Series 6 -> Coordinated DC Drives

[motion guru 0]

I have a customer that would like us to replace his Series 6 PLC that is managing upwards of 8 DC drives. He does not have prints of the machine and he does not have code listings. Before jumping into the bidding process - can anyone comment on whether or not the Series 6 PLC has some kind of drive coordination capabilities. ie does the series 6 have some kind of network connection to the drives? This machine looks like it was manufactured in the late 80's . . . The I/O and logic on the machine are managed by a PLC5 - I am thinking that it might be easier to have the machine and drives use a common PLC platform, but the budget wont stand for new drives at this time and in order for me to figure out coordination of the drives, I need to have some idea of how the Series 6 GE PLC interacts with the GE drives. (I believe the drives are older DC2000 series drives). Anyone familiar with this kind of PLC / Drive combo? Thanks,

[Steve Bailey 118]

Back in the days when the Series Six was GE's flagship PLC offering, there was fairly close coordination between the PLC and Drives engineering groups. Unfortunately, that's no longer the case. There was a network card that resided in the Series Six that could communicate with multiple drives. In appearance, it is similar to GE's Genius remote I/O network, but it uses a different (proprietary) protocol). There is a migration path to a card that resides in the 90-70. Since the 90-70 used a VME backplane, the same card may be compatible with the newer Rx7i controller system. The drive network interface card for the 90-70 was never made available to the casual user. You could only get it as part of a package from GE engineering.

[motion guru 0]

Steve - thank you for the information. I have quite a bit of experience with the 9070 PLC and using third party cards on the VME bus - but it sounds like the communications gateway card that would be available to interface at the drive might be problematic in this case. My experience with approaching the drives supplier for this kind of option is that I eventually find myself bidding against them for the work - I don't want to go there. My preference is to coordinate the drives with a controller that has a ControlNet interface (can I say that on the GE section of this forum?) :) I see lots of retrofits of these drives with Avtron front ends, Siemens front ends, etc. Time to do some more research.

[Steve Bailey 118]

Here's a link to the manual for the DLAN module. http://www.geindustrial.com/support/documents/GFK0729E.pdf It looks like it can be installed in a RX7i system. There is a note in on page 3-1 to the effect that the sample ladder included with the card has limited functionality and for a system comprising multiple drives, the user is advised to conta GE for a quatation on creating a custom application. So, you may be able to purchase a DLAN card from your local distributor, but it looks like you won't be able to count on much technical support from GE. Of course, now that GE and Fanuc are dissolving the joint venture and drives and Fuji have already dissolved their joint venture, there may be a reconciliation between GE automation (Intelligent Platforms) and GE drives. If you Google "GE Drives DLAN", you'll find links to some threads in other forums that have discussed the DLAN. Edited 31 Aug 2009 by Steve Bailey

[motion guru 0]

I was able to get a few photos of the cabinets and a better estimate of date of manufacture - Built in early 90's, GE2000 Drives with DLAN to Series 6 PLC. Specifically, it was referred to as DLAN- Do you know if it is possible to do a lobotomy on the drive and ditch the DLAN altogether? The motors have encoders with dual outputs on them - it might be easier to use one of those outputs with a velocity loop controller (MO2AE Logix Motion Card) to manage coordination. Of course, this would only work if the drives could be controlled in velocity mode from an analog command on the front of the drive . . . which seems like a really basic function that it should be able to do.

[Steve Bailey 118]

Yes, but..... Certainly each of the drives are capable of standing on their own. I'd expect that the current and velocity loops are both closed in the DC2000 drive. If the only data being passed on the DLAN is operational information and not control, then it shouldn't be too hard. The question you need to find an answer to is how much control data is going from the Series Six to the drives. I never had any direct hands-on experience with any of thos coordinated drives systems, but my understanding is that the DLAN data included a speed setpoint for each drive. What I don't know for sure is whether or not the Series Six is doing any closed-loop modulaion of those speed setpoints or whether it simply passes along the values based on operator setup. Is this a paper mill application? There were probably only a small handful of GE startup people covering the Pacific Northwest when these systems were being installed. There are probably people at the mills who know their names and how to get in touch with them. You might be able to get one of them to consult with you to figure out exactly what this application is doing.

[motion guru 0]

Our market focus is coordinated drive systems and this is a fairly common web converting application that we have done for a number of customers. Our approach in the past has been to gut the DC drives / motors and replace with ACVector and deploy all new draw / tension control algorithms. The Machine already has an Allen Bradley PLC for state logic and draw / tension calculations and this data passed to the Series 6 PLC via a serial connection. In this case, the customer does not have the budget to replace drives / motors / PLC / HMI. Their Achilles heel is the Series 6 PLC. I would rather put something in that we know works and that can be used later with new drives (DC or AC depending on budget) without throwing any of the investment away. I am confident that we can manage the coordination of the motors with any number of controllers - at this point, we would prefer to simply give the drive an analog velocity command (or torque command - which would keep all the tuning in the central controller) and close the velocity loop using the encoder feedback external to the drive. If the DLAN network connection was open - and you could purchase a LAN card that slipped into a Logix PLC rack, this would be a slam dunk. . . but since it appears to be closed and they want to get rid of the Series 6 PLC - we will look for ways to manage coordination of the motor shafts with a separate controller and "hopefully" interface with the drives via. an analog Velocity or Torque command.

[RussB 22]

This may not help much but D-Lan is a proprietary protocol that ran on Arp-Net. There are not many (maybe none?) arp-net suppliers around any more. Edited 4 Sep 2009 by RussB