Discussion Forum

Hi

I believe you have a GND issue, you add one GND and one terminal on your EC physics, (remember a GND is just setting a "gauge" potential. Then you add a circuit, by dfalt 0 is GND (andimplicitely already connected to your other physics, 1 is floating, until you connect up a source, if its a AC voltage you must define it accordingly and then connect it with a Circuit source term onto the terminal 1 in your EC physics. Now, as I'm not by my workstation I cannot open your model, so either you have another circuit for the measurement, hence a sencond terminal fixed to some other electrode, here you need to link it to your CIR circuit via a specific source or sink node attached to a CIR ID of 2 (since 0 is GND and 1 is the potential source, and select to connect the twophysics boundary links, then you must add your load resistor between 0 (GND) and 2 your return from the circuit.

COMSOL proposes automatically the lumpoed parameters in the Derived Values list for your terminals

Note in AC use the frequency harmnic solver and do not forget to fix your frequency or list of frequencies in the solver tab.

Final note, there is no real eason to use CIR also for the source, you could as well define the voltage amplitude in the EC terminal physics, and simply add a ressitor between 0 and 1 in the CIR and use node 1 to link to the second "measurment termainal in EC.

If you want to learn something, for a simple resistance, remove fully the CIR physics, and connect the average current on your otherwise terminal node to the GND via a weak expression ;)

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Good luck
Ivar

Thank you for your reply Ivar. Unfortunately I could not get it to work still. I think what I had done was same as what you tell. Or at least it seems the same to me. But as before, I am getting the "DAE is structurally inconsistent" error. Is it possible for you to take a quick look at my files from before. I think my issue is that my circuit is not able to correlate electrostatics nodes with its own nodes. I think that is where I am doing wrong.

Thanks.

Kedar,

There were two problems in your setup:

1) The circuit was not connected to the Electric Currents interface. The External I vs. U node should be used to make this connection. The voltage specified on this node should be equal to the potential difference between the two electrodes.

2) The circuit components did not form a closed circuit.

The implementation is simplest if one of the electrodes is grounded. See the attached file for a corrected setup.

Luke Gritter
AltaSim Technologies

Thank a lot Luke. I am glad you got it to work. But unfortunately I am not able to open the file you attached. I am guessing it is due to some version number conflict. I am using 4.2. I thought that version number should not make a difference. Do you know of a way to fix this? Once again thanks a lot.

Kedar,

I've attached a file in 4.2. I noticed that the coupling in the previous file (using the drop down menus) was not working correctly, so this file has the variable names manually entered on the Terminal node and the External I vs U node. Note that you need to enter the length of the wires on the Electric Currents node (the default is 1 m).

Luke Gritter
AltaSim Technologies

This one works. Perfect. Now I see what one needs to do for such a problem. Thank you very much Luke.

Hi Luck

It seems that you have much experience dealing with import electrical circuit.


Im trying to simulate an electrical machine. It worked so far. But when I replace the "single turn coil" with a "circuit current" and use SPICE Netlist i get this error


The DAE is structurally inconsistent

Variabels 11
Equation 8

I attached my model would you please take a look over it

Thanks in Advance

AH,

You forgot to attach your model, so I cannot say for sure, but this error can occur when multiple current or voltage sources (including External features) are incorrectly combined in the circuit model.

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Luke Gritter
AltaSim Technologies

Hello Luke

nice to meet you here and it seems that you can solve my problem


I want to apply a sine voltage source to a piezoelectric ceramic. it's a model of COMSOL named"thickness_shear_quartz_oscillator.mph". the model works well but when I change the AC source to sine source, set the frequency 50Hz, same as AC. error occurs:

The DAE is structurally inconsistent

Variabels 2
Equation 0

you can see the model in the model library, hope you can help me

Thanks in Advance

Lance,

The sine source is intended for a time-dependent analysis. If you are using a Frequency Domain study step, then you should use the AC source. The AC source is simply a sine source with the specified amplitude and phase, and the frequency is specified in the settings for the Frequency Domain study step.

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Luke Gritter
AltaSim Technologies

I have already solved the problem, but thank you all the same, that's very kind of you

Hello Luke,

I am trying to model series RLC circuit working as resonator.In the model two inductor should couple at the resonating frequency.

The model is not giving error,but the value of surface magnetic field is zero.

you can see the model in the model library, hope you can help me

Thanks in Advance

Hi Chinmayi,
I feel your circuit is incomplete. Can you please post the schematic too just to check the connection.

Thanks,