how do i go about finding power factor and kva for questions like these

Discussion in 'Homework Help' started by Rance, Mar 26, 2016.

  1. Rance

    Thread Starter New Member

    Mar 26, 2016
    2
    0
    Im not sure how to get the answer for this question and cant find anything that helps. Any help would be apprecitied. IMG_3135.JPG IMG_3135.JPG
     
  2. WBahn

    Moderator

    Mar 31, 2012
    17,788
    4,808
    This is Homework Help, not Homework Done For You. You need to show YOUR best attempt at a solution. That gives us a starting point from which to help you identify where you are going wrong and help guide you toward the answer.

    Hint: Just tabulate the real and reactive powers, add them up, and convert to apparent power and power factor.
     
  3. Rance

    Thread Starter New Member

    Mar 26, 2016
    2
    0
    not sure how to go about this problem this is what i have tried don't know where im going wrong
    real power = kva x pf
    so i did 100kva x .9pf =90kw for the induction motor being added
    and 400kva x .75pf =300kw
    add together 300kw +90kw= 390kw
    new kva is 100kw / .9 = 111.1kva + 400kva = 511.1kva
    then 390kw / 500kva = .78 new power factor
     
  4. WBahn

    Moderator

    Mar 31, 2012
    17,788
    4,808
    Note that the additional motor, in either case, is NOT 100 kVA -- it is 100 kW. They are giving you the real power load of the motor along with it's power factor.
     
  5. WBahn

    Moderator

    Mar 31, 2012
    17,788
    4,808
    Also, note that you can't add kVA values together because kVA is apparent power that makes no allowance for phase angle.
     
Loading...