Invented toward the end of the 1800s, litz wire has drastically changed the way wires are configured. A litz wire is any wire that is composed of individually insulated strands of copper braided or otherwise woven together — as opposed to simply twisted — in specialized patterns.
The Benefits of Litz Wire
Litz wire offers a number of important benefits, especially when used in magnetic components. As discussed below, litz wire was specifically made to help reduce skin effect, but its unique design provides a range of other advantages as well, which we’ve outlined below.
Reduces Skin Effect
The skin effect is a phenomenon occurring in conductors of alternating current (AC). As AC current flows through a conductor, such as a copper wire, the fluctuating magnetic field it creates leads to the generation of opposing eddy currents. These eddy currents, in turn, cause the main AC current to form in greater densities along the surface of the conductor. Skin depth, the depth from the outer diameter of the wire through which the current flows, decreases with frequency.
By using a number of wires within a single cable, however, litz wire minimizes the skin effect by ensuring that the AC current is carried more evenly throughout the wire. Smaller-diameter copper wires are used so that the radius of each individual strand is smaller than their skin depth, so the higher the frequency, the smaller the individual conductor.
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. 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 face 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.
Allows for Use With High Frequencies
Because litz wire reduces or negates both the skin and proximity effects, it allows for the use of 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.
The increased resistance and consequent losses that are 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, like inductors and transformers, allows those components to operate at much higher levels of efficiency than comparable ones made using standard copper wire.
Because litz wire reduces the risks of proximity and skin effects, lower volumes of conductive material are required.
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.
Solutions From Agile
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, request a quote or design consultation today.