For a D.C. machines laboratory following type of D.C. supply will be suitable___________?

Related Mcqs:

1. In case of D.C. machines, mechanical losses are primary function of____________?

   A. current
   B. voltage
   C. speed
   D. none of above

2. Brushes of D.C. machines are made of_________?

   A. carbon
   B. soft copper
   C. hard copper
   D. all of above

3. Satisfactory commutation of D.C. machines requires______________?

   A. brushes should be of proper grade and size
   B. brushes should smoothly run in the holders
   C. smooth, concentric commutator properly undercut
   D. all of the above

4. Two D.C. shunt generators, each with armature resistance of 0.02 ohm and field resistance of 50 ohm run in parallel and supply a total current of 1000 amperes to the load circuit. If their e.m.fs. are 270 V and 265 V, their bus bar voltage will be_____________________?

   A. 270 V
   B. 267.5 V
   C. 265 V
   D. 257.4 V

5. The following constitute short-circuit in the armature winding.

   A. Insulation failure between two commutator bars
   B. Insulation failure between two turns of a coil
   C. Two of more turns of the same coil getting grounded
   D. All of the above

6. Which of the following statement about D.C. generators is false ?

   A. Compensating winding in a D.C. machine helps in commutation
   B. In a D. C. generator interpoles winding is connected in series with the armature winding
   C. Back pitch and front pitch are both odd and approximately equal to the pole pitch
   D. Equilizing bus bars are used with parallel running of D.C. shunt gen¬erators

7. Which of the following components of a D.C, generator plays vital role for providing direct current of a D.C. generator ?

   A. Dummy coils
   B. Commutator
   C. Eye bolt
   D. Equilizer rings

8. Which of the following generator will have negligible terminal voltage while running on no-load?

   A. Series generator
   B. Shunt generator
   C. Compound generator
   D. Separately excited generator

9. Following D.C. generator will be in a position to build up without any residual magnetism in the poles______________?

   A. series generator
   B. shunt generator
   C. compound generator
   D. self-excited generator

10. Following energized winding of a D.C. machine should not be opened as it would produce high inductive voltage which may be dangerous to personnel and may cause its own insulation failure.

    A. Series field
    B. Compensating field
    C. Inter pole field
    D. Shunt field