How do you reverse the direction of a 3-phase motor?

• A. Switch 2 of the legs
• B. Swap the ground wire
• C. Reverse the shaft
• D. Change the supply frequency

Answer: (A)

In a three-phase motor, the direction it spins is set by the order of the three phase voltages—the phase sequence. The rotating magnetic field that drives the motor depends on which phase leads the others. Swapping two of the supply lines changes that sequence (for example, from ABC to ACB), which reverses the rotating magnetic field and makes the motor spin in the opposite direction. This is the standard electrical way to reverse a three-phase motor.

Swapping the ground wire isn’t part of the energized circuit and won’t change the phase sequence. Changing the supply frequency changes speed, not direction. Reversing the shaft is a mechanical change and not how you control the motor’s direction electronically or electrically.