This series has 40 standard constructions with a copper cross-section from 0.5 to 20 mm². A 0.15 mm strand is optimal up to 50 kHz — at these frequencies the litz wire delivers the highest winding Q factor by minimizing the skin and proximity effects. For higher-frequency tasks you move to a 0.1 mm strand; for lower frequencies, 0.2 mm. All constructions are manufactured by DIADA LLC (Diada-Electro) to TU 27.32.11-019-59596873-2025 and are available in 50+ insulation grades — from PTFE and polyimide to rectangular forming.
| Designation | Strands | Cross-section, mm² | Ø, mm | Mass, kg/km | R, Ω/km |
|---|---|---|---|---|---|
| 28×0.15 | 28 | 0.5 | 1.287 | 3.376 | 35.21 |
| 60×0.15 | 60 | 1 | 1.884 | 10.128 | 16.43 |
| 85×0.15 | 85 | 1.5 | 2.242 | 14.348 | 11.6 |
| 115×0.15 | 115 | 2 | 2.608 | 19.412 | 8.57 |
| 140×0.15 | 140 | 2.5 | 2.878 | 23.632 | 7.04 |
| 170×0.15 | 170 | 3 | 3.171 | 28.696 | 5.8 |
| 200×0.15 | 200 | 3.5 | 3.439 | 33.76 | 4.93 |
| 225×0.15 | 225 | 4 | 3.648 | 37.98 | 4.38 |
| 255×0.15 | 255 | 4.5 | 3.884 | 43.044 | 3.87 |
| 285×0.15 | 285 | 5 | 4.106 | 48.108 | 3.46 |
| 312×0.15 | 312 | 5.5 | 4.296 | 52.666 | 3.16 |
| 340×0.15 | 340 | 6 | 4.484 | 57.392 | 2.9 |
| 368×0.15 | 368 | 6.5 | 4.665 | 62.118 | 2.68 |
| 396×0.15 | 396 | 7 | 4.84 | 66.845 | 2.49 |
| 425×0.15 | 425 | 7.5 | 5.014 | 71.74 | 2.32 |
| 450×0.15 | 450 | 8 | 5.159 | 75.96 | 2.19 |
| 480×0.15 | 480 | 8.5 | 5.328 | 81.024 | 2.05 |
| 510×0.15 | 510 | 9 | 5.492 | 86.088 | 1.93 |
| 540×0.15 | 540 | 9.5 | 5.651 | 91.152 | 1.83 |
| 570×0.15 | 570 | 10 | 5.806 | 96.216 | 1.73 |
| 594×0.15 | 594 | 10.5 | 5.927 | 100.267 | 1.66 |
| 620×0.15 | 620 | 11 | 6.056 | 104.656 | 1.59 |
| 650×0.15 | 650 | 11.5 | 6.2 | 109.72 | 1.52 |
| 680×0.15 | 680 | 12 | 6.342 | 114.784 | 1.45 |
| 705×0.15 | 705 | 12.5 | 6.457 | 119.004 | 1.4 |
| 740×0.15 | 740 | 13.1 | 6.616 | 124.912 | 1.33 |
| 765×0.15 | 765 | 13.5 | 6.727 | 129.132 | 1.29 |
| 792×0.15 | 792 | 14 | 6.844 | 133.69 | 1.24 |
| 825×0.15 | 825 | 14.6 | 6.985 | 139.26 | 1.19 |
| 850×0.15 | 850 | 15 | 7.09 | 143.48 | 1.16 |
| 880×0.15 | 880 | 15.5 | 7.214 | 148.544 | 1.12 |
| 912×0.15 | 912 | 16 | 7.344 | 153.946 | 1.08 |
| 936×0.15 | 936 | 16.5 | 7.44 | 157.997 | 1.05 |
| 960×0.15 | 960 | 17 | 7.535 | 162.048 | 1.03 |
| 990×0.15 | 990 | 17.5 | 7.652 | 167.112 | 1 |
| 1020×0.15 | 1020 | 18 | 7.767 | 172.176 | 0.97 |
| 1050×0.15 | 1050 | 18.55 | 7.881 | 177.24 | 0.94 |
| 1075×0.15 | 1075 | 19 | 7.974 | 181.46 | 0.92 |
| 1100×0.15 | 1100 | 19.4 | 8.066 | 185.68 | 0.9 |
| 1134×0.15 | 1134 | 20 | 8.19 | 190 | 0.87 |
Three parameters drive the choice: frequency (sets the strand diameter), current (sets the copper cross-section), and temperature and environment (set the insulation grade). We work backwards: frequency first — it unambiguously narrows the series.
The copper skin depth falls as frequency rises. Once it becomes comparable to the strand radius, a thicker strand stops helping — you need a thinner one.
| Frequency | Strand diameter |
|---|---|
| up to 15 kHz | 0.25 mm |
| up to 25 kHz | 0.2 mm |
| up to 50 kHz | 0.15 mm |
| up to 100 kHz | 0.1 mm |
| up to 200 kHz | 0.071 mm |
| above 200 kHz | 0.05 mm (made to order) |
This series — 0.15 mm, up to 50 kHz.
For transformer and inductor windings, a typical current density is 3–5 A/mm² (depending on the cooling regime and the allowable temperature rise).
| Operating current | Cross-section |
|---|---|
| 2–3 A | 0.5 mm² |
| 4–6 A | 1 mm² |
| 7–10 A | 2 mm² |
| 15–20 A | 4 mm² |
| 30–40 A | 8 mm² |
| 60–80 A | 16 mm² |
For an accurate calculation, account for the waveform (sine / PWM / pulse) — it sets the RMS value and the losses.
Once the cross-section is set, you choose the grade — it determines the operating temperature, chemical resistance, breakdown voltage and cross-section shape.
Not sure — use the winding calculator: it picks the nearest standard construction for your turns count, inductance and current. Or read the article on skin effect and proximity effect — with formulas and examples.
The frequency-range boundaries are calculated by the Sullivan criterion d ≤ δ/2 (copper skin depth δ = 2.09/√f[kHz] mm). Source: Sullivan C.R., Zhang R.Y. "Simplified Design Method for Litz Wire" — IEEE APEC 2014.
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