Which of the following brushes can be used for high values of current density ?

Related Mcqs:

1. 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...

2. For 275 kV transformers, using cold rolled grain oriented steel, which of the following values of flux density may be used?

   A. 1.0 Wb/m2 B. 1.1 Wb/m2 C. 1.3 Wb/m2 D. 1.6 Wb/m2 E. None of the above...

3. The density of hydrogen is __________ times the density of air?

   A. 0.07 B. 1.5 C. 2.5 D. 3.5...

4. ___________ brushes are fragile and cause excessive wear of commutator?

   A. Natural graphite B. Hard carbon C. Electro graphitic D. Metal graphite...

5. ____________ is the common method of applying brushes to the commntator?

   A. Radial B. Trailing C. Reaction D. All of the above...

6. A current density of __________ is ilsed for large power transformers with forced circulation of oil or with water cooling coils?

   A. 1.5 to 2.5 A/mm2 B. 3.5 to 4.5 A/mm2 C. 4.0 to 5.0 A/mm2 D. 5.4 to 6.2 A/mm2...

7. 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...

8. The usual values of maximum flux densities for distribution transformers using hot rolled silicon steel are______________?

   A. 0.5 to 0.8 Wb/m2 B. 0.8 to 1.0 Wb/m2 C. 1.1 to 1.35 Wb/m2 D. 1.4 to 1.8 Wb/m2...

9. The high voltage winding is usually which of the following type ?

   A. Cylindrical winding with circular conductors B. Cross-over winding with either circular or small rectangular conductors C. Continuous disc type winding with rectangular conductors D. All of the above types...

10. A practical formula for determining the thickness of insulation between low voltage and high voltage windings is__________________?

    A. 1 + 0.2 kVmm B. 2 + 0.5 kVmm C. 4 + 0.7 kV mm D. 5 + 0.9 kV mm...