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Power Loss on a PCS7 System

4/8/2011 11:16 PM	Rate (0)
Roussey Posts: 37 Rating: (0)	Hi everyone, I am new with Siemens PLC and at my actual job there is a PCS7 that I am starting to study. The problem is: the UPS is not working so everytime a power loss happens the S7-400 CPU goes to stop and all the communications goes down, it is normal, but when people of maintenance restarts the power they have the procedure of downloading all the programming blocks and communications. But I don't think it is the right thingto do. On a rockwell system I can shutdown the PLC and then power on, the program is there. Can someone help me. If there is some more information needed just ask. Thanks, Andre Roussey
Roussey Posts: 37 Rating: (0)
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4/9/2011 7:22 PM	Rate (0)
umencho Diamond Member Joined: 3/21/2006 Last visit: 3/30/2025 Posts: 10239 Rating: (1183)	Hello Andrey, How can you write the program to the FLASH Memory Card when using a SIMATIC S7-400 CPU? Which memory cards can you use with the S7-400H fault-tolerant system? How do you provide an external backup supply for an S7-400 CPU? Where can you find information about the S7-300/400 backup batteries? And UPS should works. If there has a problem. Immediately repair it. Best regards, Hristo Mihalev

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4/11/2011 4:13 PM	Rate (0)
dmertens Bronze Member Joined: 10/3/2007 Last visit: 6/25/2024 Posts: 188 Rating: (34)	If your power supply has battery supply or you provide DC power directly to the CPU (special connector is present on the CPU for this) then the program and all settings will remain in memory and once power is restored you don't need to download anything, your CPU returns to its previous state (Usually RUN). The restart of the CPU will normally make sure everything goes to manual, all valves remain in their safe state and all motors are switched off, however your program has to make sure they are not put into automatic and activated if it is not safe to do so. The procedure of reloading the software usually ensures this as you start from a predefined situation, whereas in the case of a restart some logic may have been active to start certain devices which may not be safe. Make sure to test the behaviour of a restarting CPU offline and add the necessary precautions if not already present before implementing this in a live plant.

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