A. improve starting torque
B. reduce copper losses
C. improve efficiency
D. improve power factor
Related Mcqs:
- In a three-phase induction motor, the number of poles in the rotor winding is always__________?
A. zero
B. more than the number of poles in stator
C. less than number of poles in stator
D. equal to number of poles in stator - In squirrel cage induction motors, the rotor slots are usually given slight skew in order to__________?
A. reduce windage losses
B. reduce eddy currents
C. reduce accumulation of dirt and dust
D. reduce magnetic hum - 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 - Blocked rotor test on induction motors is used to find out?
A. leakage reactance
B. power factor on short circuit
C. short-circuit current under rated voltage
D. all of the above - If a 3-phase supply is given to the stator and rotor is short circuited rotor will move___________?
A. in the opposite direction as the direction of the rotating field
B. in the same direction as the direction of the field
C. in any direction depending upon phase squence of supply - A 3-phase 440 V, 50 Hz induction motor has 4% slip. The frequency of rotor e.m.f. will be____________?
A. 200 Hz
B. 50 Hz
C. 2 Hz
D. 0.2 Hz - 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. - 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 - When /?2 is the rotor resistance, .X2 the rotor reactance at supply frequency and s the slip, then the condition for maximum torque under running conditions will be_____________?
A. sR2X2 = 1
B. sR2 = X2
C. R2 = sX2
D. R2 = s2X2 - Temperature of the stator winding of a three phase induction motor is obtained by___________?
A. resistance rise method
B. thermometer method
C. embedded temperature method
D. all above methods
