Litz wire
Introduction
Litz Wire is a type of cable used in electronics to carry alternating current. The wire is designed to reduce the skin effect and proximityeffect losses in conductors used at frequencies up to about 1 MHz. It consists of many thin wires strands, individually insulated and twisted or woven together; following one of several carefully prescribed patterns often involving several levels (groups of twisted wires are twisted together, etc.).
Term
The word "Litz" is derived from the German word "Litzendraht" meaning woven wire. It refers to wire consisting of a number of individually insulated magnet wires twisted or braided into a uniform pattern, so that each strand tends to take all possible positions in the cross-section of the entire conductor.
Typical applications
Typical applications for Litz wire conductors include high-frequency inductors and transformers, motors, relays, inverters, power supplies, DC/DC converters, communications equipment, ultra-sonic equipment, sonar equipment, television equipment, and heat induction equipment.
Skin effect
Skin effect refers to the tendency of current flow in a conductor to be confined to a layer in the conductor close to its outer surface. At low frequencies, skin effect is negligible, and current is distributed uniformly across the conductor. However, as the frequency increases, the depth to which the flow can penetrate is reduced. Litz wire constructions counteract this effect by increasing the amount of surface area without significantly increasing the size of the conductor.
Proximity effect
A changing magnetic field will influence the distribution of an electric current flowing within an electrical conductor. When an alternating current (AC) flows through an isolated conductor, it creates an associated alternating magnetic field. The alternating magnetic field induces eddy currents in adjacent conductors, altering the overall distribution of current flowing through them.
The proximity effect can significantly increase the AC resistance of adjacent conductors when compared to its resistance to a DC current. The effect increases with frequency.
This effect can be reduced by using stranded wire so that each wire will link with the same number of flux as every other wire and the current will divided equally among the strands. Such a stranded cable is called a Litz conductor.
Further information
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