Wire flattening is an optimization method for round wire transformer designs. Wire flattening allows you to increase the filling factor on the layer by minimizing the gaps between round wires, resulting in lower-diameter, compact transformers.
Below you can see a 1448 micron diameter copper conductor (1.5 mm) with a cross-section area of 1.648 mm2 and the cross-section change in the flattened wire:

Figure 1. 1.648 〖mm〗^2cross-section and 1448 microndiametercopperconductor

Figure 2. Two flattened point-to-point distance on 1.511 〖mm〗^2cross-sections and 1231 micron diameter copper conductor with flattening applied

The cross-section difference between the flattening process is measured microscopically as 8.22%. When making round wire flattening on transformers, the cross-section loss in the wire must be considered in calculations.