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Simple AC current driven coax not working

Posted 6 apr 2018, 14:49 GMT-4 Electromagnetics, Low-Frequency Electromagnetics Version 5.2a 2 Replies

James Garbus
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I've created a simple coax geometry with one end shorted, driven from the other with 1amp at 100Hz through a lumped port using the magnetic fields physics. Current in and out measured with boundary probes is not exactly one amp. Boundary probes at the terminated end show essentially zero current. Boundary probes along the inner surfaces of the coax measure large currents (hundreds of amps). Can anyone help me with what I am doing wrong? I am trying to run a more complicated geometry and am having similar problems with currents not making sense, so I made simple one. Is there problem with the cunductivity of air I am using (1S/m)? Even if I add the electric currents physics and apply insulation on the walls of the coax I get similar results.

2 Replies Last Post 4 mag 2018, 14:25 GMT-4
Sergei Yushanov Certified Consultant
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Posted: 6 years ago 3 mag 2018, 08:42 GMT-4

James,

In (mf) physics interface, current path must be solenoidal, it must form a closed loop back upon itself. You don't have closed loop for current flow, which violates Maxwell's equations - no physically meaningfull results can be expected from the model.

Regards, Sergei

James, In (mf) physics interface, current path must be solenoidal, it must form a closed loop back upon itself. You don't have closed loop for current flow, which violates Maxwell's equations - no physically meaningfull results can be expected from the model. Regards, Sergei
James Garbus
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Posted: 6 years ago 4 mag 2018, 14:25 GMT-4

Sergei,

I added a return on the other end of the coax structure and moved the lumped port excitation to the center and still have similar results.

Any idea of what may still be wrong with my model? This geometry is not literally a soleniod but there is a complete loop for current to flow.

I looked at the eddy currents example in the application library and it uses an edge current on a line with a second segment returning to its origin (was not selected to be closed geometry); I tried removing this second segment and it had no effect on the model.

James

Sergei, I added a return on the other end of the coax structure and moved the lumped port excitation to the center and still have similar results. Any idea of what may still be wrong with my model? This geometry is not literally a soleniod but there is a complete loop for current to flow. I looked at the eddy currents example in the application library and it uses an edge current on a line with a second segment returning to its origin (was not selected to be closed geometry); I tried removing this second segment and it had no effect on the model. James

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