Polyphase Induction Motors Set 2

200 Hz ✘ 50 Hz ✘ 2 Hz ✘ 0.2 Hz ✔

Low horsepower motors ✘ Variable speed motors ✘ High horsepower motors ✘ High speed motors ✔

Supply frequency ✘ Supply voltage ✘ Copper losses in motor ✘ None of the above ✔

Slip ring motor only but not with squirrel cage induction motor ✘ Squirrel cage induction motor only but not with slip ring motor ✘ Squirrel cage as well as slip ring induction motor ✘ None of the above ✔

Changing supply frequency ✘ Changing number of poles ✘ Changing winding resistance ✘ Reducing supply voltage ✔

Rotor leakage reactance ✘ Stator reactance ✘ The reactive lagging magnetizing current necessary to generate the magnetic flux ✘ All of the above ✔

Zero frequency ✘ The same frequency as the slip frequency ✘ The same phase as the rotor e.m.f. ✘ High value for the satisfactory speed control ✔

The motor will run in reverse direction ✘ The motor will run at reduced speed ✘ The motor will not run ✘ The motor will burn ✔

Magnetic field and rotor rotate in opposite direction ✘ Rotor speed is less than the synchronous speed of the field and are in the same direction ✘ Rotor speed is more than the synchronous speed of the field and are in the same direction ✘ None of the above ✔

Rotor current ✘ Rotor power factor ✘ Rotor e.m.f. ✘ Shaft diameter ✔