MotorsQuestion 1277 of 1506

A motor has a 4-pole winding and an 8-pole winding in its stator. How can the motor change speed?

Energize one of the windings or the other
Run both windings at once to add the speeds
Change the number of rotor bars with a switch
Raise the supply frequency through the rotor

Show answer

Correct answer: Energize one of the windings or the other

Each winding gives its own synchronous speed: 1800 rpm for 4 poles and 900 rpm for 8 poles on 60 Hz. The motor only needs to switch between the two.

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

Practice motors

Questions last reviewed: 18 October 2026

Red Seal Electrician Practice needs JavaScript to run. Use its questions for practice. The real pass mark is usually 70%. Check it with your province or territory's apprenticeship office.