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.Management Sciences
Category: Electrical Machine Design
The heat dissipating capability of transformers of ratings higher than 30 kVA in increased by providing which of the following ?
0
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
In _________ machines, the size of the shaft is decided by the critical speed which depends on the deflection of the shaft?
A. small
B. medium
C. large
D. any of the above.
With direct water cooling it is possible to have ratings of about_____________?
A. 200 MW
B. 300 MW
C. 400 MW
D. 600 MW
Direct water cooling of rotor winding presents_____________?
A. no mechanical difficulties
B. lesser mechanical difficulties
C. greater mechanical difficulties
D. none of the above
Multi-layer helical windings are commonly used in the transformers as high voltage windings_______________?
A. upto 20 kV
B. upto 50 kV
C. upto 80 kV
D. for 110 kV and above
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