Do AC induction motors have an armature?

• A. Yes
• B. No
• C. Sometimes
• D. Only in certain designs

Answer: (B)

AC induction motors operate by induction, not by feeding a rotor armature from the power source. The stator is energized with AC to create a rotating magnetic field. The rotor, typically a squirrel-cage or wound-rotor, sits in that field and currents are induced in the rotor conductors as the field sweeps by. These induced rotor currents interact with the stator field to produce torque. Because the rotor currents are induced rather than supplied externally, there isn’t a separate armature winding connected to the power supply in normal operation. Even in the wound-rotor design, the rotor circuits aren’t treated as a conventional armature that’s powered from the outside.