Electrical and Physical Properties of Common Metals Used in Manufacturing Cables

Custom Search
The tables below indicate the electrical and physical properties of metals commonly used in the manufacture of electric cables in the electrical industry. Familiarity with these properties is required to fully grasp the key advantages and disadvantages of the various materials used and to understand from a practical standpoint why they are applied in the area they are used.

Electrical Properties
The table below indicates the electrical properties of the common metals used in cables. Taking price into consideration the below listed properties, Copper and Aluminium are clearly the best choice for conductors the manufacture of all manner of electric cables although there has been experimentation with other metals for example Sodium in certain applications:

Metals
Relative Conductivity (Copper = 100)
Electrical Resistivity at 20°C (Ωm, 10-8)
Temperature Coefficient of Resistance (per °C)
Silver 106 1.626 0.0041
Copper (HC, anealed) 100 1.724 0.0039
Copper (HC, Hard drawn) 97 1.777 0.0039
Tinned Copper 95 - 99 1.741 - 1.814 0.0039
Aluminium (EC grade, Soft) 61 2.803 0.0040
Aluminium (EC grade,         1/2H - H)                            61 2.826 0.0040
Sodium 35 4.926 0.0054
Mild Steel 12 13.80 0.0045
Lead 8 21.4 0.0040


Physical Properties of Metals Used in Electric Cables
The physical properties of metals used for conductors and sheaths are given in the table below:

Property
Unit
Aluminium
Copper
Lead
Density at 20°C
Kg/m3
8890 2703 11370
Coefficient of thermal expansion per °C
x 10-6
17 23 29
Melting point oC 1083 659 327
Thermal Conductivity
W/cm oC
3.8 2.4 0.34
Ultimate Tensile Stress



Soft temper MN/m2 225 70 - 90    -
3/4H to H MN/m2 385 125 - 205    -
Elastic Modulus MN/m2 26 14    - 
Hardness



Soft DPHN 50 20 - 25  5
3/4H to H DPHN 115 30 - 40     -
Stress Fatigue Endurance Limit (Approximate) MN/m2
±65
±40 ±2.8

Except for conductors of self-supporting overhead cables, Copper is invariably used in the annealed condition. Solid Aluminium conductors are also mainly used in a soft condition but stranded Aluminium conductors are 3H (hard) to H. Aluminium sheaths are now extruded directly onto cables and hence of soft temper but a small amount of work hardening occurs during corrugation.