Conductor(redirected from conductress)
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a military rank of reenlisted men in the Russian Army and Navy before the Revolution.
The rank was conferred on draftsmen and designers in chief, district, and field engineering administrations. In the navy a conductor was the closest assistant of an officer-specialist. Conductors included the ranks of senior boatswain, helmsman, and signal, telegraph, artillery, mine, and other conductors. They were recruited from among noncommissioned officers who had completed their term of compulsory service and passed an examination.
in electrical engineering, a metallic electrical conductor consisting of one or more wires. Conductors are used for the transmission of electrical energy. They are also used in the manufacture of conducting windings for electrical machines, transformers, electromagnets, and induction coils and in the wiring of electrical equipment and radio apparatus. The structural characteristics of conductors include the number of current-carrying strands, the material of the strands, the shape of the cross section, the number of wires in each strand, the type of insulation, the operating voltage, and the thermal stability. These characteristics are determined by the purpose and operating conditions of the conductors.
Conductors may be either bare or insulated. Bare conductors are used mainly in overhead power lines and in contact systems for electrical transportation systems. They are fastened to supports by means of insulators and fittings. Such factors as wind, icing, and vibration subject the conductors to large mechanical loads. For this reason, the conductors are made from materials possessing high mechanical strength and corrosion resistance, such as steel, aluminum (in some cases), copper, and alloys of these substances, including bronze and Aldrey. Conductors for overhead power lines in the USSR generally use multiple steel or aluminum strands or a composite steel-aluminum construction, wherein aluminum wire surrounds a single- or multiple-wire steel core. Such composite conductors are widely used in transmission lines with voltages of 110 kilovolts or more; their cross sections reach 600 to 700 mm2. To meet particular service conditions, bare conductors of special design are manufactured, such as hollow conductors, reinforced conductors, lightweight conductors, and conductors with an anticorrosion filler in the space between the wires. The copper or bronze conductors used in overhead contact systems have circular or specially shaped cross sections.
Insulated conductors are classified according to their purpose as installation conductors, magnet wires, and hookup conductors. Installation conductors made of copper or aluminum are usually circular in cross section and are covered with polyvinyl chloride or rubber insulation. Most conductors of this type have one or two insulated current-carrying strands, but in some cases the number may reach 37. The insulated strands are usually covered with a cotton braid, which is sometimes impregnated with a preservative compound. For protection from mechanical damage, some installation conductors are covered with an armor, or braid of steel wires; more rarely, they are enclosed in a continuous, thin metal conduit or tubing. The chief uses of installation conductors include fixed open and hidden wiring, electrical power and lighting networks, and electrical machines and apparatus. The insulation of most installation wires is designed for an operating voltage of 220 to 660 volts (V); for some types the operating voltage may be as high as 3000 V. The insulation is generally designed for an ambient temperature of - 40° to 50°-70°C.
Magnet wires have a single strand and are generally made of copper or, less often, aluminum. They are circular or rectangular in cross section. Their insulation is of such materials as enamel, paper, cotton, or glass fiber. Magnet wires often have several layers of insulation; thus, a layer of enamel may be covered with a layer of, for example, silk, cotton yarn, or polyethylene terephthalate. The most common magnet wires have a circular cross section and enamel insulation. Special-purpose magnet wires are also used, including high-voltage types with insulation designed for higher operating voltages; high-frequency types, whose current-carrying strands consist of a large number (up to 1,100) of fine wires; types having a supplementary adhesive coating for the fabrication of casingless windings and coils; types with current-carrying strands made of alloys that have a high electrical resistance, such as constantan and manganin; and very thin wires, or microconductors, in solid glass insulation.
Hookup conductors are made primarily of copper. They have a circular cross section and a film or fiberrous insulation. They consist of one or more current-carrying strands, and some are made with metal armor. The hookup conductors generally used in industry are insulated with polyethylene or polyvinyl chloride. Special types are also manufactured—for example, types with increased vibration resistance and heat-resistant types with fluoroplastic insulation. Most hookup conductors are designed to operate at voltages of 24 to 500 or even 1,000 V and at temperatures of –40° to 70°C; heat-resistant types are designed for temperatures of –90° to 250°C. The uses of hookup conductors include the electrical junction of elements of electronic and electrical equipment, the connection of the instruments and apparatus mounted on control panels and control boards, and the wiring of switching equipment.
Household appliances and other portable electric devices with voltages up to 250 V are connected to the power-supply system by means of conductors, called cords, consisting of two or three flexible multiple-wire current-carrying strands with polyvinyl chloride or rubber insulation.
In addition to the conductors described above, special-design conductors are also in use. An example is conductors with super-heat-resistant coverings. In the 1960’s there came into use conductors made of superconducting materials—chiefly niobium alloys with zirconium and titanium—which have no resistance at low temperatures (~4°K).
REFERENCESElektrotekhnicheskii spravochnik, 5th ed., vol. 1. Moscow, 1974.
Osnovy kabel’noi tekhniki, 2nd ed. Moscow-Leningrad, 1975.
F. A. MAGIDIN
an electrical engineering device for transmission of electric power over short distances, such as from a generator to a step-up transformer. A conductor consists of current-carrying strands (stranded conductor) or busbars (bus conductor), insulators, and protective covers. It may contain built-in bus-and-switch structures, instrument transformers, and protective devices. Bus conductors are assembled on-site from individual factory-made sections or modules.
Metal wires, cables, rods, tubes, and bus-bars used for the purpose of carrying electric current. (The most common forms are wires, cables, and busbars.) Although any metal assembly or structure can conduct electricity, the term conductor usually refers to the component parts of the current-carrying circuit or system.
Wires employed as electrical conductors are slender rods or filaments of metal, usually soft and flexible. They may be bare or covered by some form of flexible insulating material. They are usually circular in cross section; for special purposes they may be drawn in square, rectangular, ribbon, or other shapes. Conductors may be solid or stranded, that is, built up by a helical lay or assembly of smaller solid conductors.
Insulated stranded conductors in the larger sizes are called cables. Small, flexible, insulated cables are called cords. Assemblies of two or more insulated wires or cables within a common jacket or sheath are called multiconductor cables.
Bus-bars are rigid, solid conductors and are made in various shapes, including rectangular, rods, tubes, and hollow squares. Bus-bars may be applied as single conductors, one bus-bar per phase, or as multiple conductors, two or more bus-bars per phase. The individual conductors of a multiple-conductor installation are identical.
Most wires, cables, and bus-bars are made from either copper or aluminum. Copper, of all the metals except silver, offers the least resistance to the flow of electric current. Both copper and aluminum may be bent and formed readily and have good flexibility in small sizes and in stranded constructions. Aluminum, because of its higher resistance, has less current-carrying capacity than copper for a given cross-sectional area. However, its low cost and light weight (only 30% that of the same volume of copper) permit wide use of aluminum for bus-bars, transmission lines, and large insulated-cable installations.
For overhead transmission lines where superior strength is required, special conductor constructions are used. Typical of these are aluminum conductors, steel reinforced, a composite construction of electrical-grade aluminum strands surrounding a stranded steel core. Other constructions include stranded, high-strength aluminum alloy and a composite construction of aluminum strands around a stranded high-strength aluminum alloy core.
For extra-high-voltage transmission lines, conductor size is often established by corona performance rather than current-carrying capacity. Thus special “expanded” constructions are used to provide a large circumference without excessive weight. Typical constructions use helical lays of widely spaced aluminum strands around a stranded steel core. The space between the expanding strands is filled with paper twine, and outer layers of conventional aluminum strands are applied.