[Getdp] Induction_Motor_TimeSteping_Initial_Values

[Nicola Chiodetto]

Dear Christophe,

Many thanks for your suggestions and guidance.

I have been working on the issue, but with few improvements:

- As for the PostOperation in the time harmonic simulation there seems to
be no problem. I can successfully create my initial state files with the
following code:

///**********************************************************************************************

   PostOperation Plot_ReaL_Vector_Potential UsingPost MagStaDyn_a_2D {
  // Plotting the Real values of the magnetic
Print[ az_real,  OnElementsOf Region[{ Domain, Rotor_Bnd_MBaux }], Format
NodeTable, LastTimeStepOnly,
File StrCat[ResDir,"TH_Potential_NodeTableFile",ExtTxt]] ;
// Save the values of the eddy currents in a run time variable ($$)
Print[ I, OnRegion DomainC, Format TimeTable,
File > StrCat[ResDir,"TH_current",ExtGnuplot], LastTimeStepOnly,
StoreInVariable $rotor_current];

///**********************************************************************************************

- As for the Init Constraint imposition it looks like to be more
complicated:

The following syntax:

///*******************************************************************************************

     Time_Harmonic_Potential[] =
ListFromFile[]{TH_Potential_NodeTableFile.txt}

///*******************************************************************************************

Is not working whatsoever, even with other sort of sintax like the one I
can find at this link:
http://comments.gmane.org/gmane.comp.cad.gmsh.general/5437 .
Keeps providing a sintax error, no matter what is the file path I am
referring to. Furthermore, I unfortunately cannot find references for the
ValueFromIndex command. However,until ListFromFile is not working, I sadly
cannot move forward.

Regarding the "Init" Constraints, after I add them in the Constraint
definition environment, how can I force them only for the first
time-domain-step from within the Function spaces definition? Do I have to
access another runtime variable, as for instance the TimeStep?

Do you have any advice or you know what I got wrong?

Thanks in advance.
Sincerely,

Nicola Chiodetto

On Sun, Mar 27, 2016 at 10:05 AM, Christophe Geuzaine <cgeuzaine at ulg.ac.be>
wrote:

>
> Hi Nicola,
>
> This is indeed a good idea. There are several ways you can impose the
> initial values. I think that the easiest in your case is to directly
> specify the constraint (of Init type) in the function space of the relevant
> quantities (the vector magnetic potential a; as well as the current Iz if
> you have circuit relations), using a list of values extracted from the
> first time-harmonic solution.
>
> (The small technical issue that prevents the use of the classical
> "TransferSolution" method is that the frequency-domain formulation leads to
> different degrees of freedom (they are complex) than the time-domain
> formulation: you can thus not simply transfer values from one system to the
> other: the unknown vector is different.)
>
> In order to import list of values for the Init constraint, you could do as
> follows:
>
> - perform the time-harmonic simulation, followed by a PostOperation that
>    - plots the (real part of the) vector potential in the domain, and
> export it as a "NodeTable" file ("Format NodeTable")
>    - saves the value of the current in a run-time variable
> (StoreInVariable $MyCurrent)
> - add an "Init" type constraint for the relevant quantities in the
> function spaces used for the time-domain solution
>    - for the vector potential, use "Value ValueFromIndex[MyPotential[]],
> where MyPotential[] = ListFromFile[]{MyNodeTableFile.txt}
>    - for the current, use "Value $MyCurrent"
>
> Let us know how this works out. If it works well we might want to add this
> to the template.
>
> Christophe
>
> > On 18 Mar 2016, at 15:04, Nicola Chiodetto <nicola.chiodetto at gmail.com>
> wrote:
> >
> >  Dear GetDP users and experts,
> >
> > I am willing to simulate an induction motor with time stepping technique.
> >
> > I alredy used and studied the examples provided in the Electrical
> Machines folder available online.
> > However, I need to avoid the initial electrical transient: in other
> words I need to set proper initial conditions. Since the Induction machines
> is intrinsically operating due to eddy currents reaction I need to perform
> a time-harmonic. At this point I was thinking to read the real part of the
> vector magnetic potential, over all the domains, and take its real part.
> However, I do not know how to force the conditions of global rotor current
> variables in the domain bars. Is it possible witout touching the source
> code?
> > Moreover, usually in literature it is proposed a time harmonic frequency
> analysis exploiting an effective permeability function, instead of a
> simpler linear one. Is it possible to do that? It could be again useful for
> determining better initial conditions for the time stepping simulation
> first point.
> >
> > Thanks in advance.
> > Best regards,
> >
> > Nicola Chiodetto
> >
> > _______________________________________________
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> > getdp at onelab.info
> > http://onelab.info/mailman/listinfo/getdp
>
> --
> Prof. Christophe Geuzaine
> University of Liege, Electrical Engineering and Computer Science
> http://www.montefiore.ulg.ac.be/~geuzaine
>
> Tetrahedron V, July 4-5 2016: http://tetrahedron.montefiore.ulg.ac.be
> Free software: http://gmsh.info | http://getdp.info | http://onelab.info
>
>
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