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) A 500 kVA, 1100 V, 50 Hz Y-connected 3 phase alternator has stator resistance of 0.1 Ω/phase and synchronous impedance of 1.5 Ω/phase. The alternator is supplying full load at unity power factor. The induced emf per phase for this condition is
A) 769 V
B) 832 V
C) 692 V
D) 935 V
Ans:A
2) The regulation of an alternator is given as
A) (V-E0)/V ✖ 100
B) (E0-V)/V ✖ 100
C) (V)/E0 ✖ 100
D) (E0-V)/E0 ✖ 100
Ans:B
3) Regulation of an alternator supplying resistive or inductive load is
A) always +ve
B) always -ve
C) either of the above or zero
D) none of the above
Ans:A
4) A leading pf load on an alternator implies that its voltage regulation shall be
A) positive
B) negative
C) zero
D) any one of these
Ans:D
5) The effect of leading power factor on the voltage regulation of an alternator is
A) increasing in nature
B) decreasing in nature
C) maintained at constant value
D) oscillating in nature
Ans:B
6) The leakage reactance of a three phase alternator is determined by performing
A) open-circuit and zero power factor tests
B) zero power factor and slip tests
C) open and short circuit tests
D) short circuit and slip tests
Ans:A
7) The 'synchronous impedance method' of finding the voltage regulation of a cylindrical rotor alternator is generally considered as
A) a pessimistic method because saturation is not considered
B) an optimistic method because saturation is not considered
C) a fairly accurate method even if power factor is not taken into account while determining synchronous impedance
D) a fairly accurate method even if power factor is taken into account while determining synchronous impedance
Ans:A
8) The regulation obtained by synchronous impedance method is always higher than actual value because
A) synchronous reactance is assumed variable while it is not
B) effective armature resistance is assumed constant
C) synchronous reactance is assumed constant while it is not
D) field current is increased to give short-circuit current about twice of full load current
Ans:C
9) The short circuit characteristic of an alternator is
A) always linear
B) always nonlinear
C) either of (a) or (b)
D) none of these
Ans:A
10) Under short circuit conditions, the power factor of an alternator is
A) unity
B) almost zero lagging
C) almost zero leading
D) none of the above
Ans:B
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1) A 500 kVA, 1100 V, 50 Hz Y-connected 3 phase alternator has stator resistance of 0.1 Ω/phase and synchronous impedance of 1.5 Ω/phase. The alternator is supplying full load at unity power factor. The induced emf per phase for this condition is
A) 769 V
B) 832 V
C) 692 V
D) 935 V
Ans:A
2) The regulation of an alternator is given as
A) (V-E0)/V ✖ 100
B) (E0-V)/V ✖ 100
C) (V)/E0 ✖ 100
D) (E0-V)/E0 ✖ 100
Ans:B
3) Regulation of an alternator supplying resistive or inductive load is
A) always +ve
B) always -ve
C) either of the above or zero
D) none of the above
Ans:A
4) A leading pf load on an alternator implies that its voltage regulation shall be
A) positive
B) negative
C) zero
D) any one of these
Ans:D
5) The effect of leading power factor on the voltage regulation of an alternator is
A) increasing in nature
B) decreasing in nature
C) maintained at constant value
D) oscillating in nature
Ans:B
6) The leakage reactance of a three phase alternator is determined by performing
A) open-circuit and zero power factor tests
B) zero power factor and slip tests
C) open and short circuit tests
D) short circuit and slip tests
Ans:A
7) The 'synchronous impedance method' of finding the voltage regulation of a cylindrical rotor alternator is generally considered as
A) a pessimistic method because saturation is not considered
B) an optimistic method because saturation is not considered
C) a fairly accurate method even if power factor is not taken into account while determining synchronous impedance
D) a fairly accurate method even if power factor is taken into account while determining synchronous impedance
Ans:A
8) The regulation obtained by synchronous impedance method is always higher than actual value because
A) synchronous reactance is assumed variable while it is not
B) effective armature resistance is assumed constant
C) synchronous reactance is assumed constant while it is not
D) field current is increased to give short-circuit current about twice of full load current
Ans:C
9) The short circuit characteristic of an alternator is
A) always linear
B) always nonlinear
C) either of (a) or (b)
D) none of these
Ans:A
10) Under short circuit conditions, the power factor of an alternator is
A) unity
B) almost zero lagging
C) almost zero leading
D) none of the above
Ans:B
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