ampacity

14:36 Feb 17, 2009 

This question was edited by providing a better definition and changing the third example sentence. Thanks Mediamatrix!

19:40 Feb 16, 2009 

There is a major problem with the English definition because it states, wrongly, that ampacity is a characteristic of 'an insulated conductor'. In fact *all* conductors - including, for example, bare copper busbars - have an 'ampacity'. The only difference is that the ampacity of uninsulated conductors depends on factors unrelated to the melting point of insulation (because there is none). The main factor affecting the ampacity of bare conductors is of course their cross-sectional area; others include their immediate environment (surrounding air temperature, air flow, heat convection and radiation, etc.), conductor surface characteristics, geometry of the conductor (e.g. horizontal/vertical), etc. etc.

Also, the third example sentence: "Correction factors such as temperature, number of conductors, and conductor length influence ***allowable ampacity***" is an extremely poor example of how 'ampacity' is used and a poor illustration of the meaning.

'ampacity' means (or at least implies, in layman's terms) 'maximum allowable current', so the example sentence is tautological, in that it refers to the 'allowable maximum allowable current'. Finally, the length of a conductor has no significant impact on the ampacity of a given conductor, at least in the vast majority of practical situations; it may have an impact on the choice of a conductor offering sufficient ampacity in a given installation - but that's not what the example sentence says.