Powerflex Drives

I realize that this is a PLC forum, but I need help with a VFD situation. I am using two drives in master/slave orientation. A Powerflex 755 as the master and a Powerflex 753 as the slave. I need them to run in torque mode so there is a quadrature shaft encoder on one of the motors.

Here is the question, does the slave drive need the encoder signal as a torque follower? Or can I just use the signal at the master?

Both motors should have encoders. I'm not sure about the PF 753 but the PF755 can operate in sensorless field oriented control mode. But the torque regulation in sensorless FOC isn't great. I would say put encoders on both motors. It will provide better torque regulation.

You say that both motors are in torque mode but that they are also in a master/slave relationship. How is the master modifying its torque reference before sending it to the salve drive?

Keith

In general, you want both motors to have encoders so that the drives can run in Flux Vector mode.

As noted, PowerFlex 755 has a very good speed controller in Sensorless Vector mode, but it's my recollection that the one in the PowerFlex 753 is less powerful.

Any sales literature you read about performance without an encoder is probably aimed at simpler applications.

The more information you can give about the mechanism and application, the better. How are the motors mechanically linked to one another ?