6/26/2009 1:24 AM | |
Joined: 10/7/2005 Last visit: 8/27/2024 Posts: 3018 Rating:
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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 |
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6/27/2009 2:49 PM | |
Joined: 5/28/2008 Last visit: 8/27/2024 Posts: 4515 Rating:
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Hello, Please have a look on the followings: Software and Hardware Redanduncy Choosing between software and hardware redundancy Regards, Attachmentbrochure_simatic-controller_en.pdf (1024 Downloads) |
Ayman Elotaify |
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7/11/2009 11:24 AM | |
Joined: 3/18/2009 Last visit: 5/6/2024 Posts: 306 Rating:
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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.
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)
It is dependent on
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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