DC Generator Objective Type Question Answer

21. In a d.c. machine, the number of commutator segments is equal to

(i) number of conductors
(ii) twice the number of poles
(iii) number of coils
(iv) none of the above

22. The nature of armature winding of a d.c. machine is decided by

(i) front pitch
(ii) commutator pitch
(iii) back pitch
(iv) none of the above

23. High-voltage d.c. machines use ……….. winding.

(i) lap
(ii) wave
(iii) either lap or wave
(iv) none of the above

24. In a lap winding, the number of the brushes required is equal to

(i) number of poles
(ii) number of pairs of poles
(iii) commutator pitch
(iv) none of the above

25. In a wave winding, the commutator pitch is approximately equal to

(i) pole pitch
(ii) twice the pole pitch
(iii) thrice the pole pitch
(iv) none of the above

26. For a given number of poles (> 2) and armature conductors, a lap winding will carry ……… a wave winding.

(i) more current than
(ii) less current than
(iii) same current as
(iv) none of the above

27. An 8-pole, 250 V, wave-wound generator has 400 conductors. If the generator is to be lap-wound, the number of conductors required is

(i) 800
(ii) 100
(iii) 3200
(iv) 1600

28. An 8-pole duplex lap winding will have ………. parallel paths

(i) 8
(ii) 4
(iii) 32
(iv) 16

29. A triplex wave winding will have ………. parallel paths.

(i) 6
(ii) 2
(iii) 4
(iv) none of the above

30. For a given d.c. generator, the generated voltage depends upon

(i) flux only
(ii) speed only
(iii) both speed and flux
(iv) none of the above

31. A 6-pole lap-wound generator has 300 conductors; the e.m. f. induced per conductor being 5 V. The generated voltage of the generator is

(i) 60 V
(ii) 1500 V
(iii) 360 V
(iv) 250 V

32. For the same rating, a d.c. machine has ……….. an a.c. machine.

(i) the same weight as
(ii) more weight than
(iii) less weight than
(iv) none of the above

33. The field winding of a d.c. shunt machine usually carries ….. of the rated current of the machine.

(i) 2% to 5%
(ii) 15% to 20%
(iii) more than 20%
(iv) less than 0.5%

34. A separately excited d.c. generator is not used because

(i) it is costly
(ii) separate d.c. source is required for field circuit
(iii) voltage drops considerably with load
(iv) none of the above

35. A d.c. compound generator having full-load terminal voltage equal to the no-load voltage is called …… generator.

(i) under-compounded
(ii) over-compounded
(iii) flat-compounded
(iv) none of the above

36. The main drawback of a d.c. shunt generator is that

(i) terminal voltage drops considerably with load
(ii) shunt field circuit has high resistance
(iii) generated voltage is small
(iv) it is expensive

37. D.C. machines which are subjected to abrupt changes of load are provided with

(i) interpole windings
(ii) compensating windings
(iii) equalisers
(iv) copper brushes