Electrical Machines Questions and Answers_pag90

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Answer: d 
Explanation: All the mentioned nature of the characteristics are correct. 
3. The external characteristic is plotted between 
a) terminal voltage vs armature current at constant excitation 
b) terminal voltage vs field current at constant armature current 
c) induced armature emf vs armature current at constant excitation 
d) none of the mentioned 
View Answer 
Answer: a 
Explanation: The external characteristic is plotted between terminal voltage and armature 
current at fixed excitation. 
4. A student forgot to mark the x-y axes in his experiments but he just noted down the cause 
and the effect for each. How will he conclude about the armature 
characteristic out of the all plotted graphs? 
a) By marking graph for constant terminal voltage 
b) By marking graph for constant field current 
c) By marking graph for constant armature current 
d) By marking graph for constant speed 
View Answer 
Answer: a 
Explanation: Armature characteristic is observed at constant terminal voltage for emf vs 
armature current. 
5. Armature characteristic is also known as 
a) regulation characteristic 
b) magnetization characteristic 
c) external characteristic 
d) load characteristic 
View Answer 
Answer: a 
Explanation: Armature characteristic is also known as regulation characteristic. It is so called 
due to the fact that the difference in the terminal voltage helps to determine the voltage 
deviation. 
6. The air gap line represents 
a) magnetic behaviour of the air gap of the dc machine 
b) magnetic behaviour of the air gap of the induction machine 
c) magnetic behaviour of the iron core 
d) all of the mentioned 
View Answer 
Answer: a 
Explanation: Air gap line in the magnetization curve represents the ideal nature of the machine 
considering no saturation for the dc machine. 
7. Identify the armature characteristic of the dc generator.