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Warning "fixed Alias set with several free start values"
Warning "fixed Alias set with several free start values"
My first experiment (as a rank beginner!) with Modelica fails with the following warning:
Code:
--------------------------------------
[1] 18:32:30 Translation Warning
fixed Alias set with several free start values
* candidate: capacitor1.v(start = 11.8255
* candidate: capacitor2.v(start = 10.0002)
=> select value from capacitor1.v(start = 11.8255) for variable: capacitor1.v
-----------------------------------------
The example consists of two parallel LC filters, coupled with a single resistor.
I want to know the step response of this system, so I put a trapezoidal source
with 1us rise-time/10V amplitude on it.
The response is radically different from what I expect (and get from SPICE).
Only two of the eigenvectors are excited, probably because the initial voltage
on the two capacitors is ignored (see message).
-marcel
parLC.mo
Thank you
Re: Warning "fixed Alias set with several free start values"
These circuits normally work wonderfully in OM.
From your message it is not clear which initial conditions you want to impose.
You added spice plots, I suppose. What initial conditions did you set in Spice?
I recommend to continue to play with OM, if you simulate circuits. You will get a lot of satisfaction!
- ceraolo
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- 147 Posts
Re: Warning "fixed Alias set with several free start values"
Dear Ceraolo,
> These circuits normally work wonderfully in OM.
> From your message it is not clear which initial conditions
> you want to impose.
12V on the one, 10V on the other, 1.4 and 6.1 mA through the
two inductors. I have edited the post and added the Modelica
file. Is there a better way?
> You added spice plots, I suppose. What initial conditions did you set in Spice?
The same as in Modelica.
> I recommend to continue to play with OM, if you simulate circuits.
> You will get a lot of satisfaction!
I am not complaining, these are just beginners errors. If I interpret correctly
what I have read (on Dymola), I have hopes that Modelica should be great for
very large / stiff networks (something like KLU).
-marcel
Re: Warning "fixed Alias set with several free start values"
Your model was a bit tangled.
I untangled it and got reasonable result.
Try this:
Code:
model parLCmod
Modelica.Electrical.Analog.Basic.Inductor inductor2(L = 500e-6, i(start = 1.4e-3, fixed = true)) annotation(Placement(visible = true, transformation(origin = {42, 52}, extent = {{-10, -10}, {10, 10}}, rotation = -90)));
Modelica.Electrical.Analog.Basic.Resistor resistor1(R = 150) annotation(Placement(visible = true, transformation(origin = {20, 18}, extent = {{10, -10}, {-10, 10}}, rotation = 0)));
Modelica.Electrical.Analog.Basic.Capacitor capacitor1(C = 10e-6, v(start = 11.8255, fixed = true)) annotation(Placement(visible = true, transformation(origin = {-4, -10}, extent = {{-10, -10}, {10, 10}}, rotation = -90)));
Modelica.Electrical.Analog.Basic.Capacitor capacitor2(C = 10e-6, v(start = 10.0002, fixed = true)) annotation(Placement(visible = true, transformation(origin = {42, -10}, extent = {{-10, -10}, {10, 10}}, rotation = -90)));
Modelica.Electrical.Analog.Basic.Ground ground1 annotation(Placement(visible = true, transformation(origin = {-4, -48}, extent = {{-10, -10}, {10, 10}}, rotation = 0)));
Modelica.Electrical.Analog.Sources.TrapezoidVoltage trapezoidVoltage1(V = 10, rising = 1e-6, width = 1, falling = 1e-6, period = 2, nperiod = -1) annotation(Placement(visible = true, transformation(origin = {-52, 20}, extent = {{-10, -10}, {10, 10}}, rotation = -90)));
Modelica.Electrical.Analog.Basic.Inductor inductor1(L = 50e-6, i(start = 6.1e-3, fixed = true)) annotation(Placement(visible = true, transformation(origin = {-4, 40}, extent = {{-10, -10}, {10, 10}}, rotation = -90)));
equation
connect(inductor1.n, capacitor1.p) annotation(Line(points = {{-4, 30}, {-3, 30}, {-3, 0}, {-4, 0}}, color = {0, 0, 255}));
connect(trapezoidVoltage1.n, capacitor1.n) annotation(Line(points = {{-52, 10}, {-52, 10}, {-52, -20}, {-4, -20}}, color = {0, 0, 255}));
connect(trapezoidVoltage1.p, inductor2.p) annotation(Line(points = {{-52, 30}, {-52, 62}, {42, 62}}, color = {0, 0, 255}));
connect(ground1.p, capacitor1.n) annotation(Line(points = {{-4, -38}, {-4, -20}}, color = {0, 0, 255}));
connect(capacitor2.p, inductor2.n) annotation(Line(points = {{42, 0}, {42, 42}}, color = {0, 0, 255}));
connect(capacitor1.n, capacitor2.n) annotation(Line(points = {{-4, -20}, {-4, -20}, {42, -20}}, color = {0, 0, 255}));
connect(resistor1.p, inductor2.n) annotation(Line(points = {{30, 18}, {42, 18}, {42, 42}}, color = {0, 0, 255}));
connect(inductor1.p, inductor2.p) annotation(Line(points = {{-4, 50}, {-4, 62}, {42, 62}}, color = {0, 0, 255}));
connect(resistor1.n, capacitor1.p) annotation(Line(points = {{10, 18}, {-4, 18}, {-4, 0}}, color = {0, 0, 255}));
annotation(Icon(coordinateSystem(extent = {{-100, -100}, {100, 100}}, preserveAspectRatio = true, initialScale = 0.1, grid = {2, 2})), Diagram(coordinateSystem(extent = {{-100, -100}, {100, 100}}, preserveAspectRatio = false, initialScale = 0.1, grid = {2, 2})), uses(Modelica(version = "3.2.1")), experiment(StopTime = 0.0009));
end parLCmod;
- ceraolo
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- 147 Posts
Re: Warning "fixed Alias set with several free start values"
Thanks a lot!
I couldn't (graphically) see what was wrong with my circuit, or what was different in your version,
but yours worked correctly and mine didn't.
I went to the text file and there it's obvious:
connect(resistor1.p, resistor1.n) annotation(Line(points = {{-22, 18}, {-2, 18}}, color = {0, 0, 255}));
The resistor is shorted. Apparently an invisible line is stuck behind.
I fixed it by deleting and re-inserting another one. Merely moving or rotating
didn't fix the problem.
Well, I am used to editing netlists by hand, so it's not a problem.
Is there a way to have plots with multiple axes (like Volts left, current right)?
-marcel
Re: Warning "fixed Alias set with several free start values"
Is there a way to have plots with multiple axes (like Volts left, current right)?
Not inside OMEdit. You can save output as CSV and do post-pocessing using other SW.
But I strongly recommend you to get accustomed to OMEdit. Maybe it has not all the features you currently use, but it has a lot of wondeful characteristics.
Even if I don't recommend it at this stage, I can mention that a program of mine reads smootly OM's CSVs, and allows several things OMEdit does not allow, e.g.:
- twin vertical axis
- Fourier analysis on plots
- seeing the numerical values (OMEdit just does a dull pixel mapping)
- combining plots with algebraic operators (sums, multiplication, subtraction, division)
- integrating.
It is called PlotXY, there is a 2015 version, and you gan get it from the following URL:
http://www.dsea.unipi.it/Members/ceraol … re/plotxy/
- ceraolo
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-
- 147 Posts
Re: Warning "fixed Alias set with several free start values"
These circuits normally work wonderfully in OM.
From your message it is not clear which initial conditions you want to impose.
12V on the one, 10V on the other, 1.4 and 6.1 mA through the two inductors. I have edited the post and added the Modelica file. Is there a better way?
You added spice plots, I suppose. What initial conditions did you set in Spice?
hdi pcb
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