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Voltage Induced in a Coil by a Moving Magnet

Posted 02.02.2016, 03:21 GMT-5 Low-Frequency Electromagnetics, Mesh Version 4.4 2 Replies

Amanda Cheu
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Dear COMSOL Community,

I am currently running a simulation which is almost identical to the tutorial on "Voltage Induced in a Coil by a Moving Magnet (I have attached the file for easy reference).

However, I want the magnet to move at a fixed linear velocity (of 60mm/s) instead of oscillatory as modeled in the tutorial. May I know how I should go about doing this?

Should I continue using Prescribed Mesh Displacement to move the magnet domain, or should I use the Prescribed Mesh Velocity setting instead? I have tried using Prescribed Mesh Velocity settings however I get an error message of "failed to find consistent initial values. last time step is not converged."

Any help is very much appreciated!!!
2 Replies Last Post 11.02.2016, 04:03 GMT-5
Nirmal Paudel COMSOL Employee

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Posted: 8 years ago 09.02.2016, 16:21 GMT-5
Hi Amanda,

You could make the magnet move with a constant velocity, for example, 60[mm/s] using the Ramp function, but still use the Prescribed Mesh Displacement boundary condition. It would be more efficient and easier for convergence if you use the Mapped Mesh in the Magnet and the air above and below it. See the example with the modification. The dimension for the rectangle (air region) was increased.

Hope this will be useful.

Best Regards,
Nirmal
Hi Amanda, You could make the magnet move with a constant velocity, for example, 60[mm/s] using the Ramp function, but still use the Prescribed Mesh Displacement boundary condition. It would be more efficient and easier for convergence if you use the Mapped Mesh in the Magnet and the air above and below it. See the example with the modification. The dimension for the rectangle (air region) was increased. Hope this will be useful. Best Regards, Nirmal
Amanda Cheu
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Posted: 8 years ago 11.02.2016, 04:03 GMT-5
Dear Nirmal,

Thank you very much for your advice, but I am unable to open the attachment because the COMSOL version that I have is an older version. Is it possible for you to attach a COMSOL model that is compatible with the version 4.4?

Furthermore, referring to the COMSOL Multiphysics User Guide (pg. 188) on Ramp Functions (i've attached the relevant page to this post), I have a few questions regarding the values that I am supposed to enter.

1. I am required to enter a location value s0 for the start of the ramp. Does this s0 value represent the starting point of my movement? i.e. if my magnet starts at r=0 and z = 5, how will I enter this value here?

2. Does the slope refer to the path of motion of the magnet? In this case, I require the magnet to move vertically downwards which implies a gradient of negative infinity.

Thank you for your time in advance, Nirmal. The guidance that you can provide is essential as this would determine whether I will pass or fail a project-based class that I am currently enrolled in.
Dear Nirmal, Thank you very much for your advice, but I am unable to open the attachment because the COMSOL version that I have is an older version. Is it possible for you to attach a COMSOL model that is compatible with the version 4.4? Furthermore, referring to the COMSOL Multiphysics User Guide (pg. 188) on Ramp Functions (i've attached the relevant page to this post), I have a few questions regarding the values that I am supposed to enter. 1. I am required to enter a location value s0 for the start of the ramp. Does this s0 value represent the starting point of my movement? i.e. if my magnet starts at r=0 and z = 5, how will I enter this value here? 2. Does the slope refer to the path of motion of the magnet? In this case, I require the magnet to move vertically downwards which implies a gradient of negative infinity. Thank you for your time in advance, Nirmal. The guidance that you can provide is essential as this would determine whether I will pass or fail a project-based class that I am currently enrolled in.

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