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REDUCE AC LOSSES IN HIGH FREQUENCY WINDINGS

Increased efficiency, mitigation of skin effect and proximity effect

Litz wire reduces the increase in resistance of wire that takes place at higher AC frequencies due to skin effect and proximity effect.

A conductor with a larger area has a lower resistance for a given length. However at high frequencies, alternating current (AC) does not penetrate deeply into conductors due to eddy currents induced in the material; it tends to flow near the surface. This is called skin effect. Therefore in a solid conductor like a wire, current tends to flow in a layer or annulus at the surface, and less current flows through the material near the center of the wire.

In applications where multiple wires carrying the same current lie side-by-side, such as in inductor and transformer windings, a second similar effect called proximity effect causes additional current crowding, resulting in an additional increase in the resistance of the wire with frequency.

To solve the problem, litz wire which employs a stranded wire with individually insulated conductors, is a very effective solution. Each thin conductor is less than a skin-depth, so an individual strand does not suffer an appreciable skin effect loss. Every strand is insulated from each other and it takes all possible positions in the cross section of the overall conductor.