Installed crane 277 volt lights and I have 480 volt 3 phase at top

Discussion in 'General Electronics Chat' started by AaronAnderson, Nov 21, 2014.

  1. AaronAnderson

    Thread Starter New Member

    Nov 21, 2014
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    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.
     
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
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    just hook them to ground and one or both legs of the 480. if you have 6 lamps, put three on one leg and three on the other, to maintain balance. of course, use the usual disconnect, fuses and such.
     
  3. gerty

    AAC Fanatic!

    Aug 30, 2007
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    Is the 480 power to your crane Wye connected ? That would mean it has a neutral plus the 3 phases, 4 wires total, not including ground. The ground should never be used as a current carrying conductor, it's a code violation. I'm not really clear on what you want to do with the transformer.
     
  4. alfacliff

    Well-Known Member

    Dec 13, 2013
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    and a crane should never not have a pulled ground. none of our cranes here have only 2 phases, all are three phase with ground. 4 wires through the shoes tothe feed rails.
     
  5. AaronAnderson

    Thread Starter New Member

    Nov 21, 2014
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    They dropped a 4-wire SO 3 hots and a ground. This is just a temporary construction tower crane. I got the lights on and everything seems good since it is only accessible to qualified personnel and grounds will not be broken I am going with it
     
  6. tcmtech

    Well-Known Member

    Nov 4, 2013
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    1,624
    In most areas a 4 wire 277/480 three phase systems with one wire sharing both common and ground duty is legal so if its allowed in your area that how I would go about it and never give it a second thought.
     
  7. takao21203

    Distinguished Member

    Apr 28, 2012
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    Could be installed between two phases or I am wrong?
     
  8. gerty

    AAC Fanatic!

    Aug 30, 2007
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    Voltage between 2 phases would be 480
     
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