Floating Ring: electromagnetic-thermal simulation

The electromagnetic-thermal coupled solution capability in ThermNet can be used to accurately predict the temperature rise in solid conductors where eddy currents are induced. Given that ohmic losses are a source of heat, the two-way coupling between the electromagnetic and thermal simulations takes into account the effects of temperature on the resistivity of the conductor, and how the resulting change in resistivity affects the eddy currents induced. MultiNet, Infolytica's coupled analysis module, makes this solution possible in problems that include at least one moving component, and where the electromagnetic solution is transient. Using this method of analysis, eddy currents due to motion are also taken into account. Although, in this problem, the eddy currents are due to the time-varying current in the coil.

For this analysis, we are using the same model that is described in the Floating Ring gallery page, except that in this case, MultiNet uses the Transient Thermal solver in ThermNet and the Transient with Motion solver in MagNet to solve the coupled electromagnetic-thermal problem.

Results

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This is a snapshot of the flux plot at 5 ms. The flux plot clearly demonstrates the effect of the induced currents in the ring.

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With the temperature rise being taken into account, it can be seen that the ring does not settle down at the same height as before (graph in black). As the temperature rises in the ring, the resistivity goes up and, as a result, the levitation force on the ring goes down. With a lower levitation force, the ring settles down at a lower height (graph in red). As demonstrated in the graph, the electromagnetic-thermal coupled simulation is necessary to get an accurate prediction of the performance.