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Thread: 5kv to 480v xfrmr

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    5kv to 480v xfrmr

    5kv switch is feeding xfrmr which is feeding the 800a panel. Anyway to determine size of 5kv switch or xfmr based only 480v switch size of 800a given? Thanks

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    All you can get is a rough guess if you assume the maximum load is actually 800A. That equates to roughly 650kVA at 480V, which will be around 95A at 4160V on the primary (5kV is the “class” of equipment, the actual utilization voltage will be 4160V in North America). The smallest typical 5kV switch will be 200A anyway.
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    If the OCPD is 800A, it would mean a full load of 800*.80 = 640A. The nearest standard transformer at 480V should be 500kVA (FL=674A). At 4160V, the full load amps will be 78A. A 150E fuse could protect the primary of the transformer.

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    Thank you. I got that @ 800A 480v side( even 640A) I would need a 500kva xfrmr. So I could fuse the 5kv switch at 150A and then I'd need to run 150A feeder from 5kv switch to primary of 500KVA xfrmr?

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    Can you get them from the same manufacturer and buss them together? 5k,xfmr,mdp. or isn't there room?

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    Quote Originally Posted by sameguy View Post
    Can you get them from the same manufacturer and buss them together? 5k,xfmr,mdp. or isn't there room?
    I def have the room. So sort of like a substation line-up but usually that's only the 5kv step don xfrmr and the 480v distribution. I could get the 5kv switch/xfmr and MDP as one? Thanks

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    That I don't know as a one piece.
    You can get the three so they just bolt together like one piece.

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    Quote Originally Posted by topgone View Post
    If the OCPD is 800A, it would mean a full load of 800*.80 = 640A. The nearest standard transformer at 480V should be 500kVA (FL=674A). At 4160V, the full load amps will be 78A. A 150E fuse could protect the primary of the transformer.
    I would not assume the .8 loading is going to be appropriate. Typically 480V equipment at this rating, i.e. 800A is going to be 100% rated. For sizing I would not make that assumption anyway.
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