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HW redundant functinality with S7300

7/10/2013 3:48 PM	Rate (1)
SolutionFinder Posts: 559 Rating: (87)	AMAZINGAHMED N. Vijay Thanks to all One more doubt. Is SW redundant is bumpless. I know that S7400 H is bumpless redundancy. Is it like that or some msec. delay will be there? Regards, Vijay Note that in S7-400 the two CPUs are in the same step of the program cycle. This is achieved by the synchronization modules. If one CPU fails, the other continues executing the program from where the master CPU has stopped. In S7-300, after detecting the failure of the master CPU, the standby CPU returns from the beginning of the program. I think there can be a few seconds for the standby CPU to get into action. If you have a critical plant, then don't go below S7-H No you are wrong. That is not few seconds. The time can not be fix for redundancy change over. It may be in ms or seconds that depends upon how much redundant data you are using for synchronisation that is defined in block call of FB 100 in OB 100 if your sync data is less u will get faster switching It can become bumpless in this case.
SolutionFinder Posts: 559 Rating: (87)
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7/10/2013 3:49 PM
SolutionFinder Posts: 559 Rating: (87)	AMAZINGAHMED N. Vijay Thanks to all One more doubt. Is SW redundant is bumpless. I know that S7400 H is bumpless redundancy. Is it like that or some msec. delay will be there? Regards, Vijay Note that in S7-400 the two CPUs are in the same step of the program cycle. This is achieved by the synchronization modules. If one CPU fails, the other continues executing the program from where the master CPU has stopped. In S7-300, after detecting the failure of the master CPU, the standby CPU returns from the beginning of the program. I think there can be a few seconds for the standby CPU to get into action. If you have a critical plant, then don't go below S7-H No you are wrong. That is not few seconds. The time can not be fix for redundancy change over. It may be in ms or seconds that depends upon how much redundant data you are using for synchronisation that is defined in block call of FB 100 in OB 100 if your sync data is less u will get faster switching It can become bumpless in this case.
SolutionFinder Posts: 559 Rating: (87)
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7/12/2013 11:43 AM	Rate (0)
Ayman Elotaify Diamond Expert Joined: 5/28/2008 Last visit: 1/21/2026 Posts: 4522 Rating: (843)	N. Vijay Thanks to all One more doubt. Is SW redundant is bumpless. I know that S7400 H is bumpless redundancy. Is it like that or some msec. delay will be there? Regards, Vijay Let me return back to the question. S7-400H. "H" is an abbriviation of Hot Standby, which was already explained from friends here. SW Redundancy over S7-300/ 400, is bumpless too. Bumpless means that in case CPU A, set the ouput Q0.0 to 1, then CPU A fails, will this output reset until CPU B work as master? The answer is "NO". It will freez the outputs during this transition switch over time. The differnces mainly in the switch over time. More details can be found here: difference between software redundancy & hardware redundancy Ayman Elotaify ............ It goes without saying that software redundancy cost is lower than HW redundancy. So, If you want to select the optimum solution,you have to think of switching over time. If freezing outputs for few seconds won't affect your plant or process, then you can use SW redundancy,If not go with HW redundancy. Finally, We can not say which system is better than the other (HW / SW redundancy?) As May be for some application, you should use HW redundancy, and for other application, it's suitable to use SW redunadancy. Any way, Siemens offers both. Regards Hope this helps.
	Ayman Elotaify
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