Do variable speed drives detect phase reversal of the incoming power supply?
AC variable speed drives (VSDs), such as the Schneider Electric Altivar range, are not sensitive to the direction of the phase rotation of the incoming supply.
This is because the AC supply (either single or 3 phase depending on the VSD) is rectified to create an internal DC bus that the last stage of the VSD (known as the inverter stage) uses to produce the variable frequency / variable voltage 3 phase supply to the motor.
The phase sequence on the incoming power supply to the VSD is therefore of no relevance to the drive, because this AC power supply is routinely rectified.
However, if detection of a phase reversal is required for other reasons, this can be done using an RM17TG00 monitoring relay.
Phase reversal needs to be detected for certain applications (e.g. when using a bypass of the VSD to ensure that the motor rotational direction is maintained).