Specifications
17
2.4 ENAMELLED WIRE: Enamelled wire is a wire coated with a very thin insulating layer. The
core material (‘wire’) is copper or aluminum, coated with a thin layer of a polyurethane, polyamide,
or polyester resin - called as “enamel”.
The thin layer of insulation coated on Enamelled wire, prevents the wire surfaces from
being in a short circuit when wound into coils. It is used mainly in the construction of motors,
electromagnets, transformers and inductors. For ease of manufacturing inductive components
like transformers and inductors, most new enamelled wire has enamel that acts as a flux when
burnt during soldering. This means that the electrical connections at the ends can be made
without stripping off the insulation first. Older enamelled copper wires normally require
sandpapering or scraping to remove the insulation before soldering.
Enamelled wires are classified by their diameter (as SWG number) or area (square
millimetres), temperature class and insulation class. Enameled wires are manufactured in both
round and rectangular shapes. Rectangular wire is used in larger machine windings to make
the most efficient use of available winding space.
Breakdown voltage depends on the thickness of the covering, which can be of 3 types:
Grade 1, Grade 2 and Grade 3. Higher grades have thicker insulation and thus higher breakdown
voltages. The temperature class indicates the temperature of the wire at which it can have a
20,000 hour service life. At lower temperatures the service life of the wire is longer (about a
factor 2 for every 10 °C lower temperature). Common temperature classes are 120, 155 and
180 °C.
S. W. G.
Gauge
No.
Standard Wire Gauge S. W. G.
S. W. G.
Gauge
No.
Standard Wire Gauge S. W. G.
Inch mm
Area
mm
2
Inch mm
Area
mm
2
0 0.324 8.230 53.17 26 0.018 0.457 0.164
1 0.300 7.620 45.6 27 0.016 0.417 0.136
2 0.276 7.010 38.6 28 0.015 0.376 0.111
3 0.252 6.401 32.2 29 0.014 0.345 0.0937
4 0.232 5.893 27.3 30 0.012 0.315 0.0779
5 0.212 5.385 22.8 31 0.012 0.295 0.0682
6 0.192 4.877 18.7 32 0.011 0.274 0.0591
7 0.176 4.470 15.7 33 0.010 0.254 0.0507
8 0.160 4.064 13.0 34 0.009 0.234 0.0429
9 0.144 3.658 10.5 35 0.008 0.213 0.0357
10 0.128 3.251 8.3 36 0.008 0.193 0.0293
11 0.116 2.946 6.82 37 0.007 0.173 0.0234
12 0.104 2.642 5.48 38 0.006 0.152 0.0182
Table 2.1 Standard wire gauge and equivalent sizes in mm and inch.