Basic Electrical Engineering MCQ- 13

Basic Electrical Engineering MCQ- 13

31. D.C. generators are connected to the busbars or disconnected from them only under the

floating condition

(a) to avoid sudden loading of the primemover

(b) to avoid mechanicaljerk to the shaft

(c) to avoid burning of switch contacts

(d) all above

Ans: d

32. Eddy currents are induced in the pole shoes of a D.C. machine due to

(a) oscillating magnetic field

(b) pulsating magnetic flux

(c) relative rotation between field and armature

(d) all above

Ans: c

33. In a D.C. machine, short-circuited field coil will result in

(a) odour of barning insulation

(b) unbalanced magnetic pull producing vibrations

(c) reduction of generated voltage for which excitation has to be increased to maintain the

voltage

(d) all above

Ans:

34. Equilizer rings are required in case armature is

(a) wave wound

(b) lap wound

(c) delta wound

(d) duplex wound

Ans: b

35. Welding generator will have

(a) lap winding

(b) wave winding

(c) delta winding

(d) duplex wave winding

Ans: a

36. In case of D.C. machine winding, number of commutator segments is equal to

(a) number of armature coils

(b) number of armature coil sides

(c) number of armature conductors

(d) number of armature turns

Ans: a

37. For a D.C. machines laboratory following type of D.C. supply will be suitable

(a) rotary converter

(b) mercury are rectifier

(c) induction motor D.C. generator set

(d) synchronous motor D.C. generator set

Ans: c

38. The function of pole shoes in the case of D.C. machine is

(a) to reduce the reluctance of the magnetic path

(b) to spread out the flux to achieve uniform flux density

(c) to support the field coil

(d) to discharge all the above functions

Ans: d

39. In the case of lap winding resultant pitch is

(a) multiplication of front and back pitches

(b) division of front pitch by back pitch

(c) sum of front and back pitches

(d) difference of front and back pitches

Ans: d

40. A D.C. welding generator has

(a) lap winding

(b) wave moving

(c) duplex winding

(d) any of the above

Ans: a