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freewayc

Powerflex 70 comm problems

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I have a cart with two axis powered by two Powerflex 70 VFD's with 20-COMM-E adapters and outfitted with encoder cards to read the location and speed of each axis. The drives are tied into (and controlled by) a compactlogix PLC. They are all connected through an ethernet switch and each have their own static IP adress assigned. In RSlinx, you can see each drive and they will respond to the drive information requests through the properties menu. The problem is that while one drive responds and the encoder data is transmitted to the compactlogix, the other drive will not respond to commands and the STS led does not change as it should to show you that it is being given a command. I swapped the 20-comm-e adapters between the drives and the problem moved with the adapters. I purchased and installed a new adapter thinking that would be the problem but to no avail. The PLC program is pretty simple and I can't see how anything could be the problem there. The drives are entirely controlled through the DPI port. Starting to get heat from the boss and I am nearly out of ideas. Anyone been down this road before and might be able to lend an idea?

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One other piece of information, the encoder information is seen at the compactlogix for the working drive, but not on the non-working drive. Remember both drives will work depending on where the 20-comm-E adapter is placed. Also, I can simply change the static IP's between the two adapters to get the working drive to switch. (I hope that last statement made sense).

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Do both drives have working I/O connections shown in RSLogix 5000 ? The problem moving with the 20-COMM-E sounds like some configuration problem (the 20-COMM-E holds some parameters in onboard nonvolatile memory) with DataLinks or DPI enabling. But the problem following the IP address sounds more like a configuration problem in RSLogix 5000 with the definition of the connection to the drives. Is the Data Type the same for both drives ? Examine the definition for each one and compare them. Better yet, post the *.ACD file if you can.

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Here is the program. I now believe the way it works is that the ethernet is simply the communication medium and that ASCII is not being communicated or translated on either the drive or the PLC side. Kind of like a modulated carrier wave in radio correct? Or am I way off? Like I said, it appears the ethernet is communicating, and you can pull up drive data through RSLinx, but the encoder and all other program data cannot be seen in the program. One other thing which is probably due simply to inexperience, in the powerflex module properties, I cannot correlate either drive. When you hit "Connect to drive " in the properties, you can't see either of the drives when you try to browse to them. Sorry if my explanations are a bit naive. CART.ACD

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I see that the communication packet to/from each drive allows for user defined information at the end of the packet. In all likelyhood (I haven't used these) there would have to be part of the setup of the drives themselves which told it to put 'this' information in that 'added-user-defined area. You appear to be tranferring the encoder counts that way via two INTs which are then combined in the ladder. If nothing is showing up are you sure the drives have been set up properly?

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Thanks for your thoughts on the problem fellas. One of the drives is functioning perfectly and the encoder data is being communicated with no problem. The parameters I set on the 20-comm-e are identical except obviously, the IP address. The encoder and encoder board have proven to be OK. I guess that leaves communication through datalink packets which I am new to and am trying to figure out how the drive recieves and interprets the packets and hoping that will lead to a solution. The funny thing is that the drive just stopped while the operator was using it and all the parameters seem to be intact. I could understand if they all were reset back to factory settings but one or two of them changed? Seems odd to me. That is, odd if that turns out to be the problem. Edited by freewayc

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OK, after a few hours working with the compactlogix and the Powerflex 70 drive I have come to these conclusion that: There is a problem with datalink communication between the cart drive and the control. Cart_Drive:I.UserDefinedData[2] and Cart_Drive:I.UserDefinedData[3] (control input datalink data from the drive) are devoid of any data at all times. I do not know how the datalink outputs on the drive (Data Out A1, Data In A2) aquire the encoder data and output the data to the control. I just have the 20-comm-e adapter book and the powerflex manual and it is just not enough information. Can anyone enlighten me to the datalink process with an encoder? Thanks,

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Don't forget the basics by double checking all the ethernet cables.

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"DataLinks" are a holdover from the old days when we used Universal Remote I/O to run drives with PLC-5 controllers. The basic input/output connection was two 16-bit words: Status/Feedback for Input and Command/Reference for Output. If you wanted to exchange more data, you set it up two 16-bit words at a time. DataLink In was input data for the drive (output data from the Controller), and DataLink Out was Output data from the drive (Input data to your controller). You put the parameter number of the parameter you want to be transmitted by the drive to the Controller into the DataLink Out A1, A2, B1, B2, C1, C2, D1, D2 parameter, and then you enable the DataLink and enable it to be part of the Master/Slave I/O connection. All those parameters looked identical in the program you posted, so check to be sure they still are. Use the HIM if you can't get online with the drive using RSLogix 5000 or DriveTools. You mentioned that the drive "just stopped" while it was in use. This makes it sound to me much more like a physical failure of an encoder or cable rather than a parameter change or configuration problem.

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I really appreciate you response Ken and thanks for checking out the project. Yeah, I thought the drive must have gone south, however I swapped the encoder with the rotation axis and found it to be OK. Also, as I mentioned before, I swapped the adapter cards between the two axis and the problem moved with the 20-comm-e proving that the drive is not the problem. Simply swapping IP addresses moved the problem. I don't believe it could be a hardware problem. Is there any chance you could go into more detail with the way the datalink works? Specifically, how do I tell the drive to output the 32 bit data onto say output A1? Also, how do you then associate that data with (in this case) Cart_Drive, the RSLogix 5000 tag? After reading the entire adapter manual and drive manual I understand vaguelly how it works. Just not in detail. I think with that understanding, I could fiqure this out quickly. Thanks

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Hmmm, there is one piece of hardware at which we have not looked yet: the ethernet switch. What type of switch is it, managed or unmanaged? Better yet, give us the manufacturer and the full model number. If it is managed, then there may be some odd configuration problem. If it's unmanaged, we may have a traffic problem. Although it probably is not a switch issue, it is something worth looking at. Edited by JStevens

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Ended up being a start inhibit bit in the parameter of the cart drive. (had another contol guy who had AB support contract make call and walked us through it.) It gave the appearance that the problem was a communication problem since it did not allow the drive to give any feedback to the controller. My thinking that neither drive was the issue was human error on my part. I think the guy that was helping me swapped the motor leads along wih the digital inputs and DPI 5 while troubleshooting. I don't know how that particular bit was changed from a one to a zero (parameter 277, fifth bit from the right if anyone cares) but I will rack it up to a power surge since I know the operator is not capable of making that change. Thanks for the help. Edited by freewayc

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