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Thread: Electrical Engineering Lab Viva Questions

  1. #1
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    Electrical Engineering Lab Viva Questions

    1. What is the need for starters?
    2. Which is the basic protective device in any circuit?
    3. Name the material used for Fuse.
    4. Why is fuse rated for amperes?
    5. What are the protective devices incorporated in DC starters?
    6. Why is the field rheostat of dc motor kept at minimum resistance position and that of generator in maximum resistance position?
    7. Why is the armature rheostat of dc motor kept at maximum resistance position?
    8. Write the emf equation of DC and AC machine.
    9. Write the torque equation of DC motor.
    10. Draw the torque-slip characteristics of 3 phase induction motor and explain.
    11.Explain the mechanical characteristics of DC shunt motor using electrical characteristics and N/Ia characteristics.
    12. How are the ammeters and voltmeters connected in any circuit?
    13. What is the difference between MI and MC type instruments?
    14. How are MI meters used for measuring both ac and dc quantities?
    15. Name the different types of DC and AC starters.
    16. What is back emf? Give its significance.
    17. What is the difference between self excited and separately excited machines?
    18. Name the types of self excited dc machine.
    19. Give the applications of each type of dc motor and dc generator.
    20. What are the losses in dc machine?
    21. How is the eddy current loss minimized in dc machine?
    22. Name the parts of dc machine.
    23. What is the use of commutator and brushes?
    24. Name the material used for armature and core of dc machine.
    25. Why is armature resistance less than field resistance of dc shunt machine?
    26. Why is armature resistance more than field resistance of dc series machine?
    27. Why is series motor best suited for traction applications?
    28. Why shouldn’t dc series motor started at no load?
    29. Define transformer.
    30. What is the secondary side frequency of transformer?
    31. What are the various types of transformer?
    32. What are the methods of speed control of dc motors?
    33. What do you mean by transformation coefficient?
    34. What is the difference between two winding transformer and auto transformer?
    35. Why transformers and alternators are rated with kVA?
    36. What is the operating power factor of dc machine?
    37. What is meant by power factor? Explain.
    38. What do you mean by complex power?
    39. What will happen if dc supply is connected to transformer?’
    40. What are the parts of transformer?
    41.What is regulation with respect to i)transformer ii)alternator
    42. Why are synchronous motors not self starting? What are the methods of starting?
    43. Why are single phase induction motors not self starting? Classify them according to the
    starting methods.
    44. What are the types of alternators?
    45. Why is regulation so important for transformers and alternators?
    46. What are the parts of synchronous machine? Name the material used in various parts.
    47. Why is synchronous motor referred as doubly excited machine?
    48. What is the result of varying the excitation of synchronous motor?
    49. What is slip of an induction motor?
    50. Why is always the induction motor running with less than the speed of rotating magnetic field?
    51. What is slip frequency?
    52. What will happen when the slip is 100% and zero?
    53. What are the types of 3 phase induction motors?
    54. How is the starting torque improved in slip ring induction motor? Justify mathematically.
    55. Why is 3 phase induction motor referred as rotating transformer with short-circuited secondary?
    56. What is the use of end rings in squirrel cage induction motor?
    57. Why transformers have highest efficiency than any other electrical machine?
    58. What is mutual inductance?
    59.What is the principle of motor, generator and transformer?
    60. How will you find the direction of induced emf in generator and the direction of motion of the conductor in motor?
    61.How will you reverse the direction of rotation of i) dc motor ii) ac motor?
    62. What is the difference between rheostat and potentiometer?
    63. What is L, F, A, N in dc starters?
    64. What is M, L, C, and V in wattmeter?
    65. What is LPF, UPF and ZPF?
    66. What is E and C in autotransformer?
    67. What do you mean by power frequency?
    68. What are the advantages and disadvantages of autotransformer?
    69. What are the disadvantages of low power factor?
    70. What are the methods of speed control of ac motors?
    71.Why are electrical loads used for generators and motors whereas mechanical loads for motors?
    72. What do you mean by stray losses in dc machine?
    73. Given transformers A and B with following details:
    A: η= 96% & reg: 5.8%
    B: η= 94% & reg: 5.2%
    Which transformer will you select? Justify your answer.
    74.Given 4 terminals without indication. How will you manage to find the field and armature terminals of i) dc shunt machine ii) dc series machine.
    75. What is the advantage of equivalent circuit?
    76. What is meant by magnetizing current and working component of current with respect to transformer?
    77. Give the relation between line and phase values of i) star connected network ii) delta connected network.
    78.When can the squirrel cage machine be loaded to its fullest capacity? i) Star connection of stator ii) delta connection of stator.
    79. How can the hysteresis loss of any machine be minimized?
    80.What are the methods of electrical braking?

  2. The Following 3 Users Say Thank You to shanth For This Useful Post:

    madhuri47 (11-11-2011), sureshreddy2406 (07-31-2011), udaykuchipudi1 (02-05-2012)

  3. #2
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    plz post answers also

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    post the answers also.....

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