Litz Wire

Single Wire Diameter vs Range of Frequency

range of frequency [kHz] dominal diameter of single wire [mm]
from to from to
0.06 1 0.4 0.254
1 10 0.254 0.2
10 20 0.2 0.127
20 50 0.127 0.102
50 100 0.102 0.079
100 200 0.079 0.063
200 350 0.063 0.05
350 850 0.05 0.04
850 1400 0.04 0.03
1400 3000 0.03 0.02

Influence of Litz Wire Parameters on Litz Wire Freatures

  construction parameters
conductor material nom. diameter single wire ØSW no. of single wires nSW no. of bundles & bunching steps length of lay SL per bunching step pitch direction SR per bunching step thickness of enamelling
litz wire features electrical total cross section litz wire AConductor,Litz; direct current resistance RDC X X X        
high frequency resistance RAC; RF-losses X X   X X    
current density J = I/AConductor,Litz   X X        
filling factor litz wire AConductor,Litz/Atot,Litz   X   X X X X
breakdown voltage UBDV             X
mechanical (AConductor,Litz = const.) outer diameter ODLitz;total cross section litz wire Atot,Litz X X X X X X X
dimensional stability   X X X X X  
flexibility   X X X X    
flexlife performance X X   X X    
max. tensile strength X            
surface structure, roundness   X X X X X  

Main influencing parameters for HF-coils

      construction parameters
      nom. diameter single wire ØSW number single wires nSW number bundles & bunching steps length of lay SL per bunching step pitch direction SR per bunching step
litz wire features electrical total conductor cross section AConductor,Litz; direct current resistance RDC X X      
resistance at high frequency RAC; RF-losses X   X X  
mechanical outer diameter litz wire OD Litz; total cross section litz wire Atot,Litz X X X X X
flexibiliy X X X X  

Optional Litz Constructions and Features

litz wire construction pitch direction SR length of lay SL [mm] bunching factor VF features
270 x 0.071 mm (54 x 0.071 mm) x 3 S,S 20;26 ≈ 15 good RF-performance, rough textured three-sided litz wire profile
((30 x 0.071 mm) x 3) x 3 S,S,S 20;26;26 ≈ 20 good RF-performance, compact bunching
((18 x 0.071 mm) x 3) x 5 S,S,S 20;26;26 ≈ 20 good RF-performance, compact bunching, evenly surface and litz wire profile
((18 x 0.071 mm) x 3) x 5 S,S,Z 20;20;26 ≈ 15 fine litz wire structure/-surface
(39 x 0.071 mm) x 7; concen. S+Z,S 20+20;24 < 13 very round, dimensional stable litze wire profile, high flexibily

Litz Wire Design for HF Coil with Specific Winding Window

practise-related approach
frequency [kHz] 50 125 200
total no. of windings NW,tot 30 30 30
no. of layers NL (winding layers) 3 3 3
no. of windings per layer NW,L 10 10 10
outer diam. litz
wire (grade 1)
ODLitz [mm]		 with servg. 2.19 2.19 2.19
without servg. 2.32 2.32 2.32
nom. diameter single wire
ØSW [mm]		 0.100 0.080 0.063
filling factor
litz wire
FillLitz [%]		 with servg. 48.2 47.7 46.1
without servg. 47.0 46.5 44.9
filling factor
winding window
FillWind [%]		 with servg. 25.9 26.3 24.9
without servg. 29.1 29.2 27.2
typ. litz wire
construction		 with servg. 225 x 0.100 mm
5x(45x0.100mm)		 360 x 0.080 mm
5x(4x(18x0.080mm))		 550 x 0.063 mm
5x(5x(22x0.063mm))
without servg. 255 x 0.100 mm
5x(51x0.100mm)		 400 x 0.080 mm
5x(4x(20x0.080mm))		 600 x 0.063 mm
5x(5x(24x0.063mm))

Comparison of The Design Approaches

practise-related approach approach acc. Ch. R. Sullivan
frequency [kHz] 50 125 200 50 125 200
total no. of windings
NW,tot		 30 30 30 30 30 30
no. of layers NL (layer winding) 3 3 3 3 3 3
no. of winding per layer
NW,L		 10 10 10 10 10 10
outer diameter litz wire (grade 1)
ODLitz [mm]		 2.19 2.19 2.19 2.17 2.18 2.19
nom. diameter litz wire
ØSW [mm]		 0.100 0.080 0.063 0.071 0.050 0.040
filling factor litz wire
FillLitz [%] 		48.2 47.7 46.1 46.9 46.1 45.2
filling factor winding window
FillWin [%]		 25.9 26.3 24.9 25.3 25.0 24.6
typ. litz wire construction 225 x 0.100 mm 5x(45x0.100mm) 360 x 0.080 mm 5x(4x(18x0.080mm)) 550 x 0.063 mm 5x(5x(22x0.063mm)) 440 x 0.071 mm 5x(4x(22x0.071mm) 875 x 0.050 mm 5x(5x(35x0.050mm)) 1350 x 0.040 mm 5x(5x(54x0.040mm))