Motor direction for VFD powered motor

[scott1971]

Hi all:

I have a piece of equipment with two (2) 480 VAC 3-phase motors on it. One of these motors is controlled by a VFD, the other is branched directly from the main feeder. When my customer has the equipment located in Room "A" both motors rotate in the correct direction. When the equipment is moved into Room "B" the motor connected to the VFD continues to rotate correctly, but the other motor rotates in the opposite direction.

Is it true that that phase order of the conductors feeding the VFD will have no effect on the connected motor's rotation? In other words, switching two of the conductors feeding the VFD will not reverse the direction of the motor, the conductors must be switched either at the motor junction box or on the output side of the drive.

The search function doesn't seem to be working, so I apologize for this simple question which has probably been answered before.

 

[krkautomation]

You are correct about the VFD.....

They convert the 3-phase input to a DC voltage before 'chopping' it back to 3-phase again at the required voltage & frequency.......

 

[rbulsara]

But if the motor leads (output of VFD) are transposed..it will reverse the direction...

 

[aolalde]

Yes, The AC power into the VFD is rectified and then converted to controlled three-phase AC.For that reason the motor driven by the VFD does not changed rotation.

It seems that the phase sequence of room B is reverse as compared to room A.