well+locations

(длительный) допустимый ток
Максимальное значение электрического тока, который может протекать длительно по проводнику, устройству или аппарату при определенных условиях без превышения определенного значения их температуры в установившемся режиме
[ ГОСТ Р МЭК 60050-826-2009]

Этот ток обозначают I_Z
[ ГОСТ Р 50571. 1-2009 ( МЭК 60364-1: 2005)]

EN

(continuous) current-carrying capacity
ampacity (US)
maximum value of electric current which can be carried continuously by a conductor, a device or an apparatus, under specified conditions without its steady-state temperature exceeding a specified value
[IEV number 826-11-13]

ampacity
The current in amperes that a conductor can carry continuously under the conditions of use without exceeding its temperature rating.
[National Electrical Cod]

FR

courant (permanent) admissible, m
valeur maximale du courant électrique qui peut parcourir en permanence, un conducteur, un dispositif ou un appareil, sans que sa température de régime permanent, dans des conditions données, soit supérieure à la valeur spécifiée
[IEV number 826-11-13]

Ampacity, the term is defined as the maximum amount of current a cable can carry before sustaining immediate or progressive deterioration. Also described as current rating or current-carrying capacity, is the RMS electric current which a device can continuously carry while remaining within its temperature rating. The ampacity of a cable depends on:

• its insulation temperature rating;
• conductor electrical properties for current;
• frequency, in the case of alternating currents;
• ability to dissipate heat, which depends on cable geometry and its surroundings;
• ambient temperature.

Electric wires have some resistance, and electric current flowing through them causes voltage drop and power dissipation, which heats the cable. Copper or aluminum can conduct a large amount of current before melting, but long before the conductors melt, their insulation would be damaged by the heat.

The ampacity for a power cable is thus based on physical and electrical properties of the material & construction of the conductor and of its insulation, ambient temperature, and environmental conditions adjacent to the cable. Having a large overall surface area may dissipate heat well if the environment can absorb the heat.

In a long run of cable, different conditions govern, and installation regulations normally specify that the most severe condition along the run governs the cable's rating. Cables run in wet or oily locations may carry a lower temperature rating than in a dry installation. Derating is necessary for multiple circuits in close proximity. When multiple cables are near, each contributes heat to the others and diminishes the amount of cooling air that can flow past the individual cables. The overall ampacity of the insulated conductors in a bundle of more than 3 must be derated, whether in a raceway or cable. Usually the de-rating factor is tabulated in a nation's wiring regulations.

Depending on the type of insulating material, common maximum allowable temperatures at the surface of the conductor are 60, 75 and 90 degrees Celsius, often with an ambient air temperature of 30°C. In the U.S., 105°C is allowed with ambient of 40°C, for larger power cables, especially those operating at more than 2 kV. Likewise, specific insulations are rated 150, 200 or 250°C.

The allowed current in cables generally needs to be decreased (derated) when the cable is covered with fireproofing material.

For example, the United States National Electric Code, Table 310-16, specifies that up to three 8 AWG copper wires having a common insulating material (THWN) in a raceway, cable, or direct burial has an ampacity of 50 A when the ambient air is 30°C, the conductor surface temperature allowed to be 75°C. A single insulated conductor in air has 70 A rating.

Ampacity rating is normally for continuous current, and short periods of overcurrent occur without harm in most cabling systems. The acceptable magnitude and duration of overcurrent is a more complex topic than ampacity.

When designing an electrical system, one will normally need to know the current rating for the following:

• Wires
• Printed Circuit Board traces, where included
• Fuses
• Circuit breakers
• All or nearly all components used

Some devices are limited by power rating, and when this power rating occurs below their current limit, it is not necessary to know the current limit to design a system. A common example of this is lightbulb holders.

[http://en.wikipedia.org/wiki/Ampacity]

Тематики

• электротехника, основные понятия

Синонимы

• длительно допустимый ток
• допустимый ток

EN

• ampacity (US)
• continuous current
• continuous current-carrying capacity
• current-carrying capacity

DE

• Dauerstrombelastbarkeit, f
• Strombelastbarkeit, f

FR

• courant admissible, m
• courant permanent admissible, m

сеть связи
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[http://www.rfcmd.ru/glossword/1.8/index.php?a=index&d=23]

EN

communication network
system of communication nodes and links that provides transmission of analog or digital signals

EXAMPLES Telecommunications networks, Internet, intranet, extranet, Wide Area Networks (WAN), Local Area Networks (LAN) and computer networking utilizing information technology.

NOTE 1 A network has its boundary. All nodes at the network boundary are called ends. In some applications, the term “node” is used instead of “end” as a communication access point to the network, as well as for interconnections between the transmission links.

NOTE 2 A “backbone” communication network consists of core network and high-speed transmission lines (national or international), connecting between major switching network nodes (interconnection of transmission lines) at various locations in a country or region.
[IEC 61907, ed. 1.0 (2009-12)]

FR

réseau de communication
système constitué de nœuds et de liaisons de communication assurant la transmission des signaux analogiques ou numériques

EXEMPLES Les réseaux de télécommunications, l’Internet, l'intranet, l’extranet, les réseaux étendus (WAN), les réseaux locaux (d'entreprise) (RLE) et les réseaux informatiques utilisant les technologies de l’information.

NOTE 1 Un réseau comporte sa propre frontière. L’ensemble des nœuds situés au niveau de la frontière d’un réseau s’appellent des terminaux. Dans certaines applications, le terme «nœud» est utilisé à la place du terme «terminal» comme point d'accès de communication au réseau, ainsi que pour désigner les interconnexions entre les liaisons de transmission.

NOTE 2 Un réseau de communication «fédérateur» est constitué d’un réseau central et de lignes de transmission à grande vitesse (nationales ou internationales) reliant entre eux des nœuds de réseaux de commutation importants (interconnexion de lignes de transmission) en divers lieux d'un pays ou d'une région.
[IEC 61907, ed. 1.0 (2009-12)]

Тематики

• защита информации

EN

• communication network

FR

• réseau de communication