How do you reverse a three-phase motor?

• A. Swap two of the stator windings
• B. Reverse the supply polarity
• C. Swap all three leads
• D. Swap any two of the leads

Answer: (D)

Reversing a three-phase motor is all about changing the phase sequence of the three supply voltages. The direction of the rotating magnetic field is determined by the order in which the phases reach their peak voltages. If you swap two of the phase connections, the sequence changes from ABC to ACB, which flips the rotating field and makes the motor run in the opposite direction. Reversing the polarity of all three lines or swapping all three leads doesn’t alter the relative phase order, so the motor would keep turning the same way. Swapping two of the windings achieves the same effect in practice, but the clear, standard action is to swap any two of the three leads, which directly changes the phase sequence and reverses rotation.