulation of this file by CASPOC.

Q	Rotate a circuit component?
A	Select a circuit component. The component is drawn with dashed lines. Press Ctrl-R to rotate the component 90'.

Q	Perform auto scaling at the end of the screen?
A	When the simulation is at the end of the screen, t=n*Tscreen, the simulation will pause and the results are auto scaled in the scopes.

Q	Zoom in a Scope window?
A	Simulation results can be zoomed in, by clicking and holding the left mouse button down, while dragging the mouse to select an area. Select 'Scale/Zoom Scale to Selected Area' or click the button, will resize the scope contents to the selected area.