Which method reverses the direction of a three-phase motor?

Which method reverses the direction of a three-phase motor?

• A. Swap two of the three-phase leads
• B. Increase supply voltage
• C. Increase frequency
• D. Swap rotor and stator connections

Answer: (A)

The direction of a three-phase motor is controlled by the phase sequence of the supply. The three windings are arranged so the currents peak in a specific order, creating a rotating magnetic field that the rotor follows. If you swap two of the three supply leads, you flip the phase sequence, which makes the magnetic field rotate in the opposite direction. The rotor then follows that reversed field, reversing the motor’s direction. Increasing supply voltage doesn’t change the direction—it mainly affects torque and potential speed under load. Increasing frequency changes speed but not the rotation direction unless you also alter the phase sequence. Swapping rotor and stator connections isn’t a valid method for reversing direction in a standard motor and can lead to improper operation or damage.

The direction of a three-phase motor is controlled by the phase sequence of the supply. The three windings are arranged so the currents peak in a specific order, creating a rotating magnetic field that the rotor follows. If you swap two of the three supply leads, you flip the phase sequence, which makes the magnetic field rotate in the opposite direction. The rotor then follows that reversed field, reversing the motor’s direction.

Increasing supply voltage doesn’t change the direction—it mainly affects torque and potential speed under load. Increasing frequency changes speed but not the rotation direction unless you also alter the phase sequence. Swapping rotor and stator connections isn’t a valid method for reversing direction in a standard motor and can lead to improper operation or damage.