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Generator Size

Discussion in 'Electrical Engineering' started by Dave, Sep 2, 2004.

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  1. Dave

    Dave Guest

    I have to rent a generator for a day to temporarily power up a 34 HP and a
    50 HP 480 V 3 Ph motors.

    Any idea what size of generator to rent?

    Thks, Dave
     
  2. SQLit

    SQLit Guest

    FLA of name plates plus 50% and do not start them at the same time
     
  3. Rule of thumb is 1 KVA per horsepower.
    For both motors you need at least an 84 KVA generator.
     
  4. Dave

    Dave Guest

    biggest motor, add the other FLA, then add 1/3 of that total.

    therefore: 65 a x 2 = 130 a + 41 = 171 + 1/3 = 228 a

    228 x 480 x 1.73 = 189 KW

    I ordered in a 175 KW generator to handle the job.

    Dave :)
     
  5. Louis Bybee

    Louis Bybee Guest

    Bigger/more than you need is often better, but in this case you might be
    shooting yourself in the foot.

    Rather than relying on "general or rules of thumb" to select your generator
    I would recommend you consult your generator supplier, and discuss your
    specific requirements. A competent purveyor of generators (especially of
    this size) will ask the necessary questions to ensure your needs will be
    met.

    Some of the items that should be considered in determining the size need (in
    addition to the usual) are; will the motors be required to start
    simultaneously or can they be staged, type of fuel to be used - a liquid gas
    model converted to Natural/bottled gas will require derating, Diesel
    Generators need to be run at least 50% or greater load or they will likely
    develop a wet stack condition (do a goggle search) which could result in
    severe damage to the prime mover.

    Relying on the "general" equations given you without knowledge of your
    specifics could be problematic, and result in a rather steep/painful
    learning curve. With the price you are going to pay I suspect a bit of
    discovery before the purchase is in order.

    Louis--
    *********************************************
    Remove the two fish in address to respond
     
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