Objective Questions with Answers Electrical Machine Design - Set 06 - ObjectiveBooks

Objective Questions with Answers Electrical Machine Design - Set 06

Practice Test: Question Set - 06

1. Which of the following problem arises in D.C. motors which are fed from thyristor bridge circuits?
    (A) Increased IR losses
    (B) Increased core losses
    (C) Poor commutation
    (D) All of the above

2. In D.C. machines the number of slots per pole usually lies
    (A) Between 2 to 4
    (B) Between 6 to 8
    (C) Between 9 to 16
    (D) Between 20 to 30

3. The insulation between windings and grounded core and the insulation between the windings of the same phase is called
    (A) Minor insulation
    (B) Major insulation
    (C) Either of the above
    (D) None of the above

4. The forced oil and air circulation method is usual one for transformers of capacities
    (A) Upto 5 MVA
    (B) Upto 10 MVA
    (C) Upto 20 MVA
    (D) 30 MVA upwards

5. The slot leakage can be calculated by making which of the following assumptions?
    (A) The current in the slot conductors is uniformly distributed over their cross-section
    (B) The leakage path is straight across the slot and around the iron at the bottom
    (C) The permanence of air paths is only considered. The reluctance of iron paths is assumed as zero
    (D) All of the above

6. The noise produced by a _________ cooled machine is less as the rotor moves in a medium of smaller density.
    (A) Air
    (B) Hydrogen
    (C) Either (A) or (B)
    (D) None of the above

7. The action of electromagnetic machines can be related to which of the following basic principles?
    (A) Induction
    (B) Interaction
    (C) Alignment
    (D) All of the above

8. The design of mechanical parts is particularly important in case of ________ speed machines.
    (A) Low
    (B) Medium
    (C) High
    (D) Any of the above

9. In self cooled motors the cooling time constant is about _________ than the heating time constant because cooling conditions are worse at standstill.
    (A) 2 to 3 times greater
    (B) 3 to 4 times greater
    (C) 4 to 5 times greater
    (D) None of the above

10. Multilayer helical windings are commonly used in the transformers as high voltage windings
    (A) Upto 20 kV
    (B) Upto 50 kV
    (C) Upto 80 kV
    (D) For 110 kV and above

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