The good power factor of an induction motor can be achieved if the average flux density in the air gap is___________?
(A) absent
(B) small
(C) large
(D) infinity
A double squirrel-cage induction motor has______________?
(A) two rotors moving in oppsite direction
(B) two parallel windings in stator
(C) two parallel windings in rotor
(D) two series windings in stator
Star-delta starting of motors is not possible in case of____________?
(A) single phase motors
(B) variable speed motors
(C) low horse power motors
(D) high speed motors
The starting torque of a squirrel-cage induction motor is___________?
(A) low
(B) negligible
(C) same as full-load torque
(D) slightly more than full-load torque
In Ns is the synchronous speed and s the slip, then actual running speed of an induction motor will be___________?
(A) Ns
(B) s.N,
(C) (l-s)Ns
(D) (Ns-l)s
In case the air gap in an induction motor is increased____________?
(A) the magnetising current of the rotor will decrease
(B) the power factor will decrease
(C) speed of motor will increase
(D) the windage losses will increase
In the circle diagram for induction motor, the diameter of the circle represents____________?
(A) slip
(B) rotor current
(C) running torque
(D) line voltage
Stepless speed control of induction motor is possible by which of the following methods ?
(A) e.m.f. injection in rotor eueuit
(B) Changing the number of poles
(C) Cascade operation
(D) None of the above
It is advisable to avoid line-starting of induction motor and use starter because__________?
(A) motor takes five to seven times its full load current
(B) it will pick-up very high speed and may go out of step
(C) it will run in reverse direction
(D) starting torque is very high