Alternator MCQ | Synchronous Generator MCQ

101. A Reactor having an inductive reactance of 4 ohms is connected to the terminals of a 120 V AC generator. Calculate the power associated with the reactor.

  1. 3.6 kVAR
  2. 30 kVAR
  3. 7.2 kVAR
  4. 4.16 kVAR
Answer
Answer. a

102. A 30 MVA, 15 kV, 1500 rpm, 3-phase synchronous generator connected to a power grid has a synchronous reactance of 9 ohms per phase. If the exciting voltage is 12 kV (line to neutral) and the system voltage is 17.3 kV (line to line). Calculate the maximum power that the generator can deliver before it falls out of step (lossless synchronous)?

  1. 78.349 MW
  2. 39.952 MW
  3. 112.89 MW
  4. 16.67 MW
Answer
Answer. b

103. A 3 Phase, 60 Hz generator connected in Y connection, generates a line to line voltage of 23900 V. Calculate the peak line voltage.

  1. 13800 V
  2. 33800 V
  3. 42300 V
  4. 23900 V
Answer
Answer. b

104. What is the pitch factor of a 4 pole alternator having 36 slots and a coil span of 1 to 8?

  1. 140°
  2. 80°
  3. 20°
  4. 40°
Answer
Answer. d

105. An alternator has a phase sequence of RYB for its phase voltages. In case the field current is reversed the phase sequence will become

  1. RBY
  2. RYB
  3. YRB
  4. None of the above
Answer
Answer. b

106. A 3-phase generating stations has two 15000 kVA generators connected in parallel each with 15% reactance. A symmetrical fault occurs at generator bus. What will be the short circuit in MVA?

  1. 300 MVA
  2. 100 MVA
  3. 250 MVA
  4. 200 MVA
Answer
Answer. d

107. Distributed winding and short chording employed in AC machines will result in

  1. reduction in both emf and harmonics emf
  2. reduction in emf and increase in harmonics emf
  3. increase in both emf and harmonics emf
  4. increase in emf and reduction in harmonics
Answer
Answer. a

108. In the case of zero power factor leading load on the alternator, the effect of armature reaction is

  1. To cross-magnetize
  2. To decrease the induced emf
  3. To de-magnetize
  4. To increase the induced emf
Answer
Answer. d

109. A magnetic flux of 300 mWb in a coil of 100 turns is reverted in 0.2 seconds. The average emf induced is

  1. -300 V
  2. 600 V
  3. 300 V
  4. -600 V
Answer
Answer. c

110. In case of leading load power factor, the terminal voltage of an alternator will

  1. Fall on removing the full load
  2. Rise on removing the full load
  3. Rise on adding the full load
  4. Fall on adding the full load
Answer
Answer. a
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