Regarding Siemens S7-400 redundancy
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Our company upgraded the S7-400 PLCs in the control room some time ago, claiming it was for redundancy purposes – an ET200M unit was added to each slave station, resulting in two units per station; the address settings remained the same, but the cards used did not change, nor did the signals at the site. Another CPU was also added, so now there are two CPUs in total, all connected via the DP bus. In my opinion, this is pointless; it only provides so-called redundancy in the event of a problem with the ET200M units or the CPUs. I would appreciate it if experts could analyze this situation for me. Thank you
1. The addition of a CPU enables CPU redundancy. 2. It’s not an ET200 that is added; rather, an IM153 interface module is added to each ET200, thereby achieving DP bus redundancy. 3. In the event of a CPU failure, a seamless switchover can be achieved. 4. With DP bus redundancy, the system will not stop operating due to failures in the communication bus or interface modules. 5. Such a configuration is useful; it also allows other modules to achieve redundancy more quickly. However, reconfiguring the hardware is required, which leads to changes in addresses and necessitates further configuration. ,