text: <s>[INST] PowerFlex 700 drives in master/follower relationship Hi, My company builds web handling equipment in which we have a single master web drive that is followed by one or more follower web drives. Until now, we have been using speed controllers made by Contrex with DC permanent magnet motors. There have been three generations of Contrex speed controllers that we have used – the M-Trim, the ML-Trim, and now the MLP-Trim. The Contrex speed controller monitors frequency feedback from a speed sensor on our drive shaft, and regulates a 0-10 VDC signal to a drive board to do closed-loop speed control. With DC motors, we use four quadrant regenerative drive boards from KB electronics. This setup gives us more than enough accuracy in terms of speed control (Contrex specs list accuracy at 0.01% of setpoint and I wouldn’t argue that). Using DC motors, however, does limit our speed range. The DC motors we get from Leeson advertise only a 30:1 constant torque speed range. I might be able to find more expensive DC motors that would give me a bit more than this, but I couldn’t imagine being able to handle any more than 50:1 (correct me if I’m wrong). Anyway, to get a higher speed range, I am considering changing to PowerFlex 700 drives with AC vector duty motors (with encoder feedback). I am trying to figure out how I would have to adapt my control scheme to make this change. Presently, to operate a Contrex in follower mode, I wire two frequency signals to the Contrex. One is the feedback frequency from the (follower) motor that the (follower) Contrex is controlling. The other is an external reference frequency from the master motor that the (follower) Contrex is following. With this wiring in place, configuring the Contrex for follower mode allows me to enter a speed setpoint as a percentage of the master speed. I was wondering if anyone here can tell me if the PF700 has the capability of monitoring both a feedback and a master frequency signal, and if it can be configured in a follower mode that would allow me to enter the setpoint as a percentage of the master speed (rather than having to enter it as a fixed speed). Whether the PF700 has this capability or not, any information or reading material you can point me to that would help me understand the best way to use PowerFlex drives in a master/follower relationship like I describe (even if the implementation is different than the Contrex implementation), will be greatly appreciated. Also, if the PF700 is not the best choice for what I want to do, please recommend a different drive that would be better suited for this application. Thanks in advance, Paul [/INST] I'd suggest the PF 750 series; I think the PF753 will do everything you're asking. There's no need to go to the PF755. Yes, you can make the PF slave drive follow the master's frequency with a set-point percentage. You can also add in several different encoder cards to the drive and do true speed control rather than just frequency following. http://literature.rockwellautomation.com/idc/groups/literature/documents/pm/750-pm001_-en-p.pdf \\n </s>