6. HX3040 Redundancy
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ATTENTION:
The odd NETs (1, 3 and 5) have the Advanced button, while the even ones (2, 4 and 6) do not.
Through this button, you can set the NETs redundancy (NIC Teaming) and select the Switch mode
as well.
I/O Drivers Configuration
By default, I/O drivers are all communication drivers used by the CPU as Modbus Client, Server,
Master, Slave, DNP3 Client drivers, Outstation, IEC61850, etc. These drivers work differently on
CPUs with redundancy.
For an I/O Driver to run, the CPU must be in RUN mode and in Active redundancy state. This means
that a CPU in Starting, Inactive or Stand-by modes will not have its I/O Drivers running, that is, its
clients and servers (MODBUS, DNP3, etc.) are stopped.
Thus, you cannot use the communication via I/O Drivers in a Non-Active state CPU.
MainTask Configurations
The settings screen associated with the MainTask (main task of a redundant CPU), which is cyclical,
can be accessed by clicking on the correspondent item in the device tree.
Set the two following parameters:
MainTask interval
Watchdog time
For the proper adjustment of the MainTask interval, notice:
The interval must be low enough to effectively control the process, noting the response times of
all control loops
The interval must be high enough to accommodate at least the sum of the two following times:
o
The maximum runtime of NonSkippedPrg and UserPrg together
o
The time required to manage redundancy (redundancy overhead)
In addition, the interval must have an additional clearance necessary for that other processes have
time to run (Ethernet communication with SCADA systems, etc.)
MasterTool is able to calculate the time required to manage the redundancy (redundancy overhead),
after the project is finished (POUs fully developed, and redundant memory areas defined).
As for the maximum execution time of NonSkippedPrg and UserPrg, you can measure it after the
POUs development. After each compilation of the project, MasterTool sums the calculated
redundancy overhead plus the parameter reporting the POUs time (NonSkippedPrg and UserPrg).
Then, it checks if the parameterized minimum clearance is being obeyed.
For example:
Parameters set on MainTask screen
o
MainTask interval: 100 ms
o
Estimated time for POUs NonSkip UserPrg: 10 ms
o
Minimum clearance: 30%
Overhead calculated for redundancy: 50 ms
In this case, the total time taken is 60 ms (10 ms + 50 ms), which consists of 60% of MainTask cycle
(100 ms). The clearance is 40% and, thus the minimum clearance of 30% being observed.
