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Litz wire with 0.25 mm strand — 40 standard constructions

This series has 40 standard constructions with a copper cross-section from 0.5 to 20 mm². A 0.25 mm strand is optimal up to 15 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 0.2 mm strand; for lower frequencies, —. 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.

40 standard constructionsup to 15 kHzManufactured to TU 27.32.11-019-59596873-2025Lead time from 7 working days
40 of 40
Designation Strands Cross-section, mm² Ø, mm Mass, kg/km R, Ω/km
10×0.25100.51.2184.66435.49
21×0.252111.7669.79416.9
31×0.25311.52.14514.45811.45
40×0.254022.43718.6568.87
51×0.25512.52.75123.7866.96
62×0.256233.03428.9175.72
72×0.25723.53.26933.5814.93
82×0.258243.48938.2454.33
92×0.25924.53.69542.9093.86
102×0.2510253.89147.5733.48
112×0.251125.54.07752.2373.17
122×0.2512264.25656.9012.91
133×0.251336.54.44362.0312.67
143×0.2514374.60766.6952.48
153×0.251537.54.76671.3592.32
163×0.2516384.91976.0232.18
174×0.251748.55.08281.1542.04
184×0.2518495.22685.8181.93
194×0.251949.55.36690.4821.83
204×0.25204105.50395.1461.74
213×0.2521310.55.62399.3431.67
225×0.25225115.779104.941.58
235×0.2523511.55.906109.6041.51
245×0.25245126.031114.2681.45
255×0.2525512.56.152118.9321.39
265×0.25265136.272123.5961.34
275×0.2527513.56.389128.261.29
285×0.25285146.504132.9241.25
296×0.2529614.56.629138.0541.2
306×0.25306156.74142.7181.16
316×0.2531615.56.849147.3821.12
325×0.25325166.946151.581.09
336×0.2533616.57.062156.711.06
345×0.25345177.156160.9081.03
357×0.2535717.57.28166.5050.99
366×0.25366187.371170.7020.97
378×0.2537818.557.491176.2990.94
388×0.25388197.589180.9630.91
399×0.2539919.587.696186.0940.89
408×0.25408207.7821900.87

Mass per km vs copper cross-section

hover over a point to see the construction
0.051.3102.6153.9205.2 0.54.48.312.216.120.0 mass, kg/km copper cross-section, mm² 10×0.25 — 4.664 kg/km, 0.5 mm²21×0.25 — 9.794 kg/km, 1 mm²31×0.25 — 14.458 kg/km, 1.5 mm²40×0.25 — 18.656 kg/km, 2 mm²51×0.25 — 23.786 kg/km, 2.5 mm²62×0.25 — 28.917 kg/km, 3 mm²72×0.25 — 33.581 kg/km, 3.5 mm²82×0.25 — 38.245 kg/km, 4 mm²92×0.25 — 42.909 kg/km, 4.5 mm²102×0.25 — 47.573 kg/km, 5 mm²112×0.25 — 52.237 kg/km, 5.5 mm²122×0.25 — 56.901 kg/km, 6 mm²133×0.25 — 62.031 kg/km, 6.5 mm²143×0.25 — 66.695 kg/km, 7 mm²153×0.25 — 71.359 kg/km, 7.5 mm²163×0.25 — 76.023 kg/km, 8 mm²174×0.25 — 81.154 kg/km, 8.5 mm²184×0.25 — 85.818 kg/km, 9 mm²194×0.25 — 90.482 kg/km, 9.5 mm²204×0.25 — 95.146 kg/km, 10 mm²213×0.25 — 99.343 kg/km, 10.5 mm²225×0.25 — 104.94 kg/km, 11 mm²235×0.25 — 109.604 kg/km, 11.5 mm²245×0.25 — 114.268 kg/km, 12 mm²255×0.25 — 118.932 kg/km, 12.5 mm²265×0.25 — 123.596 kg/km, 13 mm²275×0.25 — 128.26 kg/km, 13.5 mm²285×0.25 — 132.924 kg/km, 14 mm²296×0.25 — 138.054 kg/km, 14.5 mm²306×0.25 — 142.718 kg/km, 15 mm²316×0.25 — 147.382 kg/km, 15.5 mm²325×0.25 — 151.58 kg/km, 16 mm²336×0.25 — 156.71 kg/km, 16.5 mm²345×0.25 — 160.908 kg/km, 17 mm²357×0.25 — 166.505 kg/km, 17.5 mm²366×0.25 — 170.702 kg/km, 18 mm²378×0.25 — 176.299 kg/km, 18.55 mm²388×0.25 — 180.963 kg/km, 19 mm²399×0.25 — 186.094 kg/km, 19.58 mm²408×0.25 — 190 kg/km, 20 mm²

How to choose a construction for your task

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.

1. By frequency → strand diameter

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.

FrequencyStrand diameter
up to 15 kHz0.25 mm
up to 25 kHz0.2 mm
up to 50 kHz0.15 mm
up to 100 kHz0.1 mm
up to 200 kHz0.071 mm
above 200 kHz0.05 mm (made to order)

This series — 0.25 mm, up to 15 kHz.

2. By current → copper cross-section

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 currentCross-section
2–3 A0.5 mm²
4–6 A1 mm²
7–10 A2 mm²
15–20 A4 mm²
30–40 A8 mm²
60–80 A16 mm²

For an accurate calculation, account for the waveform (sine / PWM / pulse) — it sets the RMS value and the losses.

3. By environment → insulation grade

Once the cross-section is set, you choose the grade — it determines the operating temperature, chemical resistance, breakdown voltage and cross-section shape.

  • PTFE (Ф) — up to 180 °C, chemical-resistant, HF
  • Polyimide (ПИ) — up to 300 °C, high loads
  • PP/A — domestic induction, low cost
  • 200 series — up to 200 °C without PTFE
  • Rectangular (Пр) — +20% winding fill

Full catalog of 50+ grades →

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.

Which insulation grades this series is available in

Popular versions — the full catalog is on the "Products" page (50+ grades).

Литц Ф Литц ПИ ЛитцПр Ф Литц 200 Литц хПП ЛитцПр ПИ

Frequently asked questions

How does litz wire with a 0.25 mm strand differ from —?
The thinner the strand, the more effective the litz wire is at high frequencies — because the skin effect is reduced. A 0.25 mm strand is optimal for frequencies up to 15 kHz. For higher frequencies you move to 0.2 mm. For lower frequencies, — is preferable on cost and manufacturability.
What frequencies can you realistically run with a 0.25 mm strand?
The effective range is up to 15 kHz. These are the frequencies at which the copper skin depth is comparable to the strand radius, and a further increase in frequency no longer improves the Q factor. For frequencies beyond this range we recommend a thinner strand.
What is the minimum order quantity?
The minimum order depends on the construction and the insulation grade. Typically from 0.5 km for standard items. Ask our engineers — we will send a quote with the exact lead time.
Are these constructions in stock?
Standard items are often in stock. The rest are made to order — production lead time from 7 working days. Availability and lead time are confirmed at quotation.
Which technical specification (TU) do you manufacture to?
TU 27.32.11-019-59596873-2025, developed and registered by DIADA LLC (Diada-Electro). The full TU package is provided on request — submit an enquiry or contact our engineers.
Can you make a non-standard construction?
Yes — strands of 0.05 / 0.12 / 0.224 / 0.315 / 0.355 / 0.4 / 0.5 mm and other cross-sections. We manufacture to the customer's specification. Send your requirements via the "Request a quote" form.

Need help choosing a construction?

Our engineers will help you select the optimal construction and insulation grade for your task

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