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Electrical Engineering Objective Questions { Alternators }



22. The emf generated in an alternator due to nth harmonic is
A. n times the fundamental emf
B. equal to the fundamental emf
C. less than the fundamental emf
D. zero
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23. The effect of cross-magnetizing field in an alternator may be reduced by
A. shifting the brush positions
B. rusing interpoles
C. using a magnetizing pole
D. none of these
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24. The nominal speed of 50 Hz, 3-phase turbo-alternator in rpm is
A.600
B.1200
C.1800
D.3000
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25. To reverse the phase sequence of voltage generated in an alternator, we should
A. reverse the connection of its field winding
B. interchange any two of its phase terminals
C. both (a) and (b) above
D. none of the above
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26. In an alternator, if Xs is the synchronous reactance, and Xc is the leakage reactance, then the reactance Xs due to armature flux is given by
A.(c) remains constant
B.(d) may increase or decrease depending on the power factor
C.
D.
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27. Hunting in synchronous machines can be reduced by using
A. damper bars
B. flywheel
C. machines having suitable synchronization power
D. all of these
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28. In alternator, during hunting when the speed becomes supersynchronous, the damper bars develop
A. reluctance torque
B. pseudo-stationary torque
C. eddy current torque
D. induction generator torque
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