QUIZ - 3



  1. The synchronous reactance of an alternator is due to
    • leakage flux only
      Reactance because of armature reaction in the machine
      synchronous machine rectance
      both leakage flux as well as armature reaction


  2. The staturated synchronous reactance of an alternator is ---------- its unsaturated synchronous reactance
    • More than
      less than
      Equal to
      None of the above


  3. Unbalanced three phase stator currents cause
    • Vibrations
      Heating of rotor
      Double frequency currents in the rotor
      all of the above



  4. The short circuit characteristic of alternator is
    • Always linear
      Always non-linear
      Either linear or non-linear.
      None of the above


  5. Mention the fault in which only positive sequence reactance is present,
    • L-L
      L-L-G
      L-L-L
      L-G


  6. Negative sequence currents rotates with respect to field winding at
    • Synchronous speed
      Twice of synchronous speed
      Half of synchronous speed
      Stationary


  7. Zero sequence current can flow from a transmission line to a transformer if the windings are
    • Grounded Star/Delta
      Delta/Star
      Star/Grounded star
      Delta/Delta


  8. In which fault the positive sequence component of voltage at fault point is zero -
    • 3-Phase fault
      L-L Fault
      L-L-G Fault
      L-G Fault


  9. If Ia1 is the positive sequence current of an alternative and Z1, Z2 & Z0 are the sequence impedences of the altermator, the voltage drop produced in L-G fault will be
    • Ia1 Z1
      Ia1 (Z1+z2)
      Ia1 (Z1+Z2+Z0)
      Ia1 (Z2+Z0)


  10. Which statement is correct for positive, negative and zero sequence impedances -
    • (Z1 greater than Z2 greater than Z0)
      (Z1 less than Z2 less than Z0)
      (Z0 less than Z1 less than Z2)
      None of these