Which of the following statements is true about AC induction motors?

• A. They have a rotor with a commutator
• B. They require brushes for commutation
• C. They do not have brushes or armature
• D. They are energized by DC supply

Answer: (C)

AC induction motors generate motion from a rotating magnetic field created by the AC supply in the stator. The rotor is not connected to the power source; currents in the rotor are induced by that rotating field, so there is no separate armature on the rotor and no commutator. Because there’s no commutation required, there are no brushes involved. In most designs the rotor has aluminum bars (squirrel-cage) or windings connected via slip rings in some cases, but even then there’s no commutator or brushes used for motor operation. The motor is powered by AC, not DC, which is why the statement that they do not have brushes or armature is true.