Hi friends, this post is about multiple choice questions on electrical engineering with emphasis on induction motor. check out and comment if you have any doubts....
1) Induction motors normally use diecast aluminium rotor because aluminium is
A) cheaper in cost
B) lighter in weight
C) easy to cast owing to its melting point and is easily available
D) of low resistivity
Ans:C
2) In a 3-phase slip-ring induction motor, the rotor winding terminals are brought out through slip rings to
A) connect extra resistance across them during starting
B) connect them either in star or in delta as per need
C) connect to 3-phase ac supply
D) close the rotor circuit externally
Ans:A
3) In a 3-phase wound rotor induction motor the short circuit gear is used to short-circuit the
A) stator phases of the motor
B) rotor at slip rings
C) starting resistances in the starter
D) none of the above
Ans:B
4) which of the following parameters in an induction motor influences the magnetizing reactance to the maximum extent?
A) Axial length of the rotor stack
B) Axial length of the stator stack
C) Radial length of air gap
D) Number of slots on the stator
Ans:C
5) Which of the following statements about a squirrel induction cage motor is incorrect?
A) It has no commutator and no slip-ring
B) It is provided with cage rotor which is simple, robust and almost instrucible in construction
C) It has high starting torque
D) Almost 90 percent of induction motors are of this type
Ans:C
6) For induction motors normally
A) the stator winding is connected to ac supply and the rotor winding is short-circuited
B) the rotor winding is connected to ac supply and the stator winding is short-circuited
C) both of the stator and rotor windings are connected to ac supply
D) the stator winding is connected to ac supply and rotor winding to dc supply
Ans:A
7) The relative speed between stator and rotor fluxes is equal to
A) synchronous speed Ns
B) rotor speed N
C) zero
D) Ns-N
Ans:C
8) The principle of operation of a 3-phase induction motor is almost similar to that of
A) synchronous motor
B) repulsion start induction motor
C) transformer with a shorted secondary
D) capacitor start induction motor
Ans:C
9) The rotor circuit of an induction motor under operating condition is
A) always closed
B) always open
C) may be open or closed depending upon the loading condition
Ans:A
10) The 3-phase induction motor with rotor circuit open will
A) run normally
B) get overheated
C) not run
D) make noise
Ans:C
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