Multiple choice questions on dc generator # 13

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objective questions on electrical engineering 13

1) In dc generator, armature reaction is produced actually by
A) its field current
B) armature conductors
C) field pole winding
D) load current in armature

Ans:D

2) In a dc generator, the effect of armature reaction on the main pole flux is to
A) reduce it
B) distort it
C) reverse it
D) both (A) and (B)

Ans:D

3) In a 6-pole dc machine, 90 mechanical degrees correspond to .............electrical degree
A) 30
B) 180
C) 45
D) 270

Ans:D

4) In a clock-wise rotating loaded dc generator, brushes have to be shifted
A) clockwise
B) counter clockwise
C) either (A) or (B)
D) neither (A) nor (B)

Ans:A

5) The primary reason for providing compensating windings in a dc generator is to
A) compensate for decrease in main flux
B) neutralize armature mmf
C) neutralize cross-magnetising flux
D) maintain uniform flux distribution

Ans:C

6) The commutation process in a dc generator basically involves
A) passage of current from moving armature to a stationary load
B) reversal of current in an armature coil as it crosses MNA
C) conversion of a.c to d.c
D) suppression of reactance voltage

Ans:B

7) The most likely causes of sparking at the brushes in a dc machine is
A) open coil in the armature
B) defective interpoles
C) incorrect brush spring pressure
D) all of the above

Ans:D

8) The main function of interpoles is to minimize .................between the brushes and the commutator when the dc machine is loaded
A) friction
B) sparking
C) current
D) wear and tear

Ans:B

9) In a 10-pole, lap wound dc generator the number of active armature conductors per pole is 50. The number of compensating conductors per pole required is
A) 5
B) 50
C) 500
D) 10

Ans:A

10) Compensating winding are employed in dc motors which are likely to operate
A) at a constant speed over wide range of load
B) with rapidly changing loads of wide range
C) over wide range of speed by field excitation control
D) both (B) and (C)

Ans:D

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