Size of a high speed motor as compared to low speed motor for the same H.P. will be__________?
(A) bigger
(B) smaller
(C) same
(D) any of the above
Slip of an induction motor is negative when_____________?
(A) magnetic field and rotor rotate in opposite direction
(B) rotor speed is less than the synchronous speed of the field and are in the same direction
(C) rotor speed is more than the synchronous speed of the field and are in the same direction
(D) none of the above
If an induction motor with certain ratio of rotor to stator slots, runs at 1/7 of the normal speed, the phenomenon will be termed as____________?
(A) humming
(B) hunting
(C) crawling
(D) cogging
In case of 3-phase induction motors, plugging means__________?
(A) pulling the motor directly on line without a starter
(B) locking of rotor due to harmonics
(C) starting the motor on load which is more than the rated load
(D) interchanging two supply phases for quick stopping
In a three-phase induction motor_______________?
(A) iron losses in stator will be negligible as compared to that in rotor
(B) iron losses in motor will be neg¬ligible as compared to that in rotor
(C) iron losses in stator will be less than that in rotor
(D) iron losses in stator will be more than that in rotor
Short-circuit test on an induction motor cannot be used to determine___________?
(A) windage losses
(B) copper losses
(C) transformation ratio
(D) power scale of circle diagram
A 3-phase slip ring motor has____________?
(A) double cage rotor
(B) wound rotor
(C) short-circuited rotor
(D) any of the above
5 H.P., 50-Hz, 3-phase, 440 V, induction motors are available for the following r.p.m. Which motor will be the costliest ?
(A) 730 r.p.m.
(B) 960 r.p.m.
(C) 1440 r.p.m.
(D) 2880 r.p.m.
A pump induction motor is switched on to a supply 30% lower than its rated voltage. The pump runs. What will eventually happen ? It will____________?
(A) stall after sometime
(B) stall immediately
(C) continue to run at lower speed without damage
(D) get heated and subsequently get damaged
Which type of bearing is provided in small induction motors to support the rotor shaft ?
(A) Ball bearings
(B) Cast iron bearings
(C) Bush bearings
(D) None of the above