The laminations of the armature of a D.C. machine are usually ___________ thick?

Related Mcqs:

1. cooling is the process of dissipating the armature and field winding losses to a cooling medium circulating within the winding insulation wall______________?

   A. Direct B. Indirect C. Conventional D. Any of the above...

2. Which of the following methods may be adopted to reduce the effects of armature reaction ?

   A. Increase in length of air gap at pole tips B. Increasing reluctance of pole tips C. Compensating windings D. Interpoles E. All of the above...

3. The weight of copper of both armature and field windings decreases with __________ in number of poles?

   A. increase B. decrease C. either of the above D. none of the above...

4. In D.C. machines, ir order to prevent excessive distortion of field form by the armature reaction, the field mmf must be made____________?

   A. equal to that of armature mmf B. less in comparison with the armature mmf C. large in comparison with the armature mmf D. none of the above...

5. 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...

6. The efficiency of a machine should be as ____________ as possible to reduce the operating cost?

   A. high B. low C. either of the above D. none of the above...

7. The time taken by the machine to attain 0.632 of its final steady temperature rise is called_____________?

   A. heating time constant B. cooling time constant C. either A. or B. D. none of the above...

8. In a D.C. machine the current per brush arm should not be more than_____________?

   A. 100 A B. 200 A E. 300 A D. 400 A...

9. In a D.C. machine, the value of peripheral speed should not, normally, exceed___________?

   A. 10 m/s B. 20 m/s C. 30 m/s D. 40 m/s...

10. 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...