Conductors
Copper and aluminum are the main materials discussed because of their balance between high conductivity and reasonable price.
The behavior of an object that has been charged is dependent
upon whether the object is made of a conductive or a nonconductive material.
Conductors are
materials that permit electrons to flow freely from particle to particle. An
object made of a conducting material will permit charge to be transferred
across the entire surface of the object. If charge is transferred to the object
at a given location, that charge is quickly distributed across the entire
surface of the object. The distribution of charge is the result of electron
movement. Since conductors allow for electrons to be transported from particle
to particle, a charged object will always distribute its charge until the
overall repulsive forces between excess electrons is minimized. If a charged
conductor is touched to another object, the conductor can even transfer its
charge to that object. The transfer of charge between objects occurs more
readily if the second object is made of a conducting material. Conductors allow
for charge transfer through the free movement of electrons.
Type of Conductors
1- Stranded Types:
Stranded conductors are composed of multiple metal strands
bunched together in any number of configurations. They are much more flexible
than solid conductors, and the higher the strand count, the more flexible they
are. While this can add some cost, it is essential for any wire or cable that
will need to withstand any kind of movement or flexing.
If a cable with a stranded conductor seems the appropriate
choice for your application, you must then consider the type of stranding.
While most constructions are specified by regulatory agencies, it is helpful to
know some basic information about each type
- Concentric strand
A concentric stranded conductor consists of a
central wire or core surrounded by one or more layers of helically laid
wires. Each layer after the first has six more wires than the preceding layer.
Except in compact stranding, each layer is usually applied in a
direction opposite to that of the layer under it. If the core is a single
wire and if it and all of the outer strands have the same diameter, the first
layer will contain six wires; the second, twelve; the third, eighteen; etc
- Bunch strand
The term bunch stranding is applied to a
collection of strands twisted together in the same direction without regard to
the geometric arrangement.
- Rope strand
A rope stranded conductor is a concentric stranded conductor
each of whose component strands is itself stranded. A rope stranded conductor
is described by giving the number of groups laid together to form the rope and
the number of wires in each group.
- Sector Conductor
A sector conductor is a stranded conductor whose
cross-section is approximately the shape ofa sector of a circle. A multiple conductor insulated cable
with sector conductors has a smaller diameter than the corresponding cable with
round conductors.
Segmental Conductor
A segmental conductor is a round, stranded conductor
composed of three or four sectors slightly insulated from one another. This
construction has the advantage of lower AC resistance due to increased surface
area and skin effect
- Annular Conductor
An annular conductor is a round, stranded conductor whose
strands are laid around a suitable core. The core is usually made wholly or
mostly of nonconducting material. This construction has the advantage of lower
total AC resistance for a given cross-sectional area of conducting material due
to the skin effect.
- Compact Strand
A compact stranded conductor is a round or
sector conductor having all layers stranded in the same direction and
rolled to a predetermined ideal shape. The finished conductor is smooth on the
surface and contains practically no interstices or air spaces. This results
in a smaller diameter.
- Compressed Strand
Compressed conductors are intermediate in
size between standard concentric conductors and compact conductors
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