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Homework Help: Transformer Calculations - determining turns/current/maximum flux

  1. Nov 26, 2012 #1
    The Question
    A single phase transformer has the following rating: 120 kVA,
    2000 V/100 V, 60 Hz with 1000 primary turns.


    (A) the secondary number of turns
    (B) the rated currents on the primary and secondary
    (C) The maximum flux
    (D) given a maximum flux density of 0.25 T, the cross sectional area of the core.

    Equations used

    NP (primary number of turns) VP (primary voltage) IS (Secondary current)
    NS (Secondary number of turns) VS (secondary voltage) IP (primary current)

    I (current) = P (Power)
    V (Voltage)

    The attempt at a solution

    (A) NP = VP
    NS = VS

    1000 Turns = 2000V
    NS 100V

    NS = 100V

    = 0.05V X 1000 Turns

    = 50 Turns

    (B)i I (current) = P (power)
    VP (primary voltage)

    I = 120000VA

    = 60 A on the primary

    ii I (current) = P (power)
    VS (seconday voltage)

    I = 120000VA

    = 1200 A on the Secondary

    (C) I am struggling with this question i understand that I must calculate the maximum flux but am completly lost could someone please advise me in the correct direction?!

    (D) as above

    Any help would be great thanks!!
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Nov 26, 2012 #2

    rude man

    User Avatar
    Homework Helper
    Gold Member

    Part C: Remember emf = -dPHI/dt?
    Part D follows immediately.
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