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Induction Heating of a Workpiece Past the Curie Point

Induction heating with MAGNET & ThermNet

A workpiece is placed inside an inductor coil; the eddy current losses raise its temperature past the Curie point, which in turn affects the distribution of the eddy currents.

To correctly simulate this process a fully coupled electromagnetic-thermal field solver and temperature dependent material database is required. This is the case for MagNet and ThermNet.

To increase the speed of the simulation, two different meshes for the thermal and magnetic problems were used:

- In ThermNet, only the workpiece itself was meshed.

- In MagNet, the coil and surrounding air must also be meshed, and moreover, the workpiece must be refined to accurately model the skin depth.

Induction Heating of a Workpiece Past the Curie Point

METHODS and RESULTS

B-H CURVES as a FUNCTION of TEMPERATURE

The workpiece is composed of a material whose magnetic properties vary as a function of temperature. The graph shows the B-H curve at different temperatures. ThermNet interpolates these curves at temperatures between those specified.

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TEMPERATURE in WORKPIECE ABOVE CURIE POINT

The temperature of the material closest to the magnetic field generating coil eventually increases beyond the Curie point and impacts its magnetic properties. The B-H curve in the hot region corresponds to the red trace in the graph of B-H curves.

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PEAK MAGNETIC FIELD

Here we see that the induced eddy currents cause an increase in the material's temperature which then impacts its properties. As the material heats up, it becomes more permeable and thus the skin depth increase. As shown, consequently, the flux lines penetrate further into the material.This effect can only be modeled if the eddy current distribution is recalculated at each transient time step, as is done in ThermNet.

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