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.Management Sciences
Category: Electrical Machine Design
The weight of copper of both armature and field windings decreases with __________ in number of poles?
0
A. increase
B. decrease
C. either of the above
D. none of the above
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
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
D.C. machines designed with a large value of air gap length have_____________?
A. worst, ventilation
B. poor ventilation
C. better ventilation
D. none of the above
The heat dissipating capability of transformers of ratings higher than 30 kVA in increased by providing which of the following ?
A. Corrugations
B. Fins
C. Tubes
D. Radiator tanks
E. All of the above
_______________is universally used for windings of electrical machines because it is easily workable without any possibility of fracture?
A. Silver
B. Steel
C. Aluminium
D. Copper
In D.C. machines the usual limit of slot pitch is________________?
A. between 5 to 10 mm
B. between 10 to 15 mm
C. between 15 to 20 mm
D. between 25 to 35 mm
Which of the following problem arises in D.C. motors which are fed from thyristor bridge circuits ?
A. Increased I R losses
B. Increased core losses
C. Poor commutation
D. Change in motor parameters
E. All of the above
The input impedance of a JFET is _____________that of an ordinary transistor?
A. equal to
B. less than
C. more than
D. none of the above
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