Hello,
I’m working with an ABB PM573 PLC and facing an issue. After a power failure, the main program that was previously in memory is no longer executed. Instead, a simple default program runs, where Input 1 controls Output 1.
Surprisingly, when I upload the main program back into the PLC, it runs normally as expected. However, after another power failure, the main program remains in memory but is not executed, and only the simple program runs again.
Can anyone provide insights into why this is happening and how I can ensure the main program is executed after a power failure? Any advice would be greatly appreciated.
The issue appears to be connected to how the PLC manages power cycle behavior & memory retention. There are some important points to examine in ABB PM573 PLCs:
Some PLCs include options for controlling what happens to the memory after a power outage. It’s possible that the PLC saves your main program but isn’t programmed to restart it following a power cycle. Check the PLC configuration to confirm that the main program is set to start automatically following a power outage.
Check that the backup battery (if applicable) is working properly. If the battery is dead (or) not performing properly, it may cause problems keeping specific system variables or flags required to restart the main application after a power failure.
Examine the startup behavior in the PLC configuration. Some PLCs allow you to specify which application or routine should run at launch. It’s possible that the simple default application was set as the startup procedure, which is why it runs when power is restored. You may need to specify your main program as the startup program.
Examine the portions of the program that may require retentive memory. If specific sections of the program, such as status flags or startup routines, are lost or reset as a result of a power failure, the main program may fail to execute properly.
Ensure that the PLC is configured to immediately enter RUN mode after power restoration. Some PLCs include a configuration that causes them to default to STOP mode following a power cycle, which may need you to manually switch it back to RUN.
Look for any fault logs (or) diagnostic messages following the power outage. This could help you understand why the main program isn’t being executed and the basic program takes over.
it appears that the PLC is defaulting to a simple program when restarted, either because the main program is not configured as the starting point program or because some settings are disabled. I’d recommend starting by analyzing the startup action & RAM settings in the setup.