A. reduces starting torque as well as maximum torque
B. increases starting torque as well as maximum torque
C. increases starting torque but maxi-mum torque remains unchanged
D. increases starting torque but maxi-mum torque decreases
Related Mcqs:
- 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 - Insertion of resistance in the rotor of an induction motor to develop a given torque?
A. decreases the rotor current
B. increases the rotor current
C. rotor current becomes zero
D. rotor current rernains same - 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 - Insertion of resistance in the stator of an induction motor___________?
A. increases the load torque
B. decreases the starting torque
C. increases the starting torque
D. none of the above - For which motor the speed can be controlled from rotor side ?
A. Squirrel-cage induction motor
B. Slip-ring induction motor
C. Both A. and (b)
D. None of the above - 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 - 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 three-phase induction motors sometimes copper bars are placed deep in the rotor to___________?
A. improve starting torque
B. reduce copper losses
C. improve efficiency
D. improve power factor - What will happen if the relative speed between the rotating flux of stator and rotor of the induction motor is zero ?
A. The slip of the motor will be 5%
B. The rotor will not run
C. The rotor will run at very high speed
D. The torque produced will be very large - 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
