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Typically, the design engineer requiring the use of Litz knows the operating frequency and RMS current required for his application. Since the primary benefit of a Litz conductor is the reduction of AC losses, the first consideration in any Litz design is the operating frequency. The operating frequency not only influences the actual Litz construction, it also determines the individual wire gauge.
Ratios of alternating current resistance to direct current resistance for an insulated solid round wire (S) in terms of a value (X) are shown below:
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Table A
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X |
0 |
0.5 |
0.6 |
0.7 |
0.8 |
0.9 |
1.0 |
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S |
1.0000 |
1.0003 |
1.0007 |
1.0012 |
1.0021 |
1.0034 |
1.0050 |
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The value of X for copper wire is determined by the following formula
X=0.271 DM (FMHZ)^(1/2)
M = Wire diameter in mils
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The following table shows recommended frequency VS. wire gauges:
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Table B
FREQUENCY |
RECOMMENDED WIRE GAUGE |
NOMINAL DIA.OVER COPPER |
DC RES.OHMS/M'
(MAX) |
SINGLE STRAND "S"
Rac Rdc |
60 HZ to 1 KHZ |
28 AWG |
.0126 |
66.37 |
1.0000 |
1 KHZ to 10 KHZ |
30 AWG |
.0100 |
105.82 |
1.0000 |
10 KHZ to 20 KHZ |
33 AWG |
.0071 |
211.70 |
1.0000 |
20 KHz to 50 KHZ |
36 AWG |
.0050 |
431.90 |
1.0000 |
50 KHZ to 100 KHZ |
38 AWG |
.0040 |
681.90 |
1.0000 |
100 KHZ TO 200 KHZ |
40 AWG |
.0031 |
1152.30 |
1.0000 |
200 KHZ TO 350 KHZ |
42 AWG |
.0025 |
1801.0 |
1.0000 |
350 KHZ TO 850 KHZ |
44 AWG |
.0020 |
2873.0 |
1.0003 |
850 KHZ TO 1.4 MHZ |
46 AWG |
.0016 |
4544.0 |
1.0003 |
1.4 MHZ TO 2.8 MHZ |
48 AWG |
.0012 |
7285.0 |
1.0003 |
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In memory of Allen Richter, engineer, whose dedication and refined technical expertise richly served the electronics industry. His life's work with Kerrigan Lewis greatly contributed to the technological advances made by the Litz-wire industry. |
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