Sunday, May 23, 2010

Factors affecting cable choice

1 - Factors affecting cable choice:
* Application and environment in which the cable will operate.
* Working voltage.
* Load current or max. Rated is current for continuous operation.
* Suitable voltage drop.
* Installation data, in pipes, underground, in air.
* Short circuit current, and time of release.

2 – DEFINITION:

2 - 1 Wire: it is a solid material (copper or aluminum) of certain uniform diameter and uniform cross section, having specified electrical resistance.

2 - 2 Conductor: it is bundle of wires stranded in a specified way and shape having a certain resistance to form a uniform pass-way for electric current. It can be circular or shaped (sect oral).

2 - 3 Core: it is a conductor insulated with a dielectric material (polyvinyl chloride, polyethylene, cross-linked polyethylene, rubber, cellular polyethylene).

2 - 4 Cable: A core or more of cores assembled together, to form single, or multi core cable, to serve in single phase or three phase system.

2 - 5 Resistance: all conductor materials resist the electric current flow. This resistance is directly proportion to the resistivity of conductor material and the conductor length, and inversely proportion to conductor cross-sectional area. It is expressed in “ohm/m”, and is given the symbol “r”
Resistance= resistivity x length / area.