a) For running different machine tools where several speeds are required b) For running paper machine requiring exact speed control c) For running electric vehicles d) For running rolling mills needing exact speed control Ans: (a)
a) Copper losses in the stator b) Friction and winding losses c) Sum of (a) and (b) above d) Total losses in the rotor on no load Ans: (d)
a) The frequency of rotor currents b) The frequency of stator currents c) Difference of the frequencies of the stator and rotor currents d) Sum of the frequencies of the stator and rotor currents Ans: (a)
a) Single-phase ac supply b) Three- phase ac supply c) Dc supply d) Supply obtained from an inverter Ans: (c)
a) Increases b) Decreases c) Remains constant d) Increases and then becomes constant Ans: (b)
a) Increases and its frequency decreases b) Increases and its frequency increases c) Decreases and its frequency increases d) Decreases and its frequency decreases Ans: (a)
a) Slip ring induction motor b) Squirrel cage induction motor c) Salient pole synchronous motor d) Wound rotor synchronous motor Ans: (a)
a) Run at dangerously high speed b) Stop c) Continue to run depending on load d) None of these Ans: (c)
a) That the motor stops b) Current decreases slightly c) Speed reduces slightly d) Motor heats up with passage of time Ans: (d)
a) Single excited machine b) Double excited machine c) Machine in which three-phase supply is fed to both stator and rotor winding d) None of these Ans: (c)