- #1
Leyden
- 39
- 4
- TL;DR Summary
- Trying to determine whether three-phase current would produce more temperature rise in a conductor than single phase.
Good Morning,
I am not coming up with an answer in my search, could anyone confirm or deny whether a circuit conductor would experience more temperature rise with three-phase current than if the same R.M.S. current was single-phase. Alternating Current, 60 Hertz.
If you want to know why I want to know this, it is because in the National Electrical Code (NFPA 70) there is allowance (310.15(B)(7) (2017)) for higher current on a select few conductors with one of the requisites being single phase. And I am trying to figure out why, I am searching for the report of when this allowance was introduced (1956) but waiting on a reply from NFPA. If you have another theory why, I would also appreciate that, I have a few. I don't believe this is a legitimate reason why, because we use thermal OCPD but I want to know anyway.
Thank you
I am not coming up with an answer in my search, could anyone confirm or deny whether a circuit conductor would experience more temperature rise with three-phase current than if the same R.M.S. current was single-phase. Alternating Current, 60 Hertz.
If you want to know why I want to know this, it is because in the National Electrical Code (NFPA 70) there is allowance (310.15(B)(7) (2017)) for higher current on a select few conductors with one of the requisites being single phase. And I am trying to figure out why, I am searching for the report of when this allowance was introduced (1956) but waiting on a reply from NFPA. If you have another theory why, I would also appreciate that, I have a few. I don't believe this is a legitimate reason why, because we use thermal OCPD but I want to know anyway.
Thank you
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