Quiznetik

DC Motor | Set 2

1. The condition for maximum efficiency for a D.C. generator is

Correct : D. variable losses = constant losses

2. D.C. generators are normally designed for maximum efficiency around

Correct : A. full-load

3. In a D.C. generator, the iron losses mainly take place in

Correct : D. armature rotor

4. D.C. generators are installed near the load centres to reduce

Correct : B. line losses

5. The purpose of retardation test on D.C. shunt machines is to find out

Correct : A. stray losses

6. Which of the following tests will be suitable for testing two similar D.C. series motors of large capacity ?

Correct : C. Field test

7. Hopkinson's test on D.C. machines is conducted at

Correct : C. full-load

8. During rheostat braking of D.C. series motors

Correct : A. motor is run as a generator

9. For which types of D.C. motor, dynamic braking is generally used ?

Correct : D. All of the above

10. Which method of braking is generally used in elevators ?

Correct : A. Plugging

11. In variable speed motor

Correct : B. a weaker commutating field is needed at low speed than at high speed

12. When the armature of a D.C. motor rotates, e.m.f. induced is

Correct : C. back e.m.f.

13. Where D.C. motor of H.P. 12 or more requires frequent starting, stopping, reversing and speed control

Correct : A. drum type controller is used

14. If a D.C. shunt motor is working at full load and if shunt field circuit suddenly opens

Correct : A. this will make armature to take heavy current, possibly burning it

15. D.C. motor is to drive a load which has certain minimum value for most of the time and some peak value for short duration. We will select the

Correct : A. series motor

16. D.C. motor is to a drive a load which is almost nil for certain part of the load cycle and peak value for short duration. We will select this

Correct : C. compound motor

17. Which D.C. motor has got maximum self relieving property ?

Correct : A. Series motor

18. In the D.C. motor the iron losses occur in

Correct : B. the armature

19. The speed of a D.C. shunt motor is required to be more than full load speed. This is possible by

Correct : A. reducing the field current

20. One D.C. motor drives another D.C. motor. The second D.C. motor when excited and driven

Correct : A. runs as a generator