Samyst64
Member
- Location
- Columbus, OH
- Occupation
- Electrical Engineer
I have a 929KVA, 2.3KV-480V 3Ø transformer. We are using an 18R fuse (390A) for primary protection.
Amperage rating of primary conductors based on xfmr size: 929KVA/(2.3KV*1.73) = 233A *1.25 = 291.25A
Do the primary conductors need to be sized based on the calculations above (291.25A), or should they be sized for the rating of the fuse 390A? The transformer is dedicated to feeding a chiller with a VFD that has overload protection and a 1600A circuit breaker. Regarding chiller load FLA: 893A and MCA: 1048A.
Using NEC Table 310.60(C)(73) in the 90 degree 2001-5000V column, which conductors would you specify?
If based on demand current of transformer I would use #250s which are rated for 315A.
If we are basing off the fuse size would #350 work which is rated at 385A, or would you have to use #500s to exceed 390A?
Thanks for your help in advance!
Amperage rating of primary conductors based on xfmr size: 929KVA/(2.3KV*1.73) = 233A *1.25 = 291.25A
Do the primary conductors need to be sized based on the calculations above (291.25A), or should they be sized for the rating of the fuse 390A? The transformer is dedicated to feeding a chiller with a VFD that has overload protection and a 1600A circuit breaker. Regarding chiller load FLA: 893A and MCA: 1048A.
Using NEC Table 310.60(C)(73) in the 90 degree 2001-5000V column, which conductors would you specify?
If based on demand current of transformer I would use #250s which are rated for 315A.
If we are basing off the fuse size would #350 work which is rated at 385A, or would you have to use #500s to exceed 390A?
Thanks for your help in advance!
