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) If the space distribution is non-sinusoidal, emf induced in the distributed winding will be
A) more sinusoidal in comparison to the flux distribution
B) less sinusoidal in comparison to the flux distribution
C) of the same shape as that of flux distribution
D) none of the above
Ans:A
2) The armature winding of a 2-pole, 3-phase alternator for each phase is distributed in a number of slots per phase. The rms value of the voltage per phase is less than the rms vaue of the voltage per coil multiplied by the number of coils in series because the
A) rms value of the voltage in different coils of the phase is different
B) equal rms voltages in different coils of the phase has mutual phase difference
C) maximum values of the induced voltages in different coils of the phase are different
D) different coils of the phase pass through different saturated regions of the magnetic circuit
Ans:B
3) Consider the following statements:
The effect of slot harmonics are effectively reduced by
1. skewing the slots 2. fractional slot winding
3. short-corded winding 4. distributed winding
Of these statements
A) 1 and 2 are correct
B) 2, 3, and 4 are correct
C) 1, 3, and 4 are correct
D) 1 and 3 are correct
Ans:B
4) The short-pitch winding is preferred over full-pitched winding for an alternator because it
A) gives improved waveform of the induced emf as the distorting harmonics can be reduced or totally eliminated
B) reduces the inductance of the winding
C) increases total induced emf
D) both (a) and (b)
Ans:D
5) Chording and distribution of armature winding for ac machines results in
A) reduction in air gap mmf harmonics
B) reduction in fundamental component or induced emf
C) increase in fundamental component or induced emf
D) reduction in noise and machine size
E) both (a) and (b)
Ans:E
6) Harmonics in the emf generated in an alternator can be reduced by
A) skewing the slots
B) chamfering the salient pole tips
C) using distributed winding
D) all of the above
Ans:D
7) Skew of rotor bar eliminates
A) the effect of space harmonics
B) the entire effect of crawling
C) magnetic noise
D) vibration due to unequal force developed on rotor
Ans:A
8) The emf generated due to nth harmonic component of flux in an alternator will be ............. the fundamental emf in magnitude
A) less than
B) more than
C) equal to
Ans:A
9) 4 pole star-connected alternator running at 1500 rpm have 72 slots with 10 conductors per slot. The number of turns per phase and slot angle is
A) 120 turns and 20 degrees
B) 100 turns and 10 degrees
C) 120 turns and 10 degrees
D) 100 turns and 20 degrees
Ans:C
10) The stator of a 3-phase, 6-pole ac machine has 45 slots. The stator winding has 45 coils with a coil span of 6 slots. what type of winding will be selected for this machine?
A) Double-layer, Fractional slot, short-pitched winding
B) Single-layer, Fractional slot, short-pitched winding
C) Single-layer, integral slot, full-pitched winding
D) Double-layer, Fractional slot, full-pitched winding
Ans:A
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1) If the space distribution is non-sinusoidal, emf induced in the distributed winding will be
A) more sinusoidal in comparison to the flux distribution
B) less sinusoidal in comparison to the flux distribution
C) of the same shape as that of flux distribution
D) none of the above
Ans:A
2) The armature winding of a 2-pole, 3-phase alternator for each phase is distributed in a number of slots per phase. The rms value of the voltage per phase is less than the rms vaue of the voltage per coil multiplied by the number of coils in series because the
A) rms value of the voltage in different coils of the phase is different
B) equal rms voltages in different coils of the phase has mutual phase difference
C) maximum values of the induced voltages in different coils of the phase are different
D) different coils of the phase pass through different saturated regions of the magnetic circuit
Ans:B
3) Consider the following statements:
The effect of slot harmonics are effectively reduced by
1. skewing the slots 2. fractional slot winding
3. short-corded winding 4. distributed winding
Of these statements
A) 1 and 2 are correct
B) 2, 3, and 4 are correct
C) 1, 3, and 4 are correct
D) 1 and 3 are correct
Ans:B
4) The short-pitch winding is preferred over full-pitched winding for an alternator because it
A) gives improved waveform of the induced emf as the distorting harmonics can be reduced or totally eliminated
B) reduces the inductance of the winding
C) increases total induced emf
D) both (a) and (b)
Ans:D
5) Chording and distribution of armature winding for ac machines results in
A) reduction in air gap mmf harmonics
B) reduction in fundamental component or induced emf
C) increase in fundamental component or induced emf
D) reduction in noise and machine size
E) both (a) and (b)
Ans:E
6) Harmonics in the emf generated in an alternator can be reduced by
A) skewing the slots
B) chamfering the salient pole tips
C) using distributed winding
D) all of the above
Ans:D
7) Skew of rotor bar eliminates
A) the effect of space harmonics
B) the entire effect of crawling
C) magnetic noise
D) vibration due to unequal force developed on rotor
Ans:A
8) The emf generated due to nth harmonic component of flux in an alternator will be ............. the fundamental emf in magnitude
A) less than
B) more than
C) equal to
Ans:A
9) 4 pole star-connected alternator running at 1500 rpm have 72 slots with 10 conductors per slot. The number of turns per phase and slot angle is
A) 120 turns and 20 degrees
B) 100 turns and 10 degrees
C) 120 turns and 10 degrees
D) 100 turns and 20 degrees
Ans:C
10) The stator of a 3-phase, 6-pole ac machine has 45 slots. The stator winding has 45 coils with a coil span of 6 slots. what type of winding will be selected for this machine?
A) Double-layer, Fractional slot, short-pitched winding
B) Single-layer, Fractional slot, short-pitched winding
C) Single-layer, integral slot, full-pitched winding
D) Double-layer, Fractional slot, full-pitched winding
Ans:A
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