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Assigning a sinusoidal electric potential to a boundary

Posted 13.05.2013, 00:37 GMT-4 Low-Frequency Electromagnetics, Modeling Tools & Definitions, Parameters, Variables, & Functions Version 4.3 5 Replies

Derek Hoyt
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Hello,

I am relatively new to COMSOL and I am building a transformer model for use in researching different hysteresis losses and associated heat energy with using different core materials. I have built a geometric model of the device. I am trying to assign an electric potential to one end of the primary winding on the transformer (the other end will be ground). I can give it a DC potential, but I want to assign a sinusoidal waveform to the voltage across the primary winding. How can I do this?

I included the Electric Currents physics engine and I defined a waveform for the primary coil voltage, but that is all the further I have gotten. I feel like if I could just define the "Equation" setting in the Electric Potential phenomenon under the "Electric Currents" physics, it would allow me to specify a sine wave potential.

I would really appreciate any input.
5 Replies Last Post 13.05.2013, 11:41 GMT-4
Robert Malkin
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Posted: 1 decade ago 13.05.2013, 10:18 GMT-4
I can help you if you are working in the time domain?

R
I can help you if you are working in the time domain? R
Derek Hoyt
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Posted: 1 decade ago 13.05.2013, 10:46 GMT-4
Yes, I am working in the time domain.
Yes, I am working in the time domain.
Robert Malkin
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Posted: 1 decade ago 13.05.2013, 11:06 GMT-4
This example I created should tell you how to do it.

The model is acoustic so you may not be able to use it.

But I choose a point or boundary and in the 'Pressure' I type...

5*sin(2*pi*f0_air*t)*(t<=2*t_pulse)

5 is the magnitude

fo_air is the frequency of the oscilation (Hz)

t is the Comsol variable for time

and

t_pulse is the duration of the cycle (1/frequency)

Just make sure that your time steps are sufficiently small to model a given frequency. I find that a CFL of 0.05 is good.

Let us know if you dont know what the above means.
This example I created should tell you how to do it. The model is acoustic so you may not be able to use it. But I choose a point or boundary and in the 'Pressure' I type... 5*sin(2*pi*f0_air*t)*(t
Derek Hoyt
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Posted: 1 decade ago 13.05.2013, 11:37 GMT-4
Yes, what does CFL refer to?

What is the purpose of specifying the time step?

As a COMSOL variable, 't' is already defined?
Yes, what does CFL refer to? What is the purpose of specifying the time step? As a COMSOL variable, 't' is already defined?
Robert Malkin
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Posted: 1 decade ago 13.05.2013, 11:41 GMT-4
I dont have time to go through time stepping in FEA for you. This will be covered in most FEA books that deal with dynamics or explicit solvers.

I suggest you do the Gaussian explosion example in Comsol. This will teach you about time stepping and CFL condition.

good luck
I dont have time to go through time stepping in FEA for you. This will be covered in most FEA books that deal with dynamics or explicit solvers. I suggest you do the Gaussian explosion example in Comsol. This will teach you about time stepping and CFL condition. good luck

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