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CPU in STOP mode - Drive not Stopping

Created by: KD.. at: 2/8/2012 4:10 AM (6 Replies)

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2/8/2012 4:10 AM	Rate (0)
KD.. Posts: 25 Rating: (7)	Hi All, Architecture: Pump drive connected to S7300 CPU on Profibus. Technical Details: To operate Pump drive there is a command register we need to write 4 value to stop the drive and 3 to Start. There is Watchdog setting on the drive to monitor PLC status, which stops the drive if Profibus network connectivity is lost. Which does not work if PLC in STOPped condition. Question: Is there any way to Stop the drive if PLC goes in STOP mode? I know following: PLC outputs turn to 0 during STOPped condition. There is no OB available which executes when PLC is STOPping Thanks in Advance, KD...
KD.. Posts: 25 Rating: (7)	Last edited by: KD.. at: 2/8/2012 4:12 AM Changed Formatting
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2/8/2012 9:50 AM	Rate (0)
Wizard Diamond Member Joined: 4/24/2006 Last visit: 11/5/2024 Posts: 8766 Rating: (1170)	Hello KD.. The Frequency converter should have a parameter to monitor the status of Profibus Master. (When the Control word is 0 for some time it will stop Frequency converter) Perhaps this link might help: /tf/WW/en/Posts/38108 Best regards, Wizard

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2/8/2012 12:42 PM	Rate (0)
KD.. Posts: 25 Rating: (7)	Dear Wizard, First of all thanks for your response. That’s correct, thesetting is available on the Pump (it’s a dosing pump connected on Profibus we are talking about) called “Watchdog Enable”. It works properly if you disconnect the Profibus cable or knock off PLC, but it fails to respond when PLC is STOPped condition. Regards, KD…
KD.. Posts: 25 Rating: (7)	Last edited by: KD.. at: 2/8/2012 12:43 PM
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2/8/2012 2:32 PM	Rate (0)
Wizard Diamond Member Joined: 4/24/2006 Last visit: 11/5/2024 Posts: 8766 Rating: (1170)	Hello KD.. Perhaps the manufacturer of the Pumpdrive might know how to proceed? Best regards, Wizard

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2/8/2012 7:47 PM	Rate (0)
0_Einstein Diamond Member Joined: 7/7/2010 Last visit: 11/6/2024 Posts: 15385 Rating: (2443)	Try this in your PLC program as a 'test'. In your lowest OB's first rung, set the command status bit for PLC control (bit 10?) to 0. In your highest # OB's last rung, set the command status bit to PLC control (bit 10?) to 1. If your program crashes in between, or you send a stop command, it should leave the bit as a 0, then your drive will stop. Please post your results if this works. Also, test it several times if it works the first time. It might be that issuing a stop versus creating a PLC program crashor watchdog timeoutmay generate different results.
	science guy
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2/10/2012 2:09 AM	Rate (1)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 11/6/2024 Posts: 3026 Rating: (1055)	KD.. To operate Pump drive there is a command register we need to write 4 value to stop the drive and 3 to Start. Hello KD.. your problem is that you need a write a value of 4 to stop the drive, which - I'm afraid to say - is not a very failsafe value. The DP Master of an an S7 PLC is set to so called "Clear" state when you stop the CPU. In the clear state, the DP Master will still poll the DP Slaves (your bus is still "healthy") and the do one of the following: 1.) DP Slaves GSD entry for"Fail_Safe" = 0: DP Master sends all Outputswith zero values cyclically to the DP Slave Note: This also applies if the optional Fail_Safeentry has been ommited from the GSD file. 2.) DP Slaves GSD entry for"Fail_Safe" = 1: DP Master does NOT send the outputs, but instead sends cyclically ashort message to let the DP Slave know that it isclear state. I suggest you talk to your Drive supplier what can be done, as your driveshould be able to handle this and go to a "failsafe" state (i.e. STOP, if not, I suggest you get the supplier to develop a new PB interfacefor it or get a drive that does support this). I hope this helps
	Cheers fritz The advice and opinion given in this thread is that of the author and does not necessarily reflect the views of I S Systems Pty Limited. To find out how I S Systems can help you with your automation needs please visit www.issystems.com.au.
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This contribution was helpful to 2 thankful Users Wizard SLA@

2/10/2012 5:54 AM	Rate (0)
KD.. Posts: 25 Rating: (7)	Hi Fritz and Wizard, Thanks for your valuable inputs. As you suggested, I need to getthis sorted by the Pump Drive. I will post again if I get any input from drive supplier. Thanks Again, KD...
KD.. Posts: 25 Rating: (7)
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This contribution was helpful to 2 thankful Users fritz Wizard

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