Electrical Machines Questions and Answers_pag53

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Answer: d 
Explanation: Ac series motor is dc series motor connected to ac supply having an unidirectional 
torque, which is not very high in magnitude.It is widely applicable for small torque requirements 
like portable drilling machines, mixers etc. 
5. Universal motor is used in vacuum cleaners, table fans and portable drilling machine. 
a) True 
b) False 
View Answer 
Answer: a 
Explanation: The universal motor is dc series motor with ac supply with smaller torque. So it can 
be used for lower torque applications. 
6. _______ generator is used in arc welding purposes. 
a) Differential compound dc 
b) Dc series 
c) Cumulative compounded dc 
d) Shunt 
View Answer 
Answer: a 
Explanation: The external characteristics of the differentially compound generator have 
minimum voltage for the high current voltages.This is best harnessed feature for a high current 
requirement by the welding application. 
7. The dc series generator is employed as 
a) a booster to maintain constant voltage at the end of the feeder. 
b) for supplying traction load 
c) for battery bank charging 
d) none of the mentioned 
View Answer 
Answer: a 
Explanation: Referring to the external characteristics of dc series generator shows that the 
terminal end voltage increases as the loading increases from no load to full load. In feeders due 
to variable requirements the voltage drops while transferring when loading is raised. 
8. If it asked by the customer to provide tappings on the transformer, the most efficient and 
economical way to provide it at 
a) middle of hv winding 
b) phase end of hv winding 
c) neutral end of hv winding 
d) middle of lv winding 
View Answer 
Answer: a 
Explanation: Tappings are provided to tap different levels of voltages at the high voltage end of 
the transformer.Providing it as low voltage side has no use and it is not economical. 
9. In a single phase induction regulator, the voltage boost is maximum when armature mmf and 
rotor mmf make an angle of