Talk:Ampacity

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US or global term?[edit]

If the word "ampacity" is only used in the US, the article should state this. Otherwise, the article should be edited to be less US-centric (is there an international standard about ampacity?) Jushi 11:27, 30 November 2006 (UTC)[reply]

the National Electrical Code, published by the National Fire Protection Association, is used throughout the world. —The preceding unsigned comment was added by 64.24.209.223 (talk • contribs).

While i'm sure there are places outside the US that use the NEC "throughout the world" is almost certainly a massive exaggeration. I don't have a specific source for what regulations are used in what countries but http://upload.wikimedia.org/wikipedia/commons/d/db/WorldMap_Voltage%26Frequency.png makes it pretty obvious that the reach of US electrical standards is mostly limited to america.

Afaict electrical standards divide into blocks, you have the US and US influenced countries using US standards (either directly or locally developed variants of them), Europeans and austrialians using the same voltages, frequencies and cable sizing system but with the details of regulations varying from country to country and many other countries following one of them (again either using the standards directly or locally derived variants).

Any electricial installation standard will standard current carrying capacity of cables. The exact rating they give to a cable type will depend on allowable temperature and what assumptions they make about cooling but in general the physics of the situation mean that similar cables will likely get similar ratings from different standards bodies.

Getting back on-topic ss a brit (who is an electrical engineering PHD student and friends with an electriciant) the only time i've ever seen the term "ampacity" is on american websites. We brits seem to just call it current carrying capacity (or just capacity when it's obvious from the context). Plugwash (talk) 04:14, 21 January 2011 (UTC)[reply]

The term (ampacity) is also used and definined by the Canadian Electrical Code but was never a real word (derived from "ampere capacity") except for the purpose of the particular codes. However, we know how English definitions aint fixed till some encyclopedia writer uses the slang for summat. 99.251.114.120 (talk) 04:31, 13 March 2012 (UTC)[reply]

lede obtuse?[edit]

The lede seems a bit hard to understand. Can't it start with defining ampacity as "the current-handling capacity of a wire or device," and define situational constraints (temperature, etc.) later? jhawkinson 09:16, 22 June 2007 (UTC)[reply]

Temperature rise in bare wire in free air[edit]

This article is too limited. It should at least have links to info about the temp rise in various bare wires in free air at various currents. -71.174.184.42 (talk) 23:21, 20 May 2009 (UTC)[reply]

formulae needed[edit]

it should be possible to make quantitative predictions of the current carrying capacity, if you know the parameters. please supply formulae -- 99.233.186.4 (talk) 18:25, 2 March 2010 (UTC)[reply]

Difference between rated current and current rating[edit]

Is there any difference between these two terms?--Malore (talk) 21:32, 19 April 2018 (UTC)[reply]

Semiconductor devices[edit]

"However the tolerance of short-term overcurrent is near zero for semiconductor devices". 'Tolerance' is quite ambiguous here. If it means 'current reserve', not 'margin of error' - then it's true for bipolar transistors, and not true for diodes and power FETs. These are always rated for both continuous and short-term surge currents (the latter for specific test conditions). Quite often, the weakest link is not the semiconductor itself, but the metal leads - so, in the end, they aren't much different from bare wire.
"as their thermal capacities are extremely small..." - that's right. But electric pulses are short, milliseconds or less, so surge-to-continuous ratio can be quite high.
"...it is not necessary to know the current limit to design a system" - big mistake. Systems, unlike standalone parts ("lightbulb holders"), inevitably contain connecting wire ... back to square one. Retired electrician (talk) 03:16, 11 September 2018 (UTC)[reply]