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drive communication interruption on profibus, SF, plc stop

Created by: zahidbd120 at: 8/2/2013 2:07 PM (4 Replies)

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8/2/2013 2:07 PM	Rate (0)
zahidbd120 Posts: 11 Rating: (0)	Good day. 7 Lenze drives are connected through profibus to cpu 313-C2DP. hmi on the mpi. Startup stage seems to be ok. Machine running fine for couple of hours. Then suddenly 1.some drives output get freezed (hmi fields value) for some time. 2.any one of the drives giving the faulty signal through profibus, no physical alarm or fault on drive itself. plc show SF and stopped. if plc is restarted everything is ok as before. we have to figure out the reason and get rid of it or bypass it safely if possible to ensure discontinued operation. so, downloaded OB85 to plc to ignore io access process image update error, but it is not a safe practice, is it? Cause of error may be interference of profibus cables. but we checked those visually and find nothing wrong. please someone shed some light on why SF is coming, is it ok to download OB, what could be the reasons for profibus communication interruption? Attached is diagnostic buffer for your consideration. thank you. Attachment Module Information - Copy.pdf (63 Downloads)
zahidbd120 Posts: 11 Rating: (0)
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8/2/2013 2:24 PM	Rate (0)
Rated X Posts: 1547 Rating: (129)	Hi, the fault of the station was very short. Only 70 ms. If it is an network problem it can't be EMC - more a loose connection or problem with cable length etc. There should be also not problem with termination. OB85 is only for Access error. You need also OB86 and OB82. There is no problem by adding into your program. Your PLC will not go into stop mode and if the Drive comes back the communication can start again, but for this short you will not have the actual values and you should check that you didn't get any risk status of your application and plant.
Rated X Posts: 1547 Rating: (129)
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8/2/2013 2:36 PM	Rate (0)
zahidbd120 Posts: 11 Rating: (0)	Rated X Hi, the fault of the station was very short. Only 70 ms. ....... but for this short you will not have the actual values and you should check that you didn't get any risk status of your application and plant. after 70 ms plc ping again drive for values. right? if drive fail again what will happen? is it going to be for long until drive respond back. or only 70ms. little bit confused here as a newbie. Thanks for the quick reply btw.
zahidbd120 Posts: 11 Rating: (0)
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8/5/2013 11:14 AM	Rate (0)
Rated X Posts: 1547 Rating: (129)	Hi, after 70ms. the values are refreshed yes, but if your application can handle this is not known, because in time between the application will recognize the fault. You should fix the reason. The OB will only help that the rest of the application can still work.
Rated X Posts: 1547 Rating: (129)
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8/5/2013 12:32 PM	Rate (0)
zahidbd120 Posts: 11 Rating: (0)	Thanks for the suggestion. We will try to remove the root cause. Meanwhile we have to depend on OB handling the brief interruption on the bus. Regards
zahidbd120 Posts: 11 Rating: (0)
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