Electrical Machine Design MCQ

121. Use of higher B_av in synchronous machines causes increase in

(a) iron losses.
(b) synchronizing power.
(c) short -circuit current.
(d) all of these.

122. Use of higher specific electric loading in synchronous machines reduces

(a) copper losses.
(b) synchronous reactance.
(c) synchronizing power.
(d) stray load losses.

123. Higher values of ampere-conductors cannot be recommended for synchronous machines as it will cause

(a) increase in copper loss leading to poor efficiency and temperature rise.
(b) increase in synchronous reactance leading to poor inherent voltage regulation.
(c) increase in stray load loss.
(d) all of the above.

124. Usual values of ac recommended for salient pole machines are

(a) 5,000 to 10,000 ampere-conductors/m.
(b) 10,000 to 20,000 amp- conductors/m.
(c) 20,000 to 50,000 amp-conductor/m.
(d) 50,000 to 100,000 amp-conductors/m.

125. Usual values of ac recommended for turbo-alternators are

(a) 50,000 to 100,000 amp-conductors/m.
(b) 20,000 to 50,000 amp-conductors/m.
(c) 10,000 to 20,000 amp-conductors/m.
(d) 5,000 to 10,000 amp-conductors/m.

126. The use of salient poles on high speed synchronous machines will cause

(a) excessive windage loss.
(b) excessive noise.
(c) reduced windage loss.
(d) reduced noise.
(e) both (a) and (b).

127. A synchronous machine with longer air gap will have

(a) lower stability limit.
(b) smaller unbalanced magnetic pull.
(c) higher noise level.
(d) poor ventilation.
(e) more tooth pulsation loss.

128. Short-circuit ratio for modern turbo-generators is usually

(a) 0.5 to 0.6
(b) 1.0 to 1.5
(c) 0.2 to 0.3
(d) 2.0 to 2.5

129. When a synchronous generator is designed with lower SCR it

(a) will give higher stability limit.
(b) will have lower SC current.
(c) will give better voltage regulation.
(d) will have high synchronizing power. [A.M.I.E. Elec. Design 1994]

130. An alternator with higher value of SCR has

(a) poor voltage regulation and lower stability limit.
(b) better voltage regulation and higher stability limit.
(c) poor voltage regulation and higher stability limit.
(d) better voltage regulation and lower stability limit. [Principles of Elec. Design 1994]

131. Which one of the following statements regarding synchronous machines is incorrect?

(a) A machine with a large air gap has a high synchronizing power.
(b) A machine designed with high flux density has better stability.
(c) A machine with higher value of SCR has poor voltage regulation.
(d) A machine designed with higher specific electric loading has a poor inherent voltage regulation.

132. Under short-circuit conditions, the power factor of a synchronous machine is

(a) 1
(b) about 0.8 lagging
(c) almost zero lagging
(d) 0.5

 

1. Electrical Machine Design MCQ Part – 1
2. Electrical Machine Design MCQ Part – 2
3. Electrical Machine Design MCQ Part – 3

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