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Thread: Bridge Crane power requirements

  1. #1
    Join Date
    Jul 2004

    Bridge Crane power requirements

    Does anyone know how I can come up with load requirements for Cranes with the following sizes: 10ton, 20ton, 50ton, and 80ton. I'm working on a budget so it doesn't need to be exact...just in the ballpark.

  2. #2
    Join Date
    Feb 2003
    Portage, Indiana NEC: 2008
    With the bridge, trolley, and hoist that can all work in unison, your going to have to know the HP of each motor and voltage they will be run on, before you can calculate the feeders and disconnect for each.

    But for a ruff estimate, I would say at 480 3 phase:

    10 ton = 30amp disco (not because it would require it but in industrial it would be the smallest I would install)
    20 ton = 30 amp

    50 ton = 60 amp

    80 ton = 100 amp

    240/208 volt 3 phase

    10 ton = 30 amp

    20 ton = 60 amp

    50 ton = 100-125 amp

    80 ton = 150- 200 amp

    again these are just ruff, with out knowing stuff like voltage, HP, DC/AC motors, wound rotors, it would be impossible to narrow it down.

    If someone who works more with DC cranes would chime in maybe get a little closer for you? most of the ones I have worked on were 100 ton + although we did have some smaller ones in the plant.
    Last edited by hurk27; 07-02-09 at 05:37 PM.
    Wayne A. From: N.W.Indiana
    Be Fair, Be Safe
    Just don't be fairly safe

  3. #3
    Join Date
    Dec 2009
    To calculate the max amps for an overhead crane take 100% nameplate FLA from the largest motor on the crane plus 50% nameplate FLA of the next largest motor, and add 25% to that total for max working amps.

    If there are multiple motors that run together (bridge motors, for example), the nameplate FLA for those motors are added together and treated as one motor.

    Example using 480 VAC:

    A single hoist motor at 25 FLA
    A single trolley motor at 3.5 FLA
    Two bridge motors at 3.0 FLA each = 6.0 FLA

    25 + (6 / 2) = 28 x 1.25 = 35A

    Calculate your load requirements to be able to supply not less than 93% of the nominal system voltage to the runway conductors at the farthest from the supply taps.

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