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Electrical Engineering Objective Questions { Synchronous Motors }

106.  If one-phase of a 3-phase synchronous motor is short-circuited, motor
A. will refuse to start
B. will overheat in spots
C. will not come upto speed
D. will fail to pull into step

107.  If the field circuit of an unloaded salientpole synchronous motor gets suddenly open-circuited, then
A. it runs at a slower speed
B. the motor stops
C. it continues to run at the same speed
D. it runs at a very high speed

108. In which of the following motor the stator and rotor fields rotate simultaneously?
A. D.C. motor
B. Reluctance motor
C. Universal motor
D. Synchronous motor

109. The speed of a synchronous motor
A. increases as the load increases
B. decreases as the load decreases
C. always remains constant
D. none of the above

110.  A rotory converter can be run as :
A. d.c. shunt motor
B. d.c. series motor
C. d.c. compound motor
D. synchronous motor

111. The maximum speed variation in a 3-phase synchronous motor is
A. 10 per cent
B. 6 per cent
C. 4 per cent
D. zero

112.  Which of the following resistances can be measured by conducting insulation resistance test on a synchronous motor?
A. Phase to phase winding resistance
B. Stator wnding to earthed frame
C. Rotor winding to earthed shaft
D. All of the above

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