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electromagnetic force on a levitated object
Posted May 2, 2012, 6:15 a.m. EDT Low-Frequency Electromagnetics Version 4.2a 1 Reply
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Dear all,
I'm trying to make a frequency domain simulation to study the electromagnetic (EM) forces generated on an aluminium micro object that is levitated by EM induction. The model is quite straightforward; it consists of a long aluminium loop, the levitated object, and the air domains. I'm using MF study mode and applying 0.6A through the coil using a lumped port condition and looking for a frequency domain solution between 10-50MHz.
My problem is unless I define a certain conductivity (say something like 1 to 1000S/m) for air, the problem cannot be solved (it gives an error message right at the beginning saying something like matrix has zero at the diagonal). When I try out different values for air conductivity I get completely different results hence I cannot rely on the solution.
Another point is that my coil and object is in the order of 6um thick hence skin effect is important in the frequency of interest (10-50MHz). For this reason, I have meshed the object with a few elements along the thickness to take into account the skin depth. However, I'm not sure if I should do the same for the coil as well which has the same thickness?
Any suggestions would greatly be appreciated. I have also attached the model for those who might be interested.
Regards,
Ibrahim
I'm trying to make a frequency domain simulation to study the electromagnetic (EM) forces generated on an aluminium micro object that is levitated by EM induction. The model is quite straightforward; it consists of a long aluminium loop, the levitated object, and the air domains. I'm using MF study mode and applying 0.6A through the coil using a lumped port condition and looking for a frequency domain solution between 10-50MHz.
My problem is unless I define a certain conductivity (say something like 1 to 1000S/m) for air, the problem cannot be solved (it gives an error message right at the beginning saying something like matrix has zero at the diagonal). When I try out different values for air conductivity I get completely different results hence I cannot rely on the solution.
Another point is that my coil and object is in the order of 6um thick hence skin effect is important in the frequency of interest (10-50MHz). For this reason, I have meshed the object with a few elements along the thickness to take into account the skin depth. However, I'm not sure if I should do the same for the coil as well which has the same thickness?
Any suggestions would greatly be appreciated. I have also attached the model for those who might be interested.
Regards,
Ibrahim
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1 Reply Last Post May 2, 2012, 5:09 p.m. EDT
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Posted:
1 decade ago
Hi
have you checked that at these frequencies you are still within valid ACDC conditions?
as well as are you sure you can use MF and do not need the solving of "V" hence MEF? (which is much heavier).
With MEF indeed you need to put some conductvity to the air, normally, my experience is that up to 1000 S/m there is little effect due to this, but that was on larger objects and lower frequences
(nb: I cannot open your model as I'm on travel, far away from my COMSOL WS ;(
--
Good luck
Ivar
have you checked that at these frequencies you are still within valid ACDC conditions?
as well as are you sure you can use MF and do not need the solving of "V" hence MEF? (which is much heavier).
With MEF indeed you need to put some conductvity to the air, normally, my experience is that up to 1000 S/m there is little effect due to this, but that was on larger objects and lower frequences
(nb: I cannot open your model as I'm on travel, far away from my COMSOL WS ;(
--
Good luck
Ivar