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Electrical Engineering Objective Questions { Induction Motors }

127. If stator voltage of a squirrel cage induction motor is reduced to 50 percent of its rated value, torque developed is reduced by percent of its full load value.

128.  In a 3-phase induction motor which of the following statements, regarding frequency of inducted rotor e.m.f. is incorrect?
A. Its speed varies inversely as slip
B. It is zero at synchronous speed
C. It is directly dependent on slip
D. It is maximum at standstill

129.  Which of the following motors are used frequently?
A. Three phase induction motor
B. D.C. shunt motor
C. Three phase commutator motor
D. A.C. induction motor

130. The starting torque of the slip ring induction motor can be increased by
A. adding resistance to the stator
B. adding resistance to the rotor
C. adding resistance to stator as well as
D. none of the above

131.  The stator frame in an induction motor is used
A. to protect the whole machine
B. to ventilate the armature
C. as a return path for the flux
D. to hold the armature stampings/stator

132.  The noise and tooth pulsation losses can be minimised by using
A. large number of narrow slots in stator
B. large number of open slots in stator
C. small number of narrow slots in stator
D. small numberof open slots in stator

133. If the rotor is open in a squirrel cage motor, it
A. will run at very high speed
B. will run at very slow speed
C. will not run
D. will make noise

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