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How do I Excite a coil through a Voltage source?
Posted Jan 9, 2011, 4:38 p.m. EST Low-Frequency Electromagnetics Version 4.0 15 Replies
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I am trying to excite the windings of a Toroidal transformer with a Voltage source from the Electrical circuit Interface and not with current injection. I am using the side view cross section of the transformer. In 2D axis symmetric .
I am not sure whether,
* I can just connect the source between the closed loop coil and the ground or
* should I make a slit such that there are now two leads to which the source can be connected( In this the slit in the coil would persist through out the geometry as it revolves around the axis, would that be a problem since coil continuity would not be there)
Hope someone can help me with this.
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indeed you do not have any voltage entry in MF for an phi orientation (or in MEF), but you should be able to define an equantion linking the voltage drop of your loop coil and the corresponding current in the coil, no ?
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Ivar
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I am new to this. So could you elaborate a bit on how I could define an equation to link the voltage drop to the corresponding coil curent.
Thank you and sorry for the trouble
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Sankara N
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To start with, why not just say U[V] = R[Ohm] * I[A], knowing that R=resistivity [Ohm/m] *Length[m] / Area[m^2],
and J[A/m^2] is I[A] / Area[m^2]
if you go to transient mode you should perhaps also add the back EMF and the inductance
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Ivar
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But wouldn't this be equivalent to injecting a current. Because I am trying to ultimately get the Inrush current in the transformer. so it would involve as u said Transient part. but for this I have to use the Voltage source. Wouldn't using the equation as a substitute deviate from the purpose?
Thank you for all your help.
Sankara N
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exactly if you are in transient mode, you must write out the equation for the voltage (supplied) versus back-emf voltage and inductive effects due to current rise, taking into account the coil area, loop lengh (2*pi*r), number of turns, fill factor material (conductivity) etc. All to extract the resulting current looping on the 2D-axial mode.
For this you need to add a new PDE or express it in the Weak form
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Ivar
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Thank you. That was helpful.
1. I was wondering whether what I am trying to do can be done by importing source from Spice network.
2. Also I used the Mef physics. In that I used the terminal option to excite the coil through its boundaries. The error I am getting is Singular matrix and Domain errors.
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a Port/terminal in 2d axi ?
clear, its OK in 3D or 2D, but its slightly trickier in 2d-Axi, that's all
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Ivar
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I am using a terminal in 2d- axi. What did u mean by clear? and you mean that the network connecting is slightly trickier in 2d-axi model right?
Also what do those errors mean?
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Because I cannot find any terminal in 2D-axi, only in 2D and 3D ?
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Ivar
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But In Comsol 4.0a classkit license am using 2d-axi and in that in the physics magnetic and electric fields I am using the terminal option. In 4.1 i dont find that option in 2d - axi.
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then I assue it was "an error " of 4.0 Because I do not see how to define a port in 2D-axi, OK perhaps restricted to Z, but probaly its not general enough to accpt for all physics. i.e. in MEF there is no velocity Lorentz term either in 2D axi. that bothers me too, as I want to have z motion/velocity and need the Lorentz terms.
will have to write it out myself
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Ivar
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This is an error that I am getting when i try to run my program.
Feautre : Stationary solver 1
Error : Singular matrix
what does this mean?
thanks
Sankara
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that is typically when there is not enough BC to solve all equations
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Ivar
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This is an error I am getting now and i do not know what it means. Could anyone explain the problem?
Failed to find consistent initial values.
System matrix is zero.
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by default COMSOL poposes "0" as initial values, but this does not mean that it makes sns w.r.t. your model and your specific BC's (Boundary Constions). You must check that your BC'a are coherent, I normally run a initial value check = Solver node: "derived values" - "comute to selected" and then look at the results.
If you are in CFDD typically I set some initial flow velociteies, some pipe head losses on the pressure, in ACDC I add an electric or magnetic field, you can use X,Y,Z or x,y,z (depending on which frame you use and the physics) to distribute these
COMSOL isdoing nothing else than solving PDE's fr that you should check that yur initial values, your eqations and you boundary values are coherent
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Good luck
Ivar