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Electrical Engineering Objective Questions { Alternators }



78. Synchronous impedance method gives more regulation as compared to ampereturn method because
A. armature reaction is considered negligible
B. saturation effect is ignored in the synchronous impedance
C. saturation effect is take into account in the synchronous impedance method
D. initial conditions are considered zero

79.  Leakage reactance of the armature of a salient pole synchronous machine which varies with the position of the rotor is due to
A. leakage flux which remains withing the slot
B. leakage flux of end connections
C. leakage flux which comes out of slot teeth, crosses the air gap and enters pole faces
D. none of the above

80. Turbo-rotor is made up of
A. solid steel forging having milled slots for field winding
B. large spider to which laminated pole shoes are secured
C. laminations
D. none of the above

81. A commercial alternator has
A. stationary armature and rotary field
B. rotating armature and stationary field
C. both armature and field rotary
D. both armature and field fixed

82. For the alternators operating in parallel, if the load shared by one of them is to be increased, its field excitation is
A. to be weakened keeping input torque same
B. to be strengthened keeping input torque same
C. to be kept constant but input torque should be increased
D. to be kept constant but input torque should be decreased

83. Which of the following methods is best for finding the voltage regulation?
A. Synchronous impedance method
B. M.M.F. method
C. Potier triangle method
D. All are equally good

84.  For a 3-phase winding with 5 slots per pole per phase and with coil span of 12 slot pitch, the value of pitch factor is
A.0.851
B.0.951
C.0.98
D.1.05

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