xguard
Senior Member
- Location
- Baton Rouge, LA
I'd like to use 800 amp (time delay) fuses on the primary of a 480:208/120 500 KVA transformer. I'm concerned about nuisance tripping. The Load is 377 KVA
Following the rule I found on the net:
601 amps x 12 = 7,212 amps @ 0.1s
601 amps x 25 = 15,025 amps @0.01s
800/600 = 1.33 (I will have secondary protection)
Several 800 amp time current curves (melting pre-arcing) I've looked at are okay at the 0.1s mark but not the 0.01s.
I'd prefer not to go up to 1000 amps, as this would also push me to a 1000 amp transfer switch (fuses would be ahead of transfer switch), require ground fault protection, bigger wires, etc.
Appreciate any recommendations.
Following the rule I found on the net:
601 amps x 12 = 7,212 amps @ 0.1s
601 amps x 25 = 15,025 amps @0.01s
800/600 = 1.33 (I will have secondary protection)
Several 800 amp time current curves (melting pre-arcing) I've looked at are okay at the 0.1s mark but not the 0.01s.
I'd prefer not to go up to 1000 amps, as this would also push me to a 1000 amp transfer switch (fuses would be ahead of transfer switch), require ground fault protection, bigger wires, etc.
Appreciate any recommendations.
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