480 volt crane power need to get a neutral for 277 lights

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AaronAnderson

Member
Location
Seattle, WA
Has anyone ran into this. I set up a 7kva transformer for 120/208V power up on a crane for the beacon light and cab power and their Christmas lights and the general contractor has 277V jib lights installed on the crane and SO is ran back to my other transformer skid I need to get a neutral out of 480 volt I am guessing the easiest way is to set another transformer up the but now everything is up and not that easy to get another heavy transformer up there.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Sorry...I had an idea about using a lighter autotransformer arrangement to derive a neutral, but 210.9 shoots that down.

In theory you could 'derive' a neutral and size the transformer to carry only the maximum neutral load (1/3 of the total KVA) and since this is by necessity an autotransformer arrangement it would be even smaller than a normal transformer of 1/3 KVA rating. But 210.9 requires the grounded conductor (the neutral) be supplied from the upstream system.

-Jon
 
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