Copper, hard drawn
Aluminum, soft, 61.2% cond.
Aluminum. 1/2 hard to fill hard
Lawrence J. Kelly and Carl C. Landinger
The fundamental concern of power cable engineering is to transmit current
(power) economically and efficiently. The choice of the conductor material,
size, and design must take into consideration such items as:
0 Ampacity (current carrying capacity)
0 Voltage stress at the conductor
0 Voltage regulation
0 Conductor losses
0 Bending radius and flexibility
0 Overall economics
0 Material considerations
0 Mechanical properties
2. MATERIAL CONSIDERATIONS [3-I]
There are several low resistivity (or high conductivity) metals that may be used
as conductors for power cables. Examples of these as ranked by low resistivity
at 20 "C are shown in Table 3-1.
Resistivity of Metals at 20 "C
1 Ohm-mmz/m x lo* 1 Ohm-cmiVft x lo4
Copyright © 1999 by Marcel Dekker, Inc.
Considering these resistivity figures and cost of each of these materials, copper
and aluminum become the logical choices. As such, they are the dominant met-
als used in the power cable industry today.
The choice between copper and aluminum conductors should carefilly compare
the properties of the two metals, as each has advantages that outweigh the other
under certain conditions. The properties most important to the cable designer are
2.1 DC Resistance
The conductivity of aluminum is about 6 1.2 to 62 percent that of copper. There-
fore, an aluminum conductor must have a cross-sectional area about 1.6 times
that of a copper conductor to have the equivalent dc resistance. This difference
in area is approximately equal to two AWG sizes.
One of the most important advantages of aluminum, other than economics, is its
low density. A unit length of bare al