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American Wire Gauge (AWG) is a logarithmic stepped 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.
AWG is also commonly used to specify body piercing jewelry sizes (especially smaller sizes), even when the material is not metallic.[2]
Origin
The AWG 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.
While the AWG is essentially identical to the Brown & Sharpe (B&S) sheet metal gauge, the B&S gauge was designed for use with sheet metals as its name suggests. These are functionally interchangeable but the use of B&S in relation to wire gauges, rather than sheet metal gauges, is technically improper.
Specifications
Increasing gauge numbers denote logarithmically decreasing wire diameters, which is similar to many other non-metric gauging systems such as British Standard Wire Gauge (SWG). However, AWG is dissimilar to IEC 60228, the metric wire-size standard used in most parts of the world, based directly on the wire cross-section area (in square millimetres, mm2).
The AWG tables are for a single, solid and 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.
Formulae
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 and B ) have diameters whose ratio (dia. B ÷ dia. A) is (approximately 1.12293), while for gauges two steps apart (e.g., A, B, and C), the ratio of the C to A is about 1.122932 ≈ 1.26098.
The diameter of an AWG wire is determined according to the following formula:
(where n is the AWG size for gauges from 36 to 0, n = −1 for No. 00, n = −2 for No. 000, and n = −3 for No. 0000. See below for rule)
or equivalently:
The gauge can be calculated from the diameter using [3]
and the cross-section area is
- .
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 B258-02 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 39√92 is very close to 2,[5] which leads to the following rules of thumb:
- When the cross-sectional area of a wire is doubled, the AWG will decrease by 3. (E.g. two No. 14 AWG wires have about the same cross-sectional area as a single No. 11 AWG wire.) This doubles the conductance.
- When the diameter of a wire is doubled, the AWG will decrease by 6. (E.g. No. 2 AWG is about twice the diameter of No. 8 AWG.) This quadruples the cross-sectional area and the conductance.
- A decrease of ten gauge numbers, for example from No. 12 to No. 2, multiplies the area and weight by approximately 10, and reduces the electrical resistance (and increases the conductance) by a factor of approximately 10.
- For the same cross section, aluminum wire has a conductivity of approximately 61% of copper, so an aluminum wire has nearly the same resistance as a copper wire smaller by 2 AWG sizes, which has 62.9% of the area.
- A solid round 18 AWG wire is about 1 mm in diameter.
- The resistance of copper cable may therefore be approximated using the rules of thumb.[6]: 27
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 a copper conductor with 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 (77 °F) 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 per unit length" is the reciprocal of the conductor diameter; it is therefore an upper limit for wire wound in the form of a helix (see solenoid), based on uninsulated wire.
AWG | Diameter | Turns of wire, without insulation |
Area | Copper wire | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Length-specific resistance[7] |
Ampacity at temperature rating[a] | Fusing current[10][11] | ||||||||||||
60 °C | 75 °C | 90 °C | Preece[12][13][14][15] | Onderdonk[16][15] | ||||||||||
(in) | (mm) | (per in) | (per cm) | (kcmil) | (mm2) | (mΩ/m[b]) | (mΩ/ft[c]) | (A) | ~10 s | 1 s | 32 ms | |||
0000 (4/0) | 0.4600[d] | 11.684[d] | 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 | 10 | 14 | 16 | Zdroj:https://en.wikipedia.org?pojem=AWG