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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