词条 | Breaking capacity |
释义 |
Choosing breaking capacityCalculation of the required breaking capacity involves determining the supply impedance and voltage. Supply impedance is calculated from the impedance of the elements making up the supply system. Customers of an electrical supply utility can request the maximum value of prospective short-circuit current available at their point of supply. Networks involving multiple sources of current, such as multiple generators, electric motors, and with variable interconnections may be analyzed with a computer. A system study will generally consider the maximum case of additions of generation and interconnection out to some projected horizon year, to allow for system growth during the useful life of the studied installation. Since practical calculations involve a number of approximations and estimates, some judgment is required in applying the results of a short-circuit calculation to the selection of apparatus.[3] Making capacity i.e. maximum fault current , device can carry ,if it is closed in to the fault should be considered. Breaking capacitiesMiniature circuit breakers and fuses may be rated to interrupt as little as 85 amperes and are intended for supplementary protection of equipment, not the primary protection of a building wiring system. In North American practice, approved general-purpose low-voltage fuses must interrupt at least 10,000 amperes and certain types useful for large commercial and industrial low-voltage distribution systems are rated to safely interrupt 200,000 amperes. The rating of power circuit breakers varies according to the application voltage; a circuit breaker that interrupts 50,000 amperes at 208 volts might be rated to interrupt only 10,000 amperes at 600 volts, for example. Direct-current systems such as are typical with batteries are more of a problem than alternating current systems, because in the latter current regularly crosses the zero-point, whereas DC current by definition does not. See also
References1. ^{{Cite web|title = Fuseology: Amp Rating and Interrupting Rating|url = http://www.cooperindustries.com/content/dam/public/bussmann/Electrical/Resources/solution-center/technical_library/BUS_Ele_Tech_Lib_Interrupting_Rating.pdf|website = www.cooperindustries.com|accessdate = 2015-05-09}} {{DEFAULTSORT:Breaking Capacity}}2. ^Donald G. Fink and H. Wayne Beaty, Standard Handbook for Electrical Engineers, Eleventh Edition,McGraw-Hill, New York, 1978, {{ISBN|0-07-020974-X}}, page 10-64 3. ^IEEE Standard 141-1993, page 113 2 : Electrical wiring|Electrical safety |
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