SRM University 2007 B.Tech Electronics and Communications Engineering BANK - Question Paper

ques. BANK
II ECE EE:216

PART-A

UNIT-I DC MACHINES

1. State fleming’s left hand rule and right hand rule?
2. State faradays legal regulations of electromagnetic induction?
3. How AC is converted in to DC in a generator?
4. What is the purpose of split rings?
5. Give a brief notes on no load characteristics of DC machine?
6. Give the expression for mechanical, electrical and overall efficiency for a generator?
7. Why is the armature core of a dc machine is always laminated?
8. Name the DC machine parts and state the material of which every part is made?
9. Why is a commutator and brush arrangement necessary for the operation of a dc machine?
10. What are the kinds of windings in a DC machine?
11. Why do the coils used in commercial generators consists of several turns in series?
12. Why electromagnets are preferred over the permanent magnets for used in large generator?
13. Why are the cast iron yokes used in small machines?
14. Why are fabricated steel yokes used in large machines?
15. Why are the graphite or carbon brushes preferred over copper brushes for use in DC machines?
16. Why mica is used to insulate adjacent segments of a commutator?
17. Why is area of the pole shoe kept more than that of pole core?
18. Why the airgap ranging from the pole pieces and the armature is kept very small?
19. What is the purpose of field coils in a DC generator?
20. What is the function of armature in DC generator?
21. What is mean by armature reaction?
22. What is the effect of armature reaction?
23. What is mean by no-load saturation curve?
24. Why does the saturation curve begins slightly higher than zero for self-excited shunt generator?
25. What do you mean by the critical resistance of DC shunt generator?
26. State DC motor principle?
27. What is mean by back emf?give its expression?
28. Give the voltage formula of the motor and state the condition for maximum power developed in a motor?
29. Define torque, armature torque, shaft torque.
30. What is mean by speed regulation?
31. Why a series motor should never be started on no-load?
32. What is mean by compound motor? provide its kinds.
33. Give a few applications of shunt, series, compound motors?
34. What are the factors that affecting the speed of a motor?
35. What is mean by stalling current?
36. What are the merits and demerits of rheostatic control method?
37. What are the advantages of field control method?
38. Why, a small motor need not be started with a help of starter?
39. What is the necessity of a starter?
40. What are the kinds of starters for a DC machine?
41. What is mean by losses?
42. What are the kinds of losses?
43. Draw the power stages of a motor?
44. Draw the power stages of a generator?
45. What is the condition for the maximum efficiency? provide the expression.
46. What are the different kinds of speed control for shunt motor?

Earning:   Approval pending.