Q71. While starting a synchronous motor its field winding should be

Q72. The field in the air gap of an induction motor rotates at

Q73. The frequency of the emf in the stator of a 4-pole induction motor is 50 Hz, and that in the rotor is 2 Hz. What is the slip and at what speed is the motor running?

Q74. A three-phase 400 V, 6-pole, 50 Hz squirrel-cage induction motor is running at a slip of 5%. The speed of rotor with respect to stator magnetic field and speed of the stator magnetic field with respect to rotor magnetic field are

Q75. In the squirrel cage induction motors, the root slots are usually given a slight skew to reduce

Q76. The advantage of starting a slip ring induction motor with the help of rotor resistances as compared to other starting methods is

Q77. In a double squirrel cage induction motor, good starting torque is produced as

Q78. The stators of which of the following motors is similar?

Q79. For a 3-phase induction motor, the increase in the air gap will mainly results in

Q80. The ratio of rotor input, rotor copper loss and rotor output is