Summary

This section describes DC-field eddy current analysis.

Explanation　

In DC-filed eddy current analysis, a conductor with uniform electrical characteristics moving or rotating at a constant speed in one direction as shown in Figs. 1.1 and 1.2 is subjected to a constant magnetic field over time to obtain a steady-state condition. From the outside (coordinate system fixed to the excitation source), the magnetic field and eddy currents flowing in the conductor do not seem to vary with time. On the other hand, when viewed from a coordinate system fixed to the moving conductor, the magnetic field fluctuates with time, which generates eddy currents.

Such steady-state conditions can also be obtained by performing a transient analysis. However, if the velocity is high and the time for the magnetic field to penetrate into the conductor is short, a large number of calculation steps may be required to reach steady state.

Also, if the excitation source is variable, this steady state may be required as the initial state of the transient analysis. When DC-field eddy current analysis becomes available, the steady state can be obtained in a single short step.

This analysis can be applied to cases where there is an excitation source consisting of coils and magnets moving along a conductor plate or rail-like conductor, or to magnetic bearings or retarders in which a uniformly rotating body rotates in a magnetic field. Here we present an example of analysis using DC-field eddy current analysis.

Fig. 1.1 Magnetic field source moving on rail conductor

Fig.1.2 Cylindrical conductor rotating in a magnetic field