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Calculating mutual induction and leak induction for an Inductiver Power Transfer system
Posted 21 avr. 2011, 10:07 UTC−4 Low-Frequency Electromagnetics Version 4.1 4 Replies
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Hi
I have created a 2D-model (with some help from Comsol support) of an Inductive Power Transfer system wich consists of two straight wires (named "track" in attached models) generating a varying magnetic field and a secondary coil wich is wound around a ferrite core (named "coil" in attached models). The track carrying a current generates according to faraday's law a voltage in the secondary coil.
What I'd like to do is to simulate the mutual inductance and the leak inductances for the system.
I got some help from Comsol support, but was guided to use this forum. I was told that I could find the inductance as follows:
"To measure the leakage inductance for a transformer terminal the standard procedure is to short-circuit the other terminal and then measure the inductance. You can do that in COMSOL by setting the coil to be excited by Voltage and setting the voltage to be zero. In short:
- Set Icoil = 0 (open circuit), Irail = 1, and measure Vtot_coil and Vtot_rail. Then: Lself_rail = imag(Vrail/Irail)/omega; Mcoil_rail = imag(Vcoil/Irail)/omega;
- Set the coil to be voltage-driven and set Vcoil = 0, set Irail = 1 and measure Vtot_rail. Then: Lleak_rail = imag Vrail/Irail)/omega."
To do this I have made four models (I could probably do this using one model, but this is what I was able to do with my Comsol-knowledge):
1. Attached model named "Self_inductance rev2 open circuit coil_Mutual induction coil rail.mph"
In this model the mutual induction Mcoil_rail is calculated by driving a current in the rail; Irail=1A and Icoil=0A. So far this looks ok for me.
2. Attached model named "Self_inductance rev2 short circuit coil_Leak induction rail.mph"
In this model the coil is set to be voltage-driven, where V=0, to calculate the leak induction for the rail. This is where the problems starts. According to the 1D-plot the leak induction is decreasing as the frequency increase, this is not what I was expecting. What am I doing wrong? As the frequency increase the mutual induction decrease, logical the leak induction should increase.
3. Attached model named "Self_inductance rev2 open circuit rail_Mutual induction rail coil.mph"
In this model the currents are set as Irail=0A and Icoil=1. By doing this it should be possible to calculate the mutual inductance Mrail_coil. This could be useful to verify model (1) because Mcoil_rail = Mrail_coil. In this case the problem is that the coil wich is generating the magnetic field don't generate current in the rail. This should be straigt forward as model (1) is ok? What could be wrong here?
4. Attached model named "Self_inductance rev2 short circuit rail_Leak induction coil.mph"
In this model the rail is set to voltage-driven, where V=0, to calculate the leak induction for the coil. Here I'm getting the same problem as in model (2). By solving the problem in (2) will hopefully solve this problem as well.
To make a better understanding of the system that I'm trying to simulate I have attached some illustrations that I found on the internet.
Thanks!
Best regards Yngve
I have created a 2D-model (with some help from Comsol support) of an Inductive Power Transfer system wich consists of two straight wires (named "track" in attached models) generating a varying magnetic field and a secondary coil wich is wound around a ferrite core (named "coil" in attached models). The track carrying a current generates according to faraday's law a voltage in the secondary coil.
What I'd like to do is to simulate the mutual inductance and the leak inductances for the system.
I got some help from Comsol support, but was guided to use this forum. I was told that I could find the inductance as follows:
"To measure the leakage inductance for a transformer terminal the standard procedure is to short-circuit the other terminal and then measure the inductance. You can do that in COMSOL by setting the coil to be excited by Voltage and setting the voltage to be zero. In short:
- Set Icoil = 0 (open circuit), Irail = 1, and measure Vtot_coil and Vtot_rail. Then: Lself_rail = imag(Vrail/Irail)/omega; Mcoil_rail = imag(Vcoil/Irail)/omega;
- Set the coil to be voltage-driven and set Vcoil = 0, set Irail = 1 and measure Vtot_rail. Then: Lleak_rail = imag Vrail/Irail)/omega."
To do this I have made four models (I could probably do this using one model, but this is what I was able to do with my Comsol-knowledge):
1. Attached model named "Self_inductance rev2 open circuit coil_Mutual induction coil rail.mph"
In this model the mutual induction Mcoil_rail is calculated by driving a current in the rail; Irail=1A and Icoil=0A. So far this looks ok for me.
2. Attached model named "Self_inductance rev2 short circuit coil_Leak induction rail.mph"
In this model the coil is set to be voltage-driven, where V=0, to calculate the leak induction for the rail. This is where the problems starts. According to the 1D-plot the leak induction is decreasing as the frequency increase, this is not what I was expecting. What am I doing wrong? As the frequency increase the mutual induction decrease, logical the leak induction should increase.
3. Attached model named "Self_inductance rev2 open circuit rail_Mutual induction rail coil.mph"
In this model the currents are set as Irail=0A and Icoil=1. By doing this it should be possible to calculate the mutual inductance Mrail_coil. This could be useful to verify model (1) because Mcoil_rail = Mrail_coil. In this case the problem is that the coil wich is generating the magnetic field don't generate current in the rail. This should be straigt forward as model (1) is ok? What could be wrong here?
4. Attached model named "Self_inductance rev2 short circuit rail_Leak induction coil.mph"
In this model the rail is set to voltage-driven, where V=0, to calculate the leak induction for the coil. Here I'm getting the same problem as in model (2). By solving the problem in (2) will hopefully solve this problem as well.
To make a better understanding of the system that I'm trying to simulate I have attached some illustrations that I found on the internet.
Thanks!
Best regards Yngve
Attachments:
- Self_inductance rev2 short circuit rail_Leak induction coil.mph
- Self_inductance rev2 open circuit coil_Mutual induction coil rail.mph
- Self_inductance rev2 open circuit rail_Mutual induction rail coil.mph
- Self_inductance rev2 short circuit coil_Leak induction rail.mph
- System concept model.JPG
- System concept model2.JPG
- System concept model3.JPG
4 Replies Last Post 8 juin 2012, 09:02 UTC−4
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Posted:
1 decade ago
Hi
I havent had time to look into all of your files, just one and I have a few minor comments:
1) you are not using boundary layers in your circular "bulk" coils, I would add that to better resolve the skin effect
2) I would reduce the thickness of the PML and increase somewhat the air around i.e. go from 350 to 400 on the inner circle. You can add the streamline and use uniform distribution, to trace how the surrounding is effecting the filed lines. Then perhaps move your model core some 40-80 mm "up" to get it more centred (minor cosmetics)
3) 2D is not really 2d-Axi I have the same issue on one of my models, how correctly to link the "looping" coils and to estimate what is really the true "depth" and resistance in this way
4) I mostly use a frequency domain ranges of the type: 1[kHz]*10^{range(0,0.1,3)} it looks better on log bode plots
5) when I have several load cases I sometimes add a Parametric Sweep and use the parameter as "switch" to change the boundary conditions, it works OK when the solver has no major issues with the convergence as it will otherwise try intermediate parameter values, which do not make sense for my "switch cases
--
Good luck
Ivar
I havent had time to look into all of your files, just one and I have a few minor comments:
1) you are not using boundary layers in your circular "bulk" coils, I would add that to better resolve the skin effect
2) I would reduce the thickness of the PML and increase somewhat the air around i.e. go from 350 to 400 on the inner circle. You can add the streamline and use uniform distribution, to trace how the surrounding is effecting the filed lines. Then perhaps move your model core some 40-80 mm "up" to get it more centred (minor cosmetics)
3) 2D is not really 2d-Axi I have the same issue on one of my models, how correctly to link the "looping" coils and to estimate what is really the true "depth" and resistance in this way
4) I mostly use a frequency domain ranges of the type: 1[kHz]*10^{range(0,0.1,3)} it looks better on log bode plots
5) when I have several load cases I sometimes add a Parametric Sweep and use the parameter as "switch" to change the boundary conditions, it works OK when the solver has no major issues with the convergence as it will otherwise try intermediate parameter values, which do not make sense for my "switch cases
--
Good luck
Ivar
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Posted:
1 decade ago
Hi
Thanks for the comments Ivar! There are still some things that are unclear for me.
I still don't understand why I'm not able to induce a current in the rail (coil "1" and "2") when I "reverse" the system to calculate the mutual induction in opposite direction (Mrail_coil) by driving the current through the multi turn coil reference is made to the model "Self_inductance rev2 open circuit rail_Mutual induction rail coil.mph".
Do you have comments to the calculations of the leak inductances, reference is made to the model "Self_inductance rev2 short circuit coil_Leak induction rail.mph"?
Reference to your comments:
1) I'm not sure if I understand it correctly on this point could you please describe more what you mean and how I can add a boundary layer for the "bulk" coil? Wouldn't the "Multi Turn Coil Domain" consider this as I have specified number of turns for the coil? Would the "skin effect" be relevant for me to consider as I only wants to see the effect of the leak inductances and mutual inductance and not the resistive losses?
2) This is ok.
3) Would it make it easier for me to build up the model as a 2D-axisymetrical model? What I want with the simulations is to look at the effects seawater will have on an inductive power transfer system compared to air so I don't think it would be a problem for me to assume a 2D-axisymetrical model.
4) This is ok.
5) I have found a description for "Parametric sweep" in the "Introduction to Comsol Multiphysics" manual so I will do some more investigation on that.
Thanks again Ivar!
Best regards Yngve
Thanks for the comments Ivar! There are still some things that are unclear for me.
I still don't understand why I'm not able to induce a current in the rail (coil "1" and "2") when I "reverse" the system to calculate the mutual induction in opposite direction (Mrail_coil) by driving the current through the multi turn coil reference is made to the model "Self_inductance rev2 open circuit rail_Mutual induction rail coil.mph".
Do you have comments to the calculations of the leak inductances, reference is made to the model "Self_inductance rev2 short circuit coil_Leak induction rail.mph"?
Reference to your comments:
1) I'm not sure if I understand it correctly on this point could you please describe more what you mean and how I can add a boundary layer for the "bulk" coil? Wouldn't the "Multi Turn Coil Domain" consider this as I have specified number of turns for the coil? Would the "skin effect" be relevant for me to consider as I only wants to see the effect of the leak inductances and mutual inductance and not the resistive losses?
2) This is ok.
3) Would it make it easier for me to build up the model as a 2D-axisymetrical model? What I want with the simulations is to look at the effects seawater will have on an inductive power transfer system compared to air so I don't think it would be a problem for me to assume a 2D-axisymetrical model.
4) This is ok.
5) I have found a description for "Parametric sweep" in the "Introduction to Comsol Multiphysics" manual so I will do some more investigation on that.
Thanks again Ivar!
Best regards Yngve
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hei Yngve
5) be aware there are 2 types of parametric sweeps in COMSOL (check search on the forum and the doc), there is one external with the name: Parametric Sweep it loops around the full model including geometry and mesh, so it allows to change the sizes of some geometries, so long you do not change the topology (no new entities: Domains or boundaries). It restarts the solver by default at their initial values, since it imply a new mesh.
Then you have the the "solver continuation sweep" that works on a predefined geometry and mesh, each solver step, start, by default, from the previous step ending point
4) -
3) 2D axi is always simpler and quicker to solve, if you have a toroidal type geometry, you can even "revolve the results into a pseudo 3D view at the end (specific Results node)
2) -
1) The multi-turn Coil does not give you insights to the interior of the coil volume, it assumes tight filled coil wires, but adds the voltage drop as specific dependent variable and solves the system taking into account wire data, material data, geometry etc. If you have seawater between the individual coils, you might be better off with several separate coils sections, each with a single coil physics described. This BC takes into account also skin effects, it too adds a specific V dependent variable. Check the v4.1 doc carefully as these BC's are "higher level" physics conditions and rather subtle, but evident once understood ;)
I agree, normally there is no reason why your system is not "symmetric, you might drive the coils in an opposite way, but you must ensure that your BC's are correctly set up, you might have missed something ;)
--
Lykke til
Ivar
5) be aware there are 2 types of parametric sweeps in COMSOL (check search on the forum and the doc), there is one external with the name: Parametric Sweep it loops around the full model including geometry and mesh, so it allows to change the sizes of some geometries, so long you do not change the topology (no new entities: Domains or boundaries). It restarts the solver by default at their initial values, since it imply a new mesh.
Then you have the the "solver continuation sweep" that works on a predefined geometry and mesh, each solver step, start, by default, from the previous step ending point
4) -
3) 2D axi is always simpler and quicker to solve, if you have a toroidal type geometry, you can even "revolve the results into a pseudo 3D view at the end (specific Results node)
2) -
1) The multi-turn Coil does not give you insights to the interior of the coil volume, it assumes tight filled coil wires, but adds the voltage drop as specific dependent variable and solves the system taking into account wire data, material data, geometry etc. If you have seawater between the individual coils, you might be better off with several separate coils sections, each with a single coil physics described. This BC takes into account also skin effects, it too adds a specific V dependent variable. Check the v4.1 doc carefully as these BC's are "higher level" physics conditions and rather subtle, but evident once understood ;)
I agree, normally there is no reason why your system is not "symmetric, you might drive the coils in an opposite way, but you must ensure that your BC's are correctly set up, you might have missed something ;)
--
Lykke til
Ivar
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Posted:
1 decade ago
I am trying to simulate the amount of induced current, in some circular shaped structure which has mutual inductance with another inductor. I want to see how much power I can transfer from the external inductor (second inductor)to the coupled inductor(stent).
to simulate that, I defined two circular coils made of Copper floated in Air. and then i applied boundary conditions with exicitation of coil ...but no use ,...can anybody suggest me right procedure as i am new to comsol
--
kishore Naik Mude