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Modeling Eddy Current due to Moving Magnet
Posted Nov 12, 2015, 3:15 p.m. EST Low-Frequency Electromagnetics Version 5.0, Version 5.1, Version 5.2 5 Replies
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Hi all,
I'm a little new to COMSOL, so I've been having a little trouble with a project I've been working on. There are several parts to it, the way I see it:
1) I'm first modeling a "halbach array." This is basically five magnets placed in an orientation such that there is a field on one side, but no field on the other side. Halbach arrays are useful because of their monopole-like nature, making them viable for levitation due to their not breaking Earnshaw's Theorem.
2) I'm then moving this halbach array over an aluminum sheet. The changing magnetic flux induces circular eddy currents in the sheet.
3) As per right hand rule, these eddy currents generate a magnetic force upward, causing a levitation in the halbach arrays.
I have been able to successfully model halbach arrays in 2D and 3D. This is actually just an easy application of the mf module, where I make sure to orient the north poles of five magnets in the orientation: left, up, right, down, left. Verified.
However, I'm now unable to model the eddy currents, which is preventing me from achieving my final goal of being able to measure this levitation force. I've tried several different modules, including mfh and mef, but to no avail. My first idea was to adapt COMSOL's eddy current braking model, but this proved to be unsuccessful, and the computer I used (it has 32gb of RAM!) timed out on my adapted code. Maybe I'm doing something wrong?
Within mef and mfh, there's an option for a Velocity (Lorentz Term). Is this the best way to "move" the magnets at a velocity? Or, should I set up some sort of moving mesh type thing? Also, I've been unable to plot the currents in the aluminum sheet. Is there some sort of other module I should use to interact with the magnetic fluxes?
I'm a little new to COMSOL, so I've been having a little trouble with a project I've been working on. There are several parts to it, the way I see it:
1) I'm first modeling a "halbach array." This is basically five magnets placed in an orientation such that there is a field on one side, but no field on the other side. Halbach arrays are useful because of their monopole-like nature, making them viable for levitation due to their not breaking Earnshaw's Theorem.
2) I'm then moving this halbach array over an aluminum sheet. The changing magnetic flux induces circular eddy currents in the sheet.
3) As per right hand rule, these eddy currents generate a magnetic force upward, causing a levitation in the halbach arrays.
I have been able to successfully model halbach arrays in 2D and 3D. This is actually just an easy application of the mf module, where I make sure to orient the north poles of five magnets in the orientation: left, up, right, down, left. Verified.
However, I'm now unable to model the eddy currents, which is preventing me from achieving my final goal of being able to measure this levitation force. I've tried several different modules, including mfh and mef, but to no avail. My first idea was to adapt COMSOL's eddy current braking model, but this proved to be unsuccessful, and the computer I used (it has 32gb of RAM!) timed out on my adapted code. Maybe I'm doing something wrong?
Within mef and mfh, there's an option for a Velocity (Lorentz Term). Is this the best way to "move" the magnets at a velocity? Or, should I set up some sort of moving mesh type thing? Also, I've been unable to plot the currents in the aluminum sheet. Is there some sort of other module I should use to interact with the magnetic fluxes?
5 Replies Last Post Dec 29, 2016, 8:21 a.m. EST
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Posted:
9 years ago
Hi,
For modeling eddy current in the aluminum/copper tube when a magnet is sliding inside it, we do recommend you to refer to this example:
www.comsol.com/model/magnet-falling-through-copper-tube-13875
This example is for a single piece of magnet, but you could have an array of magnets defined similar to the one done here.
Hope this will be useful.
Best Regards,
Nirmal Paudel
For modeling eddy current in the aluminum/copper tube when a magnet is sliding inside it, we do recommend you to refer to this example:
www.comsol.com/model/magnet-falling-through-copper-tube-13875
This example is for a single piece of magnet, but you could have an array of magnets defined similar to the one done here.
Hope this will be useful.
Best Regards,
Nirmal Paudel
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Posted:
9 years ago
Hi Nirmal,
I tried to do this with a 3D model, but am unable to define a force term in my variable. I integrate over my track (and name this inttrack) then I tried to define Fy with the expression inttrack(-mfh.Fltzz*m) where m is my mass and Fl is the Lorentz Term.
This is based on defining the force due to the lorentz term in COMSOL's eddy current example. I noticed that 2D mf has allowance for the Lorentz Term, but 3D mf does not. So, I am trying the mfh module, except that it does not seem to allow me to account for the lorentz force.
Do you know how to resolve this for 3D?
I tried to do this with a 3D model, but am unable to define a force term in my variable. I integrate over my track (and name this inttrack) then I tried to define Fy with the expression inttrack(-mfh.Fltzz*m) where m is my mass and Fl is the Lorentz Term.
This is based on defining the force due to the lorentz term in COMSOL's eddy current example. I noticed that 2D mf has allowance for the Lorentz Term, but 3D mf does not. So, I am trying the mfh module, except that it does not seem to allow me to account for the lorentz force.
Do you know how to resolve this for 3D?
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Posted:
8 years ago
Hi Nirmal,
If we want to model a moving conductor over a magnet or an AC coil, I think the model"www.comsol.com/model/magnet-fa...ling-through-copper-tube-13875" may not work, as the the Velocity (Lorentz term) would not work when the moving conductor is finite, right?
So, if we want to calculate the Lorentz force on a moving conductor over a magnet or AC coil, do you have any recommended example?
Thank you.
If we want to model a moving conductor over a magnet or an AC coil, I think the model"www.comsol.com/model/magnet-fa...ling-through-copper-tube-13875" may not work, as the the Velocity (Lorentz term) would not work when the moving conductor is finite, right?
So, if we want to calculate the Lorentz force on a moving conductor over a magnet or AC coil, do you have any recommended example?
Thank you.
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Posted:
8 years ago
Hey Vidur.
I've been trying the same problem, but it's not working. This is for the 2D model. Did you manage to do this? If so can you help me out?
I've been trying the same problem, but it's not working. This is for the 2D model. Did you manage to do this? If so can you help me out?
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Posted:
8 years ago
What I did is I made the Al sheet infinite by using the infinite elements domain on two end pieces of the Al sheet. This seemed to resolve that problem for me, but I'm still not getting a solution.