Litz Wire: An Ideal Solution for High-Frequency Applications

Invented toward the end of the 1800s, litz wire changed the way wires are configured. Its name is a shortening of the German word, “litzendraht,” which means “woven wire.” A litz wire is composed of individually insulated strands of copper which are braided or otherwise woven together in specialized patterns, as opposed to simply twisting the copper strands together.

 Litz wire is typically used to improve the efficiency of high frequency transformers, inductors, and coils, and carries AC currents at radio frequencies.

The Top 5 Benefits of Litz Wire

This type of wire offers a number of important benefits, especially when used in magnetic components. Lite wire offers these five primary benefits: 

  1. Reduces Skin Effects

The skin effect is happens in conductors of alternating current (AC). As AC current flows through a copper wire, the fluctuating magnetic field it creates generates conflicting eddy currents. Eddy currents occur more densely near the conductor’s surface. Skin depth decreases with as frequencies are reduced, making this issue more common in high-frequency applications. By using multiple wires within one cable, however, litz wire minimizes this effect by distributing AC current throughout the entirety of the wire rather than letting it travel along the surface. Using thinner copper wires ensure that each unique strand possesses a smaller radius than the skin depth. As such, the diameter of each copper wire must be smaller, correlating directly with the height of the frequency.

  1. Mitigates Proximity Effect

The proximity effect is another common issue in copper wire carrying AC current. Like the skin effect, the proximity effect is caused by eddy currents and leads to increased resistance and resultant current losses. The proximity effect differs from the skin effect in that it only occurs in scenarios with multiple conductors, and instead of focusing the current at the surface of a conductor, it focuses the current at the point farthest away from other conductors.

Litz-Wire-Transformers

 

For example, in a wire made of two copper strands laid side by side, the proximity effect would focus the current on the sides of each strand that faces away from where they join. The weave or braided pattern of a litz wire works to counter the proximity effect, with strands being placed strategically to ensure that the current load is as evenly distributed as possible.

  1. Allows for Use With High Frequencies

  2. Because litz wire reduces or negates both the skin and proximity effects, it allows high-current conductors with low resistance to be used at very high frequencies, well into the hundreds of kilohertz. This makes litz wire an ideal coil material for high-frequency magnetic components.Transformers and inductors can benefit from litz wire. A wide range of applications in a variety of industries, from personal electronics and solar energy to electric vehicles, are growing increasingly dependent on high-performance, high-frequency magnetics.
  3. Increases Efficiency

The increased resistance and consequent losses caused by the proximity effect and the skin effect correlate to notable decreases in efficiency. This is true in wires, and doubly so in transformers and inductors that use affected wires. However, use of litz wire in custom magnetics, such as inductors and transformers, allows those components to operate at much higher levels of efficiency than comparable ones made using standard copper wire.

  1. Reduces Weight

Lower volumes of conductive material are required, Because litz wire reduces the risks of proximity and skin effects. A standard single-strand copper wire would have to have a much larger circumference than the combined circumferences of all the strands of a litz wire to effectively carry the same amount of high-frequency current.

Though litz wire may require a greater number of conductive strands, the combined volume is lower, thus reducing the weight — as well as the cost and, in some cases, the size — of litz wire when compared to standard wire. This is ideal for a number of magnetics applications, particularly custom inductors and transformers, which are decreasing in size as operating frequencies increase.

Other important benefits of litz wire include:

  • Reduction of AC power loss in high-frequency winding
  • Improved efficiency
  • Avoids the occurrence of “hot spots”
  • Minimizes eddy current losses
  • Allows for lower operating temperatures
  • The final product has a reduced footprint

Types of Litz Wire

Litz wire comes in a wide variety of insulation and weaving options. The common insulator material used for the individual strands or bundles is a polyurethane-nylon film, which provides insulation while also adapting well to soldering.

There are eight standard types of litz wire available, including:

  • Type 1: A single twist with elective external insulation.
  • Type 2: A twisted bundle of Type 1 weaved together with an option for external insulation.
  • Type 3: Pre-insulated bundles of Type 2 braided/weaved together with an option for external insulation around the full bundle.
  • Type 4: Twisted bundles of non-insulated Type 2 with a fiber core.
  • Type 5: Bundles of insulated Type 2 with a fiber core.
  • Type 6: Bundles of Type 4 with a fiber core.
  • Type 7: Braided insulated wire then formed in a rectangular shape.
  • Type 8: Single twisted insulated strands compressed into a rectangular shape.

How Litz Wire Works

The objective of using litz wire is to reduce resistance by placing more conductive material near the surface of the conductor, which is where high frequency currents travel. Litz wire reduces skin and proximity resistance in the following ways:

  • Thin conductors less than a skin-depth in size largely mitigate skin effect losses.
  • Polyurethane-nylon film insulation reduces electromagnetic resistance produced by the proximity effect.
  • The weaving and/or twisting patterns reduce EM field resistance by allowing each strand to alternate between the inside and outside of the weave, twist, or braid pattern. EM fields have the highest resistance inside the pattern, and the lowest resistance outside the pattern.
  • The magnetic fields in the strands generated by the flowing current move in directions that reduce their tendency to generate opposing electromagnetic fields between the various strands. Eliminating or significantly reducing these two resistance factors in high-frequency applications is what makes it effective.

Litz Wire Applications

There are a wide variety of applications for which litz wire provides an ideal solution. Those applications tend to be higher frequency setups where lower resistance improves overall power efficiency to the various components. The following applications are among the most common:

  • Antennas
  • Wire coils
  • Sensor wiring
  • Acoustic telemetry (sonar)
  • Electromagnetic induction (heating)
  • High-frequency switch mode power converters
  • Ultrasonic devices
  • Grounding
  • Radio transmitters
  • Wireless power transmission systems
  • Electric chargers for automotive applications
  • Chokes (high-frequency inductors)
  • Motors (linear motors, stator windings, generators)
  • Chargers for medical devices
  • Transformers
  • Hybrid vehicles
  • Wind turbines
  • Communication (radio, transmission, etc.)

Litz Wire Solutions from Agile Magnetics

Agile Magnetics is a global leader in custom OEM magnetics, offering delivery reliability and extraordinary repeatability of manufacture. Our expert staff is on hand to quickly respond to inquiries and orders.

We’re proud to offer a diverse selection of both standard and custom high-performance litz wire transformers; we design and manufacture flyback bias, forward converter, gate drive, and universal winding transformers, as well as LLC and PFC chokes, with various types of this versatile wire.

To learn more about litz wire magnetics components from Agile Magnetics or discuss how we can help with your project, please don’t hesitate to request a quote or design consultation



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