-
1 air current drop
English-German dictionary of Architecture and Construction > air current drop
-
2 длительный допустимый ток
- Strombelastbarkeit, f
- Dauerstrombelastbarkeit, f
(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 IZ
[ 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
EN
DE
- Dauerstrombelastbarkeit, f
- Strombelastbarkeit, f
FR
- courant admissible, m
- courant permanent admissible, m
Русско-немецкий словарь нормативно-технической терминологии > длительный допустимый ток
См. также в других словарях:
Drop the Dead Donkey — Format Satirical sitcom Created by Andy Hamilton Guy Jenkin … Wikipedia
Air New Zealand — IATA NZ ICAO ANZ Callsign NEW ZEALAND … Wikipedia
Air gun — Air rifle and Air pistol redirect here. For other uses, see Air gun (disambiguation) An air gun (air rifle or air pistol) is a rifle or pistol which fires projectiles by means of compressed air or other gas, (in contrast to a firearm which uses… … Wikipedia
Air Canada — IATA AC ICAO ACA Callsign AIR CANADA … Wikipedia
drop — [dräp] n. [ME drope < OE dropa, akin to ON drūpa, DROOP, Ger triefen: for IE base see DRIP] 1. a small quantity of liquid that is somewhat spherical, as when falling 2. a very small quantity of liquid 3. [pl.] liquid medicine taken or applied… … English World dictionary
Current-to-voltage converter — In electronics, a transimpedance amplifier is an amplifier that converts current to voltage. Its input ideally has zero impedance, and the input signal is a current. Its output may have low impedance, or in high frequency applications, may be… … Wikipedia
Air Movement and Control Association — The Air Movement and Control Association International, Inc. (AMCA; pronounced Am Cah ) is a nonprofit organization that creates standards for, tests, and rates Heating, Ventilating, and Air Conditioning (HVAC) equipment. It is best known for its … Wikipedia
drop — I. noun Usage: often attributive Etymology: Middle English, from Old English dropa; akin to Old High German tropfo drop Date: before 12th century 1. a. (1) the quantity of fluid that falls in one spherical mass (2) plural a dose of medicine… … New Collegiate Dictionary
Air University (Pakistan) — Infobox University name =Air University established =2002 type =Public endowment = staff = faculty = chancellor =Air Marshal Qazi Javed Ahmed rector = pro rector = students = undergrad = postgrad = doctoral = profess = city =Islamabad state =… … Wikipedia
air — n. & v. n. 1 an invisible gaseous substance surrounding the earth, a mixture mainly of oxygen and nitrogen. 2 a the earth s atmosphere. b the free or unconfined space in the atmosphere (birds of the air; in the open air). c the atmosphere as a… … Useful english dictionary
Current characters of Neighbours — The following is a list of the current main characters in the Australian soap opera Neighbours .B;Ringo Brown :(Sam Clark) Tenure: 2007 Lives at: Number 28 Parents: Graham and Prue Brown Siblings: Johnny, George, Pauline and Paul Brown Younger… … Wikipedia
