Which of the following statements is correct regarding an AC induction motor?

• A. Uses a stator to act as a rotating field
• B. Uses a rotor to act as a rotating field
• C. Requires a DC supply
• D. Does not use a rotating field

Answer: (A)

In an AC induction motor, the driving action comes from the stator winding currents. When the stator is supplied with polyphase AC, the currents are phase-shifted so the magnetic fields from the windings combine to form a rotating magnetic field. This rotating field sweeps past the rotor and induces currents in the rotor bars, and the interaction between those rotor currents and the rotating field produces torque that makes the rotor turn. The rotor itself does not generate the rotating field; it responds to it. The motor uses AC, not DC, so a DC supply isn’t correct. And there is indeed a rotating field in an AC induction motor, so that part isn’t correct either.