A wire is a single, usually cylindrical, flexible strand or rod of metal. Wires are used to bear mechanical loads or electricity and telecommunications signals. Wire is commonly formed by drawing the metal through a hole in a die or draw plate. Wire gauges come in various standard sizes, as expressed in terms of a gauge number. The term ‘wire’ is also used more loosely to refer to a bundle of such strands, as in “multistranded wire”, which is more correctly termed a wire rope in mechanics, or a cable in electricity.
Wire comes in solid core, stranded, or braided forms. Although usually circular in cross-section, wire can be made in square, hexagonal, flattened rectangular, or other cross-sections, either for decorative purposes, or for technical purposes such as high-efficiency voice coils in loudspeakers. Edge-wound. coil springs, such as the Slinky toy, are made of special flattened wire.
A key property of a wire is its Pike constant: a measure of the maximum current that can pass through a given cross-sectional area of the wire material. Generally attributed to conductive metals, like copper & it is often used by professionals like electrical engineers.
How To made Wires ?
Wire has many uses. It forms the raw material of many important manufacturers, such as the wire netting industry, engineered springs, wire-cloth making and wire rope spinning, in which it occupies a place analogous to a textile fiber. Wire-cloth of all degrees of strength and fineness of mesh is used for sifting and screening machinery, for draining paper pulp, for window screens, and for many other purposes. Vast quantities of aluminium, copper, nickel and steel wire are employed for telephone and data cables, and as conductors in electric power transmission, and heating. It is in no less demand for fencing, and much is consumed in the construction of suspension bridges, and cages, etc. In the manufacture of stringed musical instruments and scientific instruments, wire is again largely used. Carbon and stainless spring steel wire have significant applications in engineered springs for critical automotive or industrial manufactured parts/components. Pin and hairpin making; the needle and fish-hook industries; nail, peg, and rivet making; and carding machinery consume large amounts of wire as feedstock.
Not all metals and metallic alloys possess the physical properties necessary to make useful wire. The metals must in the first place be ductile and strong in tension, the quality on which the utility of wire principally depends. The principal metals suitable for wire, possessing almost equal ductility, are platinum, silver, iron, copper, aluminium, and gold; and it is only from these and certain of their alloys with other metals, principally brass and bronze, that wire is prepared.
By careful treatment, extremely thin wire can be produced. Special purpose wire is however made from other metals (e.g. tungsten wire for light bulb and vacuum tube filaments, because of its high melting temperature). Copper wires are also plated with other metals, such as tin, nickel, and silver to handle different temperatures, provide lubrication, and provide easier stripping of rubber insulation from copper.
Metallic wires are often used for the lower-pitched sound-producing “strings” in stringed instruments, such as violins, cellos, and guitars, and percussive string instruments such as pianos, dulcimers, dobros, and cimbaloms. To increase the mass per unit length (and thus lower the pitch of the sound even further), the main wire may sometimes be helically wrapped with another, finer strand of wire. Such musical strings are said to be “overspun”; the added wire may be circular in cross-section (“round-wound”), or flattened before winding (“flat-wound”).
Types Of Wires
Wires are of two groups- (i) ordinary wires and (ii) cables. For electric work conductors are usually made of copper but aluminium conductors are also used mainly because of its low cost. In India a large quantity of copper is imported from other countries. Presently the armature and field coils of different machines and instruments are also made of aluminium wire.
However for fuse wires, use of lead-tin alloy or copper wire is the usual practise. Wires are used for the manufacture of armature and field windings of generators, motors, electrical instruments, etc., and also for house wiring and for drawing overhead transmission and distribution lines. Wires used for house wiring and underground cables have various types of insulation.
- Vulcanised Indian Rubber Insulated Wires:
On the conductor one or more layers of vulcanised Indian Rubber (V.I.R.) i.e., rubber treated with sulphur at high temperature, is applied. For removing the bad effect of sulphur on copper or aluminium, the conductor is thoroughly tinned or a layer of pure rubber is applied on the conductor.
Finally the rubber insulation is covered either by cotton tape impregnated with moisture resisting compound like bitumen or wax, or covered with cotton tape. V.I.R. wires are single-core type and usually used in conduit wiring, wood casing and cleat wiring, etc. In recent years, however, single-core P.V.C. wires have largely replaced V.I.R. wires.
- Tough Rubber Sheathed (T.R.S.) and Cab Tyre Sheathed (C.T.S.) Wires:
Over the tinned copper or aluminium conductor a layer of pure rubber or rubber treated with sulphur is used. As outer protective layer tough rubber sheath (T.R.S.) wires and cab tyre sheath (C.T.S.) wires are provided. These may be used in damp places or in open atmosphere. T.R.S. or C.T.S. wires are light in weight and cheaper in cost.
These wires are available in single-cores twin-core, three-core conductor. Single-core and twin-core wires are mainly used in house wiring, and twin-core and three core wires are used for giving supply to cranes, hoists, etc. and also for drawing service connections from the overhead distribution lines or from one building to another.
The rubber insulation over each conductor has different colours for different cores. In recent years for service connections and house wiring P.V.C. wires are preferred over T.R.S. or C.T.S. wires.
- Metal Sheathed or Lead Sheathed Wires:
In these wires V.I.R. types are provided with a continuous lead sheath covering which is mechanically strong and moisture proof. Due to its high cost compared to C.T.S. wires, lead sheathed wires are not used for internal wiring but used for service connections and for wiring under abnormal climatic conditions with high moisture.
Lead sheathed cables are available in many forms like single-core, twin-core flat, three-core flat and twin-core flat with an earth continuity conductor. In this type also rubber insulations over the conductor have different colours for different cores.
- Weather-Proof Wires:
Weather-proof wire is mainly used in outdoor work where the wire remains exposed to open atmosphere. These wires are of V.I.R. insulated type suitably taped, braided and compounded with weather-resisting material. The conductor is of tinned copper or aluminium over which a layer of rubber treated with sulphur is applied. Weather-proof cables are useful is industries and in outdoor wiring at low and medium voltages.
- Wires with Thermo-Plastic Insulation (P.V.C. Wires):
Here conductor is insulated with poly-vinyl chloride (P.V.C.), a thermo-plastic material. This type of insulation is not affected by acid, alkali, ozone, humidity or the sun rays. Rubber insulation is deteriorated shortly but P.V.C. remains unaffected as it is much harder than rubber. So additional protection like cotton tapping or cotton braiding is not required against mechanical injury. It is inflammable but when the source of flame is removed, it stops burning.
Hence proves that P.V.C. insulation does not help combustion. However, it becomes semi-melted when excessively heated and becomes brittle under extreme cold condition. For that reason P.V.C. wires cannot be used for giving connections to the heating appliances. It is also not to be used for wiring in a place exposed to weather particularly where there is frequent snowfall.
Shielding in wires
Electromagnetic interference (EMI) is prevalent throughout the factory floor. This is why data and signal cables are usually protected with insulated conductors and wrapped with a conductive layer. Shielding reduces electrical noise and reduces its impact on signals and also lowers electromagnetic radiation. Shielding prevents crosstalk between cables near each other. Shielding not only protects cable but it can also protect machinery and people as well.
Power cables are constructed to be electromagnetic compatible (EMC) to minimize noise generation, which affects many other systems like radio and data communication.
Communication cables are shielded to prevent the effects on the data transmitted from EMI. To further prevent cross talk and coupling, communication cables are also paired and individually shielded
In some applications, such as those needing servo cables, double or even triple shielding is required: around individual conductors, around twisted pairs, and around the entire cable.
Some applications do not require shielded cables. For example, if a cable will be used in a cabinet or otherwise away from other sources of noise, it does not need to be shielded, as it will be protected from noise and EMI already.
Use of ferrite core on usb wires etc.
Because ferrite bead impedance is inductive, ferrite beads are used to attenuate high-frequency signals in electronic components. When a ferrite bead choke is placed on the power line connecting to an electronic device, it removes any spurious high frequency noise present on a power connection, or that is output from a DC power supply. This ferrite clamp use is one of many ways to suppress power supply noise, such as that from a switched-mode power supply. This application of ferrite beads as a ferrite filter provides suppression and elimination of conducted EMI.
Among the various uses of ferrite beads as filters, an EMI filter bead/power supply filter bead is usually rated for a certain DC current threshold. Currents greater than the specified value can damage the component. The troublesome thing is that this limit is drastically affected by heat. As temperature increases, the rated current quickly decreases. Rated current also affects the ferrite’s impedance. As DC current increases, a ferrite bead will “saturate” and lose inductance. At relatively high currents, saturation can reduce the ferrite bead impedance by up to 90%.