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software and hardware redundancy in siemens

Created by: Lucky123 at: 6/25/2009 11:42 PM (7 Replies)

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6/25/2009 11:42 PM	Rate (1)
Lucky123 Gold Member Joined: 12/20/2008 Last visit: 8/12/2024 Posts: 556 Rating: (236)	I have heard about siemens also has software redundancy apart from hardware redundancy? My question is, is s400 series is totally hardware redundant and no s/w config program required? Weather S7300 series can also be configured in similar way? How actually redundancy works in S7300 & S7400

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6/26/2009 1:24 AM	Rate (0)
fritz Diamond Expert Joined: 10/7/2005 Last visit: 11/4/2024 Posts: 3025 Rating: (1055)	Dear lalit Software redundancy (aka SWR) can be used in S7-300's and S7-400's and is essentially the "poor" cousin" of a "H" system (H= High availability). You do however have a form of "hardware redundancy" when using SWR, it is however limited to the CPU's (i.e there is NO redundancy of the I/O's possible with SWR). With H system you must go for an S7-400 "H" CPU system and will have a wealth of coices how far you want to "expand" your redundancywith regards to the I/O level. Please note that there is however nothing wrong with SWR, you simply need to be aware of the imitations when compared to aH system. Have a look at these two links to find out more about the two: Software Redundancy for SIMATIIC S7-300 and S7-400 SIMATIC Fault-tolerant Systems S7-400H I hope this helps cheers fritz
	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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6/27/2009 2:49 PM	Rate (0)
Ayman Elotaify Platinum Member Joined: 5/28/2008 Last visit: 11/4/2024 Posts: 4516 Rating: (839)	Hello, Please have a look on the followings: Software and Hardware Redanduncy Choosing between software and hardware redundancy Regards, Attachment brochure_simatic-controller_en.pdf (1124 Downloads)
	Ayman Elotaify
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7/9/2009 5:12 PM	Rate (0)
deepak_plc Posts: 3 Rating: (0)	Dear lalit if i consider the concept of R system , the changeover in case of 400H is bumpless andmay be in time of usec , but in case of 300 R it can be upto 1 sec depending on the data (DB ) in the system and during that time the system will freeze the outputs for that much time i do not suggest 300 R for very critical processes , u must go for 400 H in such cases regards deepak
deepak_plc Posts: 3 Rating: (0)
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7/10/2009 3:56 AM	Rate (0)
Lucky123 Gold Member Joined: 12/20/2008 Last visit: 8/12/2024 Posts: 556 Rating: (236)	Hi Deepak, Thanks for your valuable inputs! As you mentioned time for switch over in Micro seccond. Is there lot of Software logic involved in creating that swicth over or it is totally HW redundancy like Control-Logix? Please let me know. Thanks

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7/10/2009 11:45 AM	Rate (0)
Ayman Elotaify Platinum Member Joined: 5/28/2008 Last visit: 11/4/2024 Posts: 4516 Rating: (839)	Hello, Siemens Offer both Software redundancy, and HW redundancy. In software redundancy, the switching over between the master CPU and the reserve CPU may take few seconds. But do you know what happened during these seconds? All Outputs freezes until the switch over procedure finish and then the reserve CPU will update the PIQ "Process Image Output". HW redundancy is a different story. Because it's built on different teqnique based on S7-400H-CPUs. 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
	Ayman Elotaify
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7/11/2009 4:39 AM	Rate (0)
Lucky123 Gold Member Joined: 12/20/2008 Last visit: 8/12/2024 Posts: 556 Rating: (236)	Ayman Elotaify Hello, Any way, Siemens offers both. Regards Hi Ayman, EventuallY I agree and understood what you have tried to say. However my question is still un answered or you can say I still need the precise answer. Is there any kind of software logic involved in doing Hardware Redundancy? I mean to say let's suppose If I select the Applicable Hardware for the S7400 System(Complete Set). Once I power up and download the hardware configuration, do I also need to write a bit or piece of logic for switch over or something like that in the routine? And how much will be the switch over time? And how much time does it take to completely synchronize and redundancy enabling after the power on.? Would also appreciate response from a person who has practically done it. Thanks

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7/11/2009 11:24 AM	Rate (3)
daga Gold Member Joined: 3/18/2009 Last visit: 5/6/2024 Posts: 306 Rating: (94)	lalit Is there any kind of software logic involved in doing Hardware Redundancy? I mean to say let's suppose If I select the Applicable Hardware for the S7400 System(Complete Set). Once I power up and download the hardware configuration, do I also need to write a bit or piece of logic for switch over or something like that in the routine? No. The firmware of H-system takes care of the CPU redundancy. You do have the possibility to fiddle with the normal operating logic using a SFC (H_CTRL), but it is generally never required. However to ensure that the system does not go to a stop because of an error all error OBs are required to be downloaded. They, of course, can be without any logic. Read chapter 12 of below mentioned manual. Please note that for IO redundancy, you have to use software logic. It is not built in firmware. Libraries for redundant IOs are supplied with Step7/PCS7. lalit And how much will be the switch over time? Switch over times are not relevant for CPUs. Basically, there is nothing such as "CPU switch over time" in H-system. In redunant mode both CPUs are active and if one fails the other continues. However, if you or your client do not agree with it, then it can be proven that switch over time is less than 10mS (at least). Switch over times are, however, relevant for profibus DP slaves switching from one DP master to redundant partner. (could be few mS to few hundred mS) lalit And how much time does it take to completely synchronize and redundancy enabling after the power on.? It is dependent on Type of CPU Size of user program It could be anything between few mS to few seconds. There are two parts to it. "Linkup" and "Update". Please read chapters 8, 9 and 16 of the "Fault Tolerant systems S7-400H - System Manual" edition 2/2009to completely understand and calculate the times that you are interested in.

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