Hi friends, this post is about objectives of synchronous machine. Mcq's on synchronous machines which are asked recently in various competitive exams like Gate , Upsc exams and so on. check out and comment if you have any doubts regarding this bits..
1) Distributed winding and short chording employed in ac machines will result in
A) increase in emf and reduction in harmonics
B) reduction in emf and increase in harmonics
C) increase in both emf and harmonics
D) reduction in both emf and harmonics
Ans:D
2) It is desirable to eliminate 5th harmonic voltage from the phase voltage of an alternator. The coils should be short pitched by an electrical angle of
A) 30°
B) 36°
C) 72°
D) 18°
Ans:B
3) In a synchronous generator, a divided winding rotor is preferable to a conventional winding rotor because of
A) higher efficiency
B) increased steady-state stability limit
C) higher short circuit ratio
D) better damping
Ans:B
4) A 4-pole, 3-phase, double layer winding is housed in a 36 slot stator for an ac machine with 60° phase spread. Coil span is 7 slot pitches. Number of slots in which top and bottom layers belong to different phases is
A) 24
B) 18
C) 12
D) 0
Ans:A
5) In a cylindrical rotor synchronous machine, the phasor addition of stator and rotor mmfs is possible because
A) two mmfs are rotating in opposite directions
B) two mmfs are rotating in same direction at different speeds
C) two mmfs are stationary with respect to each other
D) one mmf is stationary and the other mmf is rotating
Ans:C
6) Three phase alternators are invariably connected in star so as to
A) reduce the size of stator conductors used
B) increase the terminal voltage
C) reduce magnetic losses
D) all of the above
Ans:B
7) The stator winding of an alternator is normally connected in star to eliminate the ........... harmonics component of the voltage waveform
A) third
B) fifth
C) seventh
Ans:A
8) If the dimensions of all the parts of a synchronous generator and the number of field and armature turns are doubled, then the generated voltage will change by a factor of
A) 1
B) 2
C) 4
D) 8
Ans:C
9) The armature of a single phase alternator is completely wound with T single turn coils distributed uniformly. The induced voltage in each turn is 2V(rms). The emf of the whole winding is
A) 2 T volts
B) 1.11 T volts
C) 1.414 T volts
D) 1.273 T volts
Ans:D
10) A 3-phase alternator is wound with a 60 degree phase spread armature windings and develops 300 KVA. If the armature is reconnected utilizing all the coils for single phase operation with a phase spread of 180 degrees, the new rating of the machine is
A) 100 KVA
B) 200 KVA
C) 250 KVA
D) 300 KVA
Ans:B
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1) Distributed winding and short chording employed in ac machines will result in
A) increase in emf and reduction in harmonics
B) reduction in emf and increase in harmonics
C) increase in both emf and harmonics
D) reduction in both emf and harmonics
Ans:D
2) It is desirable to eliminate 5th harmonic voltage from the phase voltage of an alternator. The coils should be short pitched by an electrical angle of
A) 30°
B) 36°
C) 72°
D) 18°
Ans:B
3) In a synchronous generator, a divided winding rotor is preferable to a conventional winding rotor because of
A) higher efficiency
B) increased steady-state stability limit
C) higher short circuit ratio
D) better damping
Ans:B
4) A 4-pole, 3-phase, double layer winding is housed in a 36 slot stator for an ac machine with 60° phase spread. Coil span is 7 slot pitches. Number of slots in which top and bottom layers belong to different phases is
A) 24
B) 18
C) 12
D) 0
Ans:A
5) In a cylindrical rotor synchronous machine, the phasor addition of stator and rotor mmfs is possible because
A) two mmfs are rotating in opposite directions
B) two mmfs are rotating in same direction at different speeds
C) two mmfs are stationary with respect to each other
D) one mmf is stationary and the other mmf is rotating
Ans:C
6) Three phase alternators are invariably connected in star so as to
A) reduce the size of stator conductors used
B) increase the terminal voltage
C) reduce magnetic losses
D) all of the above
Ans:B
7) The stator winding of an alternator is normally connected in star to eliminate the ........... harmonics component of the voltage waveform
A) third
B) fifth
C) seventh
Ans:A
8) If the dimensions of all the parts of a synchronous generator and the number of field and armature turns are doubled, then the generated voltage will change by a factor of
A) 1
B) 2
C) 4
D) 8
Ans:C
9) The armature of a single phase alternator is completely wound with T single turn coils distributed uniformly. The induced voltage in each turn is 2V(rms). The emf of the whole winding is
A) 2 T volts
B) 1.11 T volts
C) 1.414 T volts
D) 1.273 T volts
Ans:D
10) A 3-phase alternator is wound with a 60 degree phase spread armature windings and develops 300 KVA. If the armature is reconnected utilizing all the coils for single phase operation with a phase spread of 180 degrees, the new rating of the machine is
A) 100 KVA
B) 200 KVA
C) 250 KVA
D) 300 KVA
Ans:B
If you like my post please share it with your friends and subscribe to latest updates.. If you have doubts you can start new topic on forum and start discussion with our readers..
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