Calculate the power of a the lift motor

  1. Please help :

    Calculate the power of a the lift motor,when is lift on a distance on a building site lift 400kg of brick50m to the top of a buiding in 24 seconds

    Ans ?

    Regards.
    taomay
     
  2. jcsd
  3. SteamKing

    SteamKing 9,939
    Staff Emeritus
    Science Advisor
    Homework Helper

    You tell us.
     

  4. Ans :

    mass= 400kg (convert mass to weight 1kg=9.81N (force of gravity on 1kg)

    400x9.81=3924N
    Workdone (j)= force xdistance
    3924x50 =196200

    Power = 196200 /24= 8175 W
    convert to KW =8.175KW
     
  5. Assuming that this is a cable driven lift and not a hydraulic lift, more data is required to calculate the HP required to lift the load:
    Desired speed of lift
    % of counterweighting
    Hoisting machine eff.
    acceleration rate and rate of change of acceleration rate (known as jerk rate)
    Hoistway eff.
    H.P. required = Speed (fpm) x capacity (lbs) x Percentage of uncounterweighted load (usually .4 to .5 / 33000) / overall eff.*
    * this can actually range anywhere from 40% to 90% depending upon machine be geared or gearless, the roping type usually being 1:1 or 2:1 as well as the types of guide shoes (roller or slide).
    If steep accelleration and jerk rates are required to meet a specific performance than a larger motor maybe required to meet those peak torque requirements.
    To convert HP to KW, multiply the HP times .746
     
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