Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.
Force calculation (magnets plus coil)
Posted Oct 31, 2016, 10:57 a.m. EDT 5 Replies
Please login with a confirmed email address before reporting spam
Hi all,
I am performing an electromagnetic analysis in an electro - mechanical actuator which consists of stationary magnets and coil and a moving plunger.
I have calculated the static force (magnet latching force), but I am having problems in calculating the force produced by the coil.
After that I have made a mechanical where I have used the global equations physics and wrote the equation of motion including all the mechanical forces and the force produced from the magnets only.
The last step is to include the force produced by the coil, based on the pulse I introduce, but I am having difficulties in calculating that.
Please any help would be appreciated.
Regards,
Pavlos.
I am performing an electromagnetic analysis in an electro - mechanical actuator which consists of stationary magnets and coil and a moving plunger.
I have calculated the static force (magnet latching force), but I am having problems in calculating the force produced by the coil.
After that I have made a mechanical where I have used the global equations physics and wrote the equation of motion including all the mechanical forces and the force produced from the magnets only.
The last step is to include the force produced by the coil, based on the pulse I introduce, but I am having difficulties in calculating that.
Please any help would be appreciated.
Regards,
Pavlos.
5 Replies Last Post Nov 3, 2016, 5:33 a.m. EDT
Please login with a confirmed email address before reporting spam
Posted:
8 years ago
Have you added the Force calculation node under the mf node?
Please login with a confirmed email address before reporting spam
Posted:
8 years ago
Yeah of course.
I have added the node to the plunger.
For the case of only magnets, I get the correct values of the holding force vs position (evaluated through testing)
The problem appears when I add the coil. I am not getting the expected force.
Cheers,
Pavlos.
I have added the node to the plunger.
For the case of only magnets, I get the correct values of the holding force vs position (evaluated through testing)
The problem appears when I add the coil. I am not getting the expected force.
Cheers,
Pavlos.
Please login with a confirmed email address before reporting spam
Posted:
8 years ago
OK, just wanted to check that you were not missing something obvious!
The Maxwell stress tensor calculation (used to calculate force) is dependant on a fine resolution mesh for accurate results. Try experimenting with mesh refinement around the plunger boundaries to get the best balance between accuracy and solve time. In previous support cases, I have been advised to add boundary elements to the internal boundaries of the plunger (to better simulate induced eddy currents within the plunger), and also the external (air) boundaries in order to better resolve the force calculation.
Have you looked at the examples in the links below?
www.comsol.com/model/electromagnetic-plunger-36671
www.comsol.com/blogs/part-1-how-to-model-a-linear-electromagnetic-plunger/
www.comsol.com/blogs/part-2-model-a-linear-electromagnetic-plunger-with-a-blocker/
The Maxwell stress tensor calculation (used to calculate force) is dependant on a fine resolution mesh for accurate results. Try experimenting with mesh refinement around the plunger boundaries to get the best balance between accuracy and solve time. In previous support cases, I have been advised to add boundary elements to the internal boundaries of the plunger (to better simulate induced eddy currents within the plunger), and also the external (air) boundaries in order to better resolve the force calculation.
Have you looked at the examples in the links below?
www.comsol.com/model/electromagnetic-plunger-36671
www.comsol.com/blogs/part-1-how-to-model-a-linear-electromagnetic-plunger/
www.comsol.com/blogs/part-2-model-a-linear-electromagnetic-plunger-with-a-blocker/
Please login with a confirmed email address before reporting spam
Posted:
8 years ago
Hi,
Thanks for your help.
I am using the Maxwell stress tensor to calculate the forces (in the case of magnets and in the case of magnets and coil as well).
I am wondering if I need to do a separate study for just the magnets and just the coil, but I don't think it is the correct way, as, in reality we have the magnets and the coil acting together and producing the force.
Should I use the Maxwell stress tensor to calculate the force produced by the coil?
Or maybe I am doing something wrong in the time dependent study? Maybe the initial conditions etc.?
Regards,
Pavlos.
Thanks for your help.
I am using the Maxwell stress tensor to calculate the forces (in the case of magnets and in the case of magnets and coil as well).
I am wondering if I need to do a separate study for just the magnets and just the coil, but I don't think it is the correct way, as, in reality we have the magnets and the coil acting together and producing the force.
Should I use the Maxwell stress tensor to calculate the force produced by the coil?
Or maybe I am doing something wrong in the time dependent study? Maybe the initial conditions etc.?
Regards,
Pavlos.
Please login with a confirmed email address before reporting spam
Posted:
8 years ago
Hi,
There is no need to do separate studies to calculate the force, although if you wanted to check that the magnet and coil were producing correct results in isolation from each other, then you could do a model just with the coil, and another model just with the magnet, just to make sure you are defining each object correctly and that you are getting expected field values for both. A good resource for modelling coils is attached. Although it is for an older version of Comsol, most of it is relevant.
It is difficult to say for sure why you are getting strange results without seeing your model. Are you working in 2D axisymmetric, or 3D?
Also, you need to ensure you are using the mf interface (rather than the mfnc).
If you can post your model, then it would help troubleshoot.
There is no need to do separate studies to calculate the force, although if you wanted to check that the magnet and coil were producing correct results in isolation from each other, then you could do a model just with the coil, and another model just with the magnet, just to make sure you are defining each object correctly and that you are getting expected field values for both. A good resource for modelling coils is attached. Although it is for an older version of Comsol, most of it is relevant.
It is difficult to say for sure why you are getting strange results without seeing your model. Are you working in 2D axisymmetric, or 3D?
Also, you need to ensure you are using the mf interface (rather than the mfnc).
If you can post your model, then it would help troubleshoot.
Attachments: