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Synchronous induction motor

  1. Oct 23, 2016 #1
    1. The problem statement, all variables and given/known data
    A star-connected, three-phase synchronous induction motor takes a current of 10 amps from a 415 volt supply at unity power factor when supplying a steady load. If the synchronous reactance is 5 ohms/phase and the resistance is negligible, draw the phasor diagram and calculate the value of the generated emf and the load angle.
    (ii) If the excitation is reduced by 10% and, as a consequence the generated e.m.f. is reduced by 10%, calculate the new value of the generated e.m.f E, the stator current, the power factor and the load angle, assuming that the load does not change.

    2. Relevant equations
    Voltage /phase:415 x Sqr3 =240 V
    IXs= 10 x 5 = 50V

    3. The attempt at a solution
    E^2=240^2 x 50^2=245V
    cosσ=240/245=0.979 (σ=load angle)

    E= 245-92454 x 0.1 =220.5
    My problem is how to calculate the current and the power factor as I=P/(√3 x V x I x power factor)
  2. jcsd
  3. Oct 23, 2016 #2


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    Staff: Mentor

    Hi zsolt2. I see that you have ticked to mark this thread as SOLVED.

    Does this mean you have been able to answer the question, so don't need further help from anyone here?
  4. Oct 23, 2016 #3
    Yes I think I have solved it
    I= 11.24
    If I am right
    Thank you
  5. Oct 13, 2018 #4
    Love to know how you got that
  6. Oct 27, 2018 #5
    The result is correct but I would like to know how you arrived at this result.
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