I currently have a tower crane that the general put 277 volt lights on and the crane is fed 480 volt 3-phase. I installed and 7.5 Kva transformer on it for 120v/208 power. I am trying to figure the best way to utilize one or two legs of the 480v available because I do get 277V to ground on it and have this be safe would an auto transformer be it I believe it would be 6.8 Kva load each light is 4.1 amps at 277V there are 6.