An Approximation Model of AC Resistance for Inductor and Transformer Windings with Partial Layers

This paper proposes an approximation model of the ac resistance for windings with partial layers. It introduces the concept of the number of layers for the partial winding without theoretical support. It is simple and with good accuracy compared to the original partial layer equation. The error between the approximation and original equation is derived and compared analytically. The approximation method is verified in two case studies with the finite element
method simulation (FEM) and experimental results. Based on the approximation equation, an optimization method is proposed for the winding with partial layers. It leads to the minimum ac resistance within the design restrictions, and
is applicable for inductors and transformers. Finally, the optimization method is verified in a case study of a 20 kHz transformer winding design.