The term “Litz” is derived from the German litzendraht meaning woven wire. Litz wire is constructed of individually insulated magnet wires bunched or braided together in a uniform pattern so that each strand takes all possible positions in the cross section of the overall conductor.
The primary benefit of Litz wire is in reducing AC losses in high frequency windings due to the “skin effect”. Current in a solid conductor is concentrated at the periphery. As frequency rises, the current migrates to the skin. The multiple strand construction of Litz allows current to divide uniformly between strands. The AC to DC resistance ratio then tends to equalize which is desirable in high Q circuit applications.
Determining the operating frequency of the application is the most important question to consider when designing a Litz wire. The operating frequency will determine both the Litz construction and the individual wire gauge. The following table shows the recommended strand gauge versus frequency for most Litz constructions.
Because of low electrical losses and ease of soldering, the magnet wire insulation most commonly used is polyurethane or polyurethane top coated with nylon. Litz wires are often insulated with an overall single or double wrap, or serve, of nylon textile that affords additional abrasion resistance and a space factor in the winding.