I've also heard the 50/50/90 rule. 50% chance it'll run forward, 50% chance it'll run backward, 90% chance I'll guess wrong. Goes back to Murphy being an optimist.
The answer is, you might have to change rotation by swapping leads on the input of the VFD instead of the output. It seems counterintuitive, but it's the nature of a dual-winding.
Seeing as keeping phase for phase is no guarantee of everything being the same as it was - or me not having a rotation meter, I shall inch it and watch the slight movement direction.
PARKY,
OP States he is using a Star Delta motor.
These are usually used in one manner with if using a VFD -
SOFT START / START DEVICE WYE - OFF - VFD DELTA RUN
If you want to change the STAR rotation you change the incoming phases because the incoming phase = the output phase of the soft start / start device.
You change the DELTA rotation at the output of the VSD, but this is common knowledge and I need no reminder.
Hang on, you're not going to keep it as 6 wires out to the VFD surely? Add the links in the terminal box to make it delta and just take 3 core plus earth to the drive (should probably be upgrading to screened VFD cable anyway).
Phase rotation meter would definitely be useful here. Pretty sure most VFDs are clockwise rotation in forward run.
Luckily I only really do pumps and fans, very easy to bump test.
If using a VFD then there is no need for all six wires to the VFD depending on the motor/power/voltage will depend on how it is re-wired (suggest motor end or on the outgoing terminals.) I.E. Start/Delta, the VFD acts like a soft start anyway.