How to choose the right litz wire?

Choosing the correct litz wire is a systematic process. If you get the wrong type, it can lead to inefficient operation and overheating. Follow these explicit steps to make the right choice.

Step 1: Define Your Operating Frequency

This is the most critical step. Litz wire fights the “skin effect,” where high-frequency current flows only on the outside of a conductor. Identify the fundamental frequency of your application (e.g., 100 kHz for a switch-mode power supply). Each individual strand’s diameter must be smaller than the skin depth at your frequency. Skin depth (δ) can be calculated or found in online tables.

For example: For 100 kHz operation, the skin depth in copper is about 0.22 mm. Therefore, you must choose a wire made of strands with a diameter smaller than this (e.g., 0.1 mm or AWG 38).

Step 2: Determine the Current Requirement (Ampacity)

The wire must carry your current without overheating. Find the RMS (root mean square) current your design requires. The total cross-sectional area of all the strands combined determines the current capacity. A larger overall gauge (a lower AWG number like 20 vs. 30) can handle more current.

For example: If you need to carry 5 Amps, you might choose a litz wire with a total cross-sectional area equivalent to a single AWG 21 wire. You can achieve this with 100 strands of AWG 38 or 50 strands of AWG 36, as long as the strand size from Step 1 is correct.

Step 3: Check the Physical Specifications

The wire must fit and survive in your application. Check Outer Diameter. Ensure the finished bundle’s diameter fits within your winding window and bobbin. Check Insulation Type. Is the insulation rated for your operating temperature (e.g., 155°C, 200°C)? Is it solderable? Does it need to be tough for automated winding? Check Flexibility. More strands mean greater flexibility, which is crucial for tight winding patterns. Check the types of litz wire, basic litz wire, served litz wire, taped litz wire, etc.

If you are still not certain what to choose, please contact our team for support.