700S AC Drive Reference

I have an application where we have an AB Poweflex 700S AC Drive connected to a controllogix via enet ip.. We have an analog signal coming in on a plc input for RAM SPEED. The customer wants the drive to follow the RAM SPEED analog input profile while running. What is the best way to do this? I really don't want to do gearing the drive because it is not following another encoder but a plc analog input. Could I just do some scaling like 0-30 in/sec ram speed == 0-1800 RPM motor speed? Just wandering about trying to match the profiles.. Any suggestions would be helpful and appreciated.. Thanks.

what you have suggested will work but is dependent on the relative rates of change (ie can the drive acceleration 0 1800 rpm keep up with the Ram speed acceleration 0 - 30 "/s)

What is the drive running (if you can tell us) ? - Hydraulic Pump? something attached to the ram?
A block diagram could be useful.

The extruder is extruding copper pipe.. the drive is located below the extruder to catch the pipe and pull it through a cooling bath. Currently, we are running the drive in torque mode and they are doing ok.. we are trying to improve the process by tying the ram speed to the drive speed... I was concerned about accel/decel by just doing the scaling thing... Hope this helps..

If the analog signal is being ramped by the PLC, then you can set the VFD accel/decel times to a minimum level to allow it to follow that signal more precisely. If you have other modes which control the VFD speed, you may need to make use of the 2nd Accel/Decel parameters so that the drive will behave properly in those modes as well.

I was trying to think of a simple way to do this without getting into cam profiling? I may just try the scaling and adjust acc/dec limits to see if it will follow the analog input. Any thoughts??? I wonder how closely it will follow if I don't do cam profiling.

I have worked on an extrusion process where the "puller" follows the ram speed, but the puller also has a set tension it keeps on the extruded material to avoid bunching. A simple scaling like you said, 0-30in/sec ram speed = 0-1800 puller motor speed, works just fine. The tension feedback (from the puller drive) limits the puller during accelerations of the ram to keep it in the required tension. This helps with different extruded items having different acceleration rates, and the math/ratio not being perfect enough to compensation correctly.

Tharon, do you have the drive running in torque mode? we are running the drive in torque mode now but when we start, we have to have high torque to achieve the speed to catch the material as it comes out of the extruder. We are doing set speeds for initial start, stall when the pipe is cut and restart.. We keep the drive in torque mode now but we could do the same with this approach but let it follow the ram speed? Is that the way you are doing it?

I'll have to check and see. I want to say it is a combination of Torque and Speed mode (Torque Regulation mode, I believe). They were 1336 Impact drives (From AB) if I remember correctly.

You told it a speed, but also a set torque, so it would dial back to keep the tension at your set value. Breaking the material would cause it to pull away quickly, but that was handled by monitoring the system and stopping it if that occurs.