Alternator MCQ | Synchronous Generator MCQ

181. How can the reactive power delivered by a synchronous generator be controlled?

1. By changing the prime mover input
2. By changing the excitation
3. By changing the direction of rotation
4. By changing the prime mover speed

182. A 10 pole, 25 Hz alternator is directly coupled to and is driven by 60 Hz synchronous motor. What is the number of poles for the synchronous motor?

1. 48
2. 12
3. 24
4. 16

183. The resultant flux density in the air gap of a synchronous generator is the lowest during

1. Open circuit
2. Solid short circuit
3. Full load
4. Half load

184. A loss-less cylindrical rotor synchronous generator is floating on the system bus-bar after being properly synchronised and is running at no-load. Now, if the prime mover is acting as a mechanical load on the machine, then

1. the torque developed by the machine will act in the same direction as the prime-mover torque.
2. the torque developed by the machine will act in the opposite direction to that of the prime-mover torque.
3. the machine rotor would fall-back and the induced emf would lag behind the terminal voltage.
4. the machine rotor would overspeed and the induced emf would lead the terminal voltage.

185. In which one of the following is reluctance power developed?

1. Salient pole alternator
2. Non-salient pole alternator
3. Squirrel cage induction motor
4. Transformer

186. What is the value of the load angle when the power output of a salient pole synchronous generator is maximum?

1. 45°
2. 0°
3. 90°
4. None of these

187. What are the conditions to be satisfied for alternator to be synchronised with an incoming supply?

1. Equal voltage
2. Equal frequency
3. Same power rating
4. Same phase sequence

Select the correct answer using the code given below

1. ii, iii and iv
2. iii and iv
3. i, ii and iii
4. i, ii and iv

188. In the measurement of X_d, X_q (in ohms), following data are obtained by the slip test on a salient pole machine:

I_d max = 10 A
I_d min = 6.5 A
V_d max = 30 V
V_d min = 25 V

Which one of the following is correct?

1. X_d = 3, X_q = 3.86
2. X_d = 4.615, X_q = 2.5
3. X_d = 3, X_q = 2.5
4. X_d = 4.61, X_q = 3.86

189. Which one of the following is not a necessary condition to be satisfied for synchronizing an incoming alternator to an already operating alternator?

1. Same voltage magnitude
2. Same frequency
3. Same prime mover speed
4. Same phase sequence

190. Which one of the following statement is Correct?

In a salient pole synchronous machine the air gap is

1. uniform under the whole pole shoe
2. least under the middle of the pole shoe and increases outwards
3. largest under the middle of the pole shoe and decreases outwards
4. least at one end of the pole shoe and increases to the maximum value at the other end