How can you determine correct motor rotation direction and how can you change it?

• A. Check the nameplate and wiring; if rotation is incorrect, swap any two supply lines to reverse direction, or adjust wiring per the motor’s schematic.
• B. Attach a tachometer and compare to a reference; adjust mechanical coupling.
• C. Reverse the direction by swapping the grounding conductor only.
• D. Increase voltage until the motor changes direction.

Answer: (A)

Rotation direction comes from the phase sequence fed to the motor windings, so the nameplate and wiring diagram tell you the correct direction for the application. To determine and set the proper rotation, check the nameplate for the indicated direction and the associated wiring scheme. If the motor is rotating the wrong way, the simplest and standard way to reverse it is to swap two of the supply lines. In a three‑phase motor, exchanging any two input leads reverses the phase sequence, and thus swaps the rotation direction. If the motor is wired through a control cabinet or a drive, follow the wiring diagram or drive settings to reverse per the schematic or the drive’s reversal option. Before making changes, ensure power is isolated and the system is secured. After the change, verify the rotation direction by running briefly and observing the shaft, and use proper diagnostic tools if needed. If a VFD is used, direction can also be changed by altering the phase sequence in the drive or its output wiring. The other options don’t address how phase sequencing determines rotation and can be unsafe or ineffective: measuring speed with a tachometer doesn’t change direction, reversing a grounding conductor won’t reverse rotation, and simply increasing voltage won’t flip the direction and can cause damage.