AC/DC Module - Latest Discussions - COMSOL Forums

induced voltage by line integration

Tue, 22 May 2012 08:38:24 +0000

Hallo Jane,

I've found this post from you in the comsol community:

hi All,

I have two coils in my model, one is transmitter working at 2MHz, the other is working as receiver.

How to do integration to get voltage on the receiver? I think I need to do line integration of Ephi, but how can I draw the line in 3D model and how to input Ephi in the expression? There are only Ex, Ey, Ez in the expression selection.

Thanks in advance

I've still the same problem. Did you find any solution how to integrate "across" the coil to get the induced voltage?

Thanks a lot in advance!

Best regards,

Stephan Gschwandtner

Stationary and Time-dependent study for Joule Heating

Mon, 21 May 2012 20:14:35 +0000

Hello,

I am working on a rather simple simulation of Joule Heating on a Pt resistor deposited on AlN substrate. Although I can perform the stationary study and have some of the results I want, I cannot perform a time-dependent study. The execution fails with error message "Failed to find consistent initial values. Last time step is not converged.".

Any ideas what might be wrong?

Cheers!

-O.

PML with SAW

Sun, 20 May 2012 09:24:29 +0000

Hi

I saw you were getting the error message "pml could not find any cylindrical or spherical regions" while working in [m]-domain. Have you been able to solve this error?

Regards, Evelyn Livermore

capacitance expresion

Sat, 19 May 2012 10:00:47 +0000

what is the expresion CONFIGURED es.c11 the capacitance value in the model capacitor_tunable in version 4.2?

Define PH

Fri, 18 May 2012 16:38:10 +0000

Hi

Anyone has any idea how I can define PH of my solution in ACDC module?

Best
Bahar

Need help with Magnetic and Electric Fields Error

Fri, 18 May 2012 15:44:27 +0000

Greetings,

I'm trying to generate a model with a cylindrical anode, two metallic electrodes, and two magnets with the MER Module so I can model both the E and B Fields together so I can look at ExB drift effects. However, I keep getting this same error:

Failed to find a solution.
Singular matrix.

There are 213295 void equations (empty rows in matrix) for the variable mod1.V.
at coordinates: (-0.308496,-0.261123,-0.294355), (-0.299595,-0.278459,-0.287582), (-0.289647,-0.29545,-0.280739), (-0.288168,-0.272107,-0.304823), (-0.278712,-0.28882,-0.298166), ...
and similarly for the degrees of freedom (empty columns in matrix).
Returned solution is not converged.

I've double-checked all of my material properties and I've input the electric potentials using the Initial Values, but it's still having a hard time looking for the voltage (?). I'm not sure what boundary conditions I've missed to get a singular matrix and nothing's popping out at me. Does anyone have any ideas?

Live Long and Prosper,
JAY

P.S.: I can't attach my file because the size of the file is too large.

Stationary study failed to converge

Fri, 18 May 2012 12:06:45 +0000

Hello, I am trying to do a stationary of a MEMS device, but Comsol keeps failing to converge.

Some background on the model:
The model is a MEMS consisting of a plate attached to 4 thin cantilever beam springs, which are in turn attached to a fixed substrate. The plate is also attached to a set of combs whose teeth act as capacitors with a set of corresponding combs attached to the fixed substrate (see attached image. Everything not in purple is attached to the plate and should be free to move). A voltage is applied to the fixed combson one side of the device, while the plate itself is grounded. This causes the plate to be displaced until the capacitive force from the comb capacitors is balanced by the restorative force of the springs.

Comsol Physics setup:
I am using the Electromechanics physics node in Comsol 4.2a to do a stationary study on how much the plate is displaced. I placed all domains in Linear Elastic material model, fixed the boundaries shown in purple in the image, applied a voltage to the three fixed combs in the right of the image, and grounded the center plate. I then created a stationary study and computed. Unfortunately, the solver fails to converge. Is there something wrong with the way I have set everything up? Does anyone have suggestions about what may be going wrong?

Josh

Ideal mesh for a regular grid export

Fri, 18 May 2012 10:09:42 +0000

Dear Comsol community,

I have a simple 3D electrostatic configuration of two separated point charges in free space. What I want to do is solving the poison-equation and exporting the data in small cubic region between the point charges on a regular grid.

What is the optimal mesh for exporting on a regular grid with about 201^3 points?

Since the error of the FE-method is minimal (vanishing) on the nodes of the mesh-elements I think it would be perfect to have a regular mesh with nodes exactly on the points of the regular grid. I found no way to achieve this yet and I would be thankful for any kind of help giving me a good exported result.

Designing Voice Coil Actuator with Flexures

Fri, 18 May 2012 00:54:41 +0000

Hi,

I am new to comsol and am trying to design a linear voice coil actuator by fixing each end to two diaphragm flexures, therefore keeping everything axisymmetric. I have designed the flexures with the structural mechanics and have placed loads and found eigenfrequencies. I am wanting to know how to incorporate a voice coil actuator to drive the flexures? I searched for some similar models without any luck. The ideal setup would be applying some step function to the voice coil and get the response of the system, and tune it with a PID controller. Any help whatsoever would be great as I am just getting used to the new software.

Thanks!

3D coil inductance with frequency domain

Thu, 17 May 2012 13:28:28 +0000

I modeled a coil to calculate the inductance in both 2d symmetric axis and 3d with frequency domain. It gives a rise an issue that the value of calculated inductances are different.

Since there is no directly option for inductance in 3D, I use the following fomula:
L=N*flux/I0
L: inductance
Flux: integration of magnetic flux density over a closed surface
N: number of turn
I0: the applied current

The value of inductance in 2D is equal to 5.0408e-5H, while in 3D is 4.226e-5H.
However, it gets closer to results from 2D when I changed frequency domain to stationary domain in 3D which is 5.0803e-5H.

Can anyone give me a favour?

Regards,
Hongyu Li

analyze movement of particles in ACDC

Thu, 17 May 2012 12:22:26 +0000

Hello everyone

I have a question and I wondered if anyone can give me some info.
I am using AC/DC module right now. However I want to add movement of A charge in my model and analyze the effect of its movement on electrical field of whole system.
Do you think it is possible to do these kind of simulations by using time dependent analysis? Because I have checked different models here that use time dependent analysis but their goal was totally different from mine.
I think in order to do this I should have access to particle tracing module. Am i right?
I would be really grateful if someone can give me some information or give me a link of example related to this.

Best
Bahar

Nonlinear electric conductivity

Thu, 17 May 2012 02:18:31 +0000

Hi,

I'm currently working on electrical transients simulation using AC/DC module. How can I define nonlinear electric conductivity of zinc oxide (ZnO) in subdomain settings?

Thank you

Magneticfield simulations of a Nanodevice

Wed, 16 May 2012 07:14:06 +0000

Hi Ivar

My name is Daniel Sandermann and I am a student at the University of Copenhagen. As the title shows I am trying to make a simulation of how the local magnetic fields will look like, if I have a Nanodevice made out of Cobalt (ferromagnet) which will then be subjected to a 1.8T magnetic field. The method I have been using is as follows:
mf->Amperes law->Remenant field of 1.8T in Y-drection. This has given me some decent 3D simulations of how the field will look like. So here are my guestions:
1) Is there a more efficient way of setting up the model? What we are basicly interested in, is to see the local fields at 67nm below the device

2) I would also like to make 1D plot of the Remenant field as a function of the distance below the device. But havent really been able to do it.

Hope you have the time to help me, it would really be appreciated.

Best Regards

Daniel Sandermann

simulation of eddy current damper

Wed, 16 May 2012 03:59:16 +0000

hi all
i am working on eddy current damper....in which beam (cantilever type) vibrations (free) are to be damped...the material of beam is aluminium....i have simulated the two electromagnets..but i am not able to simulate the beam vibration with initial conditions @t=0 displacement of free end is 0.003m and velocity =0. i have used the eigen frequency study but the tip displacement is very large as per our initial condition....when i used the time dependent study it gives an error of singular matrix...and one thing more should i use the moving mesh for beam...

plz help

i've attached the model...

Thanks and regards
Mohit

boundary settings- Thin layer (surface thickness)

Fri, 11 May 2012 17:28:17 +0000

Hello everyone

I have a question about settings for boundary conditions. In most of physics, when you use 3d and you want to define a boundary condition like dielectric shielding for one surface there is one option called "Thin layer".
For this "Thine layer" you should define "Surface thickness" which is by default 1m.
My question is that what exactly this surface thickness means? because it seems it can affect my results a lot.
I know it is not thickness of my domain (if the domain is a cube with dimension of 0.1 um). So what exactly is this? I went through some tutorials and i couldn't find any explanation.

Best
Bahar

Temperature Sensor Model

Tue, 08 May 2012 21:11:51 +0000

Hello,

I am designing a temperature sensor using an interdigitated capacitor. Using the electrostatics modules, I was successfully able to design the sensor with the starting capacitance value I wanted. However, regarding changing capacitance with temperature is where I run into problems. Thus far, I have been using the joule heating and thermal expansion module. Can anyone tell me if this is the correct module for my goal?

I have had some measure of success using it. However I find that when I remove the surrounding rectangle with air associated with it in the positive z direction and silicon in the negative z direction, the study completes, but with that rectangle, I get an error of singular matrix/solution does not converge and cannot complete the study. Why is this?

Also, without the surrounding rectangle, and without the proper dielectric in place, it seems that I cannot calculate capacitance correctly, and the values are all very small, approaching zero.

I have attached my model.

I would greatly appreciate help understanding this, thank you.

Trouble coupling heat transfer physics for both fluids and solids

Wed, 25 Apr 2012 03:19:20 +0000

Hey all,

So I'm getting stuck with my model where I try to couple three different physics. The three physics are: Electric Currents, Heat transfer in Solids, and Heat transfer in Fluids. Basically what I'm trying to model is a silicon microbridge which is doped, which makes it so that it has a temperature gradient accross it when heated. I am able to couple and run the electric currents and heat transfer in solids physics, where the power dissipated from the ec physics is inputed into the ht physics as the heat source, and then the temperature that is calculated is used to calculate a new resistivity value for the silicon, until the model converges to a value for the temperature at the given voltage.

The problem arises when I try to incorporate the ht2 physics to mimic the effects of natural convection from the sorrounding gases. I set a temperature boundary condition within the ht2 physics which tells the program that the temperature of the microbridge is given by T, which is calculated in the ht physics. However, when I run this, I get the following error:

"Constraing found for variables in different Segregated groups. Try to merge these groups.
-Feature: Stationary Solver 1 (sol1/s1)
-Error: Constraint found for variables in different Segragated groups. Try to merge these groups."

Any ideas? Attached you will find my model. Thanks.

Circuit terminal question

Mon, 09 Apr 2012 01:37:00 +0000

Hi, All,

I'm trying to build a model four terminal nodes. Two of them are COMSOL voltage (terminal 1) and ground (terminal 0), another two is connected to 'external' resistor which is not defined as part of the multiphysics model.

Should I name the two terminal as type 'circuit', and name them 2,3? Then choose the nodes in electric circuit (cir) to be 2 and 3? What else should I do? I'm have an error says The DAE is structurally inconsistent .

Thanks!

Dielectric heating between parallel plate electrodes

Fri, 09 Mar 2012 23:25:06 +0000

Hello all, I'm fairly new to Comsol. What I'm trying to do is model the heating of a dielectric in between two parallel plate electrodes at a frequency of 27.12 MHz. I would appreciate any suggestion as to which physics to use. Thanks in advance.

voltage induction due to changing magnetic field

Tue, 24 May 2011 12:14:58 +0000

hello,

I'm a relative newbie to comsol. what I'm trying to do is (I think) relatively easy, but I have no idea how to tackle it. what I need to do is model voltage induction in a coil due to a changing magnetic field. I know how to how to create a coil in a fixed magnetic field, but I don't know how to set up time varying field. but, more importantly, I don't know how to measure the induced voltage. should the coil be open and then specify two points where the voltage would be measured? thanks for any suggestions.

r.