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2D axisymmetric, two coils, induced current

Posted 2011/05/19 10:58 GMT-4 Low-Frequency Electromagnetics Version 4.1 6 Replies

Isabel Gil
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Hello!

I use a 2D axisymmetric model.

I want to see the current density induced by one coil ("c1") with one turn located at r=r1 with radius=ra to another coil ("c2") with one turn located at r=r2 (r2>r1) with radius=ra.

The geometry would be:

:
:
:
: o(c1) o(c2)
:
:
:
:
r=0

In order to create an induced current density into coil "c2", the current density in "c1" must be variable, how could I do it?

I use Model physics:mf
I put External Current Density in "c1", but I don't know how to put it varible.
Am I supposed to use a time-dependent solver oder a frequency domain solver?

Thanks in advance.

Best regards,
Isa
6 Replies Last Post 2011/05/20 7:53 GMT-4
Edgar Kaiser
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Posted: 1 decade ago 2011/05/19 11:44 GMT-4
Hi Isabel,

yes, in case you want harmonic excitation you can use the frequency domain study, if your excitation is non-harmonic you would use the transient study and define a current density as a function of time.

Cheers
Edgar
Hi Isabel, yes, in case you want harmonic excitation you can use the frequency domain study, if your excitation is non-harmonic you would use the transient study and define a current density as a function of time. Cheers Edgar
Isabel Gil
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Posted: 1 decade ago 2011/05/19 11:59 GMT-4
Hi Edgar,

thank-you for your answer.

I would like to have an External Current Density in "c1" of "A*sin(time)", where "A" is a constant but I don't know how to introduce the function of time.

Could you help me?

Thanks in advance.
Best regards,
Isa
Hi Edgar, thank-you for your answer. I would like to have an External Current Density in "c1" of "A*sin(time)", where "A" is a constant but I don't know how to introduce the function of time. Could you help me? Thanks in advance. Best regards, Isa
Edgar Kaiser
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Posted: 1 decade ago 2011/05/20 3:33 GMT-4
Isa,

if your external current density is a sine wave you can use frequency domain and there is no need to define a function of time unless you want to study the instationary build up of the oscillation. Frequency domain gives you the stationary situation after long times.
Just define the current density on the boundary and the frequency or a range of frequencies in the frequency domain study node.

If you really want a transient study you define your funtion in the model or global definitions. The internal variable for time is 't', so the sine wave looks like c1 = A*sin(t). I guess you have an angular frequency omega too, so it becomes c1 = A*sin(omega*t).
I would recommend not to use simple variable names like A or c1, because they may be occupied by COMSOL.

Cheers
Edgar
Isa, if your external current density is a sine wave you can use frequency domain and there is no need to define a function of time unless you want to study the instationary build up of the oscillation. Frequency domain gives you the stationary situation after long times. Just define the current density on the boundary and the frequency or a range of frequencies in the frequency domain study node. If you really want a transient study you define your funtion in the model or global definitions. The internal variable for time is 't', so the sine wave looks like c1 = A*sin(t). I guess you have an angular frequency omega too, so it becomes c1 = A*sin(omega*t). I would recommend not to use simple variable names like A or c1, because they may be occupied by COMSOL. Cheers Edgar
Isabel Gil
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Posted: 1 decade ago 2011/05/20 4:35 GMT-4
Dear Edgar,

thank-you for your answer.

Then, as I am interested in a stationary solution, I decide to use frequency domain.
So, if I want to use f=50Hz (for example).

In External Current Density, I would set:
Je=Amplitude*sin(2*pi*freq) [A/m^2]
But as this variable "freq" has the value of 50Hz, Je=0, so...

Or perhaps I should set simply Je=Amplitude [A/m^2].

Moreover, you talk about define the current density on the boundary and the frequency or a range of frequencies in the frequency domain study node, but I would like to define the current density on the total circule that represent the coil1.

Could you help with this?

Thanks again in advance.

Best regards,
Isa
Dear Edgar, thank-you for your answer. Then, as I am interested in a stationary solution, I decide to use frequency domain. So, if I want to use f=50Hz (for example). In External Current Density, I would set: Je=Amplitude*sin(2*pi*freq) [A/m^2] But as this variable "freq" has the value of 50Hz, Je=0, so... Or perhaps I should set simply Je=Amplitude [A/m^2]. Moreover, you talk about define the current density on the boundary and the frequency or a range of frequencies in the frequency domain study node, but I would like to define the current density on the total circule that represent the coil1. Could you help with this? Thanks again in advance. Best regards, Isa
Edgar Kaiser
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Posted: 1 decade ago 2011/05/20 5:18 GMT-4
Isa,

yes, you define the current density on your circular coil domain, not a boundary. This was my error.

The current density is just the amplitude, you don't need the sine function because this is the time dependent part that is not needed for frequency domain.

Cheers
Edgar
Isa, yes, you define the current density on your circular coil domain, not a boundary. This was my error. The current density is just the amplitude, you don't need the sine function because this is the time dependent part that is not needed for frequency domain. Cheers Edgar
Isabel Gil
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Posted: 1 decade ago 2011/05/20 7:53 GMT-4
Thank-you very much!

Best regards,
Isa
Thank-you very much! Best regards, Isa

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