The stator of a D.C. machine comprises of_____________?
(A) main poles
(B) interpoles
(C) frame
(D) all of the above
Transformers with a capacity of up to __________ have a cooling radiator system with natural cooling?
(A) 2 MVA
(B) 5 MVA
(C) 7.5 MVA
(D) 10 MVA
The voltage control in electric supply networks in required on account of which of the following reasons ?
(A) Adjustment of voltage at consumers premises within statutory limits
(B) Control of active and reactive power
(C) Adjustment of short period daily and seasonal voltage variations in accordance with variations of load
(D) All of the above
Which of the following is the basic consideration in the design of insulation ?
(A) Electrical considerations
(B) Mechanical considerations
(C) Thermal considerations
(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
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
(D) None of the above
D.C. windings are____________?
(A) sometimes 2-layer type
(B) never 2-layer type
(C) always 2-layer type
(D) none of the above
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
The flash point of transformer oil should be higher than_______________?
(A) 40°C
(B) 60°C
(C) 80°C
(D) 104°C
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