An "E" rated fuse (100E and above), by definition, must melt in 10 mins at 220 to 264% of E (ampere) rating.
I am doing a coordination study at our mill and began to wonder this...it can then therefore sustain 200% of it's rating indefinately? The manufacturer's TCC's do not show otherwise.
How can this "E" ampere rating be used to meet, for example, NEC art 450 req'ts?
Take a 750KVA xfmr 4160V delta delta. Primary protection only. NEC states fuse rating within 250% of xfmr rated current. 250% x 104 FLA = 262.5, bumped up to next standard size 300A.
So if a fuse rated 300E can sustain 600A indefinately, there seems to be an issue (considering the xfmr is only rated for 104A).
I hope this isn't a dumb question, but am I missing something here??
I am doing a coordination study at our mill and began to wonder this...it can then therefore sustain 200% of it's rating indefinately? The manufacturer's TCC's do not show otherwise.
How can this "E" ampere rating be used to meet, for example, NEC art 450 req'ts?
Take a 750KVA xfmr 4160V delta delta. Primary protection only. NEC states fuse rating within 250% of xfmr rated current. 250% x 104 FLA = 262.5, bumped up to next standard size 300A.
So if a fuse rated 300E can sustain 600A indefinately, there seems to be an issue (considering the xfmr is only rated for 104A).
I hope this isn't a dumb question, but am I missing something here??
