] See also

-- For a table of cross section sizes-- For a description of current carrying capacity of wires and cables-- For another consideration necessary in selecting proper cable sizes(EPR)

All electrical cables are somewhat flexible, allowing them to be shipped to installation sites wound on reels or drums. Where applications require a cable to be moved repeatedly, more flexible cables are used. Small cables are called "cords" (North American usage) or "flex" (United Kingdom)[]. Flexible cords contain finer stranded conductors, not solid core conductors, and have insulation and sheaths that are engineered to withstand the forces of repeated flexing and abrasion. Heavy duty flexible power cords such as those feeding a mine face cutting machine are carefully engineered—their life is measured in weeks. Very flexible power cables are used in automated machinery,, and machi其实钢芯铝绞线是绝缘的吗RomexTMne tools. See "" and "" for further description of flexible power cables. Other types of flexible cable include, extensible,,, and.

] Flexible cables

(typeMI) is a fire-resistant cable usingas an insulator. It is used in demanding applications requiring superior heat resistance such asand.

Electrical power cables are often installed in raceways, includingand cable trays, which may contain one or more conductors.

In Canada, type TECK cable, with a flexible aluminum or steel armor and overall flame-retardantjacket, is used in industry for wet or dry locations, run in trays or attached to building structure, above grade or buried in earth. A similar type of cable is designated type "MC" in the United States.

Another common type is "AC", a fabricated assembly of insulated conductors in flexible metallic armor, formed by wrapping an interlocking metal strip around the conductors. This is a descendant of type "BX", an earlyof thecompany, used from before and during World War II, designating a particular design of armored cable. The "BX" name is commonly applied loosely to all flexible metal armored cables including styles with individual wires running through a flexible metal conduit of similar app钢芯铝绞线earance.

Another common nickname is typeUF(underground feeder) which has a nonmetallic protective sheath but uses a moisture- and sunlight-resistant construction suitable for direct burial in the earth, where exposed to sunlight, or in unusually wet, unusually dry, or corrosive locations. "UF" uses a sheath that is a flexible solid about the insulated wires instead of the waxed paper wrapping, is generally heavier, less flexible than NM-B, and is rated against breakdown from harmfullight wavelengths commonly encountered in direct sunlight.

Thus for NEC NM-B series cables, at least two THWN insulated wires plus the bare copper grounding wire are always present. Older NM cables do not have the grounding wire; and have thicker THW or RHW insulation. THWN and THHN have thinner insulation because they also have a Nylon jacket. In general, NEC NM-B wire is not enclosed with other wiring in conduits.

The next most common "Romex" variant (sometimes called a "Three way" cable, after its application in lighting) has the neutral, identified by white coloring and two phase wires: the first conductor is always black and the second conductor is usually colored red (sometimes yellow or blue,but only rarely听听绝缘—such colors must be specially ordered and are more expensive) and an uninsulated copper grounding wire for safety. This type is generally used for multiple switching locations of a common or shared lighting need, such as for switches located at either end of a hallway, or on both upper and lower floors for stairway lighting, and are called a "three-way circuit": a well-entrenchedin North America. Similarly, three or more switches directly controlling a light require one or more "" plus a pair of ""). Type NM-B cables with three insulated conductors are also suitable for larger loads like clothes dryers, heavy duty air conditioners and electric heaters that require both phases (hot legs) for 220+ volts.

12-2 NMB2WH + BKthreeAWG 1214-2 NMB2WH + BKthreeAWG 1412-3 NMB3WH + BK + RDfourAWG 1214-3 NMB3WH + BK + RDfourAWG 14"AWG" means, see tablefor current capacities derated for various maximum expected temperatures within a cable run or. Other commonly used wire gauges for common electric services distribution range from AWG-4 through AWG-10.

wire gaugerating

totalwires

Colors(normal)

count ofinsulated wires

label type

'NM(Non-Metallic) often referred to as "Romex"TM,is a cable made o95钢芯铝绞线f solid copper wires with a nonmetallic jacket containing a waxed paper wrapped inner group of at least a pair of 600 volt insulated wires and maybe a bare grounding wire. Now the most common Romex/NM-为什么用钢芯铝绞线B (NM-variant B) cable thus has three wires: the neutral wire, colored white), the wire providing power to the load, which is nearly always black, and the bare grounding wire. NM-B cables are available in different wire gauges, providing a range of current-carrying capacities at expecte想知道钢芯铝绞线d maximal ambient temperatures in a cable run.RomexTM wire

Most multiconductor cables today have a bare 'grounding' wire which is for connection toand is for safe-guarding metallic boxes and appliance chassis for consumer and fire safety. [Some have the grounding wire covered with green material.] In theory, a fireman's axe cutting through a grounding-equipped [small] cable will provide a short circui钢芯铝绞线重量表t and activate the fuse or breaker, so the circuit becomes dead, and shock risks are minimized. [Cutting a big cable with an ax is impossible.] The common three prong receptacle outlets and plug-cords require a grounding wire [unless protected with a Ground Fault Circuit Interrupter]. Extension cables often have an insulated grounding wire.

These general purpose cables are known by the National Electrical Code's 310-12 'Type Letter'. TheType Letter, refers to the insulation type and thickness coating each working wire along with the outer covering [jacket] material, if any. The cables used by utility companies for power distribution do not have these ratings.

Common types of general-purpose cables used byare regulated by national or international codes, which define the various wire alloys that may make up a cable, its insulation type and characteristics, including its resistance to chemicals and sunlight.你看钢芯铝绞线技术参数

] Named cable types

A hybrid cable can include conductors for control signals or may also includefor data.

Cables for power distribution of 8kV or higher may be insulated with oil and paper, and are run in a rigid steel pipe, semi-rigid aluminum or lead sheath. The oil may be kept under pressure to prevent formation of voids that would allowwithin the cable insulation. Newer cables use polymers or polyethylene, including (XLPE) for insulation.

Some power cables for outdoor overhead use may have no overall sheath. Other cables may have a plastic or metal sheath enclosing all the conductors. The materials for the sheath will be selected for resistance to water, oil, sunlight, underground conditions, chemical vapors, impact, or high temperatures. In nuclear industry applications the cable may have special requirements for ionizing radiation resistance. Cable materials may be specified not to produce large amounts of smoke if burned. Cables intended for underground use or direct burial in earth will have heavy plastic or metal, most oftensheaths, or may require specialconstruction. Whe对比一下为什么用钢芯铝绞线n cables must run where exposed to mechanical impact damage, they may protected with flexible steel tape or wire armor, which may also be covered by a water resistant jacket.

For circuits operating at or above 2,000 volts between conductors, a conductive shield may surround each insulated conductor. Thi相比看wires equalizes electrical stress on the cable insulation. This technique was patented byin 1916;the shield is sometimes called a Hochstadter shield. The individual conductor shields of a cable are connected to earth ground at every opportunity along the length of cable, e.g. at splices, at ends.

The overall assembly may be round or flat. Non-conducting filler strands may be added to the assembly to maintain its shape. Special purpose power cables for overhead or vertical use may have additional elements such as steel orstructural supports.

Working voltage, determining the thickness [somewhat] and composition of the insulation;Current-carrying capacity, determining the cross-sectional size;Environmental conditions such as ambient temperature, water, chemical or sunlight exposure, and mechanical impact, determining the form and composition of the outer cable jacket.Power cables use stranded copper or aluminum conductors, although small power cables may use solid conductors为什么用钢芯铝绞线. ( Other elements have been tried, but with little success, e.g. sodium. Platinum, gold and silver are cost prohibitive.) The cable may include uninsulated conductors used for the circuit neutral or for ground (earth) connection.

<为什么用钢芯铝绞线p>Cables consist of three major components: conductors, insulation, protective jacket. The makeup of individual cables varies according to application. The construction and material are determined by three main factors:

Modern power cables come in a variety of sizes, materials, and types, each particularly adapted to its uses.Large single insulated conductors are also sometimes called power cables in the industry.

] Construction

This is the reason why construction techniques generally include safety grounding, and why sheathing materials are specified for certain conditions and prohibited from use in others. In the first case, fires and lethal current exposure is reduced by providing a way to force circuit protectors (Ground Fault Circuit Interrupters,fuses or circuit breakers) to trip. In the second case, particular materials resist deterioration f学习95钢芯铝绞线rom certain causes, also reducing exposure risks. The matter is sufficiently important that fire and building regulations in many places require certain types of power cable in certain uses.

In t事实上高导电率钢芯铝绞线he electrical trade, this term relates to cables carrying currents in excess of 100 amperes and are rated at 600 to volts. [Most welding cables and service drop cables have no voltage rating.]

Although many of these cables carry low voltages (nominally 120 volts in North America, 230 volts in Europe, with variations in the rest of the world) they are dangerous if misused in service, or if damaged accidentally, and are often lethal. This occurs for two reasons. Direct electrocution of humans or animals because accidental current flows through the heart in case of a failure, or because there is enough current available due to Induced Voltage from adjacent conductors; or Due to imperfect connections (for instance, a loose screw around which terminating wire is wrapped at a connection), or inadvertent contact with machinery or structures, can generate enough heat to start a fire which may in turn kill and often causes considerable damage and loss.

] Safety

The first commercial power distrib听说romextmution system developed byin 1882 in New York City usedrods, wrapped in jute and placed in rigid pipes filled with a bituminous compound.Rubber-insulated cable was used for 11,000 volt circuits in 1897 inst你看wirealled for thepower project. Oil-impregnated paper-insulated high voltage cables were commercially practical by 1895. Duringseveral varieties of synthetic rubber andinsulation were applied to cables.

Earlysystems used the first forms of electrical cabling, transmitting small amounts of current.insulation used on the firstwas unsuitable for building wiring use since it deteriorated rapidly when exposed to air.

] History

[hide]

Contents

A power cable is anof two or more, usually held together with an overall. The assembly is used for transmission of. Powermay be installed as permanentwithin buildings, buried in the ground, run overhead, or exposed. Flexible power cables are used for portable devices, mobile tools and machinery.

A electrical power cable found commonly in modern European houses. The cable consists of 3 wires (2 wires + 1 grounding) and is double-insulated

This article is about electric power conveyances. For the fictional town, see. For portable equipment, see.

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From Wikipedia, the free encyclopedia

钢芯铝绞线是绝缘的吗RomexTM——电力系统中用来传输和分配大功率电能的电缆。如常见的额定运行电压低于1000V的低压电缆、额定运行电压在3.6/6~26/35kV之间的中压电缆，被称为裸线。电缆中的缆芯由导电性能良好的材料制成，是用以传输、电和实现电磁能转换的线材产品。

按其应用可分为以下类别：

电缆通常由传输或电信号的缆芯和起到保护、作用的护套组成。只含有一条缆芯而且直径较细的电缆通常被称为电线。也有些电线没有绝缘护套，自由的百科全书

电缆，跳转到:,

维基百科，

事实上wire