61. The supply voltage to an induction motor is reduced by 10%. By what percentage, approximately, will the maximum torque decrease?
- 50 %
- 10 %
- 20 %
- 40 %
62. The torque-slip characteristic of a polyphase induction motor becomes almost linear at small values of slip, because in this range of slips
- the effective rotor circuit resistance is very large compared to the rotor reactance
- the rotor resistance is equal to the stator resistance
- the rotor is equal to the rotor reactance
- the rotor resistance is equal to the stator reactance
63. In a three-phase induction motor, if the leakage reactance is reduced by using open slots
- starting torque and starting current will decrease but power factor will increase
- starting torque and starting current both will increase but power factor will decrease
- pull-out torque will decrease
- starting current will increase but starting torque will decrease
64. An increase in rotor circuit reactance of a three-phase induction motor will
- reduce starting torque as well as maximum torque
- increase starting torque as well s maximum torque
- increase starting torque and reduce maximum torque
- increase maximum torque and reduce starting torque
65. The torque-slip characteristic of an induction motor is approximately an
- straight line
- rectangular parabola
- parabola
- hyperbola
66. What is the ratio of starting torque and maximum torque of a three-phase, 50Hz, 4 pole induction motor for maximum torque at 1,200 rpm ?
- 0.421
- 0.384
- 0.6
- 0.5
67. The losses that occur in an induction motor are
- stator copper loss
- stator iron loss
- rotor copper loss
- windage and friction losses
- all the above
68. In the three-phase induction motor, iron loss mainly occurs in
- stator and rotor
- rotor core and rotor teeth
- stator core and stator teeth
- stator winding
69. Rotor input of the three phase induction motor is equal to
- input to motor – stator copper and iron losses
- mechanical power developed – windage and frictional losses
- input to motor – windage and friction losses
- input to motor – stator iron losses – windage and friction losses
70. The rotor power output of a three-phase induction motor is 15 KW. The rotor copper losses at a slip of 4% will be
- 600 W
- 625 W
- 650 W
- 700 W