How to change direction of three phase motor in Starters and VFD??

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Phase Sequence Change in 3-Phase Motors

In electrical systems, there are certain applications where the phase sequence of a 3-phase motor needs to be changed. This usually happens in plants that rely on external power distribution companies instead of their own captive power supply, as utility-supplied phase sequence may vary at times.

The phase sequence determines the direction of rotation of a 3-phase induction motor. By interchanging any two supply phases, the motor’s direction can be reversed.

1. Phase Sequence Change in Star-Delta Starter

  • In a Star-Delta Starter, six motor leads are connected to the starter.

  • Phase sequence can be changed by interchanging two phases in each group of three-phase connections.

  • This ensures that the motor rotates in the desired direction when switching between star and delta modes.

2. Phase Sequence Change in DOL / Soft Starters

  • For Direct-On-Line (DOL) Starters and Soft Starters, phase sequence can be easily changed at the main incoming supply by swapping any two phases.

  • This directly reverses the motor’s rotation without internal rewiring.

3. Is Phase Sequence Change Required in VFDs?

  • No, there is no need to change the phase sequence in Variable Frequency Drives (VFDs).



  • Reason:

    • A VFD first rectifies the incoming 3-phase AC supply into DC.

    • Then, through its inverter section, it reconstructs a controlled 3-phase AC output to feed the motor.

    • Since the output is digitally synthesized, the input phase sequence has no effect on the motor rotation.

  • The motor’s rotation direction can instead be set within the VFD’s programming/parameters, without physically altering the supply phases.

✅ Key Takeaway:

  • Star-Delta & DOL/Soft Starters → Phase sequence is changed by swapping two incoming phases.

  • VFDs → Phase sequence does not matter; motor direction is controlled through drive settings.


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