Which statement correctly describes reversing the direction of a three-phase squirrel-cage motor?

Which statement correctly describes reversing the direction of a three-phase squirrel-cage motor?

• A. You can reverse direction by swapping any two line leads (L1, L2, L3) with the corresponding motor terminals (T1, T2, T3).
• B. Reversing direction requires swapping a specific pair of leads, not any two.
• C. Direction reversal is achieved by swapping all three line leads.
• D. Direction reversal is not possible in a three-phase motor.

Answer: (B)

The key idea is that the rotation of a three-phase motor is set by the order of the three phase voltages applied to the windings. If you interchange two of the supply lines, you change the phase sequence (for example from A-B-C to A-C-B), which flips the direction of the rotating magnetic field and thus reverses the motor’s rotation. You don’t need to swap a specific predetermined pair—any two of the three lines will produce reversal. Swapping all three lines leaves the sequence effectively unchanged, so it won’t reverse direction. Reversing a three-phase squirrel-cage motor is indeed possible by changing the phase sequence.

The key idea is that the rotation of a three-phase motor is set by the order of the three phase voltages applied to the windings. If you interchange two of the supply lines, you change the phase sequence (for example from A-B-C to A-C-B), which flips the direction of the rotating magnetic field and thus reverses the motor’s rotation. You don’t need to swap a specific predetermined pair—any two of the three lines will produce reversal. Swapping all three lines leaves the sequence effectively unchanged, so it won’t reverse direction. Reversing a three-phase squirrel-cage motor is indeed possible by changing the phase sequence.