Optimal inductor winding geometries for minimizing winding loss in gapped inductor designs

This paper summarizes geometrical effects on inductor winding loss based on fixed and variable wire diameter methods as well as core gap effects. Relevant AC and DC winding resistance equations are derived and an effective inductor design method is given to consider the ratio of alternating to direct current and ratio of skin depth to wire radius r. The core gap effect on the ac winding resistance can be minimized by increasing the distance far away from the gap, however the dc winding resistance will increase. Hence the optimal distance results in the minimum total winding resistance. Finally, a new concept of a two step core gap solution is verified by FEA simulation showing the further winding loss improvement by the smart design method of core gap geometries.