A shielded wire is a type of electrical wire made of
several layers of covering and conductors. It is useful for different
types of applications where protecting covering of conductor is needed.
Due to the specific characteristics it has found varieties of
applications in different fields. It show preferable electric
attributes. Each of the its cores is protected and the ground wire is
closely contacted with the shield layer.
Construction of Shielded Wire
A shielded wire must have a protecting coat of layer outside it. It has
a central core and an insulation layer provided. Then there is a shield
layer which separates the insulation layer from a ground wire. This
layer is made by a composite tape having a metal surface along with an
adhesive surface. The metallic surface of the wire is longitudinally
folded so that it can cover a portion of the adhesive surface. Then this
tape is helically binded with the folded layer on the outer cover so
that to form alternate helical patterns of the metal and adhesive
layers. A sheath is used to wrap the shielded layer and the ground wire.
After it the sheath layer is attached to the adhesive layer while the
ground wire remains in touch with the outer metallic layer. The metal
surface used inside makes the shield.
Typical types of the conventional shielded wires are:
- A single core type shielded wire
- Double core type shielded wire
Composition of Shielded Wire
The shielded wire is composed of a coaxial core and many outer layers:
- A central conductor
- A plastic insulation layer ( which is made of polyethylene - a
ethylene copolymer, or foamed materials)
- A shield layer which is made of soft-copper wires or tin plated
soft copper wires. Each wire is longitudinally placed along the
plastic insulation layer.
- A ground wire which is made of bare soft copper wire or soft
copper wire covered with tin (Sn). It is laid along the length of
the coaxial core or is spirally wound thereabout with a relatively
large pitch.
- A plastic sheath which is made of polyethylene or polyvinyl
chloride. This layer covers the coaxial core and the grounded wire.
Applications of Shielded Wires
Shielded wires are used and applied in a large number of fields and
industries. Some of the most important of them are:
- Hydro power stations
- Automation Industry
- Tool Making Machinery
- Conveyor Systems
- Steel Industry
- Chemical Industry
- Cement Industry
