The redundant control system
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Function
The two controllers establish a high-performance synchronization connection via the SYNC
interface. Before each cycle, the PRIMARY controller transmits the data that is to be syn
-
chronized to the BACKUP controller.
If one of the controllers fails, the other controller takes over the control tasks without inter
-
ruption.
Data synchronization
times
The time required to synchronize the data between the PRIMARY and BACKUP controllers
depends on the amount of redundancy data that needs to be synchronized:
The amount of redundancy data represents the sum data of all variables marked as redun
-
).
Figure 3
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2
Marking a variable as redundant in PLCnext Engineer
Recommended:
• For the cyclic task “SyncTask”, set a cycle time as follows:
Cycle time = Data synchronization time + 5 ms
This ensures that the
entire
amount of redundancy data is sent to the BACKUP con
-
troller in each cycle.
Table 3
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1
Data synchronization time depending on the amount of redundancy data
Amount of redundancy data
Data synchronization time
32 MB
1265 ms
16 MB
635 ms
8 MB
320 ms
4 MB
160 ms
2 MB
80 ms
1 MB
40 ms
512 kB
20 ms
256 kB
10 ms
128 kB
5 ms
64 kB
5 ms
32 kB
5 ms