Electrical Machines Questions and Answers_pag86

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a) constant 
b) linear 
c) non-linear 
d) none of the mentioned 
View Answer 
Answer: a 
Explanation: Because the constant losses are known in advance of the test is conducted. 
15. Similarity between Hopkinonson’s and field’s test is that 
a) both need similar mechanically coupled motor 
b) both need similar electrically coupled motor 
c) regenerative power 
d) negligible power 
View Answer 
Answer: a 
Explanation: The machines have to be mechanically coupled together. 
This set of Electrical Machines Multiple Choice Questions & Answers (MCQs) focuses on “DC 
Machine Applications”. 
1. Inspite of heavy initial investments, dc motors are used due to 
a) flexibility and ease of control 
b) lower losses 
c) improved power factor of the system 
d) all of the mentioned 
View Answer 
Answer: a 
Explanation: The control of dc machines is very much simplified when compared to other 
machines. So this makes it very useful when compared. 
2. Separately excited dc generators are used in 
a) Ward leonard system of speed control 
b) Hopkinson’s testing 
c) Voltage control 
d) None of the mentioned 
View Answer 
Answer: a 
Explanation: Separately excited dc generators are used in Ward leonard system of speed 
control. 
3. Maximum torque in dc series motor is limited by 
a) commutation 
b) heating 
c) field control 
d) all of the mentioned 
View Answer 
Answer: a 
Explanation: Commutation is the process which reduces the induced emf and so the torque.