-
1 длительный допустимый ток
- courant permanent admissible, m
- courant admissible, m
(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-французский словарь нормативно-технической терминологии > длительный допустимый ток
См. также в других словарях:
specific capacity — The rate of discharge of water from a well per unit of drawdown. It is commonly expressed as gpm/ft or m3/day/m and varies with pumping test duration [6] … Lexicon of Cave and Karst Terminology
specific capacity — noun : the amount of water furnished under a standard unit head : the amount of water that is furnished under unit lowering of the surface of the water in a well by pumping … Useful english dictionary
Well test — This article discusses water well testing; the testing of other wells, eg. petroleum wells, is a separate field.A well test is conducted to evaluate the amount of water that can be pumped from a particular water well. More specifically, a well… … Wikipedia
Specific heat capacity — Specific heat capacity, also known simply as specific heat, is the measure of the heat energy required to increase the temperature of a unit quantity of a substance by a certain temperature interval. The term originated primarily through the work … Wikipedia
Specific performance — is an order of a court which requires a party to perform a specific act, usually what is stated in a contract. It is an alternative to award/ for awarding damages, and is classed as an equitable remedy commonly used in the form of injunctive… … Wikipedia
Capacity — Ca*pac i*ty (k[.a]*p[a^]s [i^]*t[y^]), n.; pl. {Capacities} ( t[i^]z). [L. capacitus, fr. capax, capacis; fr. F. capacit[ e]. See {Capacious}.] 1. The power of receiving or containing; extent of room or space; passive power; used in reference to… … The Collaborative International Dictionary of English
Capacity for heat — Capacity Ca*pac i*ty (k[.a]*p[a^]s [i^]*t[y^]), n.; pl. {Capacities} ( t[i^]z). [L. capacitus, fr. capax, capacis; fr. F. capacit[ e]. See {Capacious}.] 1. The power of receiving or containing; extent of room or space; passive power; used in… … The Collaborative International Dictionary of English
Well logging — Gamma ray logging Spontaneous potential logging Resistivity logging Density logging Sonic logging Caliper logging Mud logging LWD/MWD v · … Wikipedia
Capacity (law) — The capacity of both natural and artificial persons determines whether they may make binding amendments to their rights, duties and obligations, such as getting married or merging, entering into contracts, making gifts, or writing a valid will.… … Wikipedia
capacity, specific — The ratio of well discharge to corresponding discharge [16] … Lexicon of Cave and Karst Terminology
Heat capacity — Thermodynamics … Wikipedia
