This series has 40 standard constructions with a copper cross-section from 0.5 to 20 mm². A 0.071 mm strand is optimal up to 200 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 0.05 mm strand; for lower frequencies, 0.1 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 |
|---|---|---|---|---|---|
| 125×0.071 | 125 | 0.5 | 1.36 | 4.736 | 35.2 |
| 255×0.071 | 255 | 1 | 1.942 | 7.96 | 17.26 |
| 378×0.071 | 378 | 1.5 | 2.364 | 15.044 | 11.64 |
| 504×0.071 | 504 | 2 | 2.73 | 20.059 | 8.73 |
| 630×0.071 | 630 | 2.5 | 3.052 | 25.074 | 6.98 |
| 750×0.071 | 750 | 3 | 3.33 | 29.85 | 5.87 |
| 875×0.071 | 875 | 3.5 | 3.597 | 34.825 | 5.03 |
| 1000×0.071 | 1000 | 4 | 3.845 | 38.208 | 4.4 |
| 1125×0.071 | 1125 | 4.5 | 4.079 | 44.775 | 3.91 |
| 1250×0.071 | 1250 | 5 | 4.299 | 51.74 | 3.52 |
| 1400×0.071 | 1400 | 5.5 | 4.55 | 55.72 | 3.14 |
| 1500×0.071 | 1500 | 6 | 4.71 | 59.7 | 2.93 |
| 1650×0.071 | 1650 | 6.5 | 4.939 | 65.67 | 2.67 |
| 1800×0.071 | 1800 | 7 | 5.159 | 71.64 | 2.44 |
| 1900×0.071 | 1900 | 7.5 | 5.3 | 75.62 | 2.32 |
| 2000×0.071 | 2000 | 8 | 5.438 | 79.6 | 2.2 |
| 2150×0.071 | 2150 | 8.5 | 5.638 | 85.57 | 2.05 |
| 2275×0.071 | 2275 | 9 | 5.8 | 90.545 | 1.93 |
| 2400×0.071 | 2400 | 9.5 | 5.957 | 95.52 | 1.83 |
| 2525×0.071 | 2525 | 10 | 6.11 | 100.495 | 1.74 |
| 2650×0.071 | 2650 | 10.5 | 6.26 | 105.47 | 1.66 |
| 2780×0.071 | 2780 | 11 | 6.411 | 110.644 | 1.58 |
| 2910×0.071 | 2910 | 11.5 | 6.56 | 115.818 | 1.51 |
| 3040×0.071 | 3040 | 12 | 6.705 | 120.992 | 1.45 |
| 3160×0.071 | 3160 | 12.5 | 6.836 | 125.768 | 1.39 |
| 3280×0.071 | 3280 | 13 | 6.964 | 130.544 | 1.34 |
| 3400×0.071 | 3400 | 13.5 | 7.09 | 135.32 | 1.29 |
| 3550×0.071 | 3550 | 14.1 | 7.245 | 141.29 | 1.24 |
| 3650×0.071 | 3650 | 14.5 | 7.346 | 145.27 | 1.21 |
| 3800×0.071 | 3800 | 15 | 7.496 | 151.24 | 1.16 |
| 3925×0.071 | 3925 | 15.5 | 7.618 | 156.215 | 1.12 |
| 4050×0.071 | 4050 | 16 | 7.739 | 161.19 | 1.09 |
| 4175×0.071 | 4175 | 16.5 | 7.857 | 166.165 | 1.05 |
| 4300×0.071 | 4300 | 17 | 7.974 | 171.14 | 1.02 |
| 4425×0.071 | 4425 | 17.5 | 8.089 | 176.115 | 0.99 |
| 4550×0.071 | 4550 | 18 | 8.202 | 181.09 | 0.97 |
| 4675×0.071 | 4675 | 18.5 | 8.314 | 186.065 | 0.94 |
| 4800×0.071 | 4800 | 19 | 8.425 | 191.04 | 0.92 |
| 4925×0.071 | 4925 | 19.5 | 8.534 | 196.015 | 0.89 |
| 5050×0.071 | 5050 | 20 | 8.641 | 200.99 | 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 — 0.071 mm, up to 200 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.
Popular versions — the full catalog is on the "Products" page (50+ grades).
Our engineers will help you select the optimal construction and insulation grade for your task