A. Metal graphite brushes
B. Hard carbon brushes
C. Electro-graphitic brushes
D. Natural graphite brushes
Related Mcqs:
- 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 - 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 - The density of hydrogen is __________ times the density of air?
A. 0.07
B. 1.5
C. 2.5
D. 3.5 - ___________ brushes are fragile and cause excessive wear of commutator?
A. Natural graphite
B. Hard carbon
C. Electro graphitic
D. Metal graphite - ____________ is the common method of applying brushes to the commntator?
A. Radial
B. Trailing
C. Reaction
D. All of the above - 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 - 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 - 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 - 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 - 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
