Hello everyone, I am currently troubleshooting communications between a Westinghouse Eq7 VFD and two compressors connected via a Moxa to a 1756-L72 PLC. Each VFD and Moxa setup for the compressors are identical, with the only difference being the Moxa IP address gateway. One of the compressors is updating data smoothly (Post Compressor) in the AOI, while the other is encountering Sts_Overlap and Sts_Overload errors (Internal Compressor). The configurations on the AOI and PLC sides are the same for both compressors. Attempts to swap IP addresses in the PLC AOI resulted in both compressors giving Sts_Overlap and Sts_Overload errors. Reverting back to the original configuration resolved the issue with the Post Compressor updating correctly. Swapping the Moxas did not change the situation, with the Post Compressor continuing to update and the Internal Compressor experiencing the same errors. We are using the standard template AOI provided by AB. Refer to the attached screenshot for details, noting that for the Internal Compressor (bottom one), Sts_Connected is highlighted. Any insights or suggestions would be greatly appreciated. Thank you, Scott
Overlap occurs when the previous task is still running when the next one begins, due to a poll rate that is too high. In this case, the task is being executed too quickly. The AOI's in question are not performing well; they are slow and overly large. I am struggling to increase their speed beyond 500 milliseconds, even when reading 10 registers in a row from a single device.
Thank you. I resolved the issue and revamped it. Everything is now running smoothly.
Hi Scott, It seems like you've tried a few good approaches for troubleshooting already, but it's still a little unclear why you're seeing these differences between the two compressors. Given that swapping the Moxas didn't change the situation, it seems like the issue is more likely related to the compressors themselves instead of the network configuration. One thing I might suggest is to check the internal fault logs on the problematic compressor's VFD. This could potentially give some insight if the compressor is having any mechanical issues that could be triggering the Sts_Overlap and Sts_Overload errors. Another area to consider exploring is the communication cycle time. If it's too short and the PLC can’t respond within that timeline, it might result in status errors. I'd recommend that you cross-verify the refresh time for both, and see if that solves your problem. Hope this helps.
Hi Scott, From your description, it sounds like a tricky situation. One thing to consider if you haven't already is to check if there are any discrepancies in the network traffic between the two VFDs and compressors. You might be experiencing network congestion, leading to Sts_Overlap and Sts_Overload errors on one end. Tools like Wireshark can help you diagnose network traffic. Also, consuming the data in a different slot or testing the setup with different PLC might help to isolate the issue further. Another thing to look into is whether any physical wiring issues could be causing data transfer difficulties. Sometimes, a simple issue like a bad Ethernet cable can cause communication havoc. I hope this gives you a new direction to look into. Good luck!
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Answer: Answer: The errors could be due to issues related to data overlap or overload in the communication process between the devices.
Answer: Answer: The difference in behavior could be attributed to specific configurations, network settings, or communication issues unique to each compressor-Moxa-PLC connection.
Answer: Answer: Troubleshooting steps may involve checking and ensuring consistent configurations, verifying network settings, analyzing communication protocols, and investigating potential hardware or software issues in the setup.
Answer: Answer: Swapping IP addresses can affect the data communication flow between devices, potentially leading to errors if not done correctly or if there are underlying issues in the setup.
Answer: Answer: Investigate the
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