Hi all-
Sorry, but I'm a little rusty here. I was wondering if anyone could check my reasoning and make sure I'm not off track?
I'm installing a 30kVA 3-phase dry-type transformer at a warehouse on a 480/277 Y system. The transformer is 480 delta primary to 120/208 Y secondary. The mfr told me I can use this so long as I don't make a neutral connection on the primary side; just bond the neutral (X0) to ground on the secondary side. Does this seem correct?
Secondly, I wanted to make the entire capacity of the xformer available for use in the building. I calculated a primary circuit breaker size of 50A (30kVA/{480x1.73} plus 125%) and 125A on the secondary side (30kVA/{208x1.73} plus 125%) which is 104, but I went up to the next size?
Lastly, do I need primary and secondary circuit breaker protection? I thought I did only because of the bonding of X0 and ground on the secondary side.
Any thoughts, advice, opinions would be welcomed. I'll read Article 450 in the meantime. Thanks!!
Sorry, but I'm a little rusty here. I was wondering if anyone could check my reasoning and make sure I'm not off track?
I'm installing a 30kVA 3-phase dry-type transformer at a warehouse on a 480/277 Y system. The transformer is 480 delta primary to 120/208 Y secondary. The mfr told me I can use this so long as I don't make a neutral connection on the primary side; just bond the neutral (X0) to ground on the secondary side. Does this seem correct?
Secondly, I wanted to make the entire capacity of the xformer available for use in the building. I calculated a primary circuit breaker size of 50A (30kVA/{480x1.73} plus 125%) and 125A on the secondary side (30kVA/{208x1.73} plus 125%) which is 104, but I went up to the next size?
Lastly, do I need primary and secondary circuit breaker protection? I thought I did only because of the bonding of X0 and ground on the secondary side.
Any thoughts, advice, opinions would be welcomed. I'll read Article 450 in the meantime. Thanks!!