Alternator MCQ | Synchronous Generator MCQ

141. ________ excitation will _______ the terminal voltage of the machine when connected _______

  1. Variable, not change, to infinite bus
  2. Fixed, change, independently
  3. Variable, change, to Infinite bus
  4. Variable, not change, independently
Answer
Answer. a

142. Synchronous generator can ________ reactive power.

  1. neither generates nor absorbs
  2. absorb
  3. generate and absorb
  4. generate
Answer
Answer. c

143. Harmonics present in alternators affect

  1. Pitch factor
  2. Chording factor
  3. Neither Chording factor nor pitch factor
  4. Chording factor and pitch factor
Answer
Answer. d

144. Damper in a large generator is used to

  1. Increase stability
  2. Reduce voltage fluctuation
  3. Reduce frequency fluctuation
  4. All the above options
Answer
Answer. a

145. Salient pole machine has

  1. large number of poles
  2. small number of poles
  3. small diameters
  4. long cores
Answer
Answer. a

146. An integral number of slots per pole is often used in an alternator in order to

  1. Eliminate harmonics in the waveform
  2. Provide insulation
  3. Permit easy installation of stator coils
  4. Provide easy removal in case of repair
Answer
Answer. a

147. In alternators during armature reaction the effect of armature flux on main flux with unity power factor is

  1. cross magnetising
  2. wholly demagnetising
  3. partially magnetising
  4. wholly magnetising
Answer
Answer. a

148. Which of the following operating aspects necessitate the computation of Regulation of an alternator?

  1. When load is thrown off
  2. For designing of an automatic voltage-control equipment
  3. For determination of steady-state and transient stability
  4. For parallel operation of alternators
  1. i, ii and iii only
  2. i, ii and iv only
  3. i, iii and iv only
  4. i, ii, iii and iv
Answer
Answer. d

149. A 3-MVA, 6-pole, 50 Hz, 3-phase synchronous generator is connected to an infinite bus of 3300 V; and it is run at 1000 rpm. The synchronous reactance of the machine is 0.915 W/phase. The synchronizing torque for 1° mechanical displacement of the rotor is

  1. 7500 N-m
  2. 7000 N-m
  3. 6000 N-m
  4. 4500 N-m
Answer
Answer. c

150. The rotor of a 4-pole ac generator is wound with a 200 turns coil. If the flux per pole is 5 mWb and the rotor runs at a speed of 1500 rpm, the rms value of the induced voltage for this ac generator is nearly

  1. 140 V
  2. 157 V
  3. 164 V
  4. 200 V
Answer
Answer. d
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