Litz Wire Construction & Skin Depth Reference Matrix
This technical sheet provides frequency-dependent skin depth thresholds, single-strand gauge constraints, and bundle packing factors for high-frequency coil design. Cross-reference specific terminology in our electromagnetic coil design and winding glossary.
Frequency vs. Skin Depth ($\delta$) & Strand Sizing
Conductor skin depth is governed by $\delta = \sqrt{\rho / (\pi \cdot f \cdot \mu_0)}$. To suppress high-frequency AC losses, individual strand diameters should not exceed $2\cdot\delta$. Review the physics in our glossary under Penetration / Skin depth and Skin effect.
| Operating Frequency ($f$) | Copper Skin Depth $\delta$ (at 100 °C) | Max Recommended Strand Diameter | Equivalent Nominal Wire Gauge |
|---|---|---|---|
| 10 – 20 kHz | ~ 0.536 mm | 0.800 mm | AWG 20 / 0.80 mm |
| 20 – 50 kHz | ~ 0.339 mm | 0.500 mm | AWG 24 / 0.50 mm |
| 50 – 100 kHz | ~ 0.240 mm | 0.355 mm | AWG 27 / 0.35 mm |
| 100 – 200 kHz | ~ 0.170 mm | 0.200 mm | AWG 32 / 0.20 mm |
| 200 – 500 kHz | ~ 0.107 mm | 0.100 mm | AWG 38 / 0.10 mm |
| 500 kHz – 1 MHz | ~ 0.076 mm | 0.050 mm | AWG 44 / 0.05 mm (See Ultra-fine wire) |
Litz Bundle Construction & Packing Factors ($k_{\text{pack}}$)
Packing factors determine the ratio of net copper cross-section to total bundle outer area. For detailed construction steps, visit our Packing factor definition and the primary Litz wire glossary entry.
| Bundle Type / Topology | Strand Count Range | Typical Packing Factor ($k_{\text{pack}}$) | Primary Application |
|---|---|---|---|
| Type 1 (Single Bundled) | 3 – 60 strands | 0.68 – 0.73 | General high-frequency inductors & SMPS transformers. |
| Type 2 (Cabled Bundles) | 60 – 1,000+ strands | 0.62 – 0.67 | High-power induction heating & EV wireless charging. |
| Type 3 (Served Litz) | Textile overbraided | 0.55 – 0.62 | Enhanced mechanical protection & precise inter-winding creepage. |
For metric-to-AWG gauge conversion tables, consult our magnet wire AWG to metric reference or read our in-depth high-frequency litz wire selection guide.