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Electrical Engineering Objective Questions { Synchronous Motors }



78. Synchronous motors are
A. not-self starting
B. self-statring
C. essentially self-starting
D. none of the above

79. The standard full-load power factor ratings for synchronous motors are
A. zero or 0.8 leading
B. unity or 0.8 lagging
C. unity or 0.8 leading
D. unity or zero

80. A synchronous motor running with normal excitation adjusts to load increases essentially by increase in
A. back e.m.f.
B. armature current
C. power factor
D. torque angle

81. A synchronous motor has better power factors as compared to that of an equivalent induction motor. This is mainly because
A. synchronous motor has no slip
B. stator supply is not required to produce magnetic field
C. mechanical load on the rotor remains constant
D. synchronous motor has large airgap

82. Asynchronous motor working at leading power factor can be used as
A. voltage booster
B. phase advancer
C. noise generator
D. mechanical synchronizer

83. Slip rings are usually made of
A. carbon or graphite
B. brass or steel
C. silver or gold
D. copper or aluminium

84. An over-excited synchronous motor is used for
A. fluctuating loads
B. variable speed loads
C. low torque loads
D. power factor corrections

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