SLC 500 and power loss

[tgaljar]

Hi,



Just one question about SLC500 memory. Few days ago I had long power loss in a plant and my PLCs were ofline for almost 1 hour. When a power came back I checked program in one SLC with last working copy and a program was not complete some of the rungs and symbols were missing. In an offline mode rungs were there but when I passed to online mode Rslogix deleted some of them. And of course program was not working correctly. How is that possible?!? PLC has a battery properly connected. Before power loss I made some online changes and I saved program, but didn’t make complete download to PLC.



Does anyone have any clues?

 

[Ken Moore]

Most of the memory losses in SLC's that I've seen, have been due to bad quality power, not the loss of power. When the power goes off and then comes back up, depending on the location, you may have many high draw pieces of equipment all trying to start at once. The memory sort of scrambles itself.

Is you PLC power conditioned?

If not you may want to consider a memory backup module, the downside is you have to take the processor out of run mode to write to the memory backup.

 

[tgaljar]

Hm, PLC is powered from UPS but it can buffer only 20minutes after that I have shutdown of my PLCs. Plant consists of several 75kW pumps and when power comes back pumps are starting so that could be the reason.

 

[jjsohio]

sounds like the slc500 has an eprom and the eprom has an older version of the app

 

[tgaljar]

JJSohio can you describe you replay more detailed! How to fix that problem, where to check eprom version?