How to Select Litz Wire

Image credit:  PACK; Zureks; New England Wire Technologies Company

Litz wire is constructed of individually insulated magnetic wires that are either twisted or braided into a uniform pattern to minimize power loss.

Construction

The term litz wire is derived from the German word Litzendraht meaning "woven wire". They are constructed of individually insulated magnet wires either twisted or braided into a uniform pattern. Litz wire construction is designed to minimize the power losses exhibited in solid conductors due to "skin effect." Skin effect is the tendency of radio frequency current to be concentrated at the surface of the conductor. Litz constructions counteract this effect by increasing the amount of surface area without significantly increasing the size of the conductor.

Types

The GlobalSpec SpecSearch database contains information about different types of litz wire, categorized by shape.

• Round wire features bundles of twisted wire bound together into a round shape.

• Rectangular wire consists of insulated wires bound together and compressed into a rectangular shape.

• Braided wire is primarily used for high frequency applications.

Specifications

Frequency

Buyers should specify the frequency range of the wire.  Litz wire is very effective at reducing the impact of skin effect below 500 kHz, moderately effective for applications up to 1 MHz, and is rarely used above 2 MHz. 

Strands

Strand specifications are important to consider when selecting litz wire.  Unlike ordinary stranded conductor wire, the number of strands in a litz wire are important in relation to power loss performance rather than mechanical flexibility. 

Strand size is also an important specification, and is directly related to the frequency of the wire application.  Generally, a higher frequency application demands a smaller strand size.  Conductor size is measured by the American Wire Gauge (AWG) in the United States.  A higher AWG number indicates a thinner wire or strand. 

Served vs. unserved

Litz wire is manufactured to be either served or unserved.  A served wire is completely wrapped with a nylon textile or yarn for added strength and protection, while an unserved wire lacks this wrapping.

References

New England Wire Technologies - Litz Wire types and construction

• Reducing Inductance in Power Distribution Systems
  ) require that special magnet wire called "LITZ" be used to reduce inductance. These bundles can be large and difficult to assemble due to the varnishing of individual strands....