American wire gauge

"AWG" redirects here. For other uses, see AWG (disambiguation).

American wire gauge (AWG), also known as the Brown & Sharpe wire gauge, is a standardized wire gauge system used since 1857 predominantly in North America for the diameters of round, solid, nonferrous, electrically conducting wire. Dimensions of the wires are given in ASTM standard B 258.[1] The cross-sectional area of each gauge is an important factor for determining its current-carrying capacity.

Increasing gauge numbers denote decreasing wire diameters, which is similar to many other non-metric gauging systems such as SWG. This gauge system originated in the number of drawing operations used to produce a given gauge of wire. Very fine wire (for example, 30 gauge) required more passes through the drawing dies than 0 gauge wire did. Manufacturers of wire formerly had proprietary wire gauge systems; the development of standardized wire gauges rationalized selection of wire for a particular purpose.

The AWG tables are for a single, solid, round conductor. The AWG of a stranded wire is determined by the cross-sectional area of the equivalent solid conductor. Because there are also small gaps between the strands, a stranded wire will always have a slightly larger overall diameter than a solid wire with the same AWG.

AWG is also commonly used to specify body piercing jewelry sizes (especially smaller sizes), even when the material is not metallic.[2]

Formula

By definition, No. 36 AWG is 0.005 inches in diameter, and No. 0000 is 0.46 inches in diameter. The ratio of these diameters is 1:92, and there are 40 gauge sizes from No. 36 to No. 0000, or 39 steps. Because each successive gauge number increases cross sectional area by a constant multiple, diameters vary geometrically. Any two successive gauges (e.g., A & B ) have diameters in the ratio (dia. B ÷ dia. A) of \sqrt [39]{92} (approximately 1.12293), while for gauges two steps apart (e.g., A, B, & C), the ratio of the C to A is about 1.122932 = 1.26098. The diameter of a No. n AWG wire is determined, for gauges smaller than 00 (36 to 0), according to the following formula:

d_n = 0.005~\mathrm{inch} \times 92^\frac{36 - n}{39} = 0.127~\mathrm{mm} \times 92^\frac{36 - n}{39}

(see below for gauges larger than No. 0 (i.e., No. 00, No. 000, No. 0000 ).)

or equivalently

d_n = e^{-1.12436 - 0.11594n}\ \mathrm{inch} = e^{2.1104 - 0.11594n}\ \mathrm{mm}

The gauge can be calculated from the diameter using [3]

n = -39\log_{92} \left( \frac{d_n}{0.005~\mathrm{inch}} \right) + 36 = -39\log_{92} \left( \frac{d_n}{0.127~\mathrm{mm}} \right) + 36

and the cross-section area is

A_n = \frac{\pi}{4} d_n^2 = 0.000019635~\mathrm{inch}^2 \times 92^\frac{36 - n}{19.5} = 0.012668~\mathrm{mm}^2 \times 92 ^ \frac{36 - n}{19.5},

The standard ASTM B258 - 02(2008) Standard Specification for Standard Nominal Diameters and Cross-Sectional Areas of AWG Sizes of Solid Round Wires Used as Electrical Conductors defines the ratio between successive sizes to be the 39th root of 92, or approximately 1.1229322.[4] ASTM B 258-02 also dictates that wire diameters should be tabulated with no more than 4 significant figures, with a resolution of no more than 0.0001 inches (0.1 mils) for wires larger than No. 44 AWG, and 0.00001 inches (0.01 mils) for wires No. 45 AWG and smaller.

Sizes with multiple zeros are successively larger than No. 0 and can be denoted using "number of zeros/0", for example 4/0 for 0000. For an m/0 AWG wire, use n = −(m − 1) = 1 − m in the above formulas. For instance, for No. 0000 or 4/0, use n = −3.

Rules of thumb

The sixth power of \sqrt [39]{92} is very close to 2,[5] which leads to the following rules of thumb:

Tables of AWG wire sizes

The table below shows various data including both the resistance of the various wire gauges and the allowable current (ampacity) based on plastic insulation. The diameter information in the table applies to solid wires. Stranded wires are calculated by calculating the equivalent cross sectional copper area. Fusing current (melting wire) is estimated based on 25 °C ambient temperature. The table below assumes DC, or AC frequencies equal to or less than 60 Hz, and does not take skin effect into account. Turns of wire is an upper limit for wire with no insulation.

AWG Diameter Turns of wire,
without insulation		 Area Copper wire
Resistance/length[6] Ampacity,[7]
insulation material temperature rating:		 Fusing current[8][9]
60 °C 75 °C 90 °C Preece Onderdonk
(in) (mm) (per in) (per cm) (kcmil) (mm2) (mΩ/m[lower-alpha 1]) (mΩ/ft[lower-alpha 2]) (A) ~10 s 1 s 32 ms
0000 (4/0) 0.4600[lower-alpha 3] 11.684[lower-alpha 3] 2.17 0.856 212 107 0.1608 0.04901 195 230 260 3.2 kA 33 kA 182 kA
000 (3/0) 0.4096 10.405 2.44 0.961 168 85.0 0.2028 0.06180 165 200 225 2.7 kA 26 kA 144 kA
00 (2/0) 0.3648 9.266 2.74 1.08 133 67.4 0.2557 0.07793 145 175 195 2.3 kA 21 kA 115 kA
0 (1/0) 0.3249 8.251 3.08 1.21 106 53.5 0.3224 0.09827 125 150 170 1.9 kA 16 kA 91 kA
1 0.2893 7.348 3.46 1.36 83.7 42.4 0.4066 0.1239 110 130 145 1.6 kA 13 kA 72 kA
2 0.2576 6.544 3.88 1.53 66.4 33.6 0.5127 0.1563 95 115 130 1.3 kA 10.2 kA 57 kA
3 0.2294 5.827 4.36 1.72 52.6 26.7 0.6465 0.1970 85 100 115 1.1 kA 8.1 kA 45 kA
4 0.2043 5.189 4.89 1.93 41.7 21.2 0.8152 0.2485 70 85 95 946 A 6.4 kA 36 kA
5 0.1819 4.621 5.50 2.16 33.1 16.8 1.028 0.3133 795 A 5.1 kA 28 kA
6 0.1620 4.115 6.17 2.43 26.3 13.3 1.296 0.3951 55 65 75 668 A 4.0 kA 23 kA
7 0.1443 3.665 6.93 2.73 20.8 10.5 1.634 0.4982 561 A 3.2 kA 18 kA
8 0.1285 3.264 7.78 3.06 16.5 8.37 2.061 0.6282 40 50 55 472 A 2.5 kA 14 kA
9 0.1144 2.906 8.74 3.44 13.1 6.63 2.599 0.7921 396 A 2.0 kA 11 kA
10 0.1019 2.588 9.81 3.86 10.4 5.26 3.277 0.9989 30 35 40 333 A 1.6 kA 8.9 kA
11 0.0907 2.305 11.0 4.34 8.23 4.17 4.132 1.260 280 A 1.3 kA 7.1 kA
12 0.0808 2.053 12.4 4.87 6.53 3.31 5.211 1.588 20 25 30 235 A 1.0 kA 5.6 kA
13 0.0720 1.828 13.9 5.47 5.18 2.62 6.571 2.003 198 A 798 A 4.5 kA
14 0.0641 1.628 15.6 6.14 4.11 2.08 8.286 2.525 15 20 25 166 A 633 A 3.5 kA
15 0.0571 1.450 17.5 6.90 3.26 1.65 10.45 3.184 140 A 502 A 2.8 kA
16 0.0508 1.291 19.7 7.75 2.58 1.31 13.17 4.016 — — 18 117 A 398 A 2.2 kA
17 0.0453 1.150 22.1 8.70 2.05 1.04 16.61 5.064 99 A 316 A 1.8 kA
18 0.0403 1.024 24.8 9.77 1.62 0.823 20.95 6.385 — — 14 83 A 250 A 1.4 kA
19 0.0359 0.912 27.9 11.0 1.29 0.653 26.42 8.051 70 A 198 A 1.1 kA
20 0.0320 0.812 31.3 12.3 1.02 0.518 33.31 10.15 58.5 A 158 A 882 A
21 0.0285 0.723 35.1 13.8 0.810 0.410 42.00 12.80 49 A 125 A 700 A
22 0.0253 0.644 39.5 15.5 0.642 0.326 52.96 16.14 41 A 99 A 551 A
23 0.0226 0.573 44.3 17.4 0.509 0.258 66.79 20.36 35 A 79 A 440 A
24 0.0201 0.511 49.7 19.6 0.404 0.205 84.22 25.67 29 A 62 A 348 A
25 0.0179 0.455 55.9 22.0 0.320 0.162 106.2 32.37 24 A 49 A 276 A
26 0.0159 0.405 62.7 24.7 0.254 0.129 133.9 40.81 20 A 39 A 218 A
27 0.0142 0.361 70.4 27.7 0.202 0.102 168.9 51.47 17 A 31 A 174 A
28 0.0126 0.321 79.1 31.1 0.160 0.0810 212.9 64.90 14 A 24 A 137 A
29 0.0113 0.286 88.8 35.0 0.127 0.0642 268.5 81.84 12 A 20 A 110 A
30 0.0100 0.255 99.7 39.3 0.101 0.0509 338.6 103.2 10 A 15 A 86 A
31 0.00893 0.227 112 44.1 0.0797 0.0404 426.9 130.1 9 A 12 A 69 A
32 0.00795 0.202 126 49.5 0.0632 0.0320 538.3 164.1 7 A 10 A 54 A
33 0.00708 0.180 141 55.6 0.0501 0.0254 678.8 206.9 6 A 7.7 A 43 A
34 0.00630 0.160 159 62.4 0.0398 0.0201 856.0 260.9 5 A 6.1 A 34 A
35 0.00561 0.143 178 70.1 0.0315 0.0160 1079 329.0 4 A 4.8 A 27 A
36 0.00500 0.127[lower-alpha 3] 200[lower-alpha 3] 78.7 0.0250 0.0127 1361 414.8 4 A 3.9 A 22 A
37 0.00445 0.113 225 88.4 0.0198 0.0100 1716 523.1 3 A 3.1 A 17 A
38 0.00397 0.101 252 99.3 0.0157 0.00797 2164 659.6 3 A 2.4 A 14 A
39 0.00353 0.0897 283 111 0.0125 0.00632 2729 831.8 2 A 1.9 A 11 A
40 0.00314 0.0799 318 125 0.00989 0.00501 3441 1049 1 A 1.5 A 8.5 A
AWG Diameter Turns of wire,
without insulation		 Area Copper wire
Resistivity/area[6] Ampacity,[10]
temperature rating:		 Fusing current[11][12]
60°C 75°C 90°C Preece Onderdonk
(in) (mm) (per in) (per cm) (kcmil) (mm2) (mΩ/m[lower-alpha 1]) (mΩ/ft[lower-alpha 2]) (A) ~10 s 1 s 32 ms
  1. 1 2 or, equivalently, Ω/km
  2. 1 2 or, equivalently, Ω/kft
  3. 1 2 3 4 Exactly, by definition

In the North American electrical industry, conductors larger than 4/0 AWG are generally identified by the area in thousands of circular mils (kcmil), where 1 kcmil = 0.5067 mm2. The next wire size larger than 4/0 has a cross section of 250 kcmil. A circular mil is the area of a wire one mil in diameter. One million circular mils is the area of a circle with 1000 mil is 1 inch diameter. An older abbreviation for one thousand circular mils is MCM.

Stranded wire AWG sizes

AWG gauges are also used to describe stranded wire. In this case, it describes a wire which is equal in cross-sectional area to the total of all the cross-sectional areas of the individual strands; the gaps between strands are not counted. When made with circular strands (see Circle packing), these gaps occupy about 10% of the wire area, thus requiring a wire about 5% thicker than equivalent solid wire.

Stranded wires are specified with three numbers, the overall AWG size, the number of strands, and the AWG size of a strand. The number of strands and the AWG of a strand are separated by a slash. For example, a 22 AWG 7/30 stranded wire is a 22 AWG wire made from seven strands of 30 AWG wire.

Nomenclature and abbreviations in electrical distribution

Alternative ways are commonly used in the electrical industry to specify wire sizes as AWG.

The industry also bundles common wire for use in electric power distribution in homes and businesses, identifying a bundle's wire size followed by the number of wires in the bundle. The most common type of distribution cable, NM-B, is generally implied:

USB data & charging cables

AWG is also used to describe USB cables, such as the common USB A to micro-B USB data / charging cables used to charge and sync smartphones and many other mobile devices. This is of particular concern to consumers, since thicker cables can potentially charge the device faster and with greater efficiency. When describing USB cables, AWG is specified with two numbers: First the gauge of the data transfer wires, followed by the gauge of the charging wires within the cable. Most USB cables are 28/28 AWG.[13] However some cables that ship with tablets, and higher quality third-party cables, can be 28/24 AWG, 30/24, 28/21, etc, meaning the charging wires are thicker.[13]

Pronunciation

AWG is colloquially referred to as gauge and the zeros in large wire sizes are referred to as aught /ˈɔːt/. Wire sized 1 AWG is referred to as "one gauge" or "No. 1" wire; similarly, smaller diameters are pronounced "x gauge" or "No. X" wire, where x is the positive integer AWG number. Consecutive AWG wire sizes larger than No. 1 wire are designated by the number of zeros:

and so on.

See also

References

  1. ↑ "ASTM B258 - 14 Standard Specification for Standard Nominal Diameters and Cross-Sectional Areas of AWG Sizes of Solid Round Wires Used as Electrical Conductors". West Conshohocken: ASTM International. Archived from the original on 22 July 2014. Retrieved 22 March 2015.(subscription required)
  2. ↑ SteelNavel.com Body Piercing Jewelry Size Reference — illustrating the different ways that size is measured on different kinds of jewelry
  3. ↑ The logarithm to the base 92 can be computed using any other logarithm, such as common or natural logarithm, using log92x = (log x)/(log 92).
  4. ↑ ASTM Standard B 258-02, page 4
  5. ↑ The result is roughly 2.0050, or one-quarter of one percent higher than 2
  6. 1 2 Figure for solid copper wire at 68 °F, (Not in accordance to NEC Codebook 2014 Ch. 9, Table 8) computed based on 100% IACS conductivity of 58.0 MS/m, which agrees with multiple sources: High-purity oxygen-free copper can achieve up to 101.5% IACS conductivity; e.g., the Kanthal conductive alloys data sheet lists slightly lower resistances than this table.
  7. ↑ NFPA 70 National Electrical Code 2014 Edition. Table 310.15(B)(16) (formerly Table 310.16) page 70-161, "Allowable ampacities of insulated conductors rated 0 through 2000 volts, 60°C through 90°C, not more than three current-carrying conductors in raceway, cable, or earth (directly buried) based on ambient temperature of 30°C." Extracts from NFPA 70 do not represent the full position of NFPA and the original complete Code must be consulted. In particular, the maximum permissible overcurrent protection devices may set a lower limit.
  8. ↑ Computed using equations from H. Wayne Beaty; Donald G. Fink, eds. (2007), The Standard Handbook for Electrical Engineers (15th ed.), McGraw Hill, pp. 4–25, ISBN 0-07-144146-8
  9. ↑ Douglas Brooks (December 1998), "Fusing Current: When Traces Melt Without a Trace" (PDF), Printed Circuit Design 15 (12): 53
  10. ↑ NFPA 70 National Electrical Code 2014 Edition. Table 310.15(B)(16) (formerly Table 310.16) page 70-161, "Allowable ampacities of insulated conductors rated 0 through 2000 volts, 60°C through 90°C, not more than three current-carrying conductors in raceway, cable, or earth (directly buried) based on ambient temperature of 30°C." Extracts from NFPA 70 do not represent the full position of NFPA and the original complete Code must be consulted. In particular, the maximum permissible overcurrent protection devices may set a lower limit.
  11. ↑ Computed using equations from H. Wayne Beaty; Donald G. Fink, eds. (2007), The Standard Handbook for Electrical Engineers (15th ed.), McGraw Hill, pp. 4–25, ISBN 0-07-144146-8
  12. ↑ Douglas Brooks (December 1998), "Fusing Current: When Traces Melt Without a Trace" (PDF), Printed Circuit Design 15 (12): 53
  13. 1 2 billcprice.com

Further reading

Donald G. Fink and H. Wayne Beaty, Standard Handbook for Electrical Engineers, Eleventh Edition,McGraw-Hill, New York, 1978, ISBN 0-07-020974-X, page 4-18 and table 4-11.

This article is issued from Wikipedia - version of the Friday, April 15, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.