8/18/2017 3:37 PM | |
Joined: 9/27/2006 Last visit: 9/20/2024 Posts: 12282 Rating: (2684)
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Hello RADI; We have to clear up 2 different concepts in your original question., since you are mixing up 2 possible configurations. First, Siemens proposes redundancy in the H-System PLCs, for fault-tolerant S7-400H CPUs. I do not know if this is one of the manuals you consulted, but this is the most complete source of information on H-systems: SIMATIC Fault-tolerant systems S7-400H Fault-tolerant CPUs implement what we programmers refer to as Hot redundancy, by which we mean that virtually no data is lost when there is a switchover between the primary and standby CPUs, because it happens in milliseconds. And the primary sends all process and configuration data to the standby at every scan cycle, so the standby is always up-to-date and ready to take over the control of the process. Look at the screenshot below, showing how the hardware you describe (plus the synch modules and F.O. cables) are used to setup a basic S7-400H system. Another option is what is called Software Redundancy (SWR) which implements "warm redundancy" between S7-300 and s7-400 CPUs (they do not have to be fault-tolerant). Synchronisation is implemented through a pair of communication processors (MPI, Profibus-DP or ethernet) and all redundant exchanges must be programmed by the user. The changeover time (when switching from primary to standby) can take up to 1 sec (which is generally considered a very long time when you consider that a PLC scan time runs around 20 ms). You can have a look at the SWR system in this manual: SIMATIC S7-300/S7-400 Software redundancy for SIMATIC S7 When you have decided which road you will take, come back to the forum for more directions... Hope this helps, Daniel Chartier |
Last edited by: dchartier at: 8/18/2017 4:23:56 PM |
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