Comparing Classic EI, EE, C foil inductors, Flat wire toroidal inductors are hot in the market, here let’s discuss why people prefer flat wire, rather than common toroidal wire:

Round Wire Limitations Frequencies >20KHz

Round wire take best efficiency in frequencies up to 20KHz. In higher frequencies, skin effect (with electrons travelling mainly on the surface area of the conductor instead of through the entire cross section) increase AC resistance, flat wire is  more efficient alternative.

Flat Wire Limits skin effect

Comparing same cross section area round wire,  flat wire surface area up to 60% more, means at higher frequencies flat wire support better skin effect, better for design higher current solutions.

Flat wire's filling factor reach to 93%~95%. In some specific field, flat wire is the only solution to fit in a limited space.

It's popular in UPS, solar, automotive ,industry application.