I've seen many discussions here about derating and terminal ratings, but it has never been put as clear as this article:
http://www.iaei.org/subscriber/magazine/00_b/pauley.htm
I understood that you could start from the wire's rating (90 deg, for example) but what I was always what puzzled me was the relationship between the derated wire ampacity and the terminal ampacity. Here are the two main points:
? The ampacity value determined after applying the derating factors must be equal to or less than the ampacity of the conductor based on the temperature limitations at its terminations.
? The derated ampacity becomes the allowable ampacity of the conductor, and the conductor must be protected against overcurrent in accordance with this allowable ampacity.
They give a good example in the article.
http://www.iaei.org/subscriber/magazine/00_b/pauley.htm
I understood that you could start from the wire's rating (90 deg, for example) but what I was always what puzzled me was the relationship between the derated wire ampacity and the terminal ampacity. Here are the two main points:
? The ampacity value determined after applying the derating factors must be equal to or less than the ampacity of the conductor based on the temperature limitations at its terminations.
? The derated ampacity becomes the allowable ampacity of the conductor, and the conductor must be protected against overcurrent in accordance with this allowable ampacity.
They give a good example in the article.