Electrical Machines Questions and Answers_pag319

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a) A-II, B-III,C-I 
b) A-III, B-II,C-I 
c) A-III, B-I,C-II 
d) A-I, B-II,C-III 
View Answer 
Answer: a 
Explanation: Speed will remain constant for a fair amount of operating range. Torque will be 
linear in small slip regions. 
13. The most acceptable application field where an induction generator cana be used is 
a) wind power system 
b) steam power system 
c) hydro power system 
d) nuclear power station 
View Answer 
Answer: a 
Explanation: Induction generator is widely acceptable in low speed and low power operation like 
wind power systems. 
14. A 3-phase induction motor has full load efficiency of 0.7 and a maximum efficiency of 0.85. It 
is operated at a slip of 0.6 by reduced voltage method. The efficiency of the motor at this 
operating point is 
a) less than 0.35 
b) greater than 0.35 
c) in the range of 0.8 to 0.2 
d) none of the mentioned 
View Answer 
Answer: a 
Explanation: For the slip more than 40%, the efficiency reduces more than 50% for an induction 
motor. 
15. Two three phase squirrel-cage induction generator are identical in all respects except the 
fact that the slot depths in machine B is more than that of A. 
Machine B as compared to machine A, will have 
a) less pull out torque but better power factor 
b) more pull out torque but poor power factor 
c) less pull out torque and poor power factor 
d) more pull out torque and better power factor 
View Answer 
Answer: a 
Explanation: As the slot depth in machine B is more than that of A, B will have higher reactance 
as the leakage flux will be lesser. 
 This set of Electrical Machines Multiple Choice Questions & Answers (MCQs) 
focuses on “Applications of Polyphase Induction Motors”. 
1. Wound rotor induction motor is most appropriate for the applications requiring 
a) high starting torque