The current in a choke coil’s interior produces local heat generation because of the skin effect, proximity effect, and current offsets caused by leakage flux near the gap. From a heat resistant design standpoint, visual confirmation of detailed current distribution using a finite element analysis (FEA) is useful because it provides feedback for the design.
This Application Note explains a case example that obtains the current distribution in a choke coil.
Current Density Distribution
The current waveform is shown in fig. 1, and the current density distribution in the coils at each time is shown in fig. 4.2. In order to evaluate in a steady state, fig. 1 shows the time from 40 μs to 80 μs.
From the figures, it is apparent that there are offsets in the current at 40 and 60 μs when the time variations in the current are severe, and that there is not much of an offset at 50 μs, when the time variations are mild. This is because variations in the magnetic field near the gap, which are the source of current offsets, cause variations in the coil current.