Red Seal Electrician Practice
MotorsQuestion 1247 of 1506

What produces the rotating magnetic field in a three-phase induction motor?

  1. Three windings connected in series and fed by one DC current
  2. A permanent magnet in the stator, with a shaded pole on the rotor
  3. One single winding fed through a centrifugal switch on the shaft
  4. Three windings 120 degrees apart, fed by currents 120 degrees apart in time
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Correct answer: Three windings 120 degrees apart, fed by currents 120 degrees apart in time

Space-shifted windings with time-shifted currents make the field move around the stator.

Source: Lessons in Electric Circuits II: AC (Kuphaldt), 13.7: Tesla Polyphase Induction Motors

Practice motors

Questions last reviewed: 18 October 2026