acc00 - 2024-03-08

I have 2 Wago PFC200 PLC, running with Runtime SP19 Patch 5, with the Redundant application.

The PLC communicates as Modbus Master with at this moment 15 Modbus Slaves -later there will be 28 in total- (Drives, Power management units,...). These devices are connected in 2 rings (1 ring of Drives, 1 ring of Power Management units), with 2 Managed Moxa Switches being part of the ring. Each PLC is connected to one of these switches.

The issue I'm encountering is that the Cycle time of the Active PLC goes very high when I'm closing the Drive ring (simulating an issue on one Cabinet supply, resulting in that one Drive shut down, which can happen on field quite often). As a result of this long cycle, the PLC fails and goes to Exception, and the Passive PLC does not take control of the system.

A normal cycle is around 30ms for the Main task, and a few ms for the Ethercat task.

When I monitor with Profiler, I see that in this Maximum Cycle, the main Task is only taking 13ms, so I'm not sure where the PLC is hanging for so long.

Is the remaining cycle time the Redundant management/sync or something else?

Thank you in advance.


Last edit: acc00 2024-03-08