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| Derating Factor (X/R ratio) https://brainfiller.com/arcflashforum/viewtopic.php?f=23&t=360 |
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| Author: | ytegegn [ Wed Mar 04, 2009 12:15 pm ] |
| Post subject: | Derating Factor (X/R ratio) |
What if the symmetrical fault current is the same as the equipment’s rated current, but the actual X/R ratio is larger than the tested X/R ratio? (MF=Iasym @ X/Rtestd-:-Iasy @X/Rcalc) |
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| Author: | acobb [ Wed Mar 04, 2009 12:58 pm ] |
| Post subject: | |
Not unless you have the sequence info as well. Unless it is very high then not a big deal anyway since most equipment is designed for x/r>1 per the standards. If I remember correctly, Vacuum Circuit Breakers are required by the ANSI/IEEE standards to interrupt at rated AIC with an offset associated with an x/r=15. |
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