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Electrical Engineering Objective Questions { Induction Motors }

113.  In an induction motor, the rotor reactance per phase is proportional to
A. s
B. 1/s
C. 1/s2
D. s2

114.  A would rotor induction motor can be distinguished from squirrel cage induction motor by
A. diameter of shaft
B. size of frame
C. presence of slip ring
D. direction or rotation

115.  Which of the following A.C. motors is used for industrial application?
A. Commutator motor
B. 3-phase induction motor
C. D.C. series motor
D. Synchronous motor

116. The shaft, on which the rotor of an induction motor is mounted is made of
A. high speed steel
B. chrome vanadium steel
C. cast-iron
D. mild steel

117. Which of the following type of bearing is generally used to support the rotor of an induction motor?
A. Ball bearing
B. Needle bearing
C. Plummer block
D. Bush bearing

118. Under which method of starting an induction motor is expected to take largest starting current?
A. Star-delta starting
B. Auto-transformer starting
C. Direct on line starting
D. Stator-rotor starting

119.  When a squirrelcage induction motor fails to start which of the following could not be the reason for the same?
A. Uneven air gap
B. Blown fuses
C. Overload
D. One or two phase open

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