Help! Having trouble with OPEN DELTA 3 Phase Connection

Discussion in 'Homework Help' started by MH Ating, Mar 8, 2016.

  1. MH Ating

    Thread Starter New Member

    Feb 9, 2016
    A 3 phase load of two 50hp, 440v, 3phase motors is to be supplied by a transformer connected in Open Delta on a 2300V Line.
    Assume a motor efficiency of 90% and a lagging pf of 85%.
    a. Determine the KVA capacity of each transformer and their transformation ratio.
    I started as 2 x 50 hp = 100hp = 74.57kw
    if i consider 1 motor only, i have 37.285kw
    Efficiency = Pout / Pin

    I = 74.57kw / ((square root of 3) x 440v x 0.85)
    = 115.1

    How would i use the value of Efficiency?
  2. StayatHomeElectronics

    AAC Fanatic!

    Sep 25, 2008
    Efficiency is going to tell us how much of the power going in is actually going to be converted into usable power out.

    Therefore, Power(out) = Efficiency × Power(in).