The direction of rotation of a three-phase induction motor is set by the sequence of the supply phases. Swapping any two of the three supply leads reverses the rotating field and the motor turns the other way. The star or delta links in the terminal box are left as they are.

Points to watch in practice:

  • The change must be made by a qualified person after the power has been isolated and locked out.
  • On pumps, fans and geared machines, check the direction with a short run, preferably with the motor uncoupled from the load. A centrifugal pump running backwards does not deliver; some fans and pumps designed for one direction may be damaged.
  • In star-delta panels six cables run to the motor; swapping only two of them leads to a wrong connection at the delta step. Reverse the direction by swapping two phases at the panel supply input.
  • If the machine must run in both directions, use a forward-reverse circuit with two contactors that are electrically and mechanically interlocked.

On inverter-driven motors, direction is changed by a drive parameter or control input without touching the cables. On single-phase motors, direction is reversed by changing the connection of the auxiliary winding, following the motor's own wiring diagram.