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.Management Sciences
Category: Electrical Machine Design
In self cooled motors the cooling time constant is about ___________ than the heating time constant because cooling conditions are worse at standstill?
0
A. 2 to 3 times greater
B. 3 to 4 times greater
C. 4 to 5 times greater
D. none of the above
The laminations of the armature of a D.C. machine are usually ___________ thick?
A. 0.1 to 0.2 mm
B. 0.2 to 0.3 mm
C. 0.3 to 0.4 mm
D. 0.4 to 0.5 mm
In D.C. machines, the ________ in field mmf results in increase in size and cost of machines?
A. increase
B. decrease
C. either of the above
D. none of the above
The stator of a D.C. machine comprises of_____________?
A. main poles
B. interpoles
C. frame
D. all of the above
In a D.C. machine the number of brush arms is _________ the number of poles?
A. less than
B. equal to
C. greater than
D. none of the above
The cylindrical windings using circular conductors are used for current rating of____________?
A. upto 20 A
B. upto 40 A
C. upto 60 A
D. upto 80 A
Which of the following is the commonly used type of electromagnets ?
A. Flat-faced armature type
B. Horse shoe type
C. Flat-faced plunger type
D. All of the above
For large power transformers, self oil cooled type or air blast type which of the following values of current density may be used?
A. 1.0 to 1.2 A/mm2
B. 1.5 to 2.0 A/mm2
C. 2.2 to 3.2 A/mm2
D. 3.2 to 4.2 A/mm2
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
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