Discussion Forum

1. How quickly do you want to disconnect the coil? If the disconnection is fast enough, the loop will radiate high frequency RF waves. If slow enough, there will be no significant radiation.
2. Are you interested in modeling the RF radiation or are you only interested in relatively low frequency electromagnetic phenomena?
3. You first say you want to build a model with "a coil at the center," but then you talk about a separate receiving coil as well. And you mention that they are each only one turn (if I understand you correctly). How are these two loops arranged? Is the coupling between them more like that between two closely-placed low-frequency coils (such as between the primary and secondary of a transformer) or is it more like the coupling between two widely spaced, higher-frequency well-separated loops (such as one used as a transmitting antenna, and the other for receiving)? For transformer-like (reactive near-field) problems, use the AC/DC module. For antenna-like (radiating near-field and far-field) problems, use the RF module.
4. Either way, for the disconnect process, you need to do a transient time-domain model. Your time steps will need to be short compared to the disconnection time.
5. If you have axial symmetry (in both the full geometry and fields) in your model, do a 2D axi-symmetric model.
6. You'll need to bound your space (whether 2D or 3D) with appropriate RF or EM boundary conditions. But the details of those conditions depend on information you have not provided.
   If you want more specific suggestions, then I encourage you to post more information about what you are trying to accomplish, as well as upload any model you have prepared so far.

1.I want to disconnect the coil at the moment of power on，When the power on time t > 0, the current is disconnected，electric current=0，what I want to study is the change of induced electromotive force in several microsecondsranges at this moment； 2.I'm interested in transient electromagnetic fields，and i want to study transient electromagnetic method； 3.I mean to establish a coil, which is both a receiving coil and a transmitting coil, that is, the overlapping loop device in the transient electromagnetic method. Through this coil, the current is transmitted, and then the signal is received immediately； 4.The model I built has been uploaded, that is, in the ac/dc module, transient research, but I don't know how to set the number of turns of the multi turn coil (receiving and transmitting are integrated) 5.

The model I built is in the ac/dc module, transient research, but I don't know how to set the number of turns of the multi turn coil (receiving and transmitting are integrated),that is, the overlapping loop device in the transient electromagnetic method

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If I understand you correctly, you have only one current loop. I wouldn't call it a transmitter or a receiver. It is simply a current loop and you want to simulate a constant current in the loop, then interrupt that current (smoothly, on a timescale of a few microseconds) and then you want to observe how the loop (which exhibits inductance) will behave after you do that. Is that correct?

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If I understand you correctly, you have only one current loop. I wouldn't call it a transmitter or a receiver. It is simply a current loop and you want to simulate a constant current in the loop, then interrupt that current (smoothly, on a timescale of a few microseconds) and then you want to observe how the loop (which exhibits inductance) will behave after you do that. Is that correct?

That's right. The model I built has been uploaded, the coil is a ring, which is obtained by rotating the rectangle.A current is applied to the coil to study the response of the surrounding magnetic field to the medium at the turning off moment.

Well, you could try using the MF application mode in 2D axisymmetry, with a time-dependent azimuthal current density applied to your loop. But if you want to study a very rapid turn-off of the current, you should use the RF module. You also might want to take a look at: K. Langenberg, "Transient fields of small loop antennas," in IEEE Transactions on Antennas and Propagation, vol. 24, no. 2, pp. 236-239, March 1976, doi: 10.1109/TAP.1976.1141303.